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0000-0002-2406-9972
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University of Wollongong
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Research Topics
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Top 5 Research Topics
ANZSRC Field of Research (FoR)
Other Physical Sciences | Synchrotrons; Accelerators; Instruments and Techniques | Medical Physics | Medical physics | Particle physics | Atomic, Molecular, Nuclear, Particle and Plasma Physics | Space instrumentation | Particle and high energy physics | Nuclear And Particle Physics | Medical Physics | Instruments And Techniques | Biological Physics | Atomic and Molecular Physics |
ANZSRC Socio-Economic Objective (SEO)
Expanding Knowledge in the Physical Sciences | Expanding Knowledge in the Earth Sciences | Expanding Knowledge in the Chemical Sciences | Scientific Instruments | Expanding Knowledge in the Biological Sciences | Medical instrumentation | Occupational health (excl. economic development aspects) | Scientific instrumentation | Expanding Knowledge in Technology |
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Publications
BrachyView: Proof-of-principle of a novel in-body gamma camera for low dose-rate prostate brachytherapy
Publisher: Wiley
Date: 15-03-2013
DOI: 10.1118/1.4794487
Abstract: The conformity of the achieved dose distribution to the treatment plan strongly correlates with the accuracy of seed implantation in a prostate brachytherapy treatment procedure. Incorrect seed placement leads to both short and long term complications, including urethral and rectal toxicity. The authors present BrachyView, a novel concept of a fast intraoperative treatment planning system, to provide real-time seed placement information based on in-body gamma camera data. BrachyView combines the high spatial resolution of a pixellated silicon detector (Medipix2) with the volumetric information acquired by a transrectal ultrasound (TRUS). The two systems will be embedded in the same probe so as to provide anatomically correct seed positions for intraoperative planning and postimplant dosimetry. Dosimetric calculations are based on the TG-43 method using the real position of the seeds. The purpose of this paper is to demonstrate the feasibility of BrachyView using the Medipix2 pixel detector and a pinhole collimator to reconstruct the real-time 3D position of low dose-rate brachytherapy seeds in a phantom. BrachyView incorporates three Medipix2 detectors coupled to a multipinhole collimator. Three-dimensionally triangulated seed positions from multiple planar images are used to determine the seed placement in a PMMA prostate phantom in real time. MATLAB codes were used to test the reconstruction method and to optimize the device geometry. The results presented in this paper show a 3D position reconstruction accuracy of the seed in the range of 0.5-3 mm for a 10-60 mm seed-to-detector distance interval (Z direction), respectively. The BrachyView system also demonstrates a spatial resolution of 0.25 mm in the XY plane for sources at 10 mm distance from Medipix2 detector plane, comparable to the theoretical value calculated for an equivalent gamma camera arrangement. The authors successfully demonstrated the capability of BrachyView for real-time imaging (using a 3 s data acquisition time) of different brachytherapy seed configurations (with an activity of 0.05 U) throughout a 60 × 60 × 60 mm(3) Perspex prostate phantom. The newly developed miniature gamma camera component of BrachyView, with its high spatial resolution and real time capability, allows accurate 3D localization of seeds in a prostate phantom. Combination of the gamma camera with TRUS in a single probe will complete the BrachyView system.
BrachyView: A novel technique for seed localisation and real-time quality assurance
Publisher: Elsevier BV
Date: 04-2016
The Microbeam Insert at the White Beam Beamline P61A at the Synchrotron PETRA III/DESY: A New Tool for High Dose Rate Irradiation Research
Publisher: MDPI AG
Date: 20-10-2022
Abstract: High dose rate radiotherapies such as FLASH and microbeam radiotherapy (MRT) both have developed to the stage of first veterinary studies within the last decade. With the development of a new research tool for high dose rate radiotherapy at the end station P61A of the synchrotron beamline P61 on the DESY c us in Hamburg, we increased the research capacity in this field to speed up the translation of the radiotherapy techniques which are still experimental, from bench to bedside. At P61, dose rates of several hundred Gy/s can be delivered. Compared to dedicated biomedical beamlines, the beam width available for MRT experiments is a very restrictive factor. We developed two model systems specifically to suit these specific technical parameters and tested them in a first set of experiments.
Indirect radio-chemo-beta therapy: A targeted approach to increase biological efficiency of x-rays based on energy
Publisher: IOP Publishing
Date: 25-09-2015
DOI: 10.1088/0031-9155/60/20/7847
Abstract: Despite the use of multimodal treatments incorporating surgery, chemotherapy and radiotherapy, local control of gliomas remains a major challenge. The potential of a new treatment approach called indirect radio-chemo-beta therapy using the synergy created by combining methotrexate (MTX) with bromodeoxyuridine (BrUdR) under optimum energy x-ray irradiation is assessed. 9L rat gliosarcoma cells pre-treated with 0.01 μM MTX and/or 10 μM BrUdR were irradiated in vitro with 50 kVp, 125 kVp, 250 kVp, 6 MV and 10 MV x-rays. The cytotoxicity was assessed using clonogenic survival as the radiobiological endpoint. The photon energy with maximum effect was determined using radiation sensitization enhancement factors at 10% clonogenic survival (SER10%). The cell cycle distribution was investigated using flow cytometric analysis with propidium iodide staining. Incorporation of BrUdR in the DNA was detected by the fluorescence of labelled anti-BrUdR antibodies. The radiation sensitization enhancement exhibits energy dependence with a maximum of 2.3 at 125 kVp for the combined drug treated cells. At this energy, the shape of the clonogenic survival curve of the pharmacological agents treated cells changes substantially. This change is interpreted as an increased lethality of the local radiation environment and is attributed to supplemented inhibition of DNA repair. Radiation induced chemo-beta therapy was demonstrated in vitro by the targeted activation of combined pharmacological agents with optimized energy tuning of x-ray beams on 9 L cells. Our results show that this is a highly effective form of chemo-radiation therapy.
PO-0901 2D solid-state array detectors: a technique for in-vivo dose verification at varying effective area
Publisher: Elsevier BV
Date: 04-2019
Evaluation of a thin microstrip detector for high spatial resolution dosimetry
Publisher: Elsevier BV
Date: 12-2011
Fabrication and First Characterization of Silicon-Based Full 3-D Microdosimeters
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2020
Review of four novel dosimeters developed for use in radiotherapy
Publisher: IOP Publishing
Date: 26-06-2013
Examining Individual and Synergistic Contributions of PTSD and Genetics to Blood Pressure: A Trans-Ethnic Meta-Analysis
Publisher: Frontiers Media SA
Date: 23-06-2021
DOI: 10.3389/FNINS.2021.678503
Abstract: Growing research suggests that posttraumatic stress disorder (PTSD) may be a risk factor for poor cardiovascular health, and yet our understanding of who might be at greatest risk of adverse cardiovascular outcomes after trauma is limited. In this study, we conducted the first examination of the in idual and synergistic contributions of PTSD symptoms and blood pressure genetics to continuous blood pressure levels. We harnessed the power of the Psychiatric Genomics Consortium-PTSD Physical Health Working Group and investigated these associations across 11 studies of 72,224 trauma-exposed in iduals of European ( n = 70,870) and African ( n = 1,354) ancestry. Genetic contributions to blood pressure were modeled via polygenic scores (PGS) for systolic blood pressure (SBP) and diastolic blood pressure (DBP) that were derived from a prior trans-ethnic blood pressure genome-wide association study (GWAS). Results of trans-ethnic meta-analyses revealed significant main effects of the PGS on blood pressure levels [SBP: β = 2.83, standard error (SE) = 0.06, p & 1E-20 DBP: β = 1.32, SE = 0.04, p & 1E-20]. Significant main effects of PTSD symptoms were also detected for SBP and DBP in trans-ethnic meta-analyses, though there was significant heterogeneity in these results. When including data from the largest contributing study – United Kingdom Biobank – PTSD symptoms were negatively associated with SBP levels (β = −1.46, SE = 0.44, p = 9.8E-4) and positively associated with DBP levels (β = 0.70, SE = 0.26, p = 8.1E-3). However, when excluding the United Kingdom Biobank cohort in trans-ethnic meta-analyses, there was a nominally significant positive association between PTSD symptoms and SBP levels (β = 2.81, SE = 1.13, p = 0.01) no significant association was observed for DBP (β = 0.43, SE = 0.78, p = 0.58). Blood pressure PGS did not significantly moderate the associations between PTSD symptoms and blood pressure levels in meta-analyses. Additional research is needed to better understand the extent to which PTSD is associated with high blood pressure and how genetic as well as contextual factors may play a role in influencing cardiovascular risk.
TiO2/(BiO)2CO3 nanocomposites for ultraviolet filtration with reduced photocatalytic activity
Publisher: Royal Society of Chemistry (RSC)
Date: 2018
DOI: 10.1039/C8TC01330F
Abstract: TiO 2 nanoparticles are typically used in sunscreens however, they have been shown to exhibit cyto- and genotoxicity, which is related to the photocatalytic activity and the subsequent formation of reactive oxygen species when exposed to ultraviolet radiation.
On the Combined Effect of Silicon Oxide Thickness and Boron Implantation under the Gate in MOSFET Dosimeters
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 03-2020
In vivo real-time rectal wall dosimetry for prostate radiotherapy
Publisher: IOP Publishing
Date: 22-06-2010
Evaluation of the PTW microDiamond in edge-on orientation for dosimetry in small fields
Publisher: Wiley
Date: 22-05-2020
DOI: 10.1002/ACM2.12906
High-Pressure EPR and Site-Directed Spin Labeling for Mapping Molecular Flexibility in Proteins
Publisher: Elsevier
Date: 2015
DOI: 10.1016/BS.MIE.2015.07.004
Abstract: High hydrostatic pressure is a powerful probe of protein conformational flexibility. Pressurization reveals regions of elevated compressibility, and thus flexibility, within in idual conformational states, but also shifts conformational equilibria such that "invisible" excited states become accessible for spectroscopic characterization. The central aim of this chapter is to describe recently developed instrumentation and methodologies that enable high-pressure site-directed spin labeling electron paramagnetic resonance (SDSL-EPR) experiments on proteins and to demonstrate the information content of these experiments by highlighting specific recent applications. A brief introduction to the thermodynamics of proteins under pressure is presented first, followed by a discussion of the principles underlying SDSL-EPR detection of pressure effects in proteins, and the suitability of SDSL-EPR for this purpose in terms of timescale and ability to characterize conformational heterogeneity. Instrumentation and practical considerations for variable-pressure continuous wave EPR and pressure-resolved double electron-electron resonance (PR DEER) experiments are reviewed, and finally illustrations of data analysis using recent applications are presented. Although high-pressure SDSL-EPR is in its infancy, the recent applications presented highlight the considerable potential of the method to (1) identify compressible (flexible) regions in a folded protein (2) determine thermodynamic parameters that relate conformational states in equilibrium (3) populate and characterize excited states of proteins undetected at atmospheric pressure (4) reveal the structural heterogeneity of conformational ensembles and provide distance constraints on the global structure of pressure-populated states with PR DEER.
“Characterization of ELEKTA SRS cone collimator using high spatial resolution monolithic silicon detector array”
Publisher: Wiley
Date: 22-05-2018
DOI: 10.1002/ACM2.12345
The effect of an air gap on a 2D monolithic silicon detector for relative dosimetry
Publisher: IOP Publishing
Date: 12-06-2019
Study of the X-ray radiation interaction with a multislit collimator for the creation of microbeams in radiation therapy
Publisher: International Union of Crystallography (IUCr)
Date: 09-02-2021
DOI: 10.1107/S1600577520016811
Abstract: Microbeam radiation therapy (MRT) is a developing radiotherapy, based on the use of beams only a few tens of micrometres wide, generated by synchrotron X-ray sources. The spatial fractionation of the homogeneous beam into an array of microbeams is possible using a multislit collimator (MSC), i.e. a machined metal block with regular apertures. Dosimetry in MRT is challenging and previous works still show differences between calculated and experimental dose profiles of 10–30%, which are not acceptable for a clinical implementation of treatment. The interaction of the X-rays with the MSC may contribute to the observed discrepancies the present study therefore investigates the dose contribution due to radiation interaction with the MSC inner walls and radiation leakage of the MSC. Dose distributions inside a water-equivalent phantom were evaluated for different field sizes and three typical spectra used for MRT studies at the European Synchrotron Biomedical beamline ID17. Film dosimetry was utilized to determine the contribution of radiation interaction with the MSC inner walls Monte Carlo simulations were implemented to calculate the radiation leakage contribution. Both factors turned out to be relevant for the dose deposition, especially for small fields. Photons interacting with the MSC walls may bring up to 16% more dose in the valley regions, between the microbeams. Depending on the chosen spectrum, the radiation leakage close to the phantom surface can contribute up to 50% of the valley dose for a 5 mm × 5 mm field. The current study underlines that a detailed characterization of the MSC must be performed systematically and accurate MRT dosimetry protocols must include the contribution of radiation leakage and radiation interaction with the MSC in order to avoid significant errors in the dose evaluation at the micrometric scale.
Functional characterisation of novel silicon beam monitors for the micro-beam radiation therapy
Publisher: IEEE
Date: 10-2016
In vitro investigation of the dose-rate effect on the biological effectiveness of megavoltage X-ray radiation doses
Publisher: Elsevier BV
Date: 10-2017
DOI: 10.1016/J.APRADISO.2017.07.008
Abstract: Radiation therapy is rapidly evolving toward the delivery of higher dose rates to improve cancer treatment. In vitro experiments were performed to investigate the response of 9L and MCF-7 cancer cell lines, exposed to 10MV X-ray radiations. Up to 8Gy was delivered at a dose-rate of 50cGy/min compared to 5Gy/min. The data obtained emphasizes the importance of taking into account not only the physical, but also the radiobiological parameters, when planning a particular cancer treatment.
X-Tream quality assurance in synchrotron X-ray microbeam radiation therapy
Publisher: International Union of Crystallography (IUCr)
Date: 26-07-2016
DOI: 10.1107/S1600577516009322
Abstract: Microbeam radiation therapy (MRT) is a novel irradiation technique for brain tumours treatment currently under development at the European Synchrotron Radiation Facility in Grenoble, France. The technique is based on the spatial fractionation of a highly brilliant synchrotron X-ray beam into an array of microbeams using a multi-slit collimator (MSC). After promising pre-clinical results, veterinary trials have recently commenced requiring the need for dedicated quality assurance (QA) procedures. The quality of MRT treatment demands reproducible and precise spatial fractionation of the incoming synchrotron beam. The intensity profile of the microbeams must also be quickly and quantitatively characterized prior to each treatment for comparison with that used for input to the dose-planning calculations. The Centre for Medical Radiation Physics (University of Wollongong, Australia) has developed an X-ray treatment monitoring system (X-Tream) which incorporates a high-spatial-resolution silicon strip detector (SSD) specifically designed for MRT. In-air measurements of the horizontal profile of the intrinsic microbeam X-ray field in order to determine the relative intensity of each microbeam are presented, and the alignment of the MSC is also assessed. The results show that the SSD is able to resolve in idual microbeams which therefore provides invaluable QA of the horizontal field size and microbeam number and shape. They also demonstrate that the SSD used in the X-Tream system is very sensitive to any small misalignment of the MSC. In order to allow as rapid QA as possible, a fast alignment procedure of the SSD based on X-ray imaging with a low-intensity low-energy beam has been developed and is presented in this publication.
Discussion: “Evidence for a transgressive barrier within a regressive strandplain system: implications for complex response to environmental change” by Hein, et al. (2013), Sedimentology 60, 46
Publisher: Wiley
Date: 18-07-2014
DOI: 10.1111/SED.12132
Measurement of multi-slice computed tomography dose profile with the Dose Magnifying Glass and the MOSkin radiation dosimeter
Publisher: Elsevier BV
Date: 08-2013
Hydrogenated amorphous silicon high flux x-ray detectors for synchrotron microbeam radiation therapy
Publisher: IOP Publishing
Date: 28-06-2023
Abstract: Objective . Microbeam radiation therapy (MRT) is an alternative emerging radiotherapy treatment modality which has demonstrated effective radioresistant tumour control while sparing surrounding healthy tissue in preclinical trials. This apparent selectivity is achieved through MRT combining ultra-high dose rates with micron-scale spatial fractionation of the delivered x-ray treatment field. Quality assurance dosimetry for MRT must therefore overcome a significant challenge, as detectors require both a high dynamic range and a high spatial resolution to perform accurately. Approach . In this work, a series of radiation hard a-Si:H diodes, with different thicknesses and carrier selective contact configurations, have been characterised for x-ray dosimetry and real-time beam monitoring applications in extremely high flux beamlines utilised for MRT at the Australian Synchrotron. Results . These devices displayed superior radiation hardness under constant high dose-rate irradiations on the order of 6000 Gy s −1 , with a variation in response of 10% over a delivered dose range of approximately 600 kGy. Dose linearity of each detector to x-rays with a peak energy of 117 keV is reported, with sensitivities ranging from (2.74 ± 0.02) nC/Gy to (4.96 ± 0.02) nC/Gy. For detectors with 0.8 μ m thick active a-Si:H layer, their operation in an edge-on orientation allows for the reconstruction of micron-size beam profiles (microbeams). The microbeams, with a nominal full-width-half-max of 50 μ m and a peak-to-peak separation of 400 μ m, were reconstructed with extreme accuracy. The full-width-half-max was observed as 55 ± 1 μ m. Evaluation of the peak-to-valley dose ratio and dose-rate dependence of the devices, as well as an x-ray induced charge (XBIC) map of a single pixel is also reported. Significance . These devices based on novel a-Si:H technology possess a unique combination of accurate dosimetric performance and radiation resistance, making them an ideal candidate for x-ray dosimetry in high dose-rate environments such as FLASH and MRT.
Characterisation and evaluation of a PNP strip detector for synchrotron microbeam radiation therapy
Publisher: IOP Publishing
Date: 21-06-2018
The effect of air gaps on Magic Plate (MP512) for small field dosimetry
Publisher: Elsevier BV
Date: 05-2017
Structure-relaxation mechanism for the response of T4 lysozyme cavity mutants to hydrostatic pressure
Publisher: Proceedings of the National Academy of Sciences
Date: 27-04-2015
Abstract: High pressure has emerged as a powerful tool for exploring the energy landscape of proteins, but structural origins of the pressure response remain controversial. The results of this study on a cavity mutant of T4 lysozyme (L99A) provide direct evidence for a structure-relaxation mechanism wherein pressure shifts conformational equilibria toward states with alternative packing arrangements that fill cavities or voids in the core. Both structure relaxation and cavity hydration can occur in response to pressure, and which dominates is found to depend on details of the energy landscape. The results also address conflicting views regarding the pressure response of L99A that have recently been published.
Potential formation of mutagenicity by low pressure-UV/H2 O2 during the treatment of nitrate-rich source waters
Publisher: Royal Society of Chemistry (RSC)
Date: 2018
DOI: 10.1039/C7EW00389G
Abstract: LP-UV/H 2 O 2 treatment of NOM-containing synthetic waters led to nitrite, nitrophenol and measurable but not mutagenic Ames responses in the presence of nitrate, where the NOM type affected the response levels.
Spectral characterisation of a blue-enhanced silicon photodetector
Publisher: IEEE
Date: 2000
Effect of Pile-Driving Playback Sound Level on Fish-Catching Efficiency in Harbor Porpoises (Phocoena phocoena)
Publisher: Aquatic Mammals Journal
Date: 15-07-2019
A.31 Development and application of a trans-rectal US probe integrated with MOSkin dosimeters: In vivo rectal wall measurements during HDR prostate brachytherapy
Publisher: Elsevier BV
Date: 02-2016
Potential high resolution dosimeters for MRT
Publisher: AIP
Date: 2010
DOI: 10.1063/1.3478205
Saturation Recovery EPR and Nitroxide Spin Labeling for Exploring Structure and Dynamics in Proteins
Publisher: Elsevier
Date: 2015
DOI: 10.1016/BS.MIE.2015.07.016
Abstract: Experimental techniques capable of determining the structure and dynamics of proteins are continuously being developed in order to understand protein function. Among existing methods, site-directed spin labeling in combination with saturation recovery (SR) electron paramagnetic resonance spectroscopy contributes uniquely to the determination of secondary and tertiary protein structure under physiological conditions, independent of molecular weight and complexity. In addition, SR of spin labeled proteins was recently demonstrated to be sensitive to conformational exchange events with characteristic lifetimes on the order of μs, a time domain that presents a significant challenge to other spectroscopic techniques. In this chapter, we present the theoretical background necessary to understand the capabilities of SR as applied to spin labeled proteins, the instrumental requirements, and practical experimental considerations necessary to obtain interpretable data, and the use of SR to obtain information on protein: (1) secondary structure via solvent accessibility measurements, (2) tertiary structure using interspin distance measurements, and (3) conformational exchange.
Dosimetry verification in eye brachytherapy using silicon pixelated detectors
Publisher: Elsevier BV
Date: 12-2011
X-tream: A novel dosimetry system for synchrotron microbeam radiation therapy
Publisher: IOP Publishing
Date: 31-07-2012
High spatial resolution microdosimetry with Δe-E detector on C-12 beam: Monte Carlo simulations
Publisher: IEEE
Date: 10-2013
The Spinal Cord as Organ of Risk: Assessment for Acute and Subacute Neurological Adverse Effects after Microbeam Radiotherapy in a Rodent Model
Publisher: MDPI AG
Date: 26-04-2023
Abstract: Microbeam radiotherapy (MRT), a high dose rate radiotherapy technique using spatial dose fractionation at the micrometre range, has shown a high therapeutic efficacy in vivo in different tumour entities, including lung cancer. We have conducted a toxicity study for the spinal cord as organ of risk during irradiation of a target in the thoracic cavity. In young adult rats, the lower thoracic spinal cord was irradiated over a length of 2 cm with an array of quasi-parallel microbeams of 50 µm width, spaced at a centre-to-centre distance of 400 µm, with MRT peak doses up to 800 Gy. No acute or subacute adverse effects were observed within the first week after irradiation up to MRT peak doses of 400 Gy. No significant differences were seen between irradiated animals and non-irradiated controls in motor function and sensitivity, open field test and somatosensory evoked potentials (SSEP). After irradiation with MRT peak doses of 450–800 Gy, dose-dependent neurologic signs occurred. Provided that long-term studies do not reveal significant morbidity due to late toxicity, an MRT dose of 400 Gy can be considered safe for the spinal cord in the tested beam geometry and field size.
IFITM3 functions as a PIP3 scaffold to amplify PI3K signalling in B cells
Publisher: Springer Science and Business Media LLC
Date: 04-11-2020
QA of stereotactic radiotherapy combined with electromagnetic MLC tracking by a silicon detector
Publisher: Elsevier BV
Date: 05-2017
Silicon 3d microdosimeters for advanced quality assurance in particle therapy
Publisher: MDPI AG
Date: 30-12-2022
DOI: 10.3390/APP12010328
Abstract: The Centre for Medical Radiation Physics introduced the concept of Silicon On Insulator (SOI) microdosimeters with 3-Dimensional (3D) cylindrical sensitive volumes (SVs) mimicking the dimensions of cells in an array. Several designs of high-definition 3D SVs fabricated using 3D MEMS technology were implemented. 3D SVs were fabricated in different sizes and configurations with diameters between 18 and 30 µm, thicknesses of 2–50 µm and at a pitch of 50 µm in matrices with volumes of 20 × 20 and 50 × 50. SVs were segmented into sub-arrays to reduce capacitance and avoid pile up in high-dose rate pencil beam scanning applications. Detailed TCAD simulations and charge collection studies in in idual SVs have been performed. The microdosimetry probe (MicroPlus) is composed of the silicon microdosimeter and low-noise front–end readout electronics housed in a PMMA waterproof sheath that allows measurements of lineal energies as low as 0.4 keV/µm in water or PMMA. Microdosimetric quantities measured with SOI microdosimeters and the MicroPlus probe were used to evaluate the relative biological effectiveness (RBE) of heavy ions and protons delivered by pencil-beam scanning and passive scattering systems in different particle therapy centres. The 3D detectors and MicroPlus probe developed for microdosimetry have the potential to provide confidence in the delivery of RBE optimized particle therapy when introduced into routine clinical practice.
Efficacy of 15 nm Gold Nanoparticles for Image-Guided Gliosarcoma Radiotherapy
Publisher: MDPI AG
Date: 26-10-2023
DOI: 10.3390/JNT4040021
Preclinical studies using a prototype high-resolution PET system with depth of interaction
Publisher: IEEE
Date: 10-2011
Charge Collection in SOI Microdosimeters and Their Radiation Hardness
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2023
Thin silicon strip detectors for beam monitoring in Micro-beam Radiation Therapy
Publisher: IOP Publishing
Date: 16-11-2015
High-resolution fiber-optic dosimeters for microbeam radiation therapy
Publisher: Wiley
Date: 17-04-2017
DOI: 10.1002/MP.12209
Abstract: A high resolution, water equivalent, optical and passive x-ray dosimeter has been constructed using plastic scintillator and optical fiber. This dosimeter has a peak edge-on spatial resolution of 100 μm in one dimension, with a 10 μm resolution dosimeter under investigation. The dosimeter design has a potential application in synchrotron x-ray microbeam radiation therapy where a high resolution is vital for accurate dose measurements and quality assurance. BC-400 plastic scintillator, of thickness 100 μm, was optically coupled to an optical fiber with core diameter 1 mm. The end was coated in optical paint to improve sensitivity. An identical fiber was made without the scintillator to measure the background Cherenkov radiation induced in the fiber, to allow background signal subtraction. The light captured by the fibers was measured by PMTs. The probe system was exposed to a 6 MV, 10 × 10 cm The measured profiles matched well with ionisation chamber data. Important beam parameters such as penumbra width and percent depth dose at various depths matched the ionisation chamber data, within uncertainty. This work demonstrates that high resolutions can be achieved with a scintillation and optical fiber system. The probe is water-equivalent, passive, energy independent, radiation hard and inexpensive, making it ideal for further improvements for use with microbeam radiation therapy.
Radiation monitoring in mixed environments at CERN: From the IRRAD6 facility to the LHC experiments
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 08-2007
Charge collection in n-SOI planar microdosimeters
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2013
First experimental measurement of the effect of cardio-synchronous brain motion on the dose distribution during microbeam radiation therapy
Publisher: Wiley
Date: 19-11-2020
DOI: 10.1002/MP.13899
Abstract: Microbeam radiation therapy (MRT) is an emerging radiation oncology modality ideal for treating inoperable brain tumors. MRT employs quasi-parallel beams of low-energy x rays produced from modern synchrotrons. A tungsten carbide multislit collimator (MSC) spatially fractionates the broad beam into rectangular beams. In this study, the MSC creates beams 50 μm wide ("peaks") separated by a center-to-center distance of 400 μm ("valleys"). The peak to valley dose ratio (PVDR) is of critical importance to the efficacy of MRT. The underlying radiobiological advantage of MRT relies on high peak dose for tumor control and low valley dose for healthy tissue sparing. Cardio synchronous brain motion of the order 100-200 μm is comparable to microbeam width and spacing. The motion can have a detrimental effect on the PVDR, full width at half maximum (FWHM) of the microbeams, and ultimately the dose distribution. We present the first experimental measurement of the effect of brain motion on MRT dose distribution. Dosimetry in MRT is difficult due to the high dose rate (up to 15-20 kGy/s) and small field sizes. A real-time dosimetry system based on a single silicon strip detector (SSSD) has been developed with spatial resolution ~10 μm. The SSSD was placed in a water-equivalent phantom and scanned through the microbeam distribution. A monodirectional positioning stage reproduced brain motion during the acquisition. Microbeam profiles were reconstructed from the SSSD and compared with Geant4 simulation and radiochromic HD-V2 film. The SSSD is able to reconstruct dose profiles within 2 μm compared to film. When brain motion is applied the SSSD shows a two time increase in FWHM of profiles and 50% reduction in PVDR. This is confirmed by Geant4 and film data. Motion-induced misalignment and distortion of microbeams at treatment delivery will result in a reduced PVDR and increased irradiation of additional healthy tissue compromising the radiobiological effectiveness of MRT. The SSSD was able to reconstruct dose profiles under motion conditions and predict similar effects on FWHM and PVDR as by the simulation. The SSSD is a simple to setup, real-time detector which can provide time-resolved high spatial resolution dosimetry of microbeams in MRT.
Characterization of proton pencil beam scanning and passive beam using a high spatial resolution solid-state microdosimeter
Publisher: Wiley
Date: 09-10-2017
DOI: 10.1002/MP.12563
Abstract: This work aims to characterize a proton pencil beam scanning (PBS) and passive double scattering (DS) systems as well as to measure parameters relevant to the relative biological effectiveness (RBE) of the beam using a silicon on insulator (SOI) microdosimeter with well-defined 3D sensitive volumes (SV). The dose equivalent downstream and laterally outside of a clinical PBS treatment field was assessed and compared to that of a DS beam. A novel silicon microdosimeter with well-defined 3D SVs was used in this study. It was connected to low noise electronics, allowing for detection of lineal energies as low as 0.15 keV/μm. The microdosimeter was placed at various depths in a water phantom along the central axis of the proton beam, and at the distal part of the spread-out Bragg peak (SOBP) in 0.5 mm increments. The RBE values of the pristine Bragg peak (BP) and SOBP were derived using the measured microdosimetric lineal energy spectra as inputs to the modified microdosimetric kinetic model (MKM). Geant4 simulations were performed in order to verify the calculated depth-dose distribution from the treatment planning system (TPS) and to compare the simulated dose-mean lineal energy to the experimental results. For a 131 MeV PBS spot (124.6 mm R The SOI microdosimeter with its well-defined 3D SV has applicability in characterizing proton radiation fields and can measure relevant physical parameters to model the RBE with submillimeter spatial resolution. It has been shown that for a physical dose of 1.82 Gy at the BP, the derived RBE based on the MKM model increased from 1.14 to 1.6 in the BP and its distal part. Good agreement was observed between the experimental and simulation results, confirming the potential application of SOI microdosimeter with 3D SV for quality assurance in proton therapy.
Polo-like kinase 1 inhibitor BI6727 sensitizes 9L gliosarcoma cells to ionizing irradiation
Publisher: IOP Publishing
Date: 24-10-2019
Validation of Geant4 for silicon microdosimetry in heavy ion therapy
Publisher: IOP Publishing
Date: 13-02-2020
Abstract: Microdosimetry is a particularly powerful method to estimate the relative biological effectiveness (RBE) of any mixed radiation field. This is particularly convenient for therapeutic heavy ion therapy (HIT) beams, referring to ions larger than protons, where the RBE of the beam can vary significantly along the Bragg curve. Additionally, due to the sharp dose gradients at the end of the Bragg peak (BP), or spread out BP, to make accurate measurements and estimations of the biological properties of a beam a high spatial resolution is required, less than a millimetre. This requirement makes silicon microdosimetry particularly attractive due to the thicknesses of the sensitive volumes commonly being ∼10 [Formula: see text]m or less. Monte Carlo (MC) codes are widely used to study the complex mixed HIT radiation field as well as to model the response of novel microdosimeter detectors when irradiated with HIT beams. Therefore it is essential to validate MC codes against experimental measurements. This work compares measurements performed with a silicon microdosimeter in mono-energetic [Formula: see text], [Formula: see text] and [Formula: see text] ion beams of therapeutic energies, against simulation results calculated with the Geant4 toolkit. Experimental and simulation results were compared in terms of microdosimetric spectra (dose lineal energy, [Formula: see text]), the dose mean lineal energy, y
A Monte Carlo study to evaluate and optimise the angular dependence of the Octa – A 2D silicon array detector used for dosimetry in stereotactic radiotherapy
Publisher: Elsevier BV
Date: 08-2023
Secular trends of life expectancy and disability-free life expectancy at age 65 and associated gender and area-level socioeconomic inequalities in Hong Kong: a serial cross-sectional study between 200
Publisher: Elsevier BV
Date: 12-2023
Development of TOF-spectrometry of laser-accelerated proton pulses using silicon microdosimeters
Publisher: IEEE
Date: 06-2017
Synthesis of potential theranostic system consisting of methotrexate-immobilized (3-aminopropyl)trimethoxysilane coated α-Bi 2 O3 nanoparticles for cancer treatment
Publisher: Royal Society of Chemistry (RSC)
Date: 2014
DOI: 10.1039/C4RA02160F
Radiation Shielding Evaluation of Spacecraft Walls Against Heavy Ions Using Microdosimetry
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 05-2021
Semiconductor dosimetry in modern external-beam radiation therapy
Publisher: IOP Publishing
Date: 31-08-2020
PO-1030: BrachyView: verification of a full LDR brachytherapy patient plan in a prostate gel phantom
Publisher: Elsevier BV
Date: 04-2018
BrachyView: Development of an algorithm for real-time automatic LDR brachytherapy seed detection
Publisher: IOP Publishing
Date: 25-02-0033
Plasmon satellites of resonantly tunnelling holes
Publisher: Springer US
Date: 1996
First extensive study of silver-doped lanthanum manganite nanoparticles for inducing selective chemotherapy and radio-toxicity enhancement
Publisher: Elsevier BV
Date: 04-2021
SP-0056 In vivo HDR brachytherapy source tracking with point dosimeters: current status and future directions
Publisher: Elsevier BV
Date: 05-2021
Thin Silicon Microdosimeter Utilizing 3-D MEMS Fabrication Technology: Charge Collection Study and Its Application in Mixed Radiation Fields
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2018
Tissue equivalence of diamond for heavy charged particles
Publisher: Elsevier BV
Date: 03-2019
Characterisation of a ΔE-E particle telescope using the ANSTO heavy ion microprobe
Publisher: Elsevier BV
Date: 07-2007
First in vitro evidence of modulated electro-hyperthermia treatment performance in combination with megavoltage radiation by clonogenic assay
Publisher: Springer Science and Business Media LLC
Date: 09-11-2018
DOI: 10.1038/S41598-018-34712-0
Abstract: Modulated electro-hyperthermia (mEHT) is a form of hyperthermia used in the treatment of cancer. It is a variation that relies on a particular form of enhanced selectivity to enable more effective cancerous cell death yet maintaining the integrity of healthy non-cancerous cells. It is yet to successfully make the major step into the wider medical community despite several encouraging trials. In this study, we investigate mEHT from an in vitro perspective. We demonstrate a supra-additive effect on 9 L gliosarcoma cells when exposed to mEHT in combination with MV X-ray radiation. The supra-additive effect is hypothesized to be induced by the mEHT mechanism that in turn causes apoptosis, membrane damage and an increase in rate of cell growth. This proves to be extremely advantageous in the case of the aggressive 9 L cell line as it is known to be radioresistant. However, the universal success of this multimodal treatment does not appear to be positive for all cell lines and requires further research. Due to the fundamental approach taken in this research, our results also provide a new prospect for mEHT to be a tool for sterilizing otherwise radioresistant cancers.
A novel silicon microdosimeter using 3D sensitive volumes: Modeling the response in neutron fields typical of aviation
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 08-2014
X-TREAM protocol for in vitro microbeam radiation therapy at the Australian Synchrotron
Publisher: AIP Publishing
Date: 28-06-2021
DOI: 10.1063/5.0040013
Abstract: Recommendations for an experimental protocol for beam alignment/optimization and dosimetry relating to in vitro studies at the Imaging and Medical Beam Line of the Australian Synchrotron are presented. An evaluation of the protocol, based upon the consistency and reproducibility of in vitro experiments performed over several years at the Australian Synchrotron, is provided for the community.
Characterization of a plastic dosimeter based on organic semiconductor photodiodes and scintillator
Publisher: Elsevier BV
Date: 04-2020
Abstract ID: 21 Simulation of synchrotron-based microbeam radiation therapy using Geant4
Publisher: Elsevier BV
Date: 10-2017
PH-0049: Organic semiconductors photodiodes for ionising radiation dosimetry
Publisher: Elsevier BV
Date: 11-2020
DoseMRT: A Software Package for Individualised Monte Carlo Dose Calculations of Synchrotron-Generated Microbeam Radiation Therapy
Publisher: MDPI AG
Date: 20-06-2023
Abstract: This work describes the creation and experimental validation of DoseMRT, a new software package, and its associated workflow for dose calculations in synchrotron-generated broad beam and microbeam radiation treatment fields. The DoseMRT software package allows users to import CT DICOM datasets into Geant4 for Monte Carlo dose calculations. It also provides basic treatment planning capabilities, simplifying the complexity of performing Geant4 simulations and making our Monte Carlo dose calculation algorithm accessible to a broader range of users. To demonstrate the new package, dose calculations are validated against experimental measurements performed in homogeneous water tank phantoms and the anatomically complex Alderson Radiotherapy Phantom for both broad-beam and microbeam configurations. Additionally, DoseMRT is successfully utilised as the primary method for patient-specific treatment prescription in an in vivo experiment involving tumour-bearing rats at the Imaging and Medical Beamline of the Australian Synchrotron.
Experimental investigation of the 100 keV X-ray dose response of the high-temperature thermoluminescence in LiF:Mg,Ti (TLD-100): Theoretical interpretation using the unified interaction model
Publisher: Oxford University Press (OUP)
Date: 24-11-2009
DOI: 10.1093/RPD/NCP272
Abstract: The dose response of LiF:Mg,Ti (TLD-100) chips was measured from 1 to 50,000 Gy using 100 keV X rays at the European Synchroton Radiation Facility. Glow curves were deconvoluted into component glow peaks using a computerised glow curve deconvolution (CGCD) code based on first-order kinetics. The normalised dose response, f(D), of glow peaks 4 and 5 and 5b (the major components of composite peak 5), as well as peaks 7 and 8 (two of the major components of the high-temperature thermoluminescence (HTTL) at high levels of dose) was separately determined and theoretically interpreted using the unified interaction model (UNIM). The UNIM is a nine-parameter model encompassing both the irradiation/absorption stage and the thermally induced relaxation/recombination stage with an admixture of both localised and delocalised recombination mechanisms. The effects of radiation damage are included in the present modelling via the exponential removal of luminescent centres (LCs) at high dose levels. The main features of the experimentally measured dose response are: (i) increase in f(D)(max) with glow peak temperature, (ii) increase in D(max) (the dose level at which f(D)(max) occurs) with increasing glow peak temperature, and (iii) decreased effects of radiation damage with increasing glow peak temperature. The UNIM interpretation of this behaviour requires both strongly decreasing values of ks (the relative contribution of localised recombination) as a function of glow peak temperature and, as well, significantly different values of the dose-filling constants of the trapping centre (TC) and LC for peaks 7 and 8 than those used for peaks 4 and 5. This suggests that different TC/LC configurations are responsible for HTTL. The relative intensity of peak 5a (a low-temperature satellite of peak 5 arising from localised recombination) was found to significantly increase at higher dose levels due to preferential electron and hole population of the trapping/recombination complex giving rise to composite glow peak 5. It is also demonstrated that possible changes in the trapping cross section of the LC and the competitive centres due to increasing s le/glow peak temperature do not significantly influence these observations/conclusions.
Thermoluminescence dose response of photon irradiated NaCl: Unified interaction model analysis of the dependence of the supralinearity on photon energy
Publisher: Elsevier BV
Date: 11-2017
Beam perturbation characteristics of a 2D transmission silicon diode array, Magic Plate
Publisher: Wiley
Date: 03-2016
SOI Thin Microdosimeters for High LET Single-Event Upset Studies in Fe, O, Xe, and Cocktail Ion Beam Fields
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2020
Innovative solid state microdosimeters for Radiobiological effect evaluation in particle therapy
Publisher: Elsevier BV
Date: 05-2017
X-Tream dosimetry of synchrotron radiation with the PTW microDiamond
Publisher: IOP Publishing
Date: 30-10-2019
Fast and accurate dose predictions for novel radiotherapy treatments in heterogeneous phantoms using conditional 3D-UNet generative adversarial networks
Publisher: arXiv
Date: 2022
Measurements in radiotherapy beams using on-line MOSFET detectors
Publisher: Oxford University Press (OUP)
Date: 08-2002
DOI: 10.1093/OXFORDJOURNALS.RPD.A006022
Abstract: When acquiring data to characterise radiation beams for radiotherapy treatment planning measurements in steep dose gradients such as beam penumbra or dose build-up are often required. A metal oxide semiconductor field effect transistor (MOSFET) with its inherent high spatial resolution was used for penumbra measurements in a 120 kVp X ray beam. The customised MOSFET system features a pulsed readout that allows the acquisition of data points in user defined time intervals of less than 1 s. Using a modified scanning beam data acquisition system the penumbra was acquired on-line in 0.1 mm steps. Measurements were made at different distances behind the beam collimator. From the extrapolation of the penumbra width to a location directly under the block the spatial resolution of the MOSFET system can be estimated to be better than 0.1 mm. This excellent spatial resolution has many potential applications in radiotherapy dosimetry, including the characterisation of multileaf collimator systems.
A 3D lateral electrode structure for diamond based microdosimetry
Publisher: AIP Publishing
Date: 02-01-2017
DOI: 10.1063/1.4973628
Abstract: A diamond based microdosimeter prototype featuring a 3D lateral electrode structure was created using laser ablation and active brazing alloys and characterised by means of ion beam induced charge collection measurements and finite element analysis, using Synopsys TCAD simulation package.
Real-time dose verification of dynamic MLC tracking using a monolithic 2D silicon diode array
Publisher: Elsevier BV
Date: 04-2018
From HEP to medical radiation dosimetry - The silicon strip detector dose magnifying glass
Publisher: Elsevier BV
Date: 12-2011
High spatial resolution microdosimetry with monolithic ΔE-E detector on 12C beam: Monte Carlo simulations and experiment
Publisher: Elsevier BV
Date: 04-2018
Fast Beam Profile Monitors for Microbeam Radiation Therapy
Publisher: Elsevier BV
Date: 02-2016
Edge-on Face-to-Face MOSFET for synchrotron microbeam dosimetry: MC modeling
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2005
Miniature semiconductor detectors for in vivo dosimetry
Publisher: Oxford University Press (OUP)
Date: 27-04-2006
DOI: 10.1093/RPD/NCI645
Abstract: Silicon mini-semiconductor detectors are found in wide applications for in vivo personal dosimetry and dosimetry and microdosimetry of different radiation oncology modalities. These applications are based on integral and spectroscopy modes of metal oxide semiconductor field effect transistor and silicon p-n junction detectors. The advantages and limitations of each are discussed.
A real-time in vivo dosimetric verification method for high-dose rate intracavitary brachytherapy of nasopharyngeal carcinoma
Publisher: Wiley
Date: 19-11-4201
DOI: 10.1118/1.4758067
Abstract: A real-time in vivo dosimetric verification method using metal-oxide-semiconductor field effect transistor (MOSFET) dosimeters has been developed for patient dosimetry in high-dose rate (HDR) intracavitary brachytherapy of nasopharyngeal carcinoma (NPC). The necessary calibration and correction factors for MOSFET measurements in (192)Iridium source were determined in a water phantom. With the detector placed inside a custom-made nasopharyngeal applicator, the actual dose delivered to the tumor was measured in vivo and compared to the calculated values using a commercial brachytherapy planning system. Five MOSFETs were independently calibrated with the HDR source, yielding calibration factors of 0.48 ± 0.007 cGy∕mV. The maximum sensitivity variation was no more than 7% in the clinically relevant distance range of 1-5 cm from the source. A total of 70 in vivo measurements in 11 NPC patients demonstrated good agreement with the treatment planning. The mean differences between the planned and the actually delivered dose within a single treatment fraction were -0.1% ± 3.8% and -0.1% ± 3.7%, respectively, for right and left side assessments. The maximum dose deviation was less than 8.5%. In vivo measurement using the real-time MOSFET dosimetry system is possible to evaluate the actual dose to the tumor received by the patient during a treatment fraction and thus can offer another line of security to detect and prevent large errors.
Feasibility study of online high-spatial-resolution MOSFET dosimetry in static and pulsed X-ray radiation fields
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2001
DOI: 10.1109/23.983173
BrachyView: Initial preclinical results for a real-time in-body HDR PBT source tracking system with simultaneous TRUS image fusion
Publisher: IOP Publishing
Date: 05-04-2019
Abstract: A prototype in-body gamma camera system with integrated trans-rectal ultrasound (TRUS) and associated real-time image acquisition and analysis software was developed for intraoperative source tracking in high dose rate (HDR) brachytherapy. The accuracy and temporal resolution of the system was validated experimentally using a deformable tissue-equivalent prostate gel phantom and a full clinical HDR treatment plan. The BrachyView system was able to measure 78% of the 200 source positions with an accuracy of better than 1 mm. A minimum acquisition time of 0.28 s/frame was required to achieve this accuracy, restricting dwell times to a minimum of 0.3 s. Additionally, the performance of the BrachyView-TRUS fusion probe for mapping the spatial location of the tracked source within the prostate volume was evaluated. A global coordinate system was defined by scanning the phantom with the probe in situ using a CT scanner, and was subsequently used for co-registration of the BrachyView and TRUS fields of view (FoVs). TRUS imaging was used to segment the prostate volume and reconstruct it into a three-dimensional (3D) image. Fusion of the estimated source locations with the 3D prostate image was performed using integrated 3D visualisation software. HDR BrachyView is demonstrated to be a valuable tool for intraoperative source tracking in HDR brachytherapy, capable of resolving source dwell locations relative to the prostate anatomy when combined with TRUS.
3D sensitive volume microdosimeter with improved tissue equivalency: Charge collection study and its application in 12C ion therapy
Publisher: IOP Publishing
Date: 2019
Summary Report Panel 1: The Need for Protocols and Standards in Research on Underwater Noise Impacts on Marine Life
Publisher: Springer New York
Date: 2016
DOI: 10.1007/978-1-4939-2981-8_159
Abstract: As concern about anthropogenic noise and its impacts on marine fauna is increasing around the globe, data are being compared across populations, species, noise sources, geographic regions, and time. However, much of the raw and processed data are not comparable due to differences in measurement methodology, analysis and reporting, and a lack of metadata. Common protocols and more formal, international standards are needed to ensure the effectiveness of research, conservation, regulation and practice, and unambiguous communication of information and ideas. Developing standards takes time and effort, is largely driven by a few expert volunteers, and would benefit from stakeholders' contribution and support.
SiPM based detector module and digital data acquisition system for PET: Initial results
Publisher: IEEE
Date: 10-2009
Online in vivo dosimetry in high dose rate prostate brchytherapy with MOSkin detectors: In phantom feasibility study
Publisher: Elsevier BV
Date: 2014
DOI: 10.1016/J.APRADISO.2013.06.001
Abstract: MOSkin detectors were studied to perform real-time in vivo dose measurements in high dose rate prostate brachytherapy. Measurements were performed inside an urethral catheter in a gel phantom simulating a real prostate implant. Measured and expected doses were compared and the discrepancy was found to be within 8.9% and 3.8% for single MOSkin and dual-MOSkin configurations, respectively. Results show that dual-MOSkin detectors can be profitably adopted in prostate brachytherapy treatments to perform real-time in vivo dosimetry inside the urethra.
Development of a silicon diode detector for skin dosimetry in radiotherapy
Publisher: Wiley
Date: 12-08-2017
DOI: 10.1002/MP.12469
Abstract: The aim of in vivo skin dosimetry was to measure the absorbed dose to the skin during radiotherapy, when treatment planning calculations cannot be relied on. It is of particularly importance in hypo-fractionated stereotactic modalities, where excessive dose can lead to severe skin toxicity. Currently, commercial diodes for such applications are with water equivalent depths ranging from 0.5 to 0.8 mm. In this study, we investigate a new detector for skin dosimetry based on a silicon epitaxial diode, referred to as the skin diode. The skin diode is manufactured on a thin epitaxial layer and packaged using the "drop-in" technology. It was characterized in terms of percentage depth dose, dose linearity, and dose rate dependence, and benchmarked against the Attix ionization chamber. The response of the skin diode in the build-up region of the percentage depth dose (PDD) curve of a 6 MV clinical photon beam was investigated. Geant4 radiation transport simulations were used to model the PDD in order to estimate the water equivalent measurement depth (WED) of the skin diode. Measured output factors using the skin diode were compared with the MOSkin detector and EBT3 film at 10 cm depth and at surface at isocenter of a water equivalent phantom. The intrinsic angular response of the skin diode was also quantified in charge particle equilibrium conditions (CPE) and at the surface of a solid water phantom. Finally, the radiation hardness of the skin diode up to an accumulated dose of 80 kGy using photons from a Co-60 gamma source was evaluated. The PDD curve measured with the skin diode was within 0.5% agreement of the equivalent Geant4 simulated curve. When placed at the phantom surface, the WED of the skin diode was estimated to be 0.075 ± 0.005 mm from Geant4 simulations and was confirmed using the response of a corrected Attix ionization chamber placed at water equivalent depth of 0.075 mm, with the measurement agreement to within 0.3%. The output factor measurements at 10 cm depth were within 2% of those measured with film and the MOSkin detector down to a field size of 2 × 2 cm This work characterizes an innovative detector for in vivo and real-time skin dose measurements that is based on an epitaxial silicon diode combined with the Centre for Medical Radiation Physics (CMRP) "drop-in" packaging technology. The skin diode proved to have a water equivalent depth of measurement of 0.075 ± 0.005 mm and the ability to measure doses accurately relative to reference detectors.
Clinical application of MOSkin dosimeters to rectal wall in vivo dosimetry in gynecological HDR brachytherapy
Publisher: Elsevier BV
Date: 09-2017
DOI: 10.1016/J.EJMP.2017.05.003
Abstract: Three MOSkins dosimeters were assembled over a rectal probe and used to perform in vivo dosimetry during HDR brachytherapy treatments of vaginal cancer. The purpose of this study was to verify the applicability of the developed tool to evaluate discrepancies between planned and measured doses to the rectal wall. MOSkin dosimeters from the Centre for Medical Radiation Physics are particularly suitable for brachytherapy procedures for their ability to be easily incorporated into treatment instrumentation. In this study, 26 treatment sessions of HDR vaginal brachytherapy were monitored using three MOSkin mounted on a rectal probe. A total of 78 measurements were collected and compared to doses determined by the treatment planning system. Mean dose discrepancy was determined as 2.2±6.9%, with 44.6% of the measurements within ±5%, 89.2% within ±10% and 10.8% higher than ±10%. When dose discrepancies were grouped according to the time elapsed between imaging and treatment (i.e., group 1: ≤90min group 2: >90min), mean discrepancies resulted in 4.7±3.6% and 7.1±5.0% for groups 1 and 2, respectively. Furthermore, the position of the dosimeter on the rectal catheter was found to affect uncertainty, where highest uncertainties were observed for the dosimeter furthest inside the rectum. This study has verified MOSkin applicability to in-patient dose monitoring in gynecological brachytherapy procedures, demonstrating the dosimetric rectal probe setup as an accurate and convenient IVD instrument for rectal wall dose verification. Furthermore, the study demonstrates that the delivered dose discrepancy may be affected by the duration of treatment planning.
Local dose enhancement of proton therapy by ceramic oxide nanoparticles investigated with Geant4 simulations
Publisher: Elsevier BV
Date: 12-2016
DOI: 10.1016/J.EJMP.2016.11.112
Abstract: Nanoparticles (NPs) have been shown to enhance X-ray radiotherapy and proton therapy of cancer. The effectiveness of radiation damage is enhanced in the presence of high atomic number (high-Z) NPs due to increased production of low energy, higher linear energy transfer (LET) secondary electrons when NPs are selectively internalized by tumour cells. This work quantifies the local dose enhancement produced by the high-Z ceramic oxide NPs Ta
MOSFET dosimetry for microbeam radiation therapy at the European Synchrotron Radiation Facility
Publisher: Wiley
Date: 25-03-2003
DOI: 10.1118/1.1562169
Abstract: Preclinical experiments are carried out with approximately 20-30 microm wide, approximately 10 mm high parallel microbeams of hard, broad-"white"-spectrum x rays (approximately 50-600 keV) to investigate microbeam radiation therapy (MRT) of brain tumors in infants for whom other kinds of radiotherapy are inadequate and/or unsafe. Novel physical microdosimetry (implemented with MOSFET chips in the "edge-on" mode) and Monte Carlo computer-simulated dosimetry are described here for selected points in the peak and valley regions of a microbeam-irradiated tissue-equivalent phantom. Such microbeam irradiation causes minimal damage to normal tissues, possible because of rapid repair of their microscopic lesions. Radiation damage from an array of parallel microbeams tends to correlate with the range of peak-valley dose ratios (PVDR). This paper summarizes comparisons of our dosimetric MOSFET measurements with Monte Carlo calculations. Peak doses at depths 22 mm and valley doses at all depths investigated (2 mm-62 mm) are within 2-13% of the Monte Carlo values. These results lend credence to the use of MOSFET detector systems in edge-on mode for microplanar irradiation dosimetry.
Tunneling spectroscopy of hole plasmons in a valence-band quantum well
Publisher: American Physical Society (APS)
Date: 15-10-1996
Highly porous hematite nanorods prepared via direct spray precipitation method
Publisher: Elsevier BV
Date: 02-2014
Radiation response and basic dosimetric characterisation of the 'Magic Plate'
Publisher: IOP Publishing
Date: 02-2017
The CBM-opathies—A Rapidly Expanding Spectrum of Human Inborn Errors of Immunity Caused by Mutations in the CARD11-BCL10-MALT1 Complex
Publisher: Frontiers Media SA
Date: 19-09-2018
Effect of scattered electrons on the 'Magic Plate' transmission array detector response
Publisher: IOP Publishing
Date: 02-2017
Evaluation of silicon strip detectors in transmission mode for online beam monitoring in microbeam radiation therapy at the Australian Synchrotron
Publisher: International Union of Crystallography (IUCr)
Date: 2022
DOI: 10.1107/S1600577521011140
Abstract: Successful transition of synchrotron-based microbeam radiation therapy (MRT) from pre-clinical animal studies to human trials is dependent upon ensuring that there are sufficient and adequate measures in place for quality assurance purposes. Transmission detectors provide researchers and clinicians with a real-time quality assurance and beam-monitoring instrument to ensure safe and accurate dose delivery. In this work, the effect of transmission detectors of different thicknesses (10 and 375 µm) upon the photon energy spectra and dose deposition of spatially fractionated synchrotron radiation is quantified experimentally and by means of a dedicated Geant4 simulation study. The simulation and experimental results confirm that the presence of the 375 µm thick transmission detector results in an approximately 1–6% decrease in broad-beam and microbeam peak dose. The capability to account for the reduction in dose and change to the peak-to-valley dose ratio justifies the use of transmission detectors as thick as 375 µm in MRT provided that treatment planning systems are able to account for their presence. The simulation and experimental results confirm that the presence of the 10 µm thick transmission detector shows a negligible impact ( .5%) on the photon energy spectra, dose delivery and microbeam structure for both broad-beam and microbeam cases. Whilst the use of 375 µm thick detectors would certainly be appropriate, based upon the idea of best practice the authors recommend that 10 µm thick transmission detectors of this sort be utilized as a real-time quality assurance and beam-monitoring tool during MRT.
Microdosimetric measurements of a clinical proton beam with micrometer-sized solid-state detector
Publisher: Wiley
Date: 13-10-2017
DOI: 10.1002/MP.12583
Abstract: Microdosimetry is a vital tool for assessing the microscopic patterns of energy deposition by radiation, which ultimately govern biological effect. Solid-state, silicon-on-insulator microdosimeters offer an approach for making microdosimetric measurements with high spatial resolution (on the order of tens of micrometers). These high-resolution, solid-state microdosimeters may therefore play a useful role in characterizing proton radiotherapy fields, particularly for making highly resolved measurements within the Bragg peak region. In this work, we obtain microdosimetric measurements with a solid-state microdosimeter (MicroPlus probe) in a clinical, spot-scanning proton beam of small spot size. The MicroPlus probe had a 3D single sensitive volume on top of silicon oxide. The sensitive volume had an active cross-sectional area of 250 μm × 10 μm and thickness of 10 μm. The proton facility was a synchrotron-based, spot-scanning system with small spot size (σ ≈ 2 mm). We performed measurements with the clinical beam current (≈1 nA) and had no detected pulse pile-up. Measurements were made in a water-equivalent phantom in water-equivalent depth (WED) increments of 0.25 mm or 1.0 mm along pristine Bragg peaks of energies 71.3 MeV and 159.9 MeV, respectively. For each depth, we measured lineal energy distributions and then calculated the dose-weighted mean lineal energy, y¯D. The measurements were repeated for two field sizes: 4 × 4 cm For both 71.3 MeV and 159.9 MeV and for both field sizes, y¯D increased with depth toward the distal edge of the Bragg peak, a result consistent with Monte Carlo calculations and measurements performed elsewhere. For the 71.3 MeV, 4 × 4 cm We performed microdosimetric measurements with a novel solid-state, silicon-on-insulator microdosimeter in a clinical spot-scanning proton beam of small spot size and unmodified beam current. For all of the proton field sizes and energies considered, the measurements of y¯D were in agreement with expected trends. Furthermore, we obtained measurements with a spatial resolution of 10 μm in the beam direction. This spatial resolution greatly exceeded that possible with a conventional gaseous tissue-equivalent proportional counter and allowed us to perform a high-resolution investigation within the Bragg peak region. The MicroPlus probe is therefore suitable for applications in proton radiotherapy.
A new virtual ring-based system matrix generator for iterative image reconstruction in high resolution small volume PET systems
Publisher: IOP Publishing
Date: 10-01-2022
DOI: 10.1088/0031-9155/60/17/6949
Abstract: A common approach to improving the spatial resolution of small animal PET scanners is to reduce the size of scintillation crystals and/or employ high resolution pixellated semiconductor detectors. The large number of detector elements results in the system matrix--an essential part of statistical iterative reconstruction algorithms--becoming impractically large. In this paper, we propose a methodology for system matrix modelling which utilises a virtual single-layer detector ring to greatly reduce the size of the system matrix without sacrificing precision. Two methods for populating the system matrix are compared the first utilises a geometrically-derived system matrix based on Siddon's ray tracer method with the addition of an accurate detector response function, while the second uses Monte Carlo simulation to populate the system matrix. The effectiveness of both variations of the proposed technique is demonstrated via simulations of PETiPIX, an ultra high spatial resolution small animal PET scanner featuring high-resolution DoI capabilities, which has previously been simulated and characterised using classical image reconstruction methods. Compression factors of 5 x 10(7) and 2.5 x 10(7)are achieved using this methodology for the system matrices produced using the geometric and Monte Carlo-based approaches, respectively, requiring a total of 0.5-1.2 GB of memory-resident storage. Images reconstructed from Monte Carlo simulations of various point source and phantom models, produced using system matrices generated via both geometric and simulation methods, are used to evaluate the quality of the resulting system matrix in terms of achievable spatial resolution and the CRC, CoV and CW-SSIM index image quality metrics. The Monte Carlo-based system matrix is shown to provide the best image quality at the cost of substantial one-off computational effort and a lower (but still practical) compression factor. Finally, a straightforward extension of the virtual ring method to a three dimensional virtual cylinder is demonstrated using a 3D DoI PET scanner.
Characterization of 3-D-Mesa Silicon Single Strip Detectors for Use in Synchrotron Microbeam Radiation Therapy
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 07-2020
In vivo verification of superficial dose for head and neck treatments using intensity-modulated techniques
Publisher: Wiley
Date: 05-12-2009
DOI: 10.1118/1.3030951
Abstract: Skin dose is one of the key issues for clinical dosimetry in radiation therapy. Currently planning computer systems are unable to accurately predict dose in the buildup region, leaving ambiguity as to the dose levels actually received by the patient's skin during radiotherapy. This is one of the prime reasons why in vivo measurements are necessary to estimate the dose in the buildup region. A newly developed metal-oxide-semiconductor-field-effect-transistor (MOSFET) detector designed specifically for dose measurements in rapidly changing dose gradients was introduced for accurate in vivo skin dosimetry. The feasibility of this detector for skin dose measurements was verified in comparison with plane parallel ionization chamber and radiochromic films. The accuracy of a commercial treatment planning system (TPS) in skin dose calculations for intensity-modulated radiation therapy treatment of nasopharyngeal carcinoma was evaluated using MOSFET detectors in an anthropomorphic phantom as well as on the patients. Results show that this newly developed MOSFET detector can provide a minimal but highly reproducible intrinsic buildup of 7 mg cm(-2) corresponding to the requirements of personal surface dose equivalent Hp (0.07). The reproducibility of the MOSFET response, in high sensitivity mode, is found to be better than 2% at the phantom surface for the doses normally delivered to the patients. The MOSFET detector agrees well with the Attix chamber and the EBT Gafchromic film in terms of surface and buildup region dose measurements, even for oblique incident beams. While the dose difference between MOSFET measurements and TPS calculations is within measurement uncertainty for the depths equal to or greater than 0.5 cm, an overestimation of up to 8.5% was found for the surface dose calculations in the anthropomorphic phantom study. In vivo skin dose measurements reveal that the dose difference between the MOSFET results and the TPS calculations was on average -7.2%, ranging from -4.3% to -9.2%. The newly designed MOSFET detector encapsulated into a thin water protective film has a minimal reproducible intrinsic buildup recommended for skin dosimetry. This feature makes it very suitable for routine IMRT QA and accurate in vivo skin dosimetry.
Study of the correlation between rectal wall in vivo dosimetry performed with MOSkins and implant modification during TRUS-guided HDR prostate brachytherapy
Publisher: Elsevier BV
Date: 11-2017
PO-1606: Measurement of dose distribution of cardiosynchronous brain motion in microbeam radiation therapy
Publisher: Elsevier BV
Date: 11-2020
Performance uniformity evaluation of two SensL's SiPM modules
Publisher: IEEE
Date: 10-2013
Characterization of an alternative diamond based microdosimeter prototype
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2014
Feasibility study of a novel multi-strip silicon detector for use in proton therapy range verification quality assurance
Publisher: Elsevier BV
Date: 11-2017
Optimizing dose enhancement with Ta2 O5 nanoparticles for synchrotron microbeam activated radiation therapy
Publisher: Elsevier BV
Date: 12-2016
DOI: 10.1016/J.EJMP.2016.10.024
Abstract: Microbeam Radiation Therapy (MRT) exploits tumour selectivity and normal tissue sparing with spatially fractionated kilovoltage X-ray microbeams through the dose volume effect. Experimental measurements with Ta
Synthesis-Dependent Surface Defects and Morphology of Hematite Nanoparticles and Their Effect on Cytotoxicity in Vitro
Publisher: American Chemical Society (ACS)
Date: 24-02-2016
Abstract: In this study, we investigate the toxicity of hematite (α-Fe2O3) nanoparticles on the Madin-Darby Canine Kidney (MDCK) cell line. The oxide particles have been synthesized through two different methods and annealing conditions. These two methods, spray precipitation and precipitation, resulted in particles with rod-like and spherical morphology and feature different particle sizes, surface features, and magnetic properties. Through flow cytometry it was found that particle morphology heavily influences the degree to which the nanomaterials are internalized into the cells. It was also found that the ability of the nanoparticles to generate free radicals species is hindered by the formation of tetrahedrally coordinated maghemite-like (γ-Fe2O3) spinel defects on the surfaces of the particles. The combination of these two factors resulted in variable cytotoxic effects of the hematite nanoparticles synthesized with different conditions. This article highlights the importance on the fabrication method, materials properties, and surface characteristics on the cytotoxicity of hematite nanomaterials.
Accurate and Fast Deep Learning Dose Prediction for a Preclinical Microbeam Radiation Therapy Study Using Low-Statistics Monte Carlo Simulations
Publisher: MDPI AG
Date: 04-04-2023
Abstract: Microbeam radiation therapy (MRT) utilizes coplanar synchrotron radiation beamlets and is a proposed treatment approach for several tumor diagnoses that currently have poor clinical treatment outcomes, such as gliosarcomas. Monte Carlo (MC) simulations are one of the most used methods at the Imaging and Medical Beamline, Australian Synchrotron to calculate the dose in MRT preclinical studies. The steep dose gradients associated with the 50μm-wide coplanar beamlets present a significant challenge for precise MC simulation of the dose deposition of an MRT irradiation treatment field in a short time frame. The long computation times inhibit the ability to perform dose optimization in treatment planning or apply online image-adaptive radiotherapy techniques to MRT. Much research has been conducted on fast dose estimation methods for clinically available treatments. However, such methods, including GPU Monte Carlo implementations and machine learning (ML) models, are unavailable for novel and emerging cancer radiotherapy options such as MRT. In this work, the successful application of a fast and accurate ML dose prediction model for a preclinical MRT rodent study is presented for the first time. The ML model predicts the peak doses in the path of the microbeams and the valley doses between them, delivered to the tumor target in rat patients. A CT imaging dataset is used to generate digital phantoms for each patient. Augmented variations of the digital phantoms are used to simulate with Geant4 the energy depositions of an MRT beam inside the phantoms with 15% (high-noise) and 2% (low-noise) statistical uncertainty. The high-noise MC simulation data are used to train the ML model to predict the energy depositions in the digital phantoms. The low-noise MC simulations data are used to test the predictive power of the ML model. The predictions of the ML model show an agreement within 3% with low-noise MC simulations for at least 77.6% of all predicted voxels (at least 95.9% of voxels containing tumor) in the case of the valley dose prediction and for at least 93.9% of all predicted voxels (100.0% of voxels containing tumor) in the case of the peak dose prediction. The successful use of high-noise MC simulations for the training, which are much faster to produce, accelerates the production of the training data of the ML model and encourages transfer of the ML model to different treatment modalities for other future applications in novel radiation cancer therapies.
Angular independent silicon detector for dosimetry in external beam radiotherapy
Publisher: Wiley
Date: 17-07-2015
DOI: 10.1118/1.4926778
Abstract: In this work, the "edgeless" silicon detector technology is investigated, in combination with an innovative packaging solution, to manufacture silicon detectors with negligible angular response. The new diode is also characterized as a dosimeter for radiotherapy with the aim to verify its suitability as a single detector for in vivo dosimetry as well as large area 2D array that does not require angular correction to their response. For the characterisation of the "edgeless-drop-in" detector technology, a set of s les have been manufactured with different sensitive areas (1 × 1 and 0.5 × 0.5 mm(2)) and different thicknesses (0.1 and 0.5 mm) in four different combinations of top and peripheral p-n junction fabricated on p-type and n-type silicon substrates. The diode probes were tested in terms of percentage depth dose (PDD), dose rate, and linearity and compared to ion chambers. Measurements of the output factor have been compared to film. The angular response of the diodes probes has been tested in a cylindrical PMMA phantom, rotated with bidirectional accuracy of 0.25° under 10 × 10 cm(2) 6 MV Linac photon beam. The radiation hardness has been investigated as well as the effect of radiation damage on the angular and dose rate response of the diode probes when irradiated with photons from a Co-60 gamma source up to dose of 40 kGy. The PDDs measured by the edgeless detectors show an agreement with the data obtained using ion chambers within ±2%. The output factor measured with the smallest area edgeless diodes (0.5 × 0.5 mm(2)-0.1 and 0.5 mm thick) matches EBT3 film to within 2% for square field size from 10 to 0.5 cm side equivalent distance. The dose rate dependence in a dose per pulse range of 0.9 × 10(-5)-2.7 × 10(-4) Gy ulse was less than -7% and +300% for diodes fabricated on p-type and n-type substrates, respectively. The edgeless diodes fabricated on the p-type substrate demonstrated degradation of the response as a function of the irradiation dose within 5%-15%, while diodes on the n-type substrate show a variation of approximately 30% after 40 kGy. The angular response of all probes is minimal (within 2%) but the N on N and P on P configurations show the best performances with an angular dependence of ±1.0% between 0° and 180° in the transversal direction. In this configuration, the space charge region of the passive diode extends from the behind and sidewall toward the anode on the top providing beneficial electric field distribution in the peripheral area of the diode. Such performance has also been tested after irradiation by Co-60 up to 40 kGy with no measurable change in angular response. A new edgeless-drop-in silicon diode fabrication and packaging technology has been used to develop detectors that show no significant angular dependence in their response for dosimetry in radiation therapy. From the characterisation of the diodes, proposed in a wide range of different geometries and configurations, the authors recommend the P-on-P detectors in conjunction with "drop in" packaging technology as the candidate for further development as single diode probe or 2D diode array for dosimetry in radiotherapy.
Characterisation of Silicon Diode Arrays for Dosimetry in External Beam Radiation Therapy
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 06-2016
Fibre optic dosimetry in synchrotron microbeam radiation therapy
Publisher: IOP Publishing
Date: 2019
BrachyView: Tomographic reconstruction using Timepix detectors in post-implant dosimetry checks for permanent prostate brachytherapy implants
Publisher: IEEE
Date: 09-2025
The dynamic behaviour of sunscreens under in-service conditions.
Publisher: Elsevier BV
Date: 05-2022
DOI: 10.1016/J.JPHOTOBIOL.2022.112435
Abstract: Discussion continues over various aspects of sunscreen science: regulation, test methods, sun protection factor (SPF), labelling claims, potentially harmful components, among others. In this paper the UV transmission properties of a number of commercial sunscreens have been determined at constant sunscreen film thickness under different local UV Index conditions. The data demonstrate difficulties facing the public and the sunscreen industry as a whole, even though SPF values and other data stated on the sunscreen packaging are assumed to be correct according to standard testing methods. This work has shown that at realistic application rates the critical factors are the intensity of the incident solar radiation and the accumulated erythema UV dose transmitted over time. In one ex le, on 'Extreme' UV Index days, an SPF 30 sunscreen under test transmitted one minimal erythema dose (MED) of UV in only 35 min. In another ex le, although it should not, in theory, transmit one MED until several hours of exposure, this level was reached in 1 h by an SPF 50 sunscreen under these typical Australian summer conditions (UV Index 12) in Wollongong, NSW (34.4°S). Such properties could have severe consequnces if these sunscreens were used by in iduals with Fitzpatrick Skin Type 1, organ transplant recipients or other immuno-compromised in iduals.
Evaluation of silicon detectors with integrated JFET for biomedical applications
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 06-2009
BrachyView: Verification of LDR patient plans - Hardware optimisation
Publisher: IOP Publishing
Date: 2019
Progress with MRI-linac image-guided radiation dose imaging
Publisher: Elsevier BV
Date: 02-2016
High spatial resolution scintillator dosimetry of synchrotron microbeams
Publisher: Springer Science and Business Media LLC
Date: 03-05-2019
DOI: 10.1038/S41598-019-43349-6
Abstract: Microbeam radiation therapy is a novel pre-clinical external beam therapy that uses high-brilliance synchrotron X-rays to deliver the necessary high dose rates. The unique conditions of high dose rate and high spatial fractionation demand a new class of detector to experimentally measure important beam quality parameters. Here we demonstrate the highest spatial resolution plastic scintillator fibre-optic dosimeter found in the literature to date and tested it on the Imaging and Medical Beam-Line at the Australian Synchrotron in a X-ray beam where the irradiation dose rate was 4435 Gy/s. With a one-dimensional spatial resolution of 10 μ m the detector is able to resolve the in idual microbeams (53.7 ± 0.4 μ m wide), and measure the peak-to-valley dose ratio to be 55 ± 17. We also investigate the role of radioluminescence in the optical fibre used to transport the scintillation photons, and conclude that it creates a significant contribution to the total light detected.
Evolution of Diamond based Microdosimetry
Publisher: IOP Publishing
Date: 2019
Study of the effect of ceramic Ta2 O5 nanoparticle distribution on cellular dose enhancement in a kilovoltage photon field
Publisher: Elsevier BV
Date: 10-2016
DOI: 10.1016/J.EJMP.2016.09.006
Abstract: The application of nanoparticles (NPs) in radiotherapy is an increasingly attractive technique to improve clinical outcomes. The internalisation of NPs within the tumour cells enables an increased radiation dose to critical cellular structures. The purpose of this study is to investigate, by means of Geant4 simulations, the dose enhancement within a cell population irradiated with a 150kVp photon field in the presence of a varying concentration of tantalum pentoxide (Ta
Multi-strip silicon sensors for beam array monitoring in micro-beam radiation therapy
Publisher: Elsevier BV
Date: 12-2016
DOI: 10.1016/J.EJMP.2016.11.005
Abstract: We present here the latest results from tests performed at the ESRF ID17 and ID21 beamlines for the characterization of novel beam monitors for Microbeam Radiation Therapy (MRT), which is currently being implemented at ID17. MRT aims at treating solid tumors by exploiting an array of evenly spaced microbeams, having an energy spectrum distributed between 27 and 600keV and peaking at 100keV. Given the high instantaneous dose delivered (up to 20kGy/s), the position and the intensity of the microbeams has to be precisely and instantly monitored. For this purpose, we developed dedicated silicon microstrip beam monitors. We have successfully characterized them, both with a microbeam array at ID17, and a submicron scanning beam at ID21. We present here the latest results obtained in recent tests along with an outlook on future developments.
A two dimensional silicon detectors array for quality assurance in stereotactic radiotherapy: MagicPlate-512
Publisher: Wiley
Date: 30-08-2020
DOI: 10.1118/1.4892384
Abstract: Silicon diode arrays are commonly implemented in radiation therapy quality assurance applications as they have a number of advantages including: real time operation (compared to the film) and high spatial resolution, large dynamic range and small size (compared to ionizing chambers). Most diode arrays have detector pitch that is too coarse for routine use in small field applications. The goal of this work is to characterize the two-dimensional monolithic silicon diode array named "MagicPlate-512" (MP512) designed for QA in stereotactic body radiation therapy (SBRT) and stereotactic radio surgery (SRS). MP512 is a silicon monolithic detector manufactured on ap-type substrate. An array contains of 512 pixels with size 0.5×0.5 mm2 and pitch 2 mm with an overall dimension of 52×52 mm2. The MP512 monolithic detector is wire bonded on a printed circuit board 0.5 mm thick and covered by a thin layer of raisin to preserve the silicon detector from moisture and chemical contamination and to protect the bonding wires. Characterization of the silicon monolithic diode array response was performed, and included pixels response uniformity, dose linearity, percent depth dose, output factor, and beam profiling for beam sizes relevant to SBRT and SRS and depth dose response in comparison with ionization chamber. MP512 shows a good dose linearity (R2=0.998) and repeatability within 0.2%. The measured depth dose response for field size of 10×10 cm2 agreed to within 1.3%, when compared to a CC13 ionization chamber for depths in PMMA up to 30 cm. The output factor of a 6 MV Varian 2100EX medical linac beam measured by MP512 at the isocenter agrees to within 2% when compared to PTW diamond, Scanditronix point EDD-2 diode and MOSkin detectors for field sizes down to 1×1 cm2. An over response of 4% was observed for square beam size smaller than 1 cm when compared to EBT3 films, while the beam profiles (FWHM) of MP512 match to within 2% the data measured by radiochromic film. The response of the 2D detector array, MP512, has been evaluated. The properties of the array demonstrated suitability for use as in phantom dosimeter for QA in SRS and SBRT. Although MP512 matches film measurements down to 1×1 cm2 well, it showed a discrepancy of 4% in the determination of output factors of beams smaller than 0.5×0.5 cm2 due to the field perturbation generated by the large amount of silicon surrounding the central diode. MP512 is highly capable of measuring beam size (FWHM) and has a discrepancy of less than 1.3% when compared to EBT3 film. A reduction in the detector pitch to less than 2 mm would improve the penumbra reconstruction accuracy at the cost readout electronics complexity.
Simulation and testing of thin microstrip silicon dosimeters for the microbeam radiation therapy
Publisher: IEEE
Date: 11-2016
Synthesis of methotrexate-loaded tantalum pentoxide–poly(acrylic acid) nanoparticles for controlled drug release applications
Publisher: Elsevier BV
Date: 03-2019
DOI: 10.1016/J.JCIS.2018.11.097
Abstract: Over the past decade, there has been increasing interest in the use of multifunctional nanoparticles (NPs) for cancer treatment. Of importance are systems that can deliver drugs at a sustained rate to target cancer cells, which can result in higher efficiency and reduced systemic toxicity. In this study, we present the route for the synthesis of tantalum pentoxide (Ta
Modulating Synchrotron Microbeam Radiation Therapy Doses for Preclinical Brain Cancer
Publisher: MDPI AG
Date: 14-10-2023
Toward personalized synchrotron microbeam radiation therapy
Publisher: Springer Science and Business Media LLC
Date: 06-2020
DOI: 10.1038/S41598-020-65729-Z
Abstract: Synchrotron facilities produce ultra-high dose rate X-rays that can be used for selective cancer treatment when combined with micron-sized beams. Synchrotron microbeam radiation therapy (MRT) has been shown to inhibit cancer growth in small animals, whilst preserving healthy tissue function. However, the underlying mechanisms that produce successful MRT outcomes are not well understood, either in vitro or in vivo . This study provides new insights into the relationships between dosimetry, radiation transport simulations, in vitro cell response, and pre-clinical brain cancer survival using intracerebral gliosarcoma (9LGS) bearing rats. As part of this ground-breaking research, a new image-guided MRT technique was implemented for accurate tumor targeting combined with a pioneering assessment of tumor dose-coverage an essential parameter for clinical radiotherapy. Based on the results of our study, we can now (for the first time) present clear and reproducible relationships between the in vitro cell response, tumor dose-volume coverage and survival post MRT irradiation of an aggressive and radioresistant brain cancer in a rodent model. Our innovative and interdisciplinary approach is illustrated by the results of the first long-term MRT pre-clinical trial in Australia. Implementing personalized synchrotron MRT for brain cancer treatment will advance this international research effort towards clinical trials.
A dual detector system for in-vivo dosimetry: transit dose verification and error identification
Publisher: Elsevier BV
Date: 04-2019
Medipix detectors in radiation therapy for advanced quality-assurance
Publisher: Elsevier BV
Date: 2020
First proof of bismuth oxide nanoparticles as efficient radiosensitisers on highly radioresistant cancer cells
Publisher: Elsevier BV
Date: 11-2016
DOI: 10.1016/J.EJMP.2016.10.015
Abstract: This study provides the first proof of the novel application of bismuth oxide as a radiosensitiser. It was shown that on the highly radioresistant 9L gliosarcoma cell line, bismuth oxide nanoparticles sensitise to both kilovoltage (kVp) or megavoltage (MV) X-rays radiation. 9L cells were exposed to a concentration of 50μg.mL
Y2O3 nanoparticles with 2D morphology as reactive oxygen species scavengers under ultraviolet radiation conditions
Publisher: Elsevier BV
Date: 09-2023
Post IVD verification and recalibration of MOSkins using a certified low dose emitting Sr-90 source
Publisher: Elsevier BV
Date: 04-2016
BrachyView, A novel inbody imaging system for HDR prostate brachytherapy: Design and Monte Carlo feasibility study
Publisher: Wiley
Date: 17-06-2013
DOI: 10.1118/1.4808360
Abstract: High dose rate (HDR) brachytherapy is a form of radiation therapy for treating prostate cancer whereby a high activity radiation source is moved between predefined positions inside applicators inserted within the treatment volume. Accurate positioning of the source is essential in delivering the desired dose to the target area while avoiding radiation injury to the surrounding tissue. In this paper, HDR BrachyView, a novel inbody dosimetric imaging system for real time monitoring and verification of the radioactive seed position in HDR prostate brachytherapy treatment is introduced. The current prototype consists of a 15 × 60 mm(2) silicon pixel detector with a multipinhole tungsten collimator placed 6.5 mm above the detector. Seven identical pinholes allow full imaging coverage of the entire treatment volume. The combined pinhole and pixel sensor arrangement is geometrically designed to be able to resolve the three-dimensional location of the source. The probe may be rotated to keep the whole prostate within the transverse plane. The purpose of this paper is to demonstrate the efficacy of the design through computer simulation, and to estimate the accuracy in resolving the source position (in detector plane and in 3D space) as part of the feasibility study for the BrachyView project. Monte Carlo simulations were performed using the GEANT4 radiation transport model, with a (192)Ir source placed in different locations within a prostate phantom. A geometrically accurate model of the detector and collimator were constructed. Simulations were conducted with a single pinhole to evaluate the pinhole design and the signal to background ratio obtained. Second, a pair of adjacent pinholes were simulated to evaluate the error in calculated source location. Simulation results show that accurate determination of the true source position is easily obtainable within the typical one second source dwell time. The maximum error in the estimated projection position was found to be 0.95 mm in the imaging (detector) plane, resulting in a maximum source positioning estimation error of 1.48 mm. HDR BrachyView is a feasible design for real-time source tracking in HDR prostate brachytherapy. It is capable of resolving the source position within a subsecond dwell time. In combination with anatomical information obtained from transrectal ultrasound imaging, HDR BrachyView adds a significant quality assurance capability to HDR brachytherapy treatment systems.
Late-Holocene sea levels from vermetids and barnacles at Ponta do Papagaio, 27° 50′S latitude and a comparison with other sectors of southern Brazil
Publisher: Elsevier BV
Date: 06-2022
Application of an SOI Microdosimeter for Monitoring of Neutrons in Various Mixed Radiation Field Environments
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 03-2022
Initial experiments with gel-water: towards MRI-linac dosimetry and imaging
Publisher: Springer Science and Business Media LLC
Date: 04-11-2016
DOI: 10.1007/S13246-016-0495-1
Abstract: Tracking the position of a moving radiation detector in time and space during data acquisition can replicate 4D image-guided radiotherapy (4DIGRT). Magnetic resonance imaging (MRI)-linacs need MRI-visible detectors to achieve this, however, imaging solid phantoms is an issue. Hence, gel-water, a material that provides signal for MRI-visibility, and which will in future work, replace solid water for an MRI-linac 4DIGRT quality assurance tool, is discussed. MR and CT images of gel-water were acquired for visualisation and electron density verification. Characterisation of gel-water at 0 T was compared to Gammex-RMI solid water, using MagicPlate-512 (M512) and RMI Attix chamber this included percentage depth dose, tissue-phantom ratio (TPR
Neutron Dosimetry with Planar Silicon p-i-n Diodes
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2003
Advances in modelling gold nanoparticle radiosensitization using new Geant4-DNA physics models
Publisher: IOP Publishing
Date: 13-11-2020
Abstract: Gold nanoparticles have demonstrated significant radiosensitization of cancer treatment with x-ray radiotherapy. To understand the mechanisms at the basis of nanoparticle radiosensitization, Monte Carlo simulations are used to investigate the dose enhancement, given a certain nanoparticle concentration and distribution in the biological medium. Earlier studies have ordinarily used condensed history physics models to predict nanoscale dose enhancement with nanoparticles. This study uses Geant4-DNA complemented with novel track structure physics models to accurately describe electron interactions in gold and to calculate the dose surrounding gold nanoparticle structures at nanoscale level. The computed dose in silico due to a clinical kilovoltage beam and the presence of gold nanoparticles was related to in vitro brain cancer cell survival using the local effect model. The comparison of the simulation results with radiobiological experimental measurements shows that Geant4-DNA and local effect model can be used to predict cell survival in silico in the case of x-ray kilovoltage beams.
The feasibility study and characterization of a two-dimensional diode array in magic phantom for high dose rate brachytherapy quality assurance
Publisher: Wiley
Date: 02-10-2013
DOI: 10.1118/1.4822736
Abstract: High dose rate (HDR) brachytherapy is a radiation treatment technique capable of delivering large dose rates to the tumor. Radiation is delivered using remote afterloaders to drive highly active sources (commonly (192)Ir with an air KERMA strength range between 20,000 and 40,000 U, where 1 U = 1 μGy m(2)/h in air) through applicators directly into the patient's prescribed region of treatment. Due to the obvious ramifications of incorrect treatment while using such an active source, it is essential that there are methods for quality assurance (QA) that can directly and accurately verify the treatment plan and the functionality of the remote afterloader. This paper describes the feasibility study of a QA system for HDR brachytherapy using a phantom based two-dimensional 11 × 11 epitaxial diode array, named "magic phantom." The HDR brachytherapy treatment plan is translated to the phantom with two rows of 10 (20 in total) HDR source flexible catheters, arranged above and below the diode array "magic plate" (MP). Four-dimensional source tracking in each catheter is based upon a developed fast iterative algorithm, utilizing the response of the diodes in close proximity to the (192)Ir source, s led at 100 ms intervals by a fast data acquisition (DAQ) system. Using a (192)Ir source in a solid water phantom, the angular response of the developed epitaxial diodes utilized in the MP and also the variation of the MP response as a function of the source-to-detector distance (SDD) were investigated. These response data are then used by an iterative algorithm for source dwelling position determination. A measurement of the average transit speed between dwell positions was performed using the diodes and a fast DAQ. The angular response of the epitaxial diode showed a variation of 15% within 360°, with two flat regions above and below the detector face with less than 5% variation. For SDD distances of between 5 and 30 mm the relative response of the epitaxial diodes used in the MP is in good agreement (within 8%) with radial dose function measurements found within the TG-43 protocol, with SDD of up to 70 mm showing a 40% over response. A method for four-dimensional localization of the HDR source was developed, allowing the source dwell position to be derived within 0.50 mm of the expected position. An estimation of the average transit speed for varying step sizes was determined and was found to increase from (12.8 ± 0.3) up to (38.6 ± 0.4) cm/s for a step size of 2.5 and 50 mm, respectively. Our characterization of the designed QA "magic phantom" with MP in realistic HDR photon fields demonstrates the promising performance for real-time source position tracking in four dimensions and measurements of transit times. Further development of this system will allow a full suite for QA in HDR brachytherapy and analysis, and for future in vivo tracking.
Real-time high spatial resolution dose verification in stereotactic motion adaptive arc radiotherapy
Publisher: Wiley
Date: 05-06-2018
DOI: 10.1002/ACM2.12364
Real-Time in-vivo dosimetry for DaRT
Publisher: IOP Publishing
Date: 10-2020
DOI: 10.1088/1742-6596/1662/1/012031
Abstract: Diffusing alpha-emitters radiation therapy (DaRT) is a revolutionary brachytherapy technique used to treat solid tumours. Implant seeds are coated with 224 Ra which, along its shortlived daughter atoms, emits alpha particles of high linear energy transfer (LET) and of high relative biological efficiency (RBE), creating a tumour-killing dose distribution a few mm wide. Those alpha particles are of energy between 5.67 and 8.78 MeV. DaRT is under investigation in clinical trials, but there currently is no obvious solution for dosimetry aimed at quality assurance of treatment. This study introduces alpha-RAD, a dosimeter based on a metal-oxide-semiconductor (MOS) sensor technology. Alpha-RAD was characterized with 241 Am, which emits alpha particles of energy 5.49 MeV. The results showed that alpha-RAD had good linearity with dose, with the signal increasing linearly in the range from 0 to 6.84 Gy. Also, an external bias in the range between 15 and 60 V, applied on the gate of alpha-RAD during irradiation, would optimize sensitivity to alpha particles of energies typical of DaRT. Alpha-RAD, owing to its compactness, can fit into a brachytherapy needle, to be placed next to 224 Ra seed implants in the tumour, for real-time in vivo dosimetry.
Characterization of MOSFET Dosimeters for Alpha Particle Therapy
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 04-2022
Conformational Flexibility and Structure in High-Pressure Excited States of Apomyoglobin Revealed by SDSL-EPR
Publisher: Elsevier BV
Date: 2014
Performance comparison of two compact multiplexed readouts with SensL's SPMArray4 for high-resolution detector module
Publisher: IEEE
Date: 10-2012
Application of semiconductors for dosimetry of fast-neutron therapy beam
Publisher: Oxford University Press (OUP)
Date: 08-2004
DOI: 10.1093/RPD/NCH223
3D radiation detectors: Charge collection characterisation and applicability of technology for microdosimetry
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 08-2014
In vivo dosimetry and seed localization in prostate brachytherapy with permanent implants
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2004
Initial testing of a pixelated silicon detector prototype in proton therapy
Publisher: Wiley
Date: 18-07-2017
DOI: 10.1002/ACM2.12120
Studies of the characteristics of a silicon neutron sensor
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 08-2009
ZnO/CeO2 nanocomposite with low photocatalytic activity as efficient UV filters
Publisher: Springer Science and Business Media LLC
Date: 27-02-2020
Skin dosimetry with new MOSFET detectors
Publisher: Elsevier BV
Date: 02-2008
Preliminary epi-diode characterization for HDR brachytherapy quality assurance
Publisher: IOP Publishing
Date: 2019
Ultra‐high dose rate dosimetry: Challenges and opportunities for FLASH radiation therapy
Publisher: Wiley
Date: 07-05-2022
DOI: 10.1002/MP.15649
Abstract: The clinical translation of FLASH radiotherapy (RT) requires challenges related to dosimetry and beam monitoring of ultra‐high dose rate (UHDR) beams to be addressed. Detectors currently in use suffer from saturation effects under UHDR regimes, requiring the introduction of correction factors. There is significant interest from the scientific community to identify the most reliable solutions and suitable experimental approaches for UHDR dosimetry. This interest is manifested through the increasing number of national and international projects recently proposed concerning UHDR dosimetry. Attaining the desired solutions and approaches requires further optimization of already established technologies as well as the investigation of novel radiation detection and dosimetry methods. New knowledge will also emerge to fill the gap in terms of validated protocols, assessing new dosimetric procedures and standardized methods. In this paper, we discuss the main challenges coming from the peculiar beam parameters characterizing UHDR beams for FLASH RT. These challenges vary considerably depending on the accelerator type and technique used to produce the relevant UHDR radiation environment. We also introduce some general considerations on how the different time structure in the production of the radiation beams, as well as the dose and dose‐rate per pulse, can affect the detector response. Finally, we discuss the requirements that must characterize any proposed dosimeters for use in UDHR radiation environments. A detailed status of the current technology is provided, with the aim of discussing the detector features and their performance characteristics and/or limitations in UHDR regimes. We report on further developments for established detectors and novel approaches currently under investigation with a view to predict future directions in terms of dosimetry approaches, practical procedures, and protocols. Due to several on‐going detector and dosimetry developments associated with UHDR radiation environment for FLASH RT it is not possible to provide a simple list of recommendations for the most suitable detectors for FLASH RT dosimetry. However, this article does provide the reader with a detailed description of the most up‐to‐date dosimetric approaches, and describes the behavior of the detectors operated under UHDR irradiation conditions and offers expert discussion on the current challenges which we believe are important and still need to be addressed in the clinical translation of FLASH RT.
BrachyView: Multiple seed position reconstruction and comparison with CT post-implant dosimetry
Publisher: IOP Publishing
Date: 03-05-2016
Technical Note: Angular dependence of a 2D monolithic silicon diode array for small field dosimetry: Angular
Publisher: Wiley
Date: 10-07-2017
DOI: 10.1002/MP.12377
Abstract: This study aims to investigate the 2D monolithic silicon diode array size of 52 × 52 mm The MP512 was placed at the center of a cylindrical phantom, irradiated using 6 MV and 10 MV photons and incrementing the incidence of the beam angle in 15° steps from 0° to 180°, and then in 1° steps between 85° and 95°. The MP512 response was characterized for square field sizes varying between 1 × 1 cm The intrinsic angular dependence of the MP512 shows maximum relative deviation from the response normalized to 0° of 18.5 ± 0.5% and 15.5 ± 0.5% for 6 MV and 10 MV, respectively, demonstrating that the angular response is sensitive to the energy. In contrast, the variation of angular response is less affected by field size. Comparison of cross-plane profiles measured by the corrected MP512 and EBT3 shows an agreement within ±2% for all field sizes when the beams irradiated the array at 0°, 45°, 135°, and 180° angles of incidence from the normal to the detector plane. At 90° incidence, corresponding to a depth dose measurement, up to a 6% discrepancy was observed for a 1 × 1 cm An angular correction factor can be adopted for small field sizes. Measurements discrepancies could be encountered when irradiating with very small fields parallel to the detector plane. Using this approach, the MP512 is shown to be a suitable detector for 2D dose mapping of small field size photon beams.
Verification of the plan dosimetry for high dose rate brachytherapy using metal-oxide-semiconductor field effect transistor detectors
Publisher: Wiley
Date: 11-05-2007
DOI: 10.1118/1.2736288
Abstract: The feasibility of a recently designed metal-oxide-semiconductor field effect transistor (MOSFET) dosimetry system for dose verification of high dose rate (HDR) brachytherapy treatment planning was investigated. MOSFET detectors were calibrated with a 0.6 cm3 NE-2571 Farmer-type ionization chamber in water. Key characteristics of the MOSFET detectors, such as the energy dependence, that will affect phantom measurements with HDR 192Ir sources were measured. The MOS-FET detector was then applied to verify the dosimetric accuracy of HDR brachytherapy treatments in a custom-made water phantom. Three MOSFET detectors were calibrated independently, with the calibration factors ranging from 0.187 to 0.215 cGy/mV. A distance dependent energy response was observed, significant within 2 cm from the source. The new MOSFET detector has a good reproducibility (<3%), small angular effect (<2%), and good dose linearity (R2=1). It was observed that the MOSFET detectors had a linear response to dose until the threshold voltage reached approximately 24 V for 192Ir source measurements. Further comparison of phantom measurements using MOSFET detectors with dose calculations by a commercial treatment planning system for computed tomography-based brachytherapy treatment plans showed that the mean relative deviation was 2.2 +/- 0.2% for dose points 1 cm away from the source and 2.0 +/- 0.1% for dose points located 2 cm away. The percentage deviations between the measured doses and the planned doses were below 5% for all the measurements. The MOSFET detector, with its advantages of small physical size and ease of use, is a reliable tool for quality assurance of HDR brachytherapy. The phantom verification method described here is universal and can be applied to other HDR brachytherapy treatments.
Urethral alarm probe for permanent prostate implants
Publisher: Informa UK Limited
Date: 06-2008
A proteomic characterization shows differences in the milk fat globule membrane of buffalo and bovine milk
Publisher: Elsevier BV
Date: 09-2017
Dual detector prototype for on line dose verification during patient radiotherapy treatment
Publisher: Elsevier BV
Date: 04-2018
Influence of polarization and a source model for dose calculation in MRT
Publisher: Wiley
Date: 13-03-2014
DOI: 10.1118/1.4867858
Abstract: Microbeam Radiation Therapy (MRT), an alternative preclinical treatment strategy using spatially modulated synchrotron radiation on a micrometer scale, has the great potential to cure malignant tumors (e.g., brain tumors) while having low side effects on normal tissue. Dose measurement and calculation in MRT is challenging because of the spatial accuracy required and the arising high dose differences. Dose calculation with Monte Carlo simulations is time consuming and their accuracy is still a matter of debate. In particular, the influence of photon polarization has been discussed in the literature. Moreover, it is controversial whether a complete knowledge of phase space trajectories, i.e., the simulation of the machine from the wiggler to the collimator, is necessary in order to accurately calculate the dose. With Monte Carlo simulations in the Geant4 toolkit, the authors investigate the influence of polarization on the dose distribution and the therapeutically important peak to valley dose ratios (PVDRs). Furthermore, the authors analyze in detail phase space information provided by Martínez‐Rovira et al. [“Development and commissioning of a Monte Carlo photon model for the forthcoming clinical trials in microbeam radiation therapy,” Med. Phys. 39(1), – (2012)] and examine its influence on peak and valley doses. A simple source model is developed using parallel beams and its applicability is shown in a semiadjoint Monte Carlo simulation. Results are compared to measurements and previously published data. Polarization has a significant influence on the scattered dose outside the microbeam field. In the radiation field, however, dose and PVDRs deduced from calculations without polarization and with polarization differ by less than 3%. The authors show that the key consequences from the phase space information for dose calculations are inhomogeneous primary photon flux, partial absorption due to inclined beam incidence outside the field center, increased beam width and center to center distance due to the beam propagation from the collimator to the phantom surface and imperfect absorption in the absorber material of the Multislit Collimator. These corrections have an effect of approximately 10% on the valley dose and suffice to describe doses in MRT within the measurement uncertainties of currently available dosimetry techniques. The source for the first clinical pet trials in MRT is characterized with respect to its phase space and the photon polarization. The results suggest the use of a presented simplified phase space model in dose calculations and hence pave the way for alternative and fast dose calculation algorithms. They also show that the polarization is of minor importance for the clinical important peak and valley doses inside the microbeam field.
A dual scintillator - Dual silicon photodiode detector module for intraoperative gamma\beta probe and portable anti-compton spectrometer
Publisher: Informa UK Limited
Date: 06-2008
Time-of-flight spectrometry of ultra-short, polyenergetic proton bunches
Publisher: AIP Publishing
Date: 12-2018
DOI: 10.1063/1.5052059
Abstract: A common approach for spectrum determination of polyenergetic proton bunches from laser-ion acceleration experiments is based on the time-of-flight (TOF) method. However, spectra obtained using this method are typically given in relative units or are estimated based on some prior assumptions on the energy distribution of the accelerated ions. In this work, we present a new approach using the TOF method that allows for an absolute energy spectrum reconstruction from a current signal acquired with a sub-nanosecond fast and 10 µm thin silicon detector. The reconstruction is based on solving a linear least-squares problem, taking into account the response function of the detection system. The general principle of signal generation and spectrum reconstruction by setting up an appropriate system response matrix is presented. Proof-of-principle experiments at a 12 MV Tandem accelerator using different nanosecond-short (quasi-)monoenergetic and polyenergetic proton bunches at energies up to 20 MeV were successfully performed. Within the experimental uncertainties of 2.4% and 12.1% for energy and particle number, respectively, reconstructed energy distributions were found in excellent agreement with the spectra calculated using Monte Carlo simulations and measured by a magnetic spectrometer. This TOF method can hence be used for absolute online spectrometry of laser-accelerated particle bunches.
Characterization of an “Edgeless” Dosimeter for Angular Independent Measurements in Advanced Radiotherapy Treatments
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 09-2201
Small beams, fast predictions: a comparison of machine learning dose prediction models for proton minibeam therapy
Publisher: Wiley
Date: 10-11-2022
DOI: 10.1002/MP.16066
Abstract: Dose calculations for novel radiotherapy cancer treatments such as proton minibeam radiation therapy is often done using full Monte Carlo (MC) simulations. As MC simulations can be very time consuming for this kind of application, deep learning models have been considered to accelerate dose estimation in cancer patients. This work systematically evaluates the dose prediction accuracy, speed and generalization performance of three selected state‐of‐the‐art deep learning models for dose prediction applied to the proton minibeam therapy. The strengths and weaknesses of those models are thoroughly investigated, helping other researchers to decide on a viable algorithm for their own application. The following recently published models are compared: first, a 3D U‐Net model trained as a regression network, second, a 3D U‐Net trained as a generator of a generative adversarial network (GAN) and third, a dose transformer model which interprets the dose prediction as a sequence translation task. These models are trained to emulate the result of MC simulations. The dose depositions of a proton minibeam with a diameter of 800μm and an energy of 20–100 MeV inside a simple head phantom calculated by full Geant4 MC simulations are used as a case study for this comparison. The spatial resolution is 0.5 mm. Special attention is put on the evaluation of the generalization performance of the investigated models. Dose predictions with all models are produced in the order of a second on a GPU, the 3D U‐Net models being fastest with an average of 130 ms. An investigated 3D U‐Net regression model is found to show the strongest performance with overall 61.00.5% of all voxels exhibiting a deviation in energy deposition prediction of less than 3% compared to full MC simulations with no spatial deviation allowed. The 3D U‐Net models are observed to show better generalization performance for target geometry variations, while the transformer‐based model shows better generalization with regard to the proton energy. This paper reveals that (1) all studied deep learning models are significantly faster than non‐machine learning approaches predicting the dose in the order of seconds compared to hours for MC, (2) all models provide reasonable accuracy, and (3) the regression‐trained 3D U‐Net provides the most accurate predictions.
BrachyView: Reconstruction of seed positions and volume of an LDR prostate brachytherapy patient plan using a baseline subtraction algorithm
Publisher: Elsevier BV
Date: 10-2019
DOI: 10.1016/J.EJMP.2019.09.237
Abstract: BrachyView is a novel in-body imaging system developed with the objective to provide real-time intraoperative dosimetry for low dose rate (LDR) prostate brachytherapy treatments. The BrachyView coordinates combined with conventional transrectal ultrasound (TRUS) imaging, provides the possibility to localise the effective position of the implanted seeds inside the prostate volume, providing a unique tool for intra-operative verification of the quality of the implantation. This research presents the first complete LDR brachytherapy plan reconstructed by the BrachyView system and is used to evaluate the effectiveness of an imaging algorithm with baseline subtraction. A plan featuring 98 I-125 brachytherapy seeds, with an average activity of 0.248 mCi, were implanted into a prostate gel phantom under TRUS guidance. Images of implanted seeds were obtained by the BrachyView after the implantation of seeds. The baseline subtraction algorithm is applied as a pixel-to-pixel counts subtraction and is applied to every second projection obtained after the implantation of each needle. Seed positions and effectiveness of the baseline reconstruction in the identification of seeds were verified by a high-resolution post-implant CT scan. A complete brachytherapy plan has been reconstructed with a 100% detection rate. This is possible due to the effectiveness of the baseline subtraction, with its application an overall increase of 11.3% in position accuracy and 8.2% increase in detection rate was noted. It has been demonstrated that the BrachyView system shows the potential to be a solution to providing clinics with the means for intraoperative dosimetry for LDR prostate brachytherapy treatments.
From imaging to dosimetry: GEANT4-based study on the application of Medipix to neutron dosimetry
Publisher: Elsevier BV
Date: 12-2010
PV-0481 IMRT/VMAT QA in heterogeneous media: first experience with a 2D solid-state detector prototype
Publisher: Elsevier BV
Date: 04-2019
157. Verification of high dose delivery in radiosurgery management of brain functional disorders
Publisher: Elsevier BV
Date: 12-2018
Measurement of rectal dose during HDR brachytherapy using the new MOSkin dosimeter
Publisher: Informa UK Limited
Date: 06-2008
Panoptes: Calibration of a dosimetry system for eye brachytherapy
Publisher: Elsevier BV
Date: 12-2014
Spectral characterization of a blue-enhanced silicon photodetector
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 08-2001
DOI: 10.1109/23.958754
3D bridge microdosimeter: charge collection study and application to Relative Biological Effectiveness RBE studies in ¹²C radiation therapy. (RSNSW & AIP Jak Kelly Award Prize Winner, 2014)
Publisher: Biodiversity Heritage Library
Date: 06-2015
DOI: 10.5962/P.361727
Flexible Polymer X-ray Detectors with Non-fullerene Acceptors for Enhanced Stability: Toward Printable Tissue Equivalent Devices for Medical Applications
Publisher: American Chemical Society (ACS)
Date: 22-11-2021
Large area silicon microdosimeter for dosimetry in high LET space radiation fields: Charge collection study
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2012
Characterization of a novel two dimensional diode array the magic plate as a radiation detector for radiation therapy treatment
Publisher: Wiley
Date: 18-04-2012
DOI: 10.1118/1.3700234
Abstract: Intensity modulated radiation therapy (IMRT) utilizes the technology of multileaf collimators to deliver highly modulated and complex radiation treatment. Dosimetric verification of the IMRT treatment requires the verification of the delivered dose distribution. Two dimensional ion chamber or diode arrays are gaining popularity as a dosimeter of choice due to their real time feedback compared to film dosimetry. This paper describes the characterization of a novel 2D diode array, which has been named the "magic plate" (MP). It was designed to function as a 2D transmission detector as well as a planar detector for dose distribution measurements in a solid water phantom for the dosimetric verification of IMRT treatment delivery. The prototype MP is an 11 × 11 detector array based on thin (50 μm) epitaxial diode technology mounted on a 0.6 mm thick Kapton substrate using a proprietary "drop-in" technology developed by the Centre for Medical Radiation Physics, University of Wollongong. A full characterization of the detector was performed, including radiation damage study, dose per pulse effect, percent depth dose comparison with CC13 ion chamber and build up characteristics with a parallel plane ion chamber measurements, dose linearity, energy response and angular response. Postirradiated magic plate diodes showed a reproducibility of 2.1%. The MP dose per pulse response decreased at higher dose rates while at lower dose rates the MP appears to be dose rate independent. The depth dose measurement of the MP agrees with ion chamber depth dose measurements to within 0.7% while dose linearity was excellent. MP showed angular response dependency due to the anisotropy of the silicon diode with the maximum variation in angular response of 10.8% at gantry angle 180°. Angular dependence was within 3.5% for the gantry angles ± 75°. The field size dependence of the MP at isocenter agrees with ion chamber measurement to within 1.1%. In the beam perturbation study, the surface dose increased by 12.1% for a 30 × 30 cm(2) field size at the source to detector distance (SDD) of 80 cm whilst the transmission for the MP was 99%. The radiation response of the magic plate was successfully characterized. The array of epitaxial silicon based detectors with "drop-in" packaging showed properties suitable to be used as a simplified multipurpose and nonperturbing 2D radiation detector for radiation therapy dosimetric verification.
Polymer Photodetectors for Printable, Flexible, and Fully Tissue Equivalent X-Ray Detection with Zero-Bias Operation and Ultrafast Temporal Responses
Publisher: Wiley
Date: 27-05-2021
Abstract: A new printable organic semiconducting material combination as a tissue equivalent photodetector for indirect X‐ray detection is demonstrated in this work. The device exhibits a higher optical‐to‐electrical conversion efficiency than any other reported printable organic systems for X‐ray photodetection while also operating efficiently with zero applied bias. Complete X‐ray detectors fabricated by coupling the photodiode with a plastic scintillator are among the first flexible and fully tissue equivalent X‐ray detectors capable of operating without external bias. The response to X‐rays is energy independent between 50 keV and 1.2 MeV, with a detection sensitivity equivalent to inorganic direct X‐ray detectors and one of the fastest temporal responses ever reported for organic X‐ray detectors. The materials can be printed into arrays with a pixel pitch of 120 μm, providing 2D spatial detection. The devices are found to be highly stable with respect to time, mechanical flexing, and large (5 kGy) radiation doses. The new materials and fully tissue equivalent X‐ray detectors reported here provide stable, printable, flexible, and tissue equivalent detectors with a high radiolucency that are ideally suited for wearable applications, where simultaneous monitoring and high transmission of the X‐ray absorbed dose into the human body is required.
Characterization of a Large Area Thinned Silicon Microdosimeter for Space and Particle Therapy
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2015
OC-0175: In vivo rectal dose measures compared to planned and reconstructed doses in US-based HDR prostate brachytherapy
Publisher: Elsevier BV
Date: 04-2015
OC-0551: High spatial and timing resolution silicon based dosimeter for quality assurance of real time adaptive radiotherapy
Publisher: Elsevier BV
Date: 04-2015
Inborn errors of type I IFN immunity in patients with life-threatening COVID-19
Publisher: American Association for the Advancement of Science (AAAS)
Date: 23-10-2020
Abstract: The immune system is complex and involves many genes, including those that encode cytokines known as interferons (IFNs). In iduals that lack specific IFNs can be more susceptible to infectious diseases. Furthermore, the autoantibody system d ens IFN response to prevent damage from pathogen-induced inflammation. Two studies now examine the likelihood that genetics affects the risk of severe coronavirus disease 2019 (COVID-19) through components of this system (see the Perspective by Beck and Aksentijevich). Q. Zhang et al. used a candidate gene approach and identified patients with severe COVID-19 who have mutations in genes involved in the regulation of type I and III IFN immunity. They found enrichment of these genes in patients and conclude that genetics may determine the clinical course of the infection. Bastard et al. identified in iduals with high titers of neutralizing autoantibodies against type I IFN-α2 and IFN-ω in about 10% of patients with severe COVID-19 pneumonia. These autoantibodies were not found either in infected people who were asymptomatic or had milder phenotype or in healthy in iduals. Together, these studies identify a means by which in iduals at highest risk of life-threatening COVID-19 can be identified. Science , this issue p. eabd4570 , p. eabd4585 see also p. 404
Two-dimensional solid-state array detectors: A technique for in vivo dose verification in a variable effective area
Publisher: Wiley
Date: 14-10-2019
DOI: 10.1002/ACM2.12744
Validation of the influence of M512 substrate resistivity on sensitivity degradation of radiation
Publisher: Elsevier BV
Date: 05-2017
Nonisothermal cure behavior and kinetics of cerium‐doped Fe3O4/epoxy nanocomposites
Publisher: Wiley
Date: 02-08-2022
DOI: 10.1002/AOC.6825
Abstract: How does the cerium (Ce) doping in ferrimagnetic magnetite (Fe 3 O 4 ) affect the crosslinking state and kinetics of epoxy crosslinking with amine curing agents? To answer this question, we electrochemically synthesized nanoparticles of Ce–Fe 3 O 4 and characterized them by FTIR, XRD, FE‐SEM, EDX, TEM, and XPS analyses. The presence of Ce atoms in Fe 3 O 4 crystalline lattice increased the surface area and active hydroxyl sites of the prepared magnetic nanoparticles (MNPs) associated with partial shrinkage of molecular lattice. The MNPs uniformly dispersed in epoxy resin and unconditionally tagged epoxy nanocomposites as Excellent cured systems. The effect of lanthanide doping on the cure kinetics of epoxy with amine was explored applying nonisothermal DSC and model‐free kinetic approaches, signifying that Ce–Fe 3 O 4 nanoparticles facilitated epoxy ring opening by intensification of etherification reaction whatever the heating rate. Even at very low loading of Ce–Fe 3 O 4 nanoparticles into the epoxy (0.1 wt.%), the average apparent activation energy significantly decreased by ≈10%. This outcome would highlight the role of crosslinking on the ultimate properties, such as anticorrosive and/or self‐healing characteristics contributed by Ce‐doped nanoparticles once added to epoxy coating formulation.
The evaluation of a 2D diode array in magic phantom for use in high dose rate brachytherapy pretreatment quality assurance
Publisher: Wiley
Date: 12-01-2015
DOI: 10.1118/1.4905233
Abstract: High dose rate (HDR) brachytherapy is a treatment method that is used increasingly worldwide. The development of a sound quality assurance program for the verification of treatment deliveries can be challenging due to the high source activity utilized and the need for precise measurements of dwell positions and times. This paper describes the application of a novel phantom, based on a 2D 11 × 11 diode array detection system, named “magic phantom” (MPh), to accurately measure plan dwell positions and times, compare them directly to the treatment plan, determine errors in treatment delivery, and calculate absorbed dose. The magic phantom system was CT scanned and a 20 catheter plan was generated to simulate a nonspecific treatment scenario. This plan was delivered to the MPh and, using a custom developed software suite, the dwell positions and times were measured and compared to the plan. The original plan was also modified, with changes not disclosed to the primary authors, and measured again using the device and software to determine the modifications. A new metric, the “position–time gamma index,” was developed to quantify the quality of a treatment delivery when compared to the treatment plan. The MPh was evaluated to determine the minimum measurable dwell time and step size. The incorporation of the TG-43U1 formalism directly into the software allows for dose calculations to be made based on the measured plan. The estimated dose distributions calculated by the software were compared to the treatment plan and to calibrated EBT3 film, using the 2D gamma analysis method. For the original plan, the magic phantom system was capable of measuring all dwell points and dwell times and the majority were found to be within 0.93 mm and 0.25 s, respectively, from the plan. By measuring the altered plan and comparing it to the unmodified treatment plan, the use of the position–time gamma index showed that all modifications made could be readily detected. The MPh was able to measure dwell times down to 0.067 ± 0.001 s and planned dwell positions separated by 1 mm. The dose calculation carried out by the MPh software was found to be in agreement with values calculated by the treatment planning system within 0.75%. Using the 2D gamma index, the dose map of the MPh plane and measured EBT3 were found to have a pass rate of over 95% when compared to the original plan. The application of this magic phantom quality assurance system to HDR brachytherapy has demonstrated promising ability to perform the verification of treatment plans, based upon the measured dwell positions and times. The introduction of the quantitative position–time gamma index allows for direct comparison of measured parameters against the plan and could be used prior to patient treatment to ensure accurate delivery.
Determination of ion recombination for absolute dosimetry in microbeam radiation therapy
Publisher: Elsevier BV
Date: 06-2013
Microbeam radiation therapy: A Monte Carlo study of the influence of the source, multislit collimator, and beam divergence on microbeams
Publisher: Wiley
Date: 14-01-2009
DOI: 10.1118/1.3049786
Abstract: Microbeam radiation therapy (MRT) is a new oncology method currently under development for the treatment of inoperable pediatric brain tumors. Monte Carlo simulation, or the computational study of radiation transport in matter, is often used in radiotherapy to theoretically estimate the dose required for treatment. However, its potential use in MRT dose planning systems is currently hindered by the significant discrepancies that have been observed between measured and theoretical dose and the PVDR (peak to valley dose ratio). The need to resolve these discrepancies is driven by the desirability of making MRT available to humans in the next few years. This article aims to resolve some of the discrepancies by examining the simplifications adopted in previous MRT Monte Carlo studies, such as the common practice of commencing microbeam transport on the surface of the target which neglects the influence of the distributed synchrotron source, multislit collimator, and the beam ergence between them. This article uses PENELOPE Monte Carlo simulation to investigate the influence of these beamline components upstream of the target on the lateral dose profiles and PVDRs of an array of 25 microbeams. It also compares the dose profiles and PVDRs of a microbeam array produced from a single simulation (full array) to those produced from the superposition of a single microbeam profile (sup array). The effect of modeling the distributed source and the beam ergence was an increase in the absorbed dose in the penumbral and valley regions of the microbeam profiles. Inclusion of the multislit collimator resulted in differences of up to 5 microm in the FWHM of microbeam profiles across the array, which led to minor variations in the corresponding PVDR yields.
New 3D Silicon detectors for dosimetry in Microbeam Radiation Therapy
Publisher: IOP Publishing
Date: 2017
Measuring Protein Conformational Exchange Rates with Pressure-Jump Site Directed Spin Labeling EPR Spectroscopy
Publisher: Elsevier BV
Date: 2012
Evaluation of pixellated, back-sided planar photodetectors for high-resolution imaging instrumentation
Publisher: Elsevier BV
Date: 05-2008
BrachyView: Combining LDR seed positions with transrectal ultrasound imaging in a prostate gel phantom
Publisher: Elsevier BV
Date: 02-2017
DOI: 10.1016/J.EJMP.2017.01.012
Abstract: BrachyView is a novel in-body imaging system which aims to provide LDR brachytherapy seeds position reconstruction within the prostate in real-time. The first prototype is presented in this study: the probe consists of a gamma camera featuring three single cone pinhole collimators embedded in a tungsten tube, above three, high resolution pixelated detectors (Timepix). The prostate was imaged with a TRUS system using a sagittal crystal with a 2.5mm slice thickness. Eleven needles containing a total of thirty 0.508U The reconstructed seed positions determined by the BrachyView probe showed a maximum discrepancy of 1.78mm, with 75% of the seeds reconstructed within 1mm of their nominal location. An accurate co-registration between the BrachyView and TRUS coordinate system was established. The BrachyView system has shown its ability to reconstruct all implanted LDR seeds within a tissue equivalent prostate gel phantom, providing both anatomical and seed position information in a single interface.
Introducing dynamic dosimaging: Potential applications for MRI-linac
Publisher: IOP Publishing
Date: 2017
Correction factors to convert microdosimetry measurements in silicon to tissue in 12C ion therapy
Publisher: IOP Publishing
Date: 17-02-2017
Abstract: Silicon microdosimetry is a promising technology for heavy ion therapy (HIT) quality assurance, because of its sub-mm spatial resolution and capability to determine radiation effects at a cellular level in a mixed radiation field. A drawback of silicon is not being tissue-equivalent, thus the need to convert the detector response obtained in silicon to tissue. This paper presents a method for converting silicon microdosimetric spectra to tissue for a therapeutic
Performance evaluation of a multipinhole small animal SPECT system
Publisher: IEEE
Date: 2003
Real-time in vivo dosimetry with MOSFET detectors in serial tomotherapy for head and neck cancer patients
Publisher: Elsevier BV
Date: 08-2011
DOI: 10.1016/J.IJROBP.2010.10.063
Abstract: A real-time dose verification method using a recently designed metal oxide semiconductor field effect transistor (MOSFET) dosimetry system was evaluated for quality assurance (QA) of intensity-modulated radiation therapy (IMRT). Following the investigation of key parameters that might affect the accuracy of MOSFET measurements (i.e., source surface distance [SSD], field size, beam incident angles and radiation energy spectrum), the feasibility of this detector in IMRT dose verification was demonstrated by comparison with ion chamber measurements taken in an IMRT QA phantom. Real-time in vivo measurements were also performed with the MOSFET system during serial tomotherapy treatments administered to 8 head and neck cancer patients. MOSFET sensitivity did not change with SSD. For field sizes smaller than 20 × 20 cm(2), MOFET sensitivity varied within 1.0%. The detector angular response was isotropic within 2% over 360°, and the observed sensitivity variation due to changes in the energy spectrum was negligible in 6-MV photons. MOSFET system measurements and ion chamber measurements agreed at all points in IMRT phantom plan verification, within 5%. The mean difference between 48 IMRT MOSFET-measured doses and calculated values in 8 patients was 3.33% and ranged from -2.20% to 7.89%. More than 90% of the total measurements had deviations of less than 5% from the planned doses. The MOSFET dosimetry system has been proven to be an effective tool in evaluating the actual dose within in idual patients during IMRT treatment.
Design and development of PETiPIX: An ultra high spatial resolution small animal PET scanner
Publisher: IEEE
Date: 10-2013
INVESTIGATING VARIABLE RBE in A 12C MINIBEAM FIELD with MICRODOSIMETRY and GEANT4
Publisher: Oxford University Press (OUP)
Date: 21-01-2019
DOI: 10.1093/RPD/NCY234
Abstract: An experimental and simulation-based study was performed on a 12C ion minibeam radiation therapy (MBRT) field produced with a clinical broad beam and a brass multi-slit collimator (MSC). Silicon-on-insulator (SOI) microdosimeters developed at the Centre for Medical Radiation Physics (CMRP) with micron sized sensitive volumes were used to measure the microdosimetric spectra at varying positions throughout the MBRT field and the corresponding dose-mean lineal energies and RBE for 10% cell survival (RBE10) were calculated using the modified Microdosimetric Kinetic Model (MKM). An increase in the average RBE10 of ∼30% and 10% was observed in the plateau region compared to broad beam for experimental and simulation values, respectively. The experimental collimator misalignment was determined to be 0.7° by comparison between measured and simulated microdosimetric spectra at varying collimator angles. The simulated dose-mean lineal energies in the valley region between minibeams were found to be higher on average than in the minibeams due to higher LET particles being produced in these regions from the MSC. This work presents the first experimental microdosimetry measurements and characterisation of the local biological effectiveness in a MBRT field.
Towards high spatial resolution tissue-equivalent dosimetry for microbeam radiation therapy using organic semiconductors
Publisher: International Union of Crystallography (IUCr)
Date: 08-07-2021
DOI: 10.1107/S1600577521006044
Abstract: Spatially fractionated ultra-high-dose-rate beams used during microbeam radiation therapy (MRT) have been shown to increase the differential response between normal and tumour tissue. Quality assurance of MRT requires a dosimeter that possesses tissue equivalence, high radiation tolerance and spatial resolution. This is currently an unsolved challenge. This work explored the use of a 500 nm thick organic semiconductor for MRT dosimetry on the Imaging and Medical Beamline at the Australian Synchrotron. Three beam filters were used to irradiate the device with peak energies of 48, 76 and 88 keV with respective dose rates of 3668, 500 and 209 Gy s −1 . The response of the device stabilized to 30% efficiency after an irradiation dose of 30 kGy, with a 0.5% variation at doses of 35 kGy and higher. The calibration factor after pre-irradiation was determined to be 1.02 ± 0.005 µGy per count across all three X-ray energy spectra, demonstrating the unique advantage of using tissue-equivalent materials for dosimetry. The percentage depth dose curve was within ±5% of the PTW microDiamond detector. The broad beam was fractionated into 50 microbeams (50 µm FHWM and 400 µm centre-to-centre distance). For each beam filter, the FWHMs of all 50 microbeams were measured to be 51 ± 1.4, 53 ± 1.4 and 69 ± 1.9 µm, for the highest to lowest dose rate, respectively. The variation in response suggested the photodetector possessed dose-rate dependence. However, its ability to reconstruct the microbeam profile was affected by the presence of additional dose peaks adjacent to the one generated by the X-ray microbeam. Geant4 simulations proved that the additional peaks were due to optical photons generated in the barrier film coupled to the sensitive volume. The simulations also confirmed that the litude of the additional peak in comparison with the microbeam decreased for spectra with lower peak energies, as observed in the experimental data. The material packaging can be optimized during fabrication by solution processing onto a flexible substrate with a non-fluorescent barrier film. With these improvements, organic photodetectors show promising prospects as a cost-effective high spatial resolution tissue-equivalent flexible dosimeter for synchrotron radiation fields.
Modelling of protons spectra encountered in space using medical accelerator and its microdosimetric characterization
Publisher: Elsevier BV
Date: 04-2021
TH‐A‐137‐03: Application of the Dose Magnifying Glass to Proton Radiosurgery
Publisher: Wiley
Date: 06-2013
DOI: 10.1118/1.4815685
Fluorescent Gold Nanoparticles in Suspension as an Efficient Theranostic Agent for Highly Radio-Resistant Cancer Cells
Publisher: MDPI AG
Date: 30-01-2023
DOI: 10.3390/JNT4010003
Abstract: Gold nanoparticles are a promising candidate for developing new strategies of therapy against cancer. Due to their high atomic number and relative biocompatibility, they are commonly investigated as radiosensitizers to locally increase the dose of radiotherapy. In order to optimize this radiosensitizing effect, it is necessary to control the positioning of the nanoparticles in the cells. The purpose of this study is to investigate, by means of fluorescent gold nanoparticles in suspension, the dose enhancement on highly radio-resistant cancer cells. These nanoparticles were successfully produced using modern click-chemistry methods, first by attaching a chelating agent Diethylenetriamine pentaacetate benzylamine to L-cysteine, bonding the resulting ligand to a gold core, grafting propargylamine and then utilizing copper-catalyzed azide-alkyne cycloaddition (CuAAC) to fuse AlexaFluor 647 to the ligands. The results of this study prove the success of the reactions to produce a minimally cytotoxic and highly stable nanoparticle suspension that increases the radiosensitivity of gliosarcoma 9L tumor cells, with a 35% increase in cell death using 5 Gy kilovoltage radiation. Their fluorescent functionalization allowed for their simple localization within living cells and detection in vivo post-mortem.
Benchmarking and validation of a Geant4-SHADOW Monte Carlo simulation for dose calculations in microbeam radiation therapy
Publisher: International Union of Crystallography (IUCr)
Date: 03-04-2014
DOI: 10.1107/S1600577514004640
Abstract: Microbeam radiation therapy (MRT) is a synchrotron-based radiotherapy modality that uses high-intensity beams of spatially fractionated radiation to treat tumours. The rapid evolution of MRT towards clinical trials demands accurate treatment planning systems (TPS), as well as independent tools for the verification of TPS calculated dose distributions in order to ensure patient safety and treatment efficacy. Monte Carlo computer simulation represents the most accurate method of dose calculation in patient geometries and is best suited for the purpose of TPS verification. A Monte Carlo model of the ID17 biomedical beamline at the European Synchrotron Radiation Facility has been developed, including recent modifications, using the Geant4 Monte Carlo toolkit interfaced with the SHADOW X-ray optics and ray-tracing libraries. The code was benchmarked by simulating dose profiles in water-equivalent phantoms subject to irradiation by broad-beam (without spatial fractionation) and microbeam (with spatial fractionation) fields, and comparing against those calculated with a previous model of the beamline developed using the PENELOPE code. Validation against additional experimental dose profiles in water-equivalent phantoms subject to broad-beam irradiation was also performed. Good agreement between codes was observed, with the exception of out-of-field doses and toward the field edge for larger field sizes. Microbeam results showed good agreement between both codes and experimental results within uncertainties. Results of the experimental validation showed agreement for different beamline configurations. The asymmetry in the out-of-field dose profiles due to polarization effects was also investigated, yielding important information for the treatment planning process in MRT. This work represents an important step in the development of a Monte Carlo-based independent verification tool for treatment planning in MRT.
Tissue equivalence study of a novel diamond-based microdosimeter for galactic cosmic rays and solar particle events
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 08-2014
PD-0275: The influence of phase space and polarisation on MRT dose distributions
Publisher: Elsevier BV
Date: 03-2013
In‐field and out‐of‐field microdosimetric characterisation of a 62 MeV proton beam at CATANA
Publisher: Wiley
Date: 23-06-2021
DOI: 10.1002/MP.14905
Abstract: A 5 and 10 μm thin silicon on insulator (SOI) 3D mushroom microdosimeter was used to characterize both the in‐field and out‐of‐field of a 62 MeV proton beam. The SOI mushroom microdosimeter consisted of an array of cylindrical sensitive volumes (SVs), developed by the Centre for Medical Radiation Physics, University of Wollongong, was irradiated with 62 MeV protons at the CATANA (Centro di AdroTerapia Applicazioni Nucleari Avanzate) facility in Catania, Italy, a facility dedicated to the radiation treatment of ocular melanomas. Dose mean lineal energy, ( ), values were obtained at various depths in PMMA along a pristine and spread out Bragg peak (SOBP). The measured microdosimetric spectra at each position were then used as inputs into the modified Microdosimetric Kinetic Model (MKM) to derive the RBE for absorbed dose in a middle of the SOBP 2Gy (RBE D ). Microdosimetric spectra were obtained with both the 5 and 10 μm 3D SOI microdosimeters, with a focus on the distal part of the BP. The in‐field and out‐of‐field measurement configurations along the Bragg curve were modeled in Geant4 for comparison with experimental results. Lateral out‐of‐field measurements were performed to study secondary particles’ contribution to normal tissue’s dose, up to 12 mm from the edge of the beam field, and quality factor and dose equivalent results were obtained. Comparison between experimental and simulation results showed good agreement between one another for both the pristine and SOBP beams in terms of and RBED. Though a small discrepancy between experiment and simulation was seen at the entrance of the Bragg curve, where experimental results were slightly lower than Geant4. The dose equivalent value measured 12 mm from the edge of the target volume was 1.27 ± 0.15 mSv/Gy with a value of 2.52 ± 0.30, both of which agree within uncertainty with Geant4 simulation. These results demonstrate that SOI microdosimeters are an effective tool to predict RBED in‐field as well as dose equivalent monitoring out‐of‐field to provide insight to probability of second cancer generation.
Correction function for MOSkin readings in realtime in vivo dosimetry in HDR prostate brachytherapy
Publisher: Elsevier BV
Date: 04-2016
Medical physics aspects of the synchrotron radiation therapies: Microbeam radiation therapy (MRT) and synchrotron stereotactic radiotherapy (SSRT)
Publisher: Elsevier BV
Date: 09-2015
DOI: 10.1016/J.EJMP.2015.04.016
Abstract: Stereotactic Synchrotron Radiotherapy (SSRT) and Microbeam Radiation Therapy (MRT) are both novel approaches to treat brain tumor and potentially other tumors using synchrotron radiation. Although the techniques differ by their principles, SSRT and MRT share certain common aspects with the possibility of combining their advantages in the future. For MRT, the technique uses highly collimated, quasi-parallel arrays of X-ray microbeams between 50 and 600 keV. Important features of highly brilliant Synchrotron sources are a very small beam ergence and an extremely high dose rate. The minimal beam ergence allows the insertion of so called Multi Slit Collimators (MSC) to produce spatially fractionated beams of typically ∼25-75 micron-wide microplanar beams separated by wider (100-400 microns center-to-center(ctc)) spaces with a very sharp penumbra. Peak entrance doses of several hundreds of Gy are extremely well tolerated by normal tissues and at the same time provide a higher therapeutic index for various tumor models in rodents. The hypothesis of a selective radio-vulnerability of the tumor vasculature versus normal blood vessels by MRT was recently more solidified. SSRT (Synchrotron Stereotactic Radiotherapy) is based on a local drug uptake of high-Z elements in tumors followed by stereotactic irradiation with 80 keV photons to enhance the dose deposition only within the tumor. With SSRT already in its clinical trial stage at the ESRF, most medical physics problems are already solved and the implemented solutions are briefly described, while the medical physics aspects in MRT will be discussed in more detail in this paper.
New silicon microdosimetry probes for RBE and biological dose studies using stationary and movable targets in 12C ion therapy
Publisher: IOP Publishing
Date: 2017
Characterization of an organic semiconductor diode for dosimetry in radiotherapy
Publisher: Wiley
Date: 03-06-2020
DOI: 10.1002/MP.14229
Abstract: The development of novel detectors for dosimetry in advanced radiotherapy modalities requires materials that have a water equivalent response to ionizing radiation such that characterization of radiation beams can be performed without the need for complex calibration procedures and correction factors. Organic semiconductors are potentially an ideal technology in fabricating devices for dosimetry due to tissue equivalence, mechanical flexibility, and relatively cheap manufacturing cost. The response of a commercial organic photodetector (OPD), coupled to a plastic scintillator, to ionizing radiation from a linear accelerator and orthovoltage x‐ray tube has been characterized to assess its potential as a dosimeter for radiotherapy. The radiation hardness of the OPD has also been investigated to demonstrate its longevity for such applications. Radiation hardness measurements were achieved by observing the response of the OPD to the visible spectrum and 70 keV x rays after pre‐exposure to 40 kGy of ionizing radiation. The response of a preirradiated OPD to 6‐MV photons from a linear accelerator in reference conditions was compared to a nonirradiated OPD with respect to direct and indirect (RP400 plastic scintillator) detection mechanisms. Dose rate dependence of the OPD was measured by varying the surface‐to‐source distance between 90 and 300 cm. Energy dependence was characterized from 29.5 to 129 keV with an x‐ray tube. The percentage depth dose (PDD) curves were measured from 0.5 to 20 cm and compared to an ionization chamber. The OPD sensitivity to visible light showed substantial degradation of the broad 450 to 600 nm peak from the donor after irradiation to 40 kGy. After irradiation, the spectral shape has a dominant absorbance peak at 370 nm, as the acceptor better withstood radiation damage. Its response to x rays stabilized to 30% after 35 kGy, with a 0.5% difference between 770 Gy increments. The OPD exhibited reproducible detection of ionizing radiation when coupled with a scintillator. Indirect detection showed a linear response from 25 to 500 cGy and constant response to dose rates from 0.31 Gy ulse to 3.4 × 10 −4 Gy ulse. However, without the scintillator, response increased by 100% at low dose rates. Energy independence between 100 keV and 1.2 MeV advocates their use as a dosimeter without beam correction factors. A dependence on the scintillator thickness used during a comparison of the PDD to the ionizing chamber was identified. A 1‐mm‐thick scintillator coupled with the OPD demonstrated the best agreement of ± 3%. The response of OPDs to ionizing radiation has been characterized, showing promising use as a dosimeter when coupled with a plastic scintillator. The mechanisms of charge transport and trapping within organic materials varies for visible and ionizing radiation, due to differing properties for direct and indirect detection mechanisms and observing a substantial decrease in sensitivity to the visible spectrum after 40 kGy. This study proved that OPDs produce a stable response to 6‐MV photons, and with a deeper understanding of the charge transport mechanisms due to exposure to ionizing radiation, they are promising candidates as the first flexible, water equivalent, real‐time dosimeter.
Pretreatment verification of high dose rate brachytherapy plans using the 'magic phantom' system
Publisher: IOP Publishing
Date: 30-07-2015
Experimental studies with two novel silicon detectors for the development of time-of-flight spectrometry of laser-accelerated proton beams
Publisher: IOP Publishing
Date: 2017
Fast and accurate dose predictions for novel radiotherapy treatments in heterogeneous phantoms using conditional 3D-UNet generative adversarial networks
Publisher: Wiley
Date: 03-03-2022
DOI: 10.1002/MP.15555
Abstract: Novel radiotherapy techniques like synchrotron X‐ray microbeam radiation therapy (MRT) require fast dose distribution predictions that are accurate at the sub‐mm level, especially close to tissue/bone/air interfaces. Monte Carlo (MC) physics simulations are recognized to be one of the most accurate tools to predict the dose delivered in a target tissue but can be very time consuming and therefore prohibitive for treatment planning. Faster dose prediction algorithms are usually developed for clinically deployed treatments only. In this work, we explore a new approach for fast and accurate dose estimations suitable for novel treatments using digital phantoms used in preclinical development and modern machine learning techniques. We develop a generative adversarial network (GAN) model, which is able to emulate the equivalent Geant4 MC simulation with adequate accuracy and use it to predict the radiation dose delivered by a broad synchrotron beam to various phantoms. The energy depositions used for the training of the GAN are obtained using full Geant4 MC simulations of a synchrotron radiation broad beam passing through the phantoms. The energy deposition is scored and predicted in voxel matrices of size 140 × 18 × 18 with a voxel edge length of 1 mm. The GAN model consists of two competing 3D convolutional neural networks, which are conditioned on the photon beam and phantom properties. The generator network has a U‐Net structure and is designed to predict the energy depositions of the photon beam inside three phantoms of variable geometry with increasing complexity. The critic network is a relatively simple convolutional network, which is trained to distinguish energy depositions predicted by the generator from the ones obtained with the full MC simulation. The energy deposition predictions inside all phantom geometries under investigation show deviations of less than 3% of the maximum deposited energy from the simulation for roughly 99% of the voxels in the field of the beam. Inside the most realistic phantom, a simple pediatric head, the model predictions deviate by less than 1% of the maximal energy deposition from the simulations in more than 96% of the in‐field voxels. For all three phantoms, the model generalizes the energy deposition predictions well to phantom geometries, which have not been used for training the model but are interpolations of the training data in multiple dimensions. The computing time for a single prediction is reduced from several hundred hours using Geant4 simulation to less than a second using the GAN model. The proposed GAN model predicts dose distributions inside unknown phantoms with only small deviations from the full MC simulation with computations times of less than a second. It demonstrates good interpolation ability to unseen but similar phantom geometries and is flexible enough to be trained on data with different radiation scenarios without the need for optimization of the model parameter. This proof‐of‐concept encourages to apply and further develop the model for the use in MRT treatment planning, which requires fast and accurate predictions with sub‐mm resolutions.
Synchrotron activation radiotherapy: Effects of dose-rate and energy spectra to tantalum oxide nanoparticles selective tumour cell radiosentization enhancement
Publisher: IOP Publishing
Date: 02-2020
Innovative detectors for quality assurance dosimetry in SBRT of stationary and movable targets
Publisher: IOP Publishing
Date: 2017
In-field and out-of-file application in 12C ion therapy using fully 3D silicon microdosimeters
Publisher: Elsevier BV
Date: 08-2018
Microbeam Irradiation of the Beating Rodent Heart: An Ex Vivo Study of Acute and Subacute Effects on Cardiac Function
Publisher: Elsevier BV
Date: 09-2022
DOI: 10.1016/J.IJROBP.2022.05.001
Abstract: Microbeam radiation therapy (MRT) has shown several advantages compared with conventional broad-beam radiation therapy in small animal models, including a better preservation of normal tissue function and improved drug delivery based on a rapidly increased vascular permeability in the target region. Normal tissue tolerance is the limiting factor in clinical radiation therapy. Knowledge of the normal tissue tolerance of organs at risk is therefore a prerequisite in evaluating any new radiation therapy approach. With an irradiation target in the thoracic cavity, the heart would be the most important organ at risk. We used the ex vivo beating rodent heart in the Langendorff perfusion system at the synchrotron to administer microbeam irradiation (MBI) with a peak dose of 40 or 400 Gy. By continuously recording the electrocardiogram, the left ventricular pressure, and the aortic pressure before, during and after MBI, we were able to assess acute and subacute effects of MBI on electrophysiological and mechanical cardiac function. In addition, we analyzed histologic and ultrastructural sequelae caused by MBI. There were no significant changes in heart rate, heart rate variability, systolic increase of left ventricular pressure or aortic pressure. Moreover, the changes of heart rate, left ventricular pressure and aortic pressure by adding 10 With respect to acute and subacute toxicity, an MBI peak dose up to 400 Gy did not result in severe changes in cardiac electrophysiology or mechanics.
BrachyView: A novel in-body imaging system for prostate brachytherapy
Publisher: IEEE
Date: 10-2011
Medical physics challenges within the Microbeam Radiation Therapy (MRT) project
Publisher: Elsevier BV
Date: 2014
2D monolithic silicon-diode array detectors in megavoltage photon beams: does the fabrication technology matter? A medical physicist’s perspective
Publisher: Springer Science and Business Media LLC
Date: 21-02-2019
DOI: 10.1007/S13246-019-00736-7
Abstract: A family of prototype 2D monolithic silicon-diode array detectors (MP512, Duo, Octa) has been proposed by the Centre for Medical Radiation Physics, University of Wollongong (Australia) for relative dosimetry in small megavoltage photon beams. These detectors, which differ in the topology of their 512 sensitive volumes, were originally fabricated on bulk p-type substrates. More recently, they have also been fabricated on epitaxial p-type substrates. In the literature, their performance has been in idually characterized for quality assurance (QA) applications. The present study directly assessed and compared that of a MP512-bulk and that of a MP512-epitaxial in terms of radiation hardness, long-term stability, response linearity with dose, dose per pulse and angular dependence. Their measurements of output factors, off-axis ratios and percentage depth doses in square radiation fields collimated by the jaws and produced by 6 MV and 10 MV flattened photon beams were then benchmarked against those by commercially available detectors. The present investigation was aimed at establishing, from a medical physicist's perspective, how the bulk and epitaxial fabrication technologies would affect the implementation of the MP512s into a QA protocol. Based on results, the MP512-epitaxial would offer superior radiation hardness, long-term stability and achievable uniformity and reproducibility of the response across the 2D active area.
The angular dependence of a two dimensional monolithic detector array for dosimetry in small radiation fields
Publisher: IOP Publishing
Date: 2017
Direct and pulsed current annealing of p-MOSFET based dosimeter: The MOSkin
Publisher: Springer Science and Business Media LLC
Date: 20-03-2014
DOI: 10.1007/S13246-014-0261-1
Abstract: Contemporary radiation therapy (RT) is complicated and requires sophisticated real-time quality assurance (QA). While 3D real-time dosimetry is most preferable in RT, it is currently not fully realised. A small, easy to use and inexpensive point dosimeter with real-time and in vivo capabilities is an option for routine QA. Such a dosimeter is essential for skin, in vivo or interface dosimetry in phantoms for treatment plan verification. The metal-oxide-semiconductor-field-effect-transistor (MOSFET) detector is one of the best choices for these purposes, however, the MOSFETs sensitivity and its signal stability degrade after essential irradiation which limits its lifespan. The accumulation of positive charge on the gate oxide and the creation of interface traps near the silicon-silicon dioxide layer is the primary physical phenomena responsible for this degradation. The aim of this study is to investigate MOSFET dosimeter recovery using two proposed annealing techniques: direct current (DC) and pulsed current (PC), both based on hot charged carrier injection into the gate oxide of the p-MOSFET dosimeter. The investigated MOSFETs were reused multiple times using an irradiation-annealing cycle. The effect of the current-annealing parameters was investigated for the dosimetric characteristics of the recovered MOSFET dosimeters such as linearity, sensitivity and initial threshold voltage. Both annealing techniques demonstrated excellent results in terms of maintaining a stable response, linearity and sensitivity of the MOSFET dosimeter. However, PC annealing is more preferable than DC annealing as it offers better dose response linearity of the reused MOSFET and has a very short annealing time.
The use of a silicon strip detector dose magnifying glass in stereotactic radiotherapy QA and dosimetry
Publisher: Wiley
Date: 14-02-2011
DOI: 10.1118/1.3549759
Abstract: Stereotactic radiosurgery/therapy (SRS/SRT) is the use of radiation ablation in place of conventional surgical excision to remove or create fibrous tissue in small target volumes. The target of the SRT/SRS treatment is often located in close proximity to critical organs, hence the requirement of high geometric precision including a tight margin on the planning target volume and a sharp dose fall off. One of the major problems with quality assurance (QA) of SRT/SRS is the availability of suitable detectors with the required spatial resolution. The authors present a novel detector that they refer to as the dose magnifying glass (DMG), which has a high spatial resolution (0.2 mm) and is capable of meeting the stringent requirements of QA and dosimetry in SRS/SRT therapy. The DMG is an array of 128 phosphor implanted n+ strips on a p-type Si wafer. The sensitive area defined by a single n+ strip is 20 x 2000 microm2. The Si wafer is 375 microm thick. It is mounted on a 0.12 mm thick Kapton substrate. The authors studied the dose per pulse (dpp) and angular response of the detector in a custom-made SRS phantom. The DMG was used to determine the centers of rotation and positioning errors for the linear accelerator's gantry, couch, and collimator rotations. They also used the DMG to measure the profiles and the total scatter factor (S(cp)) of the SRS cones. Comparisons were made with the EBT2 film and standard S(cp) values. The DMG was also used for dosimetric verification of a typical SRS treatment with various noncoplanar fields and arc treatments when applied to the phantom. The dose per pulse dependency of the DMG was found to be < 5% for a dpp change of 7.5 times. The angular response of the detector was investigated in the azimuthal and polar directions. The maximum polar angular response was 13.8% at the gantry angle of 320 degrees, which may be partly due to the phantom geometry. The maximum azimuthal angular response was 15.3% at gantry angles of 90 degrees and 270 degrees. The angular response at the gantry angle of 180 degrees was 6.3%. A correction function was derived to correct for the angular dependence of the detector, which takes into account the contribution of the azimuthal and polar angular response at different treatment couch positions. The maximum positioning errors due to collimator, gantry, and couch rotation were 0.2 +/- 0.1, 0.4 +/- 0.1, and 0.4 +/- 0.2 mm, respectively. The SRS cone S(cp) agrees very well with the standard data with an average difference of 1.2 +/- 1.1%. Comparison of the relative intensity profiles of the DMG and EBT2 measurements for a simulated SRS treatment shows a maximum difference of 2.5%. The DMG was investigated for dose per pulse and angular dependency. Its application to SRS/SRT delivery verification was demonstrated. The DMG with its high spatial resolution and real time capability allows measurement of dose profiles for cone applicators down to 5 mm in diameter, both accurately and rapidly as required in typical SRS/SRT deliveries.
X-ray microbeam measurements with a high resolution scintillator fibre-optic dosimeter
Publisher: Springer Science and Business Media LLC
Date: 29-09-2017
DOI: 10.1038/S41598-017-12697-6
Abstract: Synchrotron microbeam radiation therapy is a novel external beam therapy under investigation, that uses highly brilliant synchrotron x-rays in microbeams 50 μ m width, with separation of 400 μ m, as implemented here. Due to the fine spatial fractionation dosimetry of these beams is a challenging and complicated problem. In this proof-of-concept work, we present a fibre optic dosimeter that uses plastic scintillator as the radiation conversion material. We claim an ideal one-dimensional resolution of 50 μ m. Using plastic scintillator and fibre optic makes this dosimeter water-equivalent, a very desirable dosimetric property. The dosimeter was tested at the Australian Synchrotron, on the Imaging and Medical Beam-Line. The in idual microbeams were able to be resolved and the peak-to-valley dose ratio and the full width at half maximum of the microbeams was measured. These results are compared to a semiconductor strip detector of the same spatial resolution. A percent depth dose was measured and compared to data acquired by an ionisation chamber. The results presented demonstrate significant steps towards the development of an optical dosimeter with the potential to be applied in quality assurance of microbeam radiation therapy, which is vital if clinical trials are to be performed on human patients.
A silicon strip detector dose magnifying glass for IMRT dosimetry
Publisher: Wiley
Date: 06-01-2010
DOI: 10.1118/1.3264176
Abstract: Intensity modulated radiation therapy (IMRT) allows the delivery of escalated radiation dose to tumor while sparing adjacent critical organs. In doing so, IMRT plans tend to incorporate steep dose gradients at interfaces between the target and the organs at risk. Current quality assurance (QA) verification tools such as 2D diode arrays, are limited by their spatial resolution and conventional films are nonreal time. In this article, the authors describe a novel silicon strip detector (CMRP DMG) of high spatial resolution (200 microm) suitable for measuring the high dose gradients in an IMRT delivery. A full characterization of the detector was performed, including dose per pulse effect, percent depth dose comparison with Farmer ion chamber measurements, stem effect, dose linearity, uniformity, energy response, angular response, and penumbra measurements. They also present the application of the CMRP DMG in the dosimetric verification of a clinical IMRT plan. The detector response changed by 23% for a 390-fold change in the dose per pulse. A correction function is derived to correct for this effect. The strip detector depth dose curve agrees with the Farmer ion chamber within 0.8%. The stem effect was negligible (0.2%). The dose linearity was excellent for the dose range of 3-300 cGy. A uniformity correction method is described to correct for variations in the in idual detector pixel responses. The detector showed an over-response relative to tissue dose at lower photon energies with the maximum dose response at 75 kVp nominal photon energy. Penumbra studies using a Varian Clinac 21EX at 1.5 and 10.0 cm depths were measured to be 2.77 and 3.94 mm for the secondary collimators, 3.52 and 5.60 mm for the multileaf collimator rounded leaf ends, respectively. Point doses measured with the strip detector were compared to doses measured with EBT film and doses predicted by the Philips Pinnacle treatment planning system. The differences were 1.1% +/- 1.8% and 1.0% +/- 1.6%, respectively. They demonstrated the high temporal resolution capability of the detector readout system, which will allow one to investigate the temporal dose pattern of IMRT and volumetric modulated are therapy (VMAT) deliveries. The CMRP silicon strip detector dose magnifying glass interfaced to a TERA ASIC DAQ system has high spatial and temporal resolution. It is a novel and valuable tool for QA in IMRT dose delivery and for VMAT dose delivery.
3D-mesa 'bridge' silicon microdosimeter: Charge collection study and application to rbe studies in 12rm c radiation therapy
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 04-2015
Intraoperative solid-state based urethral dosimetry in low dose rate prostate brachytherapy
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 06-2006
Brachyview: An in-body imaging system for real-time QA in HDR prostate brachytherapy
Publisher: IEEE
Date: 10-2013
Silicon planar structures as detectors for microbeam radiation therapy
Publisher: IEEE
Date: 10-2013
Design and simulation of continuous scintillator with pixellated photodetector
Publisher: IEEE
Date: 2000
Optimisation of output factor measurements using the Magic Plate 512 silicon dosimeter array in small megavoltage photon fields
Publisher: IOP Publishing
Date: 2017
A feasibility study of PETiPIX: An ultra high resolution small animal PET scanner
Publisher: IOP Publishing
Date: 06-12-2013
PD-0189: US-probe integrated MOSkin detectors for rectal wall in vivo dosimetry in HDR prostate brachytherapy
Publisher: Elsevier BV
Date: 2014
The effect of rectal heterogeneity on wall dose in high dose rate brachytherapy
Publisher: Wiley
Date: 22-12-2009
DOI: 10.1118/1.3031111
Abstract: When treating prostate cancer using high dose rate (HDR) brachytherapy, overdosing the rectal wall may lead to post-treatment rectal complications. An area of concern is related to how the rectal wall dose is calculated by treatment planning systems (TPSs). TPSs are used to calculate the dose delivered to the rectal wall, but they assume that the rectum is a water-equivalent homogeneous medium of infinite size and do not consider the effect that an air-filled "empty" rectal cavity would have on the dose absorbed along the rectal wall. The aim of this research is to quantify the effect that an air cavity has on the rectal wall dose, as its presence changes the backscatter conditions in the region. The MO Skin and RADFET dosimeters proved capable of measuring absolute dose with increasing distance from the HDR Ir-192 brachytherapy source. However, the anterior rectal wall doses measured by the MOSkin and RADFET in an empty rectal cavity were 14.7 +/- 0.2% and 13.7 +/- 0.6% lower than the dose measured in a homogeneous rectal phantom. Monte Carlo simulations corroborated the experimentally obtained results, reporting a -13.2 +/- 0.6% difference. The dose measured at the posterior wall of an empty rectal cavity was between 22% and 26% greater than the dose measured in a full rectal cavity. The heterogeneity of the rectal volume appears to have a significant effect on the rectal dose when compared to calculated rectal dose.
A 2D silicon detector array for quality assurance in small field dosimetry: DUO:
Publisher: Wiley
Date: 02-2017
DOI: 10.1002/MP.12060
Abstract: Nowadays, there are many different applications that use small fields in radiotherapy treatments. The dosimetry of small radiation fields is not trivial due to the problems associated with lateral disequilibrium and source occlusion and requires reliable quality assurance (QA). Ideally such a QA tool should provide high spatial resolution, minimal beam perturbation and real time fast measurements. Many different types of silicon diode arrays are used for QA in radiotherapy however, their application in small filed dosimetry is limited, in part, due to a lack of spatial resolution. The Center of Medical Radiation Physics (CMRP) has developed a new generation of a monolithic silicon diode array detector that will be useful for small field dosimetry in SRS/SRT. The objective of this study is to characterize a monolithic silicon diode array designed for dosimetry QA in SRS/SRT named DUO that is arranged as two orthogonal 1D arrays with 0.2 mm pitch. DUO is two orthogonal 1D silicon detector arrays in a monolithic crystal. Each orthogonal array contains 253 small pixels with size 0.04 × 0.8 mm The DUO detector shows a dose per pulse dependence of 5% for a range of dose rates from 2.7 × 10 The CMRP's monolithic silicon detector array, DUO, is suitable for SRS/SRT dosimetry and QA because of its very high spatial resolution (0.2 mm) and real time operation.
Analytical Modelling and Simulation of Single and Double Cone Pinholes for Real-Time In-Body Tracking of an HDR Brachytherapy Source
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 06-2016
MOSFET dosimetry with high spatial resolution in intense synchrotron-generated x-ray microbeams
Publisher: Wiley
Date: 11-03-2009
DOI: 10.1118/1.3081934
Abstract: Various dosimeters have been tested for assessing absorbed doses with microscopic spatial resolution in targets irradiated by high-flux, synchrotron-generated, low-energy (approximately 30-300 keV) x-ray microbeams. A MOSFET detector has been used for this study since its radio sensitive element, which is extraordinarily narrow (approximately 1 microm), suits the main applications of interest, microbeam radiation biology and microbeam radiation therapy (MRT). In MRT, micrometer-wide, centimeter-high, and vertically oriented swaths of tissue are irradiated by arrays of rectangular x-ray microbeams produced by a multislit collimator (MSC). We used MOSFETs to measure the dose distribution, produced by arrays of x-ray microbeams shaped by two different MSCs, in a tissue-equivalent phantom. Doses were measured near the center of the arrays and maximum/minimum (peak/valley) dose ratios (PVDRs) were calculated to determine how variations in heights and in widths of the microbeams influenced this for the therapy, potentially important parameter. Monte Carlo (MC) simulations of the absorbed dose distribution in the phantom were also performed. The results show that when the heights of the irradiated swaths were below those applicable to clinical therapy (< 1 mm) the MC simulations produce estimates of PVDRs that are up to a factor of 3 higher than the measured values. For arrays of higher microbeams (i.e., 25 microm x 1 cm instead of 25 x 500 microm2), this difference between measured and simulated PVDRs becomes less than 50%. Closer agreement was observed between the measured and simulated PVDRs for the Tecomet MSC (current collimator design) than for the Archer MSC. Sources of discrepancies between measured and simulated doses are discussed, of which the energy dependent response of the MOSFET was shown to be among the most important.
Independent quality assurance of a helical tomotherapy machine using the dose magnifying glass
Publisher: Wiley
Date: 30-03-2011
DOI: 10.1118/1.3566067
Abstract: Helical tomotherapy is a complex delivery technique, integrating CT image guidance and intensity modulated radiotherapy in a single system. The integration of the CT detector ring on the gantry not only allows patient position verification but is also often used to perform various QA procedures. This convenience lacks the rigor of a machine-independent QA process. In this article, a Si strip detector, known as the Dose Magnifying Glass (DMG), was used to perform machine-independent QA measurements of the multileaf collimator alignment, leaf open time threshold, and leaf fluence output factor (LFOF). The DMG measurements showed good agreements with EDR2 film for the MLC alignment test while the CT detector agrees well with DMG measurements for leaf open time threshold and LFOF measurements. The leaf open time threshold was found to be approximately 20 ms. The LFOF measured with the DMG agreed within error with the CT detector measured LFOF. The DMG with its 0.2 mm spatial resolution coupled to TERA ASIC allowed real-time high temporal resolution measurements of the tomotherapy leaf movement. In conclusion, DMG was shown to be a suitable tool for machine-independent QA of a tomotherapy unit.
Readout of LYSO using a new silicon photodetector for positron emission tomography
Publisher: IEEE
Date: 2003
Characterization of an innovative p-type epitaxial diode for dosimetry in modern external beam radiotherapy
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2013
Development of a large-area silicon α-particle detector
Publisher: Elsevier BV
Date: 09-2014
DOI: 10.1016/J.APRADISO.2014.06.009
Abstract: Circular ion-implanted silicon detector of α-particles with a large, 5-cm(2), sensitive area has been developed. An advantage of the detector is that the detector surface is easily cleanable with chemicals. The hardened surface of the detector shows no signs of deterioration of the spectroscopic and electrical characteristics upon repeated cleaning. The energy resolution along the diameters of the detector was (1.0±0.1)% for the 5.486-MeV α-particles. Detailed tests of the charge collection efficiency and uniformity of the detector entrance window were also performed with a 5.5-MeV He(2+) microbeam.
OC-0247: MOSkin detectors for on line in vivo dosimetry in HDR prostate brachytherapy
Publisher: Elsevier BV
Date: 03-2013
Comparison of phantom materials for use in quality assurance of microbeam radiation therapy
Publisher: International Union of Crystallography (IUCr)
Date: 18-05-2017
DOI: 10.1107/S1600577517005641
Abstract: Microbeam radiation therapy (MRT) is a promising radiotherapy modality that uses arrays of spatially fractionated micrometre-sized beams of synchrotron radiation to irradiate tumours. Routine dosimetry quality assurance (QA) prior to treatment is necessary to identify any changes in beam condition from the treatment plan, and is undertaken using solid homogeneous phantoms. Solid phantoms are designed for, and routinely used in, megavoltage X-ray beam radiation therapy. These solid phantoms are not necessarily designed to be water-equivalent at low X-ray energies, and therefore may not be suitable for MRT QA. This work quantitatively determines the most appropriate solid phantom to use in dosimetric MRT QA. Simulated dose profiles of various phantom materials were compared with those calculated in water under the same conditions. The phantoms under consideration were RMI457 Solid Water (Gammex-RMI, Middleton, WI, USA), Plastic Water (CIRS, Norfolk, VA, USA), Plastic Water DT (CIRS, Norfolk, VA, USA), PAGAT (CIRS, Norfolk, VA, USA), RW3 Solid Phantom (PTW Freiburg, Freiburg, Germany), PMMA, Virtual Water (Med-Cal, Verona, WI, USA) and Perspex. RMI457 Solid Water and Virtual Water were found to be the best approximations for water in MRT dosimetry (within ±3% deviation in peak and 6% in valley). RW3 and Plastic Water DT approximate the relative dose distribution in water (within ±3% deviation in the peak and 5% in the valley). PAGAT, PMMA, Perspex and Plastic Water are not recommended to be used as phantoms for MRT QA, due to dosimetric discrepancies greater than 5%.
The design and characterization of a novel dynamic collimator system for synchrotron radiotherapy applications
Publisher: Wiley
Date: 02-08-2023
DOI: 10.1002/MP.16664
Abstract: Novel synchrotron radiotherapy techniques are currently limited to using prefabricated beam‐limiting blocks for field definition. For large experiments, a single square tungsten block is often used for every treatment since conformal blocks are both patient and field specific, and require long lead times for fabrication. Future synchrotron radiotherapy treatments would benefit from a dynamic collimator system. We developed and tested a novel collimator design for use on the Imaging and Medical Beamline (IMBL) at the ANSTO Australian Synchrotron. The maximum usable beam size on IMBL is 50‐mm wide by 3‐mm tall. Given the beam shape, targets must be vertically scanned through the synchrotron beam to cover the target volume. To shape the beam, a novel collimator design was developed, consisting of two semi‐circular leaves made from 4‐mm thick tungsten sheets, with each leaf capable of both vertical and horizontal movement. A software model was created to optimize motor trajectories and generate deliverable treatment fields. A series of geometric field shapes and clinical target volumes were delivered using the collimator and imaged with a digital imaging detector. Four similarity metrics (volumetric similarity, DICE, and the average and maximum Hausdorff distances) were used to measure differences between the input and planned fields, and the planned and delivered fields. Differences between input and planned fields increased with delivery speed, and were worse for rectangular and square fields compared to circular fields. However, the differences between planned and delivered fields were small, where the maximum average deviation between the fields was 0.25 mm (one pixel). Field repeatability was consistent with no difference (σ = 0 for all metrics) observed in consecutively delivered fields. We have successfully built and demonstrated a novel collimator for synchrotron radiotherapy applications on IMBL. Several design improvements have been highlighted and will be addressed in future revisions the collimator. However, in its current state, the collimator enables dynamically delivered conformal treatment fields to be utilized on IMBL, and is ready to support the forthcoming canine treatments on IMBL.
Neutron dosimeter development based on Medipix2
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2010
Investigation of track structure and condensed history physics models for applications in radiation dosimetry on a micro and nano scale in Geant4
Publisher: IOP Publishing
Date: 15-02-2018
Glycoproteome remodeling in MLL-rearranged B-cell precursor acute lymphoblastic leukemia.
Publisher: Ivyspring International Publisher
Date: 2021
DOI: 10.7150/THNO.65398
Ultra-thin 3-D detector: Charge collection characterization and application for microdosimetry
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2014
Response of silicon diodes for synchrotron radiation
Publisher: IEEE
Date: 10-2012
Characterization of a novel large area microdosimeter system for low dose rate radiation environments
Publisher: Elsevier BV
Date: 06-2021
Solid state diode - Ionization chamber method for measuring out-of-field neutron dose in proton therapy
Publisher: Elsevier BV
Date: 12-2011
CoALA-SPECT: A Coded Aperture Laboratory Animal SPECT System for Pre Clinical Imaging
Publisher: IEEE
Date: 2002
Cigarette Smoking, Diabetes, and Diabetes Complications: Call for Urgent Action
Publisher: Springer Science and Business Media LLC
Date: 08-2017
DOI: 10.1007/S11892-017-0903-2
Abstract: This review aimed to examine the latest evidence linking cigarette smoking and cessation to risk of incident diabetes and its complications. Abundant evidence has demonstrated that smoking is associated with increased risk of type 2 diabetes and cardiovascular disease among diabetic patients, while its relationship with microvascular complications is more limited to diabetic nephropathy and neuropathy in type 1 diabetes. In addition, diabetes risk remains high in the short term after smoking cessation, while it reduces gradually in the long term. Risk of cardiovascular complications also substantially decreases after quitting smoking, but results for microvascular complications are not consistent. Smoking is associated with increased risks of incident diabetes in the general population and cardiovascular complications among diabetic patients. Although the short-term post-cessation diabetes risk needs to be acknowledged, this review calls for urgent action to implement population-wide policies and in idual pharmaceutical and lifestyle interventions (if evidence accumulated in future) to aid smoking cessation and prevent diabetes and its complications.
Semiconductor real-time quality assurance dosimetry in brachytherapy
Publisher: Elsevier BV
Date: 2018
DOI: 10.1016/J.BRACHY.2017.08.013
Abstract: With the increase in complexity of brachytherapy treatments, there has been a demand for the development of sophisticated devices for delivery verification. The Centre for Medical Radiation Physics (CMRP), University of Wollongong, has demonstrated the applicability of semiconductor devices to provide cost-effective real-time quality assurance for a wide range of brachytherapy treatment modalities. Semiconductor devices have shown great promise to the future of pretreatment and in vivo quality assurance in a wide range of brachytherapy treatments, from high-dose-rate (HDR) prostate procedures to eye plaque treatments. The aim of this article is to give an insight into several semiconductor-based dosimetry instruments developed by the CMRP. Applications of these instruments are provided for breast and rectal wall in vivo dosimetry in HDR brachytherapy, urethral in vivo dosimetry in prostate low-dose-rate (LDR) brachytherapy, quality assurance of HDR brachytherapy afterloaders, HDR pretreatment plan verification, and real-time verification of LDR and HDR source dwell positions.
Experimental characterization of magnetically focused electron contamination at the surface of a high-field inline MRI-linac
Publisher: Wiley
Date: 21-10-2019
DOI: 10.1002/MP.13847
Abstract: The fringe field of the Australian MRI-linac causes contaminant electrons to be focused along the central axis resulting in a high surface dose. This work aims to characterize this effect using Gafchromic film and high-resolution detectors, MOSkin The Australian MRI-linac has the unique feature that the linac is mounted on rails allowing for measurements to be performed at different magnetic field strengths while maintaining a constant source-to-surface distance (SSD). Percentage depth doses (PDD) were collected at SSD 1.82 m in a solid water phantom positioned in a low magnetic field region and then at isocenter of the MRI where the magnetic field is 1 T. Measurements for a range of field sizes were taken with the MOSkin Skin dose in the MRI, as measured with the MOSkin Experimental characterization of the high electron contamination at the surface was performed for a range of field sizes. The relative response of MOSkin
Dose verification of eye plaque brachytherapy using spectroscopic dosimetry
Publisher: Springer Science and Business Media LLC
Date: 19-07-2016
DOI: 10.1007/S13246-016-0453-Y
Abstract: Eye plaque brachytherapy has been developed and refined for the last 80 years, demonstrating effective results in the treatment of ocular malignancies. Current dosimetry techniques for eye plaque brachytherapy (such as TLD- and film-based techniques) are time consuming and cannot be used prior to treatment in a sterile environment. The measurement of the expected dose distribution within the eye, prior to insertion within the clinical setting, would be advantageous, as any errors in source loading will lead to an erroneous dose distribution and inferior treatment outcomes. This study investigated the use of spectroscopic dosimetry techniques for real-time quality assurance of I-125 based eye plaques, immediately prior to insertion. A silicon detector based probe, operating in spectroscopy mode was constructed, containing a small (1 mm(3)) silicon detector, mounted within a ceramic holder, all encapsulated within a rubber sheath to prevent water infiltration of the electronics. Preliminary tests of the prototype demonstrated that the depth dose distribution through the central axis of an I-125 based eye plaque may be determined from AAPM Task Group 43 recommendations to a deviation of 6 % at 3 mm depth, 7 % at 5 mm depth, 1 % at 10 mm depth and 13 % at 20 mm depth, with the deviations attributed to the construction of the probe. A new probe design aims to reduce these discrepancies, however the concept of spectroscopic dosimetry shows great promise for use in eye plaque quality assurance in the clinical setting.
The relative biological effectiveness for carbon, nitrogen, and oxygen ion beams using passive and scanning techniques evaluated with fully 3D silicon microdosimeters
Publisher: Wiley
Date: 10-04-2018
DOI: 10.1002/MP.12874
Abstract: The aim of this study was to measure the microdosimetric distributions of a carbon pencil beam scanning (PBS) and passive scattering system as well as to evaluate the relative biological effectiveness (RBE) of different ions, namely Two different silicon microdosimeters with rectangular parallelepiped and cylindrical shaped SVs, both 10 μm in thickness were used in this study. The microdosimeters were connected to low noise electronics which allowed for the detection of lineal energies as low as 0.15 keV/μm in tissue. The silicon microdosimeters provide extremely high spatial resolution and can be used for in-field and out-of-field measurements in both passive scattering and PBS deliveries. The response of the microdosimeters was studied in 290 MeV/u For a 180 MeV/u These SOI microdosimeters with well-defined three-dimensional (3D) SVs have applicability in characterizing heavy ion radiation fields and measuring lineal energy deposition with sub-millimeter spatial resolution. It has been shown that the dose-mean lineal energy increased significantly at the distal part of the BP and SOBP due to very high LET particles. Good agreement was observed for the experimental and simulation results obtained with silicon microdosimeters in
Supporting Physics Teachers to Deliver the New High School Certificate Syllabus: What are the Priorities?
Publisher: IEEE
Date: 12-2019
Nano-sunscreens – a double-edged sword in protecting consumers from harm: viewing Australian regulatory policies through the lenses of the European Union
Publisher: Informa UK Limited
Date: 07-02-2019
DOI: 10.1080/10408444.2019.1579780
Abstract: Nanotechnology has the potential to bring about revolutionary changes in manufacturing products, including sunscreens. However, a knowledge gap between benefits and detriments of engineered nano-materials used in sunscreens exists, which gives rise to safety concerns. This article is concerned with the protection of consumers without impairing the embellishment of this promising technology. It is widely argued that the harm associated with nano-sunscreens may only occur under certain conditions related mainly to users skin vulnerability, which can be avoided by informed and careful use of such a product. We thus recognize the need for fostering the growth of nanotech simultaneously with preventing potential harm. We revisit the Australian sunscreens regulatory policies, which embrace a "wait and see" approach, through the lens of regulatory policies in the European Union (EU) that are influenced by a "precautionary principle." We highlight the importance of informing consumers about the sunscreen they are using and recommend that product labels should disclose the presence of nano-ingredients in line with the EU disclosure requirements. This will allow users to carefully apply the product in order to avoid any potential harm and to protect manufacturers from possible costly litigation in future. This can be achieved through a combined collaborative effort of regulators, supply chain entities, and end users.
Comparison of the new MOSkin detector and fiber optic dosimetry system for radiotherapy
Publisher: Informa UK Limited
Date: 06-2008
Dosimetry of intensive synchrotron microbeams
Publisher: Elsevier BV
Date: 12-2011
Modification of the Langendorff system of the isolated beating heart for experimental radiotherapy at a synchrotron: 4000 Gy in a heart beat
Publisher: International Union of Crystallography (IUCr)
Date: 18-05-2022
DOI: 10.1107/S1600577522004489
Abstract: Microbeam radiotherapy could help to cure malignant tumours which are currently still considered therapy-resistant. With an irradiation target in the thoracic cavity, the heart would be one of the most important organs at risk. To assess the acute adverse effects of microbeam irradiation in the heart, a powerful ex vivo tool was created by combining the Langendorff model of the isolated beating mammalian heart with X-Tream dosimetry. In a first pilot experiment conducted at the Biomedical and Imaging Beamline of the Australian Synchrotron, the system was tested at a microbeam peak dose approximately ten times higher than the anticipated future microbeam irradiation treatment doses. The entire heart was irradiated with a dose of 4000 Gy at a dose rate of Gy s −1 , using an array of 50 µm-wide microbeams spaced at a centre-to-centre distance of 400 µm. Although temporary arrhythmias were seen, they reverted spontaneously to a stable rhythm and no cardiac arrest occurred. This amazing preservation of cardiac function is promising for future therapeutic approaches.
Supercapacitor Electrodes with Remarkable Specific Capacitance Converted from Hybrid Graphene Oxide/NaCl/Urea Films
Publisher: American Chemical Society (ACS)
Date: 26-06-2017
Abstract: A novel approach to improve the specific capacitance of reduced graphene oxide (rGO) films is reported. We combine the aqueous dispersion of liquid-crystalline GO incorporating salt and urea with a blade-coating technique to make hybrid films. After drying, stacked GO sheets mediated by solidified NaCl and urea are hydrothermally reduced, resulting in a nanoporous film consisting of rumpled N-doped rGO sheets. As a supercapacitor electrode, the film exhibits a high gravimetric specific capacitance of 425 F g
Ph-Induced Oligomerization of the Voltage Dependent Anion Channel
Publisher: Elsevier BV
Date: 02-2017
Na-doped ZnO UV filters with reduced photocatalytic activity for sunscreen applications
Publisher: Springer Science and Business Media LLC
Date: 16-10-2020
Mosfet dosimetry of an X-ray mlcrobeam
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-1999
DOI: 10.1109/23.819153
A system for radiation damage monitoring
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-1999
DOI: 10.1109/23.819152
Monte Carlo modelling of a silicon strip detector for microbeam radiation therapy
Publisher: Elsevier BV
Date: 12-2011
High toxicity of Bi(OH)3 and α-Bi2 O3 nanoparticles towards malignant 9L and MCF-7 cells
Publisher: Elsevier BV
Date: 12-2018
DOI: 10.1016/J.MSEC.2018.09.001
Abstract: Here we report the extreme toxicity in vitro of Bi(OH)
How to measure high dose in functional disorder treatment: an innovative silicon diode detector.
Publisher: Elsevier BV
Date: 04-2019
Real-time eye lens dose monitoring during cerebral angiography procedures
Publisher: Springer Science and Business Media LLC
Date: 23-05-2016
DOI: 10.1007/S00330-015-3818-9
Abstract: To develop a real-time dose-monitoring system to measure the patient's eye lens dose during neuro-interventional procedures. Radiation dose received at left outer canthus (LOC) and left eyelid (LE) were measured using Metal-Oxide-Semiconductor Field-Effect Transistor dosimeters on 35 patients who underwent diagnostic or cerebral embolization procedures. The radiation dose received at the LOC region was significantly higher than the dose received by the LE. The maximum eye lens dose of 1492 mGy was measured at LOC region for an AVM case, followed by 907 mGy for an aneurysm case and 665 mGy for a diagnostic angiography procedure. Strong correlations (shown as R(2)) were observed between kerma-area-product and measured eye doses (LOC: 0.78, LE: 0.68). Lateral and frontal air-kerma showed strong correlations with measured dose at LOC (AKL: 0.93, AKF: 0.78) and a weak correlation with measured dose at LE. A moderate correlation was observed between fluoroscopic time and dose measured at LE and LOC regions. The MOSkin dose-monitoring system represents a new tool enabling real-time monitoring of eye lens dose during neuro-interventional procedures. This system can provide interventionalists with information needed to adjust the clinical procedure to control the patient's dose. Real-time patient dose monitoring helps interventionalists to monitor doses. Strong correlation was observed between kerma-area-product and measured eye doses. Radiation dose at left outer canthus was higher than at left eyelid.
A Solid-State Microdosimeter for Dose and Radiation Quality Monitoring for Astronauts in Space
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2020
Radiation dose enhancement at tissue-tungsten interfaces in HDR brachytherapy
Publisher: IOP Publishing
Date: 17-10-2014
DOI: 10.1088/0022-3727/59/21/6659
Abstract: HDR BrachyView is a novel in-body dosimetric imaging system for real-time monitoring and verification of the source position in high dose rate (HDR) prostate brachytherapy treatment. It is based on a high-resolution pixelated detector array with a semi-cylindrical multi-pinhole tungsten collimator and is designed to fit inside a compact rectal probe, and is able to resolve the 3D position of the source with a maximum error of 1.5 mm. This paper presents an evaluation of the additional dose that will be delivered to the patient as a result of backscatter radiation from the collimator. Monte Carlo simulations of planar and cylindrical collimators embedded in a tissue-equivalent phantom were performed using Geant4, with an (192)Ir source placed at two different source-collimator distances. The planar configuration was replicated experimentally to validate the simulations, with a MOSkin dosimetry probe used to measure dose at three distances from the collimator. For the cylindrical collimator simulation, backscatter dose enhancement was calculated as a function of axial and azimuthal displacement, and dose distribution maps were generated at three distances from the collimator surface. Although significant backscatter dose enhancement was observed for both geometries immediately adjacent to the collimator, simulations and experiments indicate that backscatter dose is negligible at distances beyond 1 mm from the collimator. Since HDR BrachyView is enclosed within a 1 mm thick tissue-equivalent plastic shell, all backscatter radiation resulting from its use will therefore be absorbed before reaching the rectal wall or other tissues. dosimetry, brachytherapy, HDR.
A Novel Anthropomorphic Phantom Composed of Tissue-Equivalent Materials for Use in Experimental Radiotherapy: Design, Dosimetry and Biological Pilot Study
Publisher: MDPI AG
Date: 31-05-2023
DOI: 10.3390/BIOMIMETICS8020230
Abstract: The production of anthropomorphic phantoms generated from tissue-equivalent materials is challenging but offers an excellent copy of the typical environment encountered in typical patients. High-quality dosimetry measurements and the correlation of the measured dose with the biological effects elicited by it are a prerequisite in preparation of clinical trials with novel radiotherapy approaches. We designed and produced a partial upper arm phantom from tissue-equivalent materials for use in experimental high-dose-rate radiotherapy. The phantom was compared to original patient data using density values and Hounsfield units obtained from CT scans. Dose simulations were conducted for broad-beam irradiation and microbeam radiotherapy (MRT) and compared to values measured in a synchrotron radiation experiment. Finally, we validated the phantom in a pilot experiment with human primary melanoma cells.
Retention and Recruitment of Oncology Pharmacists
Publisher: Wiley
Date: 06-2007
DOI: 10.1002/J.2055-2335.2007.TB00031.X
Abstract: A noticeable turnover of staff through the specialty of oncology pharmacy has been observed nationally. Literature searches failed to identify research directly relating to oncology pharmacist retention. Studies in pharmacists and non‐pharmacist oncology staff have determined that, while patient care and contact, personal accomplishment and satisfaction are important, stress levels and lack of professional support were factors considered when leaving the profession. To explore why pharmacists choose to remain in or leave the specialty of oncology pharmacy and identify strategies to ensure retention of current staff and aid recruitment of new oncology pharmacists. Electronic surveys designed to obtain retrospective quantitative and qualitative data were sent to: current oncology pharmacists former oncology pharmacists and directors of pharmacy at institutions with oncology services. Participants were identified through databases of the Society of Hospital Pharmacists of Australia, Clinical Oncological Society of Australia, and International Society of Oncology Pharmacy Practice. Reasons for pharmacists remaining in oncology generally related to job satisfaction issues (closely associated with clinical involvement). Reasons for leaving included stress levels, staffing issues, lack of recognition from hospital management and remuneration. Strategies for retaining staff should include improved pay structure, opportunities for professional development and continuing education, peer support, availability of suitably trained staff to cover periods of leave, positive feedback and support from hospital management, and devising methods for reducing work‐related stress. Implementation of information gained from this study will facilitate recruitment and retention of experienced, well‐trained oncology staff.
Spatial resolution of a small cubic LYSO scintillator crystal detector with depth-of-interaction capabilities in a small animal PET scanner
Publisher: IEEE
Date: 2007
Dual detector system for measuring out-of-field neutron dose in proton therapy
Publisher: IEEE
Date: 10-2009
Inelastic design of low-axially loaded high-strength reinforced concrete columns
Publisher: Elsevier BV
Date: 07-2003
Radiosensitisation enhancement effect of BrUdR and Ta2 O5 NSPs in combination with 5-Fluorouracil antimetabolite in kilovoltage and megavoltage radiation
Publisher: IOP Publishing
Date: 17-04-2018
A comparative analysis of multichannel Data Acquisition Systems for quality assurance in external beam radiation therapy
Publisher: IOP Publishing
Date: 05-06-2014
In vivo dosimetry and seed localization in prostate brachytherapy with permanent implants
Publisher: IEEE
Date: 2003
Absorbed dose-to-water protocol applied to synchrotron-generated x-rays at very high dose rates
Publisher: IOP Publishing
Date: 07-2016
Engineering of bismuth oxide nanoparticles to induce differential biochemical activity in malignant and nonmalignant cells
Publisher: Wiley
Date: 09-04-2014
Introduction to Mini-Micro-Nano Dosimetry (MMND) 2016
Publisher: IOP Publishing
Date: 2017
BrachyView, a novel in-body imaging system for HDR prostate brachytherapy: Experimental evaluation
Publisher: Wiley
Date: 19-11-2015
DOI: 10.1118/1.4935866
Abstract: This paper presents initial experimental results from a prototype of high dose rate (HDR) BrachyView, a novel in-body source tracking system for HDR brachytherapy based on a multipinhole tungsten collimator and a high resolution pixellated silicon detector array. The probe and its associated position estimation algorithms are validated and a comprehensive evaluation of the accuracy of its position estimation capabilities is presented. The HDR brachytherapy source is moved through a sequence of positions in a prostate phantom, for various displacements in x, y, and z. For each position, multiple image acquisitions are performed, and source positions are reconstructed. Error estimates in each dimension are calculated at each source position and combined to calculate overall positioning errors. Gafchromic film is used to validate the accuracy of source placement within the phantom. More than 90% of evaluated source positions were estimated with an error of less than one millimeter, with the worst-case error being 1.3 mm. Experimental results were in close agreement with previously published Monte Carlo simulation results. The prototype of HDR BrachyView demonstrates a satisfactory level of accuracy in its source position estimation, and additional improvements are achievable with further refinement of HDR BrachyView's image processing algorithms.
Nanostructures, concentrations and energies: An ideal equation to extend therapeutic efficiency on radioresistant 9L tumor cells using Ta2 O5 ceramic nanostructured particles
Publisher: IOP Publishing
Date: 31-01-2017
Measuring the excitations in a new S = 1/2 quantum spin chain material with competing interactions
Publisher: IOP Publishing
Date: 03-05-2018
Thin silicon strip detectors for beam monitoring in Micro-beam Radiation Therapy
Publisher: arXiv
Date: 2015
SOI thin microdosimeter detectors for low-energy ions and radiation damage studies
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2019
IBIC microscopy – The powerful tool for testing micron – Sized sensitive volumes in segmented radiation detectors used in synchrotron microbeam radiation and hadron therapies
Publisher: Elsevier BV
Date: 11-2019
A game-theoretic approach to advertisement dissemination in ephemeral networks
Publisher: Springer Science and Business Media LLC
Date: 24-03-2017
Silicon strip detector for quality assurance in synchrotron microbeam radiation therapy
Publisher: Elsevier BV
Date: 12-2014
Design and simulation of continuous scintillator with pixellated photodetector
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 08-2001
DOI: 10.1109/23.958369
Synchrotron X-ray microbeam dosimetry with a 20 micrometre resolution scintillator fibre-optic dosimeter
Publisher: International Union of Crystallography (IUCr)
Date: 24-04-2018
DOI: 10.1107/S1600577518003016
Abstract: Cancer is one of the leading causes of death worldwide. External beam radiation therapy is one of the most important modalities for the treatment of cancers. Synchrotron microbeam radiation therapy (MRT) is a novel pre-clinical therapy that uses highly spatially fractionated X-ray beams to target tumours, allowing doses much higher than conventional radiotherapies to be delivered. A dosimeter with a high spatial resolution is required to provide the appropriate quality assurance for MRT. This work presents a plastic scintillator fibre optic dosimeter with a one-dimensional spatial resolution of 20 µm, an improvement on the dosimeter with a resolution of 50 µm that was demonstrated in previous work. The ability of this probe to resolve microbeams of width 50 µm has been demonstrated. The major limitations of this method were identified, most notably the low-light signal resulting from the small sensitive volume, which made valley dose measurements very challenging. A titanium-based reflective paint was used as a coating on the probe to improve the light collection, but a possible effect of the high- Z material on the probes water-equivalence has been identified. The effect of the reflective paint was a 28.5 ± 4.6% increase in the total light collected it did not affect the shape of the depth-dose profile, nor did it explain an over-response observed when used to probe at low depths, when compared with an ionization chamber. With improvements to the data acquisition, this probe design has the potential to provide a water-equivalent, inexpensive dosimetry tool for MRT.
Cerium oxide nanoparticles: Influence of the high-Z component revealed on radioresistant 9L cell survival under X-ray irradiation
Publisher: Elsevier BV
Date: 10-2013
DOI: 10.1016/J.NANO.2013.02.008
Abstract: This article pioneers a study into the influence of the high-Z component of nanoparticles on the efficacy of radioprotection some nanoparticles offer to exposed cells irradiated with X-rays. We reveal a significant decrease in the radioprotection efficacy for cells exposed to CeO2 nanoparticles and irradiated with 10 MV and 150 kVp X-rays. In addition, analysis of the 150 kVp survival curve data indicates a change in radiation quality, becoming more lethal for irradiated cells exposed to CeO2 nanoparticles. We attribute the change in efficacy to an increase in high linear energy transfer Auger electron production at 150 kVp which counterbalances the CeO2 nanoparticle radioprotection capability and locally changes the radiation quality. This study highlights an interesting phenomenon that must be considered if radiation protection drugs for use in radiotherapy are developed based on CeO2 nanoparticles. CeO2 nanoparticles are thought to offer radioprotection however, this study reveals significant decrease in the radioprotection efficacy for cells exposed to CeO2 nanoparticles and irradiated with 10 MV and 150 kVp X-rays. This phenomenon must be considered when developing radiation protection drugs based on CeO2 nanoparticles.
A convenient verification method of the entrance photo-neutron dose for an 18 MV medical linac using silicon p-i-n diodes
Publisher: Elsevier BV
Date: 11-2017
Monte Carlo Studies for Microbeam Radiation Therapy
Publisher: CRC Press
Date: 20-10-2021
OC-0272: Magic phantom - a quality assurance system for high dose rate brachytherapy
Publisher: Elsevier BV
Date: 04-2015
2D mapping of the MV photon fluence and 3D dose reconstruction in real time for quality assurance during radiotherapy treatment
Publisher: IOP Publishing
Date: 17-09-2015
High-Z nanostructured ceramics in radiotherapy: First evidence of Ta 2 O5 -induced dose enhancement on radioresistant cancer cells in an MV photon field
Publisher: Wiley
Date: 16-10-2014
Characterization of a novel diamond-based microdosimeter prototype for radioprotection applications in space environments
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2012
Clinical application of MOSkin dosimeters to rectal wall in vivo doismetry in gynecological and prostate HDR brachytherapy
Publisher: Elsevier BV
Date: 09-2016
Bridging Global and Local Models of Service-Oriented Systems
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 05-2008
Validation of a Monte Carlo simulation for Microbeam Radiation Therapy on the Imaging and Medical Beamline at the Australian Synchrotron
Publisher: Springer Science and Business Media LLC
Date: 27-11-2019
DOI: 10.1038/S41598-019-53991-9
Abstract: Microbeam Radiation Therapy (MRT) is an emerging cancer treatment modality characterised by the use of high-intensity synchrotron-generated x-rays, spatially fractionated by a multi-slit collimator (MSC), to ablate target tumours. The implementation of an accurate treatment planning system, coupled with simulation tools that allow for independent verification of calculated dose distributions are required to ensure optimal treatment outcomes via reliable dose delivery. In this article we present data from the first Geant4 Monte Carlo radiation transport model of the Imaging and Medical Beamline at the Australian Synchrotron. We have developed the model for use as an independent verification tool for experiments in one of three MRT delivery rooms and therefore compare simulation results with equivalent experimental data. The normalised x-ray spectra produced by the Geant4 model and a previously validated analytical model, SPEC, showed very good agreement using wiggler magnetic field strengths of 2 and 3 T. However, the validity of absolute photon flux at the plane of the Phase Space File (PSF) for a fixed number of simulated electrons was unable to be established. This work shows a possible limitation of the G 4 SynchrotronRadiation process to model synchrotron radiation when using a variable magnetic field. To account for this limitation, experimentally derived normalisation factors for each wiggler field strength determined under reference conditions were implemented. Experimentally measured broadbeam and microbeam dose distributions within a Gammex RMI457 Solid Water ® phantom were compared to simulated distributions generated by the Geant4 model. Simulated and measured broadbeam dose distributions agreed within 3% for all investigated configurations and measured depths. Agreement between the simulated and measured microbeam dose distributions agreed within 5% for all investigated configurations and measured depths.
Incorporating clinical imaging into the delivery of microbeam radiation therapy
Publisher: MDPI AG
Date: 30-09-2021
DOI: 10.3390/APP11199101
Abstract: Synchrotron microbeam radiation therapy is a promising pre-clinical radiation treatment modality however, it comes with many technical challenges. This study describes the image guidance protocol used for Australia’s first long-term pre-clinical MRT treatment of rats bearing 9L gliosarcoma tumours. The protocol utilises existing infrastructure available at the Australian Synchrotron and the adjoining Monash Biomedical Imaging facility. The protocol is designed and optimised to treat small animals utilising high-resolution clinical CT for patient specific tumour identification, coupled with conventional radiography, using the recently developed SyncMRT program for image guidance. Dosimetry performed in small animal phantoms shows patient dose is comparable to standard clinical doses, with a CT associated dose of less than 1.39cGy and a planar radiograh dose of less than 0.03cGy. Experimental validation of alignment accuracy with radiographic film demonstrates end to end accuracy of less than ±0.34mm in anatomical phantoms. Histological analysis of tumour-bearing rats treated with microbeam radiation therapy verifies that tumours are targeted well within applied treatment margins. To date, this technique has been used to treat 35 tumour-bearing rats.
Thulium Oxide Nanoparticles: A new candidate for image-guided radiotherapy
Publisher: IOP Publishing
Date: 14-06-2018
X-Tream dosimetry of highly brilliant X-ray microbeams in the MRT hutch of the Australian Synchrotron
Publisher: Elsevier BV
Date: 2016
BrachyView: A Real-time In-body HDR Source Tracking System with Simultaneous TRUS Image Fusion
Publisher: Elsevier BV
Date: 04-2019
Three-dimensional dosimetry imaging of I-125 plaque for eye cancer treatment
Publisher: Elsevier BV
Date: 05-2011
Impact of a monolithic silicon detector operating in transmission mode on clinical photon beams
Publisher: Elsevier BV
Date: 11-2017
DOI: 10.1016/J.EJMP.2017.10.017
Abstract: To investigate the effect on surface dose, as a function of different field sizes and distances from the solid water phantom to transmission detector (D The influence of operating the MP512T in transmission mode on the surface dose of a phantom for SSD 100cm was evaluated by using a Markus IC. The MP512T was fixed to an adjustable stand holder and was positioned at different D For all D The study demonstrated that positioning the MP512T in air between the Linac head and the phantom produced negligible perturbation of the surface dose for D
Multichannel Data Acquisition System comparison for Quality Assurance in external beam radiation therapy
Publisher: Elsevier BV
Date: 12-2014
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