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0000-0002-9289-7956
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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)
Atomic, Molecular, Nuclear, Particle and Plasma Physics | Nuclear And Particle Physics | Medical Physics | Instruments And Techniques | Medical physics | Particle physics | Other Physical Sciences | Medical Devices | Space instrumentation | Biomedical Engineering | Medical Physics | Particle and high energy physics | Atomic and Molecular Physics |
ANZSRC Socio-Economic Objective (SEO)
Medical instrumentation | Occupational health (excl. economic development aspects) | Scientific instrumentation | Expanding Knowledge in the Physical Sciences | Medical Instruments | Scientific Instruments | Cancer and Related Disorders |
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Publications
Effect of a magnetic field on the track structure of low-energy electrons: A Monte Carlo study
Publisher: Springer Science and Business Media LLC
Date: 26-05-2010
Recent progress of GEANT4 electromagnetic physics for LHC and other applications
Publisher: IOP Publishing
Date: 10-2017
Fabrication and First Characterization of Silicon-Based Full 3-D Microdosimeters
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2020
First application of a high-resolution silicon detector for proton beam Bragg peak detection in a 0.95 T magnetic field
Publisher: Wiley
Date: 04-11-2020
DOI: 10.1002/MP.13871
Abstract: To report on experimental results of a high spatial resolution silicon-based detector exposed to therapeutic quality proton beams in a 0.95 T transverse magnetic field. These experimental results are important for the development of accurate and novel dosimetry methods in future potential real-time MRI-guided proton therapy systems. A permanent magnet device was utilized to generate a 0.95 T magnetic field over a 4 × 20 × 15 cm The nominal Bragg peak for each proton energy was successfully observed with a 0.2 mm spatial resolution in the 0.95 T transverse magnetic field in both a depth and lateral profiles. The proton beam deflection (at 0.95 T) was a consistent 2 ±0.5 mm at the center of the magnetic volume for each beam energy. However, a pristine Bragg peak was not observed for each energy. This was caused by the detector packaging having small air gaps between layers of the phantom material surrounding the diode array. These air gaps act to degrade the shape of the Bragg peak, and further to this, the nonwater equivalent silicon chip acts to separate the Bragg peak into multiple peaks depending on the proton path taken. Overall, a promising performance of the silicon detector array was observed, however, with a qualitative assessment rather than a robust quantitative dosimetric evaluation at this stage of development. For the first time, a high-resolution silicon-based radiation detector has been used to measure proton beam Bragg peak deflections in a phantom due to a strong magnetic field. Future efforts are required to optimize the detector packaging to strengthen the robustness of the dosimetric quantities obtained from the detector. Such high-resolution silicon diode arrays may be useful in future efforts in MRI-guided proton therapy research.
SOI microdosimetry and modified MKM for evaluation of relative biological effectiveness for a passive proton therapy radiation field
Publisher: IOP Publishing
Date: 23-11-2018
Abstract: With more patients receiving external beam radiation therapy with protons, it becomes increasingly important to refine the clinical understanding of the relative biological effectiveness (RBE) for dose delivered during treatment. Treatment planning systems used in clinics typically implement a constant RBE of 1.1 for proton fields irrespective of their highly heterogeneous linear energy transfer (LET). Quality assurance tools that can measure beam characteristics and quantify or be indicative of biological outcomes become necessary in the transition towards more sophisticated RBE weighted treatment planning and for verification of the Monte Carlo and analytical based models they use. In this study the RBE for the CHO-K1 cell line in a passively delivered clinical proton spread out Bragg peak (SOBP) is determined both in vitro and using a silicon-on-insulator (SOI) microdosimetry method paired with the modified microdosimetric kinetic model. The RBE along the central axis of a SOBP with 2 Gy delivered at the middle of the treatment field was found to vary between 1.11-1.98 and the RBE for 10% cell survival between 1.07-1.58 with a 250 kVp x-ray reference radiation and between 1.19-2.34 and 0.95-1.41, respectively, for a Co60 reference. Good agreement was found between RBE values calculated from the SOI-microdosimetry-MKM approach and in vitro. A strong correlation between proton lineal energy and RBE was observed particularly in the distal end and falloff of the SOBP.
Comparative analysis of the secondary electron yield from carbon nanoparticles and pure water medium Topical Issue: COST Action Nano-IBCT: Nano-scale Processes behind Ion-Beam Cancer Therapy Andrey Solov'yovNigel Mason, Gustavo García and Eugene Surdutovich
Publisher: Springer Science and Business Media LLC
Date: 04-2015
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.
Progress in Geant4 Electromagnetic Physics Modelling and Validation
Publisher: IOP Publishing
Date: 23-12-2015
Microdosimetry of a therapeutic proton beam with a mini-TEPC and a MicroPlus-Bridge detector for RBE assessment
Publisher: IOP Publishing
Date: 09-12-2020
Abstract: Proton beams are widely used worldwide to treat localized tumours, the lower entrance dose and no exit dose, thus sparing surrounding normal tissues, being the main advantage of this treatment modality compared to conventional photon techniques. Clinical proton beam therapy treatment planning is based on the use of a general relative biological effectiveness (RBE) of 1.1 along the whole beam penetration depth, without taking into account the documented increase in RBE at the end of the depth dose profile, in the Bragg peak and beyond. However, an inaccurate estimation of the RBE can cause both underdose or overdose, in particular it can cause the unfavourable situation of underdosing the tumour and overdosing the normal tissue just beyond the tumour, which limits the treatment success and increases the risk of complications. In view of a more precise dose delivery that takes into account the variation of RBE, experimental microdosimetry offers valuable tools for the quality assurance of LET or RBE-based treatment planning systems. The purpose of this work is to compare the response of two different microdosimetry systems: the mini-TEPC and the MicroPlus-Bridge detector. Microdosimetric spectra were measured across the 62 MeV spread out Bragg peak of CATANA with the mini-TEPC and with the Bridge microdosimeter. The frequency and dose distributions of lineal energy were compared and the different contributions to the spectra were analysed, discussing the effects of different site sizes and chord length distributions. The shape of the lineal energy distributions measured with the two detectors are markedly different, due to the different water-equivalent sizes of the sensitive volumes: 0.85 μm for the TEPC and 17.3 μm for the silicon detector. When the Loncol’s biological weighting function is applied to calculate the microdosimetric assessment of the RBE, both detectors lead to results that are consistent with biological survival data for glioma U87 cells. Both the mini-TEPC and the MicroPlus-Bridge detector can be used to assess the RBE variation of a 62 MeV modulated proton beam along its penetration depth. The microdosimetric assessment of the RBE based on the Loncol’s weighting function is in good agreement with radiobiological results when the 10% biological uncertainty is taken into account.
Review of the Geant4-DNA Simulation Toolkit for Radiobiological Applications at the Cellular and DNA Level
Publisher: MDPI AG
Date: 22-12-2021
Abstract: The Geant4-DNA low energy extension of the Geant4 Monte Carlo (MC) toolkit is a continuously evolving MC simulation code permitting mechanistic studies of cellular radiobiological effects. Geant4-DNA considers the physical, chemical, and biological stages of the action of ionizing radiation (in the form of x- and γ-ray photons, electrons and β±-rays, hadrons, α-particles, and a set of heavier ions) in living cells towards a variety of applications ranging from predicting radiotherapy outcomes to radiation protection both on earth and in space. In this work, we provide a brief, yet concise, overview of the progress that has been achieved so far concerning the different physical, physicochemical, chemical, and biological models implemented into Geant4-DNA, highlighting the latest developments. Specifically, the “dnadamage1” and “molecularDNA” applications which enable, for the first time within an open-source platform, quantitative predictions of early DNA damage in terms of single-strand-breaks (SSBs), double-strand-breaks (DSBs), and more complex clustered lesions for different DNA structures ranging from the nucleotide level to the entire genome. These developments are critically presented and discussed along with key benchmarking results. The Geant4-DNA toolkit, through its different set of models and functionalities, offers unique capabilities for elucidating the problem of radiation quality or the relative biological effectiveness (RBE) of different ionizing radiations which underlines nearly the whole spectrum of radiotherapeutic modalities, from external high-energy hadron beams to internal low-energy gamma and beta emitters that are used in brachytherapy sources and radiopharmaceuticals, respectively.
Neutron shielding for a new projected proton therapy facility: A Geant4 simulation study
Publisher: Elsevier BV
Date: 12-2016
DOI: 10.1016/J.EJMP.2016.12.003
Abstract: In this work, we used the Monte Carlo-based Geant4 simulation toolkit to calculate the ambient dose equivalents due to the secondary neutron field produced in a new projected proton therapy facility. In particular the facility geometry was modeled in Geant4 based on the CAD design. Proton beams were originated with an energy of 250MeV in the gantry rooms with different angles with respect to the patient a fixed 250MeV proton beam was also modeled. The ambient dose equivalent was calculated in several locations of interest inside and outside the facility, for different scenarios. The simulation results were compared qualitatively to previous work on an existing facility bearing some similarities with the design under study, showing that the ambient dose equivalent ranges obtained are reasonable. The ambient dose equivalents, calculated by means of the Geant4 simulation, were compared to the Australian regulatory limits and showed that the new facility will not pose health risks for the public or staff, with a maximum equivalent dose rate equal to 7.9mSv/y in the control rooms and maze exit areas and 1.3·10
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
High spatial resolution microdosimetry with Δe-E detector on C-12 beam: Monte Carlo simulations
Publisher: IEEE
Date: 10-2013
Design and development of PETiPIX: An ultra high spatial resolution small animal PET scanner
Publisher: IEEE
Date: 10-2013
Experimental investigation of the characteristics of radioactive beams for heavy ion therapy
Publisher: Wiley
Date: 11-05-2020
DOI: 10.1002/MP.14177
Abstract: This work has two related objectives. The first is to estimate the relative biological effectiveness of two radioactive heavy ion beams based on experimental measurements, and compare these to the relative biological effectiveness of corresponding stable isotopes to determine whether they are therapeutically equivalent. The second aim is to quantitatively compare the quality of images acquired postirradiation using an in‐beam whole‐body positron emission tomography scanner for range verification quality assurance. The energy deposited by monoenergetic beams of C at 350 MeV/u, O at 250 MeV/u, C at 350 MeV/u, and O at 430 MeV/u was measured using a cruciform transmission ionization chamber in a water phantom at the Heavy Ion Medical Accelerator in Chiba (HIMAC), Japan. Dose‐mean lineal energy was measured at various depths along the path of each beam in a water phantom using a silicon‐on‐insulator mushroom microdosimeter. Using the modified microdosimetric kinetic model, the relative biological effectiveness at 10% survival fraction of the radioactive ion beams was evaluated and compared to that of the corresponding stable ions along the path of the beam. Finally, the postirradiation distributions of positron annihilations resulting from the decay of positron‐emitting nuclei were measured for each beam in a gelatin phantom using the in‐beam whole‐body positron emission tomography scanner at HIMAC. The depth of maximum positron‐annihilation density was compared with the depth of maximum dose deposition and the signal‐to‐background ratios were calculated and compared for images acquired over 5 and 20 min postirradiation of the phantom. In the entrance region, the was 1.2 ± 0.1 for both C and C beams, while for O and O it was 1.4 ± 0.1 and 1.3 ± 0.1, respectively. At the Bragg peak, the was 2.7 ± 0.4 for C and 2.9 ± 0.4 for C, while for O and O it was 2.7 ± 0.4 and 2.8 ± 0.4, respectively. In the tail region, could only be evaluated for carbon the was 1.6 ± 0.2 and 1.5 ± 0.1 for C and C, respectively. Positron emission tomography images obtained from gelatin targets irradiated by radioactive ion beams exhibit markedly improved signal‐to‐background ratios compared to those obtained from targets irradiated by nonradioactive ion beams, with 5‐fold and 11‐fold increases in the ratios calculated for the O and C images compared with the values obtained for O and C, respectively. The difference between the depth of maximum dose and the depth of maximum positron annihilation density is 2.4 ± 0.8 mm for C, compared to −5.6 ± 0.8 mm for C and 0.9 ± 0.8 mm for O vs −6.6 ± 0.8 mm for O. The values for C and O were found to be within the 95% confidence interval of the RBEs estimated for their corresponding stable isotopes across each of the regions in which it was evaluated. Furthermore, for a given dose, C and O beams produce much better quality images for range verification compared with C and O, in particular with regard to estimating the location of the Bragg peak.
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.
Evaluation of organ doses following high dose rate (HDR) brachytherapy of breast cancer: A Geant4 Monte Carlo simulation study
Publisher: IOP Publishing
Date: 06-2019
DOI: 10.1088/1742-6596/1248/1/012048
Abstract: This study aimed to evaluate the absorbed doses received by the organs at risk (OARs) following Iridium-192 ( 192 Ir) high dose rate (HDR) brachytherapy of the left breast. The MIRD5 adult female anthropomorphic phantom, readily available in the Geant4 Monte Carlo package was used. However, the left breast was modified from 195 to 145 cm 3 , to represent a breast following lumpectomy. Left breast was chosen due to its higher cancer occurrence than the right breast. The HDR sources were constructed with an outer cylindrical dimension of 4.5 mm (length) × 0.9 mm (diameter). Various influencing parameters were studied, i.e. catheter arrangement (single versus dual plane), source inter-dwell distances (5 versus 10 mm), and different radionuclides, i.e. Cobalt-60 ( 60 Co) and 192 Ir, by delivering a total treatment dose of 32 Gy to the left breast. Absorbed doses to the OARs (e.g. left lung, heart, right breast, spleen, etc.) were then evaluated. A maximum left lung dose of 1.5 Gy was recorded, while doses to the other OARs were all below 1 Gy. The treatment using dual plane catheter arrangement contributed to a slightly higher dose to the OARs, despite equal dose to the breast. There was no dose difference between different inter-dwell distances used in this study. 60 Co resulted in a slightly higher left lung dose than that of 192 Ir, while the results were the opposite for the other OARs. HDR brachytherapy allows high dose to be delivered to the breast within a short period of time, with minimal absorbed doses to the OARs.
Modelling of protons spectra encountered in space using medical accelerator and its microdosimetric characterization
Publisher: Elsevier BV
Date: 04-2021
Evaluation of organ doses following prostate treatment with permanent brachytherapy seeds: A Geant4 Monte Carlo simulation study
Publisher: IOP Publishing
Date: 06-2019
DOI: 10.1088/1742-6596/1248/1/012049
Abstract: This study aimed to evaluate the absorbed doses received by the organs at risk (OARs) following prostate treatment with permanent Iodine-125 ( 125 I) brachytherapy seeds. In order to simulate an enlarged abnormal prostate due to malignancy, the MIRD5 adult male anthropomorphic phantom (readily available in the Geant4 Monte Carlo package) was modified by increasing the prostate volume to 35 cm 3 . The permanent seeds were constructed with an outer cylindrical dimension of 4.5 mm (length) × 0.8 mm (diameter). The effects of various activity per seed (0.5, 0.6 and 0.8 mCi), number of seeds (62, 78, 94 and 110 seeds) and radionuclides, i.e. Palladium-103 ( 103 Pd), 125 I and Cesium-131 ( 131 Cs), towards the absorbed dose to the OARs (i.e. rectum, urinary bladder and both testicles) were investigated. In this study, prostate dose of up to 237 Gy was simulated, which resulted in 11 Gy dose to rectum, 7 Gy to urinary bladder and 4 Gy to each testicle. The doses were considered as reasonable, given the low dose rate nature of the treatment, allowing tissue repair for the OARs. Optimal seeds arrangement was found to consist of 78 or fewer seeds, as it resulted in the lowest dose to the OARs. For similar prostate dose, 103 Pd resulted in the lowest dose to the OARs, followed by 125 I and 131 Cs. Permanent seed brachytherapy allows high dose to be delivered to the prostate, while ensuring minimal dose to the OARs.
Geant4-DNA simulation of human cancer cells irradiation with helium ion beams
Publisher: Elsevier BV
Date: 08-2023
Evaluation of the influence of physical and chemical parameters on water radiolysis simulations under MeV electron irradiation using Geant4-DNA
Publisher: AIP Publishing
Date: 20-09-2019
DOI: 10.1063/1.5107511
Abstract: This paper presents the influence of electron elastic scattering models, electron thermalization models, and chemical parameters on Geant4-DNA simulations of liquid water radiolysis under mega-electron-volt electron irradiation. The radiochemical yields are simulated using a new Geant4-DNA ex le. In particular, the influence of the new elastic scattering model recently developed is presented as well as the influence of improved electron thermalization models. The influence of a new chemistry constructor using parameters of another Monte Carlo track structure code is also described. The results calculated using these different models are compared with each other and with experimental data. For sub-mega-electron-volt electron simulations, the combination of the “G4EmDNAPhysics_option2” physics constructor with the recently developed elastic scattering model, the Meesungnoen electron thermalization model, and the “G4EmDNAChemistry_option1” chemistry constructor is recommended.
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 correction in silicon microdosimetry for protons characteristic of the LEO space environment
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2008
Simulation of DNA damage using Geant4‐DNA: an overview of the “molecularDNA” example application
Publisher: Wiley
Date: 13-02-2023
DOI: 10.1002/PRO6.1186
Abstract: The scientific community shows great interest in the study of DNA damage induction, DNA damage repair, and the biological effects on cells and cellular systems after exposure to ionizing radiation. Several in silico methods have been proposed so far to study these mechanisms using Monte Carlo simulations. This study outlines a Geant4‐DNA ex le application, named “molecularDNA”, publicly released in the 11.1 version of Geant4 (December 2022). It was developed for novice Geant4 users and requires only a basic understanding of scripting languages to get started. The ex le includes two different DNA‐scale geometries of biological targets, namely “cylinders” and “human cell”. This public version is based on a previous prototype and includes new features, such as: the adoption of a new approach for the modeling of the chemical stage, the use of the standard DNA damage format to describe radiation‐induced DNA damage, and upgraded computational tools to estimate DNA damage response. Simulation data in terms of single‐strand break and double‐strand break yields were produced using each of the available geometries. The results were compared with the literature, to validate the ex le, producing less than 5% difference in all cases. Conclusion: “molecularDNA” is a prototype tool that can be applied in a wide variety of radiobiology studies, providing the scientific community with an open‐access base for DNA damage quantification calculations. New DNA and cell geometries for the “molecularDNA” ex le will be included in future versions of Geant4‐DNA.
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.
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
The evolution in the stellar mass of brightest cluster galaxies over the past 10 billion years
Publisher: Oxford University Press (OUP)
Date: 19-05-2016
Improved integrated nucleus-nucleus inelastic cross sections for light nuclides in Geant4
Publisher: Elsevier BV
Date: 2020
Charge Collection in SOI Microdosimeters and Their Radiation Hardness
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2023
Deriving spatially resolved beta dose rates in sediment using the Timepix pixelated detector
Publisher: Elsevier BV
Date: 11-2017
Development of a Geant4 application to characterise a prototype neutron detector based on three orthogonal 3He tubes inside an HDPE sphere
Publisher: Elsevier BV
Date: 2017
DOI: 10.1016/J.EJMP.2016.12.016
Abstract: The Bonner Sphere Spectrometer (BSS) system is a well-established technique for neutron dosimetry that involves detection of thermal neutrons within a range of hydrogenous moderators. BSS detectors are often used to perform neutron field surveys in order to determine the ambient dose equivalent H*(10) and estimate health risk to personnel. There is a potential limitation of existing neutron survey techniques, since some detectors do not consider the direction of the neutron field, which can result in overly conservative estimates of dose in neutron fields. This paper shows the development of a Geant4 simulation application to characterise a prototype neutron detector based on three orthogonal
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.
Comparison of nanodosimetric parameters of track structure calculated by the Monte Carlo codes Geant4-DNA and PTra
Publisher: IOP Publishing
Date: 14-02-2012
DOI: 10.1088/0031-9155/57/5/1231
Abstract: The concept of nanodosimetry is based on the assumption that initial damage to cells is related to the number of ionizations (the ionization cluster size) directly produced by single particles within, or in the close vicinity of, short segments of DNA. The ionization cluster-size distribution and other nanodosimetric quantities, however, are not directly measurable in biological targets and our current knowledge is mostly based on numerical simulations of particle tracks in water, calculating track structure parameters for nanometric target volumes. The assessment of nanodosimetric quantities derived from particle-track calculations using different Monte Carlo codes plays, therefore, an important role for a more accurate evaluation of the initial damage to cells and, as a consequence, of the biological effectiveness of ionizing radiation. The aim of this work is to assess the differences in the calculated nanodosimetric quantities obtained with Geant4-DNA as compared to those of the ad hoc particle-track Monte Carlo code 'PTra' developed at Physikalisch-Technische Bundesanstalt (PTB), Germany. The comparison of the two codes was made for incident electrons of energy in the range between 50 eV and 10 keV, for protons of energy between 300 keV and 10 MeV, and for alpha particles of energy between 1 and 10 MeV as these were the energy ranges available in both codes at the time this investigation was carried out. Good agreement was found for nanodosimetric characteristics of track structure calculated in the high-energy range of each particle type. For lower energies, significant differences were observed, most notably in the estimates of the biological effectiveness. The largest relative differences obtained were over 50% however, generally the order of magnitude was between 10% and 20%.
New silicon microdosimetry probes for RBE and biological dose studies using stationary and movable targets in 12C ion therapy
Publisher: IOP Publishing
Date: 2017
Charge collection in n-SOI planar microdosimeters
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2013
In-silico calculations of DNA damage induced by α-particles in the 224Ra DaRT decay chain for a better understanding of the radiobiological effectiveness of this treatment
Publisher: Elsevier BV
Date: 08-2023
Characterization of prompt gamma-ray emission with respect to the Bragg peak for proton beam range verification: A Monte Carlo study
Publisher: Elsevier BV
Date: 2017
DOI: 10.1016/J.EJMP.2016.12.011
Abstract: In this paper we report a Geant4 simulation study to investigate the characteristic prompt gamma (PG) emission in a water phantom for real-time monitoring of the Bragg peak (BP) during proton beam irradiation. The PG production, emission spatial correlation with the BP, and position preference for detection with respect to the BP have been quantified in different PG energy windows as a function of proton pencil-beam energy from 100 to 200MeV. The PG response to small BP shifts was evaluated using a 2cm-thick slab with different human body materials embedded in a water phantom. Our results show that the prominent characteristic PG emissions of 4.44, 5.21 and 6.13MeV exhibit distinctive correlation with the dose deposition curve. The accuracy in BP position identification using these characteristic PG rays is highly consistent as the beam energy increases from 100 to 200MeV. There exists a position preference for PG detection with respect to the BP position, which has a strong dependence on the proton beam energy and PG energies. It was also observed that a submillimeter shift of the BP position can be realized by using PG signals. These results indicate that the characteristic PG signal is sensitive and reliable for BP tracking. Although the maximization of the PG measurement associated with the BP is difficult, it can be optimized with energy and detection position preferences.
Monte Carlo calculation of the maximum therapeutic gain of tumor antivascular alpha therapy
Publisher: Wiley
Date: 17-02-2012
DOI: 10.1118/1.3681010
Abstract: Metastatic melanoma lesions experienced marked regression after systemic targeted alpha therapy in a phase 1 clinical trial. This unexpected response was ascribed to tumor antivascular alpha therapy (TAVAT), in which effective tumor regression is achieved by killing endothelial cells (ECs) in tumor capillaries and, thus, depriving cancer cells of nutrition and oxygen. The purpose of this paper is to quantitatively analyze the therapeutic efficacy and safety of TAVAT by building up the testing Monte Carlo microdosimetric models. Geant4 was adapted to simulate the spatial nonuniform distribution of the alpha emitter (213)Bi. The intraluminal model was designed to simulate the background dose to normal tissue capillary ECs from the nontargeted activity in the blood. The perivascular model calculates the EC dose from the activity bound to the perivascular cancer cells. The key parameters are the probability of an alpha particle traversing an EC nucleus, the energy deposition, the lineal energy transfer, and the specific energy. These results were then applied to interpret the clinical trial. Cell survival rate and therapeutic gain were determined. The specific energy for an alpha particle hitting an EC nucleus in the intraluminal and perivascular models is 0.35 and 0.37 Gy, respectively. As the average probability of traversal in these models is 2.7% and 1.1%, the mean specific energy per decay drops to 1.0 cGy and 0.4 cGy, which demonstrates that the source distribution has a significant impact on the dose. Using the melanoma clinical trial activity of 25 mCi, the dose to tumor EC nucleus is found to be 3.2 Gy and to a normal capillary EC nucleus to be 1.8 cGy. These data give a maximum therapeutic gain of about 180 and validate the TAVAT concept. TAVAT can deliver a cytotoxic dose to tumor capillaries without being toxic to normal tissue capillaries.
Monte Carlo characterisation of the Dose Magnifying Glass for proton therapy quality assurance
Publisher: IOP Publishing
Date: 2017
Monte Carlo study of the energy response and depth dose water equivalence of the MOSkin radiation dosimeter at clinical kilovoltage photon energies
Publisher: Springer Science and Business Media LLC
Date: 11-05-2011
DOI: 10.1007/S13246-011-0075-3
Abstract: Skin dose is often the quantity of interest for radiological protection, as the skin is the organ that receives maximum dose during kilovoltage X-ray irradiations. The purpose of this study was to simulate the energy response and the depth dose water equivalence of the MOSkin radiation detector (Centre for Medical Radiation Physics (CMRP), University of Wollongong, Australia), a MOSFET-based radiation sensor with a novel packaging design, at clinical kilovoltage photon energies typically used for superficial/orthovoltage therapy and X-ray CT imaging. Monte Carlo simulations by means of the Geant4 toolkit were employed to investigate the energy response of the CMRP MOSkin dosimeter on the surface of the phantom, and at various depths ranging from 0 to 6 cm in a 30 × 30 × 20 cm water phantom. By varying the thickness of the tissue-equivalent packaging, and by adding thin metallic foils to the existing design, the dose enhancement effect of the MOSkin dosimeter at low photon energies was successfully quantified. For a 5 mm diameter photon source, it was found that the MOSkin was water equivalent to within 3% at shallow depths less than 15 mm. It is recommended that for depths larger than 15 mm, the appropriate depth dose water equivalent correction factors be applied to the MOSkin at the relevant depths if this detector is to be used for depth dose assessments. This study has shown that the Geant4 Monte Carlo toolkit is useful for characterising the surface energy response and depth dose behaviour of the MOSkin.
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.
Report on G4-Med, a Geant4 benchmarking system for medical physics applications developed by the Geant4 Medical Simulation Benchmarking Group
Publisher: Wiley
Date: 12-12-2021
DOI: 10.1002/MP.14226
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.
Systematic investigation on the validity of partition model dosimetry for 90Y radioembolization using Monte Carlo simulation
Publisher: IOP Publishing
Date: 22-08-2017
Abstract: We aimed to investigate the validity of the partition model (PM) in estimating the absorbed doses to liver tumour ([Formula: see text]), normal liver tissue ([Formula: see text]) and lungs ([Formula: see text]), when cross-fire irradiations between these compartments are being considered. MIRD-5 phantom incorporated with various treatment parameters, i.e. tumour involvement (TI), tumour-to-normal liver uptake ratio (T/N) and lung shunting (LS), were simulated using the Geant4 Monte Carlo (MC) toolkit. 10
Microdosimetry for Targeted Alpha Therapy of Cancer
Publisher: Hindawi Limited
Date: 2012
DOI: 10.1155/2012/153212
Abstract: Targeted alpha therapy (TAT) has the advantage of delivering therapeutic doses to in idual cancer cells while reducing the dose to normal tissues. TAT applications relate to hematologic malignancies and now extend to solid tumors. Results from several clinical trials have shown efficacy with limited toxicity. However, the dosimetry for the labeled alpha particle is challenging because of the heterogeneous antigen expression among cancer cells and the nature of short-range, high-LET alpha radiation. This paper demonstrates that it is inappropriate to investigate the therapeutic efficacy of TAT by macrodosimetry. The objective of this work is to review the microdosimetry of TAT as a function of the cell geometry, source-target configuration, cell sensitivity, and biological factors. A detailed knowledge of each of these parameters is required for accurate microdosimetric calculations.
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
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
In-field and out-of-file application in 12C ion therapy using fully 3D silicon microdosimeters
Publisher: Elsevier BV
Date: 08-2018
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
Fully integrated Monte Carlo simulation for evaluating radiation induced DNA damage and subsequent repair using Geant4-DNA
Publisher: Springer Science and Business Media LLC
Date: 27-11-2020
DOI: 10.1038/S41598-020-75982-X
Abstract: Ionising radiation induced DNA damage and subsequent biological responses to it depend on the radiation’s track-structure and its energy loss distribution pattern. To investigate the underlying biological mechanisms involved in such complex system, there is need of predicting biological response by integrated Monte Carlo (MC) simulations across physics, chemistry and biology. Hence, in this work, we have developed an application using the open source Geant4-DNA toolkit to propose a realistic “fully integrated” MC simulation to calculate both early DNA damage and subsequent biological responses with time. We had previously developed an application allowing simulations of radiation induced early DNA damage on a naked cell nucleus model. In the new version presented in this work, we have developed three additional important features: (1) modeling of a realistic cell geometry, (2) inclusion of a biological repair model, (3) refinement of DNA damage parameters for direct damage and indirect damage scoring. The simulation results are validated with experimental data in terms of Single Strand Break (SSB) yields for plasmid and Double Strand Break (DSB) yields for plasmid/human cell. In addition, the yields of indirect DSBs are compatible with the experimental scavengeable damage fraction. The simulation application also demonstrates agreement with experimental data of $$\\gamma$$ γ -H2AX yields for gamma ray irradiation. Using this application, it is now possible to predict biological response along time through track-structure MC simulations.
Optimisation of the design of SOI microdosimeters for hadron therapy quality assurance
Publisher: IOP Publishing
Date: 24-10-2018
Abstract: Silicon-on-insulator (SOI) microdosimeters offer a promising method for routine quality assurance (QA) for hadron therapy due to their ease of operation and high spatial resolution. However, one complication which has been shown previously is that the traditional use of the mean chord length, [Formula: see text], calculated using Cauchy's formula, for SOI devices in clinical carbon ion fields is not appropriate due to the strong directionality of the radiation field. In a previous study, we demonstrated that the mean path length, [Formula: see text], which is the mean path of charged particles in the sensitive volume (SV), is a more appropriate method to obtain microdosimetric quantities and biological relevant values, namely the relative biological effectiveness (RBE) by means of the microdosimetric kinetic model. The previous work, which was limited to mono-energetic [Formula: see text] ion beams typical of heavy ion therapy (HIT), is extended here to investigate the [Formula: see text] in a pristine proton beam as well as for spread out Bragg peaks (SOBP) for both proton and carbon ion clinical beams. In addition, the angular dependence of the SOI device for a number of different SV designs is also investigated to quantify the effects which the alignment has on the [Formula: see text]. It is demonstrated that the [Formula: see text] can be accurately estimated along the depth of a pristine or SOBP using the energy deposition spectra for both proton and [Formula: see text] ion beams. This observation allows a quick and accurate estimation of the [Formula: see text] for experimental use.
Comparative study of alternative Geant4 hadronic ion inelastic physics models for prediction of positron-emitting radionuclide production in carbon and oxygen ion therapy
Publisher: IOP Publishing
Date: 07-08-2019
Abstract: The distribution of fragmentation products predicted by Monte Carlo simulations of heavy ion therapy depend on the hadronic physics model chosen in the simulation. This work aims to evaluate three alternative hadronic inelastic fragmentation physics options available in the Geant4 Monte Carlo radiation physics simulation framework to determine which model most accurately predicts the production of positron-emitting fragmentation products observable using in-beam PET imaging. Fragment distributions obtained with the BIC, QMD, and INCL + + physics models in Geant4 version 10.2.p03 are compared to experimental data obtained at the HIMAC heavy-ion treatment facility at NIRS in Chiba, Japan. For both simulations and experiments, monoenergetic beams are applied to three different block phantoms composed of gelatin, poly(methyl methacrylate) and polyethylene. The yields of the positron-emitting nuclei
Development of a more accurate Geant4 quantum molecular dynamics model for hadron therapy
Publisher: IOP Publishing
Date: 04-11-2022
Abstract: Objective . Although in heavy-ion therapy, the quantum molecular dynamics (QMD) model is one of the most fundamental physics models providing an accurate daughter-ion production yield in the final state, there are still non-negligible differences with the experimental results. The aim of this study is to improve fragment production in water phantoms by developing a more accurate QMD model in Geant4. Approach . A QMD model was developed by implementing modern Skyrme interaction parameter sets, as well as by incorporating with an ad hoc α -cluster model in the initial nuclear state. Two adjusting parameters were selected that can significantly affect the fragment productions in the QMD model: the radius to discriminate a cluster to which nucleons belong after the nucleus–nucleus reaction, denoted by R , and the squared standard deviation of the Gaussian packet, denoted by L . Squared Mahalanobis’s distance of fragment yields and angular distributions with 1, 2, and the higher atomic number for the produced fragments were employed as objective functions, and multi-objective optimization (MOO), which make it possible to compare quantitatively the simulated production yields with the reference experimental data, was performed. Main results . The MOO analysis showed that the QMD model with modern Skyrme parameters coupled with the proposed α -cluster model, denoted as SkM * α , can drastically improve light fragments yields in water. In addition, the proposed model reproduced the kinetic energy distribution of the fragments accurately. The optimized L in SkM * α was confirmed to be realistic by the charge radii analysis in the ground state formation. Significance . The proposed framework using MOO was demonstrated to be very useful in judging the superiority of the proposed nuclear model. The optimized QMD model is expected to improve the accuracy of heavy-ion therapy dosimetry.
Radiation Shielding Evaluation of Spacecraft Walls Against Heavy Ions Using Microdosimetry
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 05-2021
Influence of track structure and condensed history physics models of Geant4 to nanoscale electron transport in liquid water
Publisher: Elsevier BV
Date: 02-2019
DOI: 10.1016/J.EJMP.2019.01.001
Abstract: The Geant4 toolkit offers a range of electromagnetic (EM) models for simulating the transport of charged particles down to sub-keV energies. They can be ided to condensed-history (CH) models (like the Livermore and Penelope models) and the track-structure (TS) models included in the Geant4-DNA low-energy extension of Geant4. Although TS models are considered the state-of-the-art for nanoscale electron transport, they are difficult to develop, computationally intensive, and commonly tailored to a single medium (e.g., water) which prohibits their use in a wide range of applications. Thus, the use of CH models down to sub-keV energies is particularly intriguing in the context of general-purpose Monte Carlo codes. The aim of the present work is to compare the performance of the CH models of Geant4 against the recently implemented TS models of Geant4-DNA for nanoscale electron transport. Calculations are presented for two fundamental quantities, the dose-point-kernel and the microdosimetric lineal energy. The influence of user-defined simulation parameters (tracking and production cuts, and maximum step size) on the above calculations is also examined. It is shown that Livermore offers the best performance among the CH models of Geant4 for nanoscale electron transport. However, even under optimally-chosen simulation parameters, the differences between the CH and TS models examined may be sizeable for low energy electrons (<1 keV) and/or nanometer size targets (<100 nm).
Development of a new Geant4-DNA electron elastic scattering model for liquid-phase water using the ELSEPA code
Publisher: AIP Publishing
Date: 13-12-2018
DOI: 10.1063/1.5047751
Abstract: This paper presents the calculation of new elastic scattering cross sections for the simulation of electron interactions in liquid water. The calculations are based on the “ELastic Scattering of Electrons and Positrons by neutral Atoms” code, which adopts a Dirac partial wave analysis. A Muffin-tin potential was used in order to account for the liquid-phase of water, and the optical parameters of the correlation-polarization and the inelastic absorption potentials were optimized against vapour-phase water data. The differential and total elastic scattering cross sections calculated in the present work show a global agreement with the experimental data. The impact of these elastic scattering cross sections on the transport of electrons in liquid water was evaluated by track-structure simulations of range, dose-point-kernel, microdosimetric spectra, and ionization clustering using the Geant4-DNA simulation toolkit. The results are compared against those obtained with the elastic scattering models already available in Geant4-DNA and are discussed.
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
Tissue equivalence of diamond for heavy charged particles
Publisher: Elsevier BV
Date: 03-2019
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
Evaluation of early radiation DNA damage in a fractal cell nucleus model using Geant4-DNA
Publisher: Elsevier BV
Date: 06-2019
DOI: 10.1016/J.EJMP.2019.04.010
Abstract: The advancement of multidisciplinary research fields dealing with ionising radiation induced biological damage - radiobiology, radiation physics, radiation protection and, in particular, medical physics - requires a clear mechanistic understanding of how cellular damage is induced by ionising radiation. Monte Carlo (MC) simulations provide a promising approach for the mechanistic simulation of radiation transport and radiation chemistry, towards the in silico simulation of early biological damage. We have recently developed a fully integrated MC simulation that calculates early single strand breaks (SSBs) and double strand breaks (DSBs) in a fractal chromatin based human cell nucleus model. The results of this simulation are almost equivalent to past MC simulations when considering direct/indirect strand break fraction, DSB yields and fragment distribution. The simulation results agree with experimental data on DSB yields within 13.6% on average and fragment distributions agree within an average of 34.8%.
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
A silicon strip detector array for energy verification and quality assurance in heavy ion therapy:
Publisher: Wiley
Date: 06-07-0016
DOI: 10.1002/MP.12736
Abstract: The measurement of depth dose profiles for range and energy verification of heavy ion beams is an important aspect of quality assurance procedures for heavy ion therapy facilities. The steep dose gradients in the Bragg peak region of these profiles require the use of detectors with high spatial resolution. The aim of this work is to characterize a one dimensional monolithic silicon detector array called the "serial Dose Magnifying Glass" (sDMG) as an independent ion beam energy and range verification system used for quality assurance conducted for ion beams used in heavy ion therapy. The sDMG detector consists of two linear arrays of 128 silicon sensitive volumes each with an effective size of 2mm × 50μm × 100μm fabricated on a p-type substrate at a pitch of 200 μm along a single axis of detection. The detector was characterized for beam energy and range verification by measuring the response of the detector when irradiated with a 290 MeV/u The relative response profiles along the single axis measured with the sDMG detector were found to have good agreement between experiment and simulation with the position of the Bragg peak determined to fall within 0.2 mm or 1.1% of the range in the detector for the two cases. The energy of the beam incident on the detector was found to vary less than 1% between experiment and simulation. The beam energy incident on the phantom was determined to be (280.9 ± 0.8) MeV/u from the experimental and (280.9 ± 0.2) MeV/u from the simulated profiles. These values coincide with the expected energy of 281 MeV/u. The sDMG detector response was studied experimentally and characterized using a Monte Carlo simulation. The sDMG detector was found to accurately determine the
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.
Investigation of optimized prompt gamma detection strategy for real-time Bragg Peak tracking in proton radiation therapy
Publisher: IEEE
Date: 10-2016
A feasibility study of PETiPIX: An ultra high resolution small animal PET scanner
Publisher: IOP Publishing
Date: 06-12-2013
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
Characterization of the mixed radiation field produced by carbon and oxygen ion beams of therapeutic energy: A Monte Carlo simulation study
Publisher: Medknow
Date: 2019
Monte Carlo investigation of the characteristics of radioactive beams for heavy ion therapy
Publisher: Springer Science and Business Media LLC
Date: 25-04-1970
DOI: 10.1038/S41598-019-43073-1
Abstract: This work presents a simulation study evaluating relative biological effectiveness at 10% survival fraction (RBE10) of several different positron-emitting radionuclides in heavy ion treatment systems, and comparing these to the RBE10s of their non-radioactive counterparts. RBE10 is evaluated as a function of depth for three positron-emitting radioactive ion beams ( 10 C, 11 C and 15 O) and two stable ion beams ( 12 C and 16 O) using the modified microdosimetric kinetic model (MKM) in a heterogeneous skull phantom subject to a rectangular 50 mm × 50 mm × 60 mm spread out Bragg peak. We demonstrate that the RBE10 of the positron-emitting radioactive beams is almost identical to the corresponding stable isotopes. The potential improvement in PET quality assurance image quality which is obtained when using radioactive beams is evaluated by comparing the signal to background ratios of positron annihilations at different intra- and post-irradiation time points. Finally, the incidental dose to the patient resulting from the use of radioactive beams is also quantified and shown to be negligible.
An inception network for positron emission tomography based dose estimation in carbon ion therapy.
Publisher: IOP Publishing
Date: 23-09-2202
Abstract: Objective . We aim to evaluate a method for estimating 1D physical dose deposition profiles in carbon ion therapy via analysis of dynamic PET images using a deep residual learning convolutional neural network (CNN). The method is validated using Monte Carlo simulations of 12 C ion spread-out Bragg peak (SOBP) profiles, and demonstrated with an experimental PET image. Approach . A set of dose deposition and positron annihilation profiles for monoenergetic 12 C ion pencil beams in PMMA are first generated using Monte Carlo simulations. From these, a set of random polyenergetic dose and positron annihilation profiles are synthesised and used to train the CNN. Performance is evaluated by generating a second set of simulated 12 C ion SOBP profiles (one 116 mm SOBP profile and ten 60 mm SOBP profiles), and using the trained neural network to estimate the dose profile deposited by each beam and the position of the distal edge of the SOBP. Next, the same methods are used to evaluate the network using an experimental PET image, obtained after irradiating a PMMA phantom with a 12 C ion beam at QST’s Heavy Ion Medical Accelerator in Chiba facility in Chiba, Japan. The performance of the CNN is compared to that of a recently published iterative technique using the same simulated and experimental 12 C SOBP profiles. Main results . The CNN estimated the simulated dose profiles with a mean relative error (MRE) of 0.7% ± 1.0% and the distal edge position with an accuracy of 0.1 mm ± 0.2 mm, and estimate the dose delivered by the experimental 12 C ion beam with a MRE of 3.7%, and the distal edge with an accuracy of 1.7 mm. Significance . The CNN was able to produce estimates of the dose distribution with comparable or improved accuracy and computational efficiency compared to the iterative method and other similar PET-based direct dose quantification techniques.
Characterization of prompt gamma ray emission for in vivo range verification in particle therapy: A simulation study
Publisher: Elsevier BV
Date: 06-2019
DOI: 10.1016/J.EJMP.2019.04.023
Abstract: In this paper we investigate the emission and detection characteristics of prompt gamma (PG) rays for in vivo range verification during hadron therapy, using Geant4 simulations. Proton,
A comparison of X-ray and proton beam low energy secondary electron track structures using the low energy models of Geant4
Publisher: Informa UK Limited
Date: 31-10-2012
DOI: 10.3109/09553002.2011.627975
Abstract: Lethal cell damage by ionising radiation is generally initiated by the formation of complex strand breaks, resulting from ionisation clusters in the DNA molecule. A better understanding of the effect of the distribution of ionisation clusters within the cell and particularly in regard to DNA segments could be beneficial to radiation therapy treatment planning. Low energy X-rays generate an abundance of low energy electrons similar to that associated with MeV protons. The study and comparison of the track structure of photon and proton beams could permit the substitution of photon microbeams for single cell ion irradiations at proton facilities used to predict the relative biological effectiveness (RBE) of charged particle fields. The track structure of X-ray photons is compared with proton pencil beams in voxels of approximate DNA strand size (2 × 2 × 5 nm). The Very Low Energy extension models of the Monte Carlo simulation toolkit GEometry ANd Tracking 4 (Geant4) is used. Simulations were performed in a water phantom for an X-ray and proton beam of energies 100 keV and 20 MeV, respectively. The track structure of the photon and proton beams are evaluated using the ionisation cluster size distribution as well as the radial dose deposition of the beam. A comparative analysis of the ionisation cluster distribution and radial dose deposition obtained is presented, which suggest that low energy X-rays could produce similar ionisation cluster distributions to MeV protons on the DNA scale of size at depths greater than ∼10 μm and at distances greater than ∼1 μm from the beam centre. Here the ionisation cluster size for each beam is less than ∼100. The radial dose deposition is also approximately equal at large depths and at distances greater than 10 μm from the beam centre.
High spatial resolution microdosimetry with monolithic ΔE-E detector on 12C beam: Monte Carlo simulations and experiment
Publisher: Elsevier BV
Date: 04-2018
Monte Carlo validation and optimisation of detector packaging for spectroscopic dosimetry for in vivo urethral dosimetry during low dose rate brachytherapy
Publisher: Springer Science and Business Media LLC
Date: 04-08-2015
DOI: 10.1007/S13246-015-0366-1
Abstract: The urethral mini-dosimeter, developed by the Centre for Medical Radiation Physics, University of Wollongong, uses spectroscopic dosimetry to provide real time point dose measurements along the urethra during low dose rate prostate brachytherapy. Spectroscopic dosimetry uses the measured spectrum of the treatment isotope to estimate the dose rate at the point of measurement, however, the silicon mini-detectors employed in the urethral mini-dosimeter require water proof encapsulation which must be capable of providing electromagnetic shielding without greatly increasing the size of the probe. The introduction of non-tissue equivalent materials within the encapsulation can change the spectrum of radiation incident on the detector, which may influence the application of spectroscopic dosimetry within the urethral dosimeter. The Monte Carlo code Geant4 was adopted to study the effect of encapsulation on the operation of the urethral mini-dosimeter, as well as to determine whether an appropriate thickness of aluminium shielding was possible for electromagnetic screening. The depth dose response and angular dependence of the urethral mini-dosimeter with three thicknesses of aluminium shielding (20, 50, 100 µm) was compared with the urethral mini-dosimeter without aluminium shielding. The aluminium shielding had the effect of increasing the depth dose response (up to 3% within 30 mm and up to 5% within 50 mm), slightly reduced the azimuth angular dependence and slightly increased the polar angular dependence. The 100 µm thick shielding provided the least azimuth angular dependence (±2 %) and provided a polar angular dependence of ±1.4 % within the angles of -45° to 45°.
3D sensitive volume microdosimeter with improved tissue equivalency: Charge collection study and its application in 12C ion therapy
Publisher: IOP Publishing
Date: 2019
Modelling of the Silicon-On-Insulator microdosimeter response within the International Space Station for astronauts’ radiation protection
Publisher: Elsevier BV
Date: 09-2019
Radiation damage on sub-cellular scales: beyond DNA.
Publisher: IOP Publishing
Date: 05-02-2013
DOI: 10.1088/0031-9155/58/5/1251
Abstract: This study investigates a model cell as a target for low-dose radiation using Monte Carlo simulations. Mono-energetic electrons and photons are used with initial energies between 10 and 50 keV, relevant to out-of-field radiotherapy scenarios where modern treatment modalities expose relatively large amounts of healthy tissue to low-dose radiation, and also to microbeam cell irradiation studies which show the importance of the cytoplasm as a radiation target. The relative proportions of number of ionizations and total energy deposit in the nucleus and cytoplasm are calculated. We show that for a macroscopic dose of no more than 1 Gy only a few hundred ionizations occur in the nucleus volume whereas the number of ionizations in the cytoplasm is over a magnitude larger. We find that the cell geometry can have an appreciable effect on the energy deposit in the cell and can cause a nonlinear increase in energy deposit with cytoplasm density. We also show that changing the nucleus volume has negligible effect on the total energy deposit but alters the relative proportion deposited in the nucleus and cytoplasm the nucleus volume must increase to approximately the same volume as the cytoplasm before the energy deposit in the nucleus matches that in the cytoplasm. Additionally we find that energy deposited by electrons is generally insensitive to spatial variations in chemical composition, which can be attributed to negligible differences in electron stopping power for cytoplasm and nucleus materials. On the other hand, we find that chemical composition can affect energy deposited by photons due to non-negligible differences in attenuation coefficients. These results are of relevance in considering radiation effects in healthy cells, which tend to have smaller nuclei. Our results further show that the cytoplasm and organelles residing therein can be important targets for low-dose radiation damage in healthy cells and warrant investigation as much as the conventional focus of a high-dose radiation DNA target in tumour cells.
Geant4 simulation model of electromagnetic processes in oriented crystals for accelerator physics
Publisher: Springer Science and Business Media LLC
Date: 29-06-2023
Software platform for simulation of a prototype proton CT scanner
Publisher: Wiley
Date: 03-2017
DOI: 10.1002/MP.12107
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
Assessment of cross-dose contributions from tumors within computational phantoms using a Geant4 radiation dosimetry tool exploiting hybrid analytical/voxelised geometries
Publisher: Wiley
Date: 08-06-2023
DOI: 10.1002/MP.16544
Abstract: Dosimetry software tools developed for Radiopharmaceutical Therapy, such as OLINDA/EXM or IDAC‐Dose, account only for radiation dose to organs from radiopharmaceutical taken up in other organs. The aim of this study is to present a methodology, that can be applied to any voxelised computational model, able to account for cross‐dose to organs from tumors of any shape and number enclosed within an organ. A Geant4 application using hybrid analytical/voxelised geometries has been developed as an extension to the ICRP110_HumanPhantom Geant4 advanced ex le and validated against ICRP publication 133. In this new Geant4 application, tumors are defined using the Geant4 Parallel Geometry functionality, which allows the co‐existence of two independent geometries in the same Monte Carlo simulation. The methodology was validated by estimating total dose to healthy tissue from 90 Y and from 177 Lu distributed within tumors of various sizes localized within the liver of the ICRP110 adult male phantom. Agreement of the Geant4 application with ICRP133 was within 5% when masses were adjusted for blood content. Total dose to healthy liver and to tumors was found to agree within 1% when compared to the ground truth. The methodology presented in this work can be extended to investigate total dose to healthy tissue from systemic uptake of radiopharmaceuticals in tumors of different sizes using any voxelised computational dosimetric model.
Prediction of DNA rejoining kinetics and cell survival after proton irradiation for V79 cells using Geant4-DNA
Publisher: Elsevier BV
Date: 2023
Neutron dosimeter development based on Medipix2
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2010
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%.
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.
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
Characterization of angular detection dependence of prompt gamma-rays with respect to the Bragg peak in a water phantom using proton beam irradiations
Publisher: IEEE
Date: 10-2017
Corrigendum: The impact of sensitive volume thickness for silicon on insulator microdosimeters in hadron therapy (2020 Phys. Med. Biol. 65 035004)
Publisher: IOP Publishing
Date: 25-02-2021
Characterization of a novel large area microdosimeter system for low dose rate radiation environments
Publisher: Elsevier BV
Date: 06-2021
Characterization of an alternative diamond based microdosimeter prototype
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2014
On the Instantaneous Dose Rate and Angular Dependence of Monolithic Silicon Array Detectors
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2019
Muon event localisation with AI
Publisher: Elsevier BV
Date: 06-2021
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
Validation of the Geant4 PIXE component for incident carbon ions
Publisher: Elsevier BV
Date: 12-2022
Tissue equivalency of phantom materials for neutron dosimetry in proton therapy
Publisher: Wiley
Date: 05-11-2009
DOI: 10.1118/1.3250857
Abstract: Previous Monte Carlo and experimental studies involving secondary neutrons in proton therapy have employed a number of phantom materials that are designed to represent human tissue. In this study, the authors determined the suitability of common phantom materials for dosimetry of secondary neutrons, specifically for pediatric and intracranial proton therapy treatments. This was achieved through comparison of the absorbed dose and dose equivalent from neutrons generated within the phantom materials and various ICRP tissues. The phantom materials chosen for comparison were Lucite, liquid water, solid water, and A150 tissue equivalent plastic, These phantom materials were compared to brain, muscle, and adipose tissues. The magnitude of the doses observed were smaller than those reported in previous experimental and Monte Carlo studies, which incorporated neutrons generated in the treatment head. The results show that for both neutron absorbed dose and dose equivalent, no single phantom material gives agreement with tissue within 5% at all the points considered. Solid water gave the smallest mean variation with the tissues out of field where neutrons are the primary contributor to the total dose. Of the phantom materials considered, solid water shows best agreement with tissues out of field.
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.
A Geant4-DNA Evaluation of Radiation-Induced DNA Damage on a Human Fibroblast
Publisher: MDPI AG
Date: 30-09-2021
Abstract: Accurately modeling the radiobiological mechanisms responsible for the induction of DNA damage remains a major scientific challenge, particularly for understanding the effects of low doses of ionizing radiation on living beings, such as the induction of carcinogenesis. A computational approach based on the Monte Carlo technique to simulate track structures in a biological medium is currently the most reliable method for calculating the early effects induced by ionizing radiation on DNA, the primary cellular target of such effects. The Geant4-DNA Monte Carlo toolkit can simulate not only the physical, but also the physico-chemical and chemical stages of water radiolysis. These stages can be combined with simplified geometric models of biological targets, such as DNA, to assess direct and indirect early DNA damage. In this study, DNA damage induced in a human fibroblast cell was evaluated using Geant4-DNA as a function of incident particle type (gammas, protons, and alphas) and energy. The resulting double-strand break yields as a function of linear energy transfer closely reproduced recent experimental data. Other quantities, such as fragment length distribution, scavengeable damage fraction, and time evolution of damage within an analytical repair model also supported the plausibility of predicting DNA damage using Geant4-DNA.The complete simulation chain application “molecularDNA”, an ex le for users of Geant4-DNA, will soon be distributed through Geant4.
Contributions of secondary fragmentation by carbon ion beams in water phantom: Monte Carlo simulation
Publisher: IOP Publishing
Date: 05-2017
Opportunistic dose amplification for proton and carbon ion therapy via capture of internally generated thermal neutrons
Publisher: Springer Science and Business Media LLC
Date: 02-11-2018
DOI: 10.1038/S41598-018-34643-W
Abstract: This paper presents Neutron Capture Enhanced Particle Therapy (NCEPT), a method for enhancing the radiation dose delivered to a tumour relative to surrounding healthy tissues during proton and carbon ion therapy by capturing thermal neutrons produced inside the treatment volume during irradiation. NCEPT utilises extant and in-development boron-10 and gadolinium-157-based drugs from the related field of neutron capture therapy. Using Monte Carlo simulations, we demonstrate that a typical proton or carbon ion therapy treatment plan generates an approximately uniform thermal neutron field within the target volume, centred around the beam path. The tissue concentrations of neutron capture agents required to obtain an arbitrary 10% increase in biological effective dose are estimated for realistic treatment plans, and compared to concentrations previously reported in the literature. We conclude that the proposed method is theoretically feasible, and can provide a worthwhile improvement in the dose delivered to the tumour relative to healthy tissue with readily achievable concentrations of neutron capture enhancement drugs.
Latest Geant4 developments for PIXE applications
Publisher: Elsevier BV
Date: 12-2018
Effect of a static magnetic field on nanodosimetric quantities in a DNA volume
Publisher: Informa UK Limited
Date: 12-0010
DOI: 10.3109/09553002.2011.641436
Abstract: With the advent of magnetic resonance imaging (MRI)-guided radiation therapy it is becoming increasingly important to consider the potential influence of a magnetic field on ionising radiation. This paper aims to study the effect of a magnetic field on the track structure of radiation to determine if the biological effectiveness may be altered. Using the Geant4-DNA (GEometry ANd Tracking 4) Monte Carlo simulation toolkit, nanodosimetric track structure parameters were calculated for electrons, protons and alpha particles moving in transverse magnetic fields up to 10 Tesla. Applying the model proposed by Garty et al., the track structure parameters were used to derive the probability of producing a double-strand break (DSB). For simulated primary particles of electrons (200 eV-10 keV), protons (300 keV-30 MeV) and alpha particles (1-9 MeV) the application of a magnetic field was shown to have no significant effect (within statistical uncertainty limits) on the parameters characterizing radiation track structure or the probability of producing a DSB. The null result found here implies that if the presence of a magnetic field were to induce a change in the biological effectiveness of radiation, the effect would likely not be due to a change in the track structure of the radiation.
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
Modelling the Biological Beamline at HIMAC using Geant4
Publisher: IOP Publishing
Date: 2019
Today's monolithic silicon array detector for small field dosimetry: The Octa
Publisher: IOP Publishing
Date: 2019
Dose quantification in carbon ion therapy using in-beam positron emission tomography.
Publisher: IOP Publishing
Date: 12-2020
Abstract: This work presents an iterative method for the estimation of the absolute dose distribution in patients undergoing carbon ion therapy, via analysis of the distribution of positron annihilations resulting from the decay of positron-emitting fragments created in the target volume. The proposed method relies on the decomposition of the total positron-annihilation distributions into profiles of the three principal positron-emitting fragment species -
Evolution of Diamond based Microdosimetry
Publisher: IOP Publishing
Date: 2019
Review of Geant4-DNA applications for micro and nanoscale simulations
Publisher: Elsevier BV
Date: 10-2016
DOI: 10.1016/J.EJMP.2016.09.007
Abstract: Emerging radiotherapy treatments including targeted particle therapy, hadron therapy or radiosensitisation of cells by high-Z nanoparticles demand the theoretical determination of radiation track structure at the nanoscale. This is essential in order to evaluate radiation damage at the cellular and DNA level. Since 2007, Geant4 offers physics models to describe particle interactions in liquid water at the nanometre level through the Geant4-DNA Package. This package currently provides a complete set of models describing the event-by-event electromagnetic interactions of particles with liquid water, as well as developments for the modelling of water radiolysis. Since its release, Geant4-DNA has been adopted as an investigational tool in kV and MV external beam radiotherapy, hadron therapies using protons and heavy ions, targeted therapies and radiobiology studies. It has been benchmarked with respect to other track structure Monte Carlo codes and, where available, against reference experimental measurements. While Geant4-DNA physics models and radiolysis modelling functionalities have already been described in detail in the literature, this review paper summarises and discusses a selection of representative papers with the aim of providing an overview of a) geometrical descriptions of biological targets down to the DNA size, and b) the full spectrum of current micro- and nano-scale applications of Geant4-DNA.
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
Geant4‐DNA example applications for track structure simulations in liquid water: A report from the Geant4‐DNA Project
Publisher: Wiley
Date: 12-07-2018
DOI: 10.1002/MP.13048
Abstract: This Special Report presents a description of Geant4-DNA user applications dedicated to the simulation of track structures (TS) in liquid water and associated physical quantities (e.g., range, stopping power, mean free path…). These ex le applications are included in the Geant4 Monte Carlo toolkit and are available in open access. Each application is described and comparisons to recent international recommendations are shown (e.g., ICRU, MIRD), when available. The influence of physics models available in Geant4-DNA for the simulation of electron interactions in liquid water is discussed. Thanks to these applications, the authors show that the most recent sets of physics models available in Geant4-DNA (the so-called "option4" and "option 6" sets) enable more accurate simulation of stopping powers, dose point kernels, and W-values in liquid water, than the default set of models ("option 2") initially provided in Geant4-DNA. They also serve as reference applications for Geant4-DNA users interested in TS simulations.
A benchmarking study of Geant4 for Auger electrons emitted by medical radioisotopes
Publisher: Elsevier BV
Date: 08-2021
A validated Geant4 model of a whole-body PET scanner with four-layer DOI detectors.
Publisher: IOP Publishing
Date: 12-2020
Abstract: The purpose of this work is to develop a validated Geant4 simulation model of a whole-body prototype PET scanner constructed from the four-layer depth-of-interaction detectors developed at the National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, Japan. The simulation model emulates the behaviour of the unique depth of interaction sensing capability of the scanner without needing to directly simulate optical photon transport in the scintillator and photodetector modules. The model was validated by evaluating and comparing performance metrics from the NEMA NU 2-2012 protocol on both the simulated and physical scanner, including spatial resolution, sensitivity, scatter fraction, noise equivalent count rates and image quality. The results show that the average sensitivities of the scanner in the field-of-view were 5.9 cps kBq
Detection and discrimination of neutron capture events for NCEPT dose quantification
Publisher: Springer Science and Business Media LLC
Date: 07-04-2022
DOI: 10.1038/S41598-022-09676-X
Abstract: Neutron Capture Enhanced Particle Therapy (NCEPT) boosts the effectiveness of particle therapy by capturing thermal neutrons produced by beam-target nuclear interactions in and around the treatment site, using tumour-specific $$^{10}$$ 10 B or $$^{157}$$ 157 Gd-based neutron capture agents. Neutron captures release high-LET secondary particles together with gamma photons with energies of 478 keV or one of several energies up to 7.94 MeV, for $$^{10}$$ 10 B and $$^{157}$$ 157 Gd, respectively. A key requirement for NCEPT’s translation is the development of in vivo dosimetry techniques which can measure both the direct ion dose and the dose due to neutron capture. In this work, we report signatures which can be used to discriminate between photons resulting from neutron capture and those originating from other processes. A Geant4 Monte Carlo simulation study into timing and energy thresholds for discrimination of prompt gamma photons resulting from thermal neutron capture during NCEPT was conducted. Three simulated $$300\\times 300\\times 300$$ 300 × 300 × 300 mm $$^3$$ 3 cubic PMMA targets were irradiated by $$^4$$ 4 He or $$^{12}$$ 12 C ion beams with a spread out Bragg peak (SOBP) depth range of 60 mm one target is homogeneous while the others include $$10\\times 10\\times 10$$ 10 × 10 × 10 mm $$^3$$ 3 neutron capture inserts (NCIs) of pure $$^{10}$$ 10 B or $$^{157}$$ 157 Gd located at the distal edge of the SOBP. The arrival times of photons and neutrons entering a simulated $$50\\times 50\\times 50$$ 50 × 50 × 50 mm $$^3$$ 3 ideal detector were recorded. A temporal mask of 50–60 ns was found to be optimal for maximising the discrimination of the photons resulting from the neutron capture by boron and gadolinium. A range of candidate detector and thermal neutron shielding materials were simulated, and detections meeting the proposed acceptance criteria (i.e. falling within the target energy window and arriving 60 ns post beam-off) were classified as true or false positives, depending on their origin. The ratio of true/false positives ( $$R_{TF}$$ R TF ) was calculated for targets with $$^{10}$$ 10 B and $$^{157}$$ 157 Gd NCIs, the detector materials which resulted in the highest $$R_{TF}$$ R TF were cadmium-shielded CdTe and boron-shielded LSO, respectively. The optimal irradiation period for both carbon and helium ions was 1 µs for the $$^{10}$$ 10 B NCI and 1 ms for the $$^{157}$$ 157 Gd NCI.
Monte Carlo study of mosfet packaging, optimised for improved energy response: Single mosfet filtration
Publisher: Oxford University Press (OUP)
Date: 11-01-2021
DOI: 10.1093/RPD/NCQ144
Abstract: Monte Carlo simulations of the energy response of a conventionally packaged single metal-oxide field effect transistors (MOSFET) detector were performed with the goal of improving MOSFET energy dependence for personal accident or military dosimetry. The MOSFET detector packaging was optimised. Two different 'drop-in' design packages for a single MOSFET detector were modelled and optimised using the GEANT4 Monte Carlo toolkit. Absorbed photon dose simulations of the MOSFET dosemeter placed in free-air response, corresponding to the absorbed doses at depths of 0.07 mm (D(w)(0.07)) and 10 mm (D(w)(10)) in a water equivalent phantom of size 30 x 30 x 30 cm(3) for photon energies of 0.015-2 MeV were performed. Energy dependence was reduced to within + or - 60 % for photon energies 0.06-2 MeV for both D(w)(0.07) and D(w)(10). Variations in the response for photon energies of 15-60 keV were 200 and 330 % for D(w)(0.07) and D(w)(10), respectively. The obtained energy dependence was reduced compared with that for conventionally packaged MOSFET detectors, which usually exhibit a 500-700 % over-response when used in free-air geometry.
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
Characterisation of a well-type NaI(Tl) detector by means of a Monte Carlo simulation for radionuclide metrology application
Publisher: Elsevier BV
Date: 10-2021
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 Monte Carlo study on the feasibility of real-time in vivo source tracking during ultrasound based HDR prostate brachytherapy treatments
Publisher: Elsevier BV
Date: 03-2019
DOI: 10.1016/J.EJMP.2019.02.012
Abstract: This study aims to assess the accuracy of in-vivo source tracking during real-time trans-rectal ultrasound (TRUS) based high dose rate (HDR) prostate brachytherapy (pBT) through Monte Carlo simulations of multiple HDR pBT treatments with a two-dimensional (2D) diode array, the Magic Plate 900 (MP900), embedded below the patient in a carbon-fibre couch. Monte Carlo simulations of source positions representing three separate real-time TRUS based HDR pBT treatments were performed using the Geant4 toolkit. For each source position, an Ir-192 source was simulated inside a voxelized patient geometry. Dose deposited from each source position to the MP900 diodes was used to perform source tracking, and the MP900 calculated position compared to known source positions from the treatment plan. Thresholding techniques were implemented to improve source tracking accuracy with the TRUS probe present. The average three-dimensional source position reconstruction discrepancy was 11.9 ± 2.4 mm and 1.5 ± 0.3 mm with and without the TRUS probe, respectively. Thresholding techniques improved the source position reconstruction discrepancy in the presence of the TRUS probe to 1.8 ± 0.4 mm. Inclusion of the TRUS probe inside the patient negatively affects source tracking accuracy when using the MP900 diode array for HDR pBT verification. Modification of the source tracking algorithm using thresholding techniques improves source tracking in the presence of the TRUS probe, achieving similar accuracy as when the TRUS probe is not present. This study demonstrates that accurate in-vivo source tracking during real-time TRUS based HDR pBT is feasible using the Magic Plate system.
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
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.
Advances in Geant4 applications in medicine
Publisher: Elsevier BV
Date: 02-2020
A New Standard DNA Damage (SDD) Data Format
Publisher: Radiation Research Society
Date: 08-11-2018
DOI: 10.1667/RR15209.1
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.
Development of a high resolution voxelised head phantom for medical physics applications
Publisher: Elsevier BV
Date: 2017
Alpha particle and proton relative thermoluminescence efficiencies in LIF:MG,CU,PIS track structure theory up to the task?
Publisher: Oxford University Press (OUP)
Date: 31-10-2012
DOI: 10.1093/RPD/NCR406
Abstract: Low-energy alpha particle and proton heavy charged particle (HCP) relative thermoluminescence (TL) efficiencies are calculated for the major dosimetric glow peak in LiF:Mg,Cu,P (MCP-N) in the framework of track structure theory (TST). The calculations employ previously published TRIPOS-E Monte Carlo track segment values of the radial dose in condensed phase LiF calculated at the Instituto National de Investigaciones Nucleares (Mexico) and experimentally measured normalised (60)Co gamma-induced TL dose-response functions, f(D), carried out at the Institute of Nuclear Physics (Poland). The motivation for the calculations is to test the validity of TST in a TL system in which f(D) is not supralinear (f(D) >1) and is not significantly dependent on photon energy contrary to the behaviour of the dose-response of composite peak 5 in the glow curve of LiF:Mg,Ti (TLD-100). The calculated HCP relative efficiencies in LiF:MCP-N are 23-87% lower than the experimentally measured values, indicating a weakness in the major premise of TST which exclusively relates HCP effects to the radiation action of the secondary electrons liberated by the HCP slowing down. However, an analysis of the uncertainties involved in the TST calculations and experiments (i.e. experimental measurement of f(D) at high levels of dose, s le light self-absorption and accuracy in the estimation of D(r), especially towards the end of the HCP track) indicate that these may be too large to enable a definite conclusion. More accurate estimation of s le light self-absorption, improved measurements of f(D) and full-track Monte Carlo calculations of D(r) incorporating improvements of the low-energy electron transport are indicated in order to reduce uncertainties and enable a final conclusion.
Electron track structure simulations in a gold nanoparticle using Geant4-DNA
Publisher: Elsevier BV
Date: 07-2019
DOI: 10.1016/J.EJMP.2019.05.023
Abstract: Gold Nanoparticles (GNPs) have recently gained a lot of attention due to their potential benefit to improve the efficacy of X-ray radiotherapy. Owing to their high atomic number, GNPs are able to absorb higher quantities of incident radiation with respect to the surrounding tissue, producing, in particular, photoelectrons and low energy Auger electrons. These additional low energy electrons increase the local energy deposition in the region surrounding the GNP. Monte Carlo simulations play a key role in the investigation of GNP radio-enhancement and it is widely recognised that track structure physics models are the state-of-the-art for nano-scale studies. In 2016, we have developed track structure physics models for the Geant4-DNA toolkit allowing electron transport for microscopic bulk gold (Geant4_DNA_AU_2016) and we have recently improved them in the low energy domain (Geant4_DNA_AU_2018). In this paper, we report the benchmarking of these newly developed physics models when calculating the physical dose and the Dose Enhancement Factor (DEF) around a GNP. We demonstrate that Geant4_DNA_AU_2018 models give similar azimuthal distribution of two dimensional absorbed dose around a single GNP, but result in larger absorbed dose and DEF than Geant4_DNA_AU_2016 models. In parallel, we investigated the performance of a newly developed multiple scattering model in Geant4 based on the Goudsmit-Saunderson (GS) model, when used together with the electromagnetic physics models with the Geant4 Livermore condensed-history approach. Our results show that the GS model does not affect the results of the simulations when studying GNP radio-enhancement with a condensed-history approach.
Performance Evaluation for Repair of HSGc-C5 Carcinoma Cell Using Geant4-DNA
Publisher: MDPI AG
Date: 30-11-2021
Abstract: Track-structure Monte Carlo simulations are useful tools to evaluate initial DNA damage induced by irradiation. In the previous study, we have developed a Gean4-DNA-based application to estimate the cell surviving fraction of V79 cells after irradiation, bridging the gap between the initial DNA damage and the DNA rejoining kinetics by means of the two-lesion kinetics (TLK) model. However, since the DNA repair performance depends on cell line, the same model parameters cannot be used for different cell lines. Thus, we extended the Geant4-DNA application with a TLK model for the evaluation of DNA damage repair performance in HSGc-C5 carcinoma cells which are typically used for evaluating proton/carbon radiation treatment effects. For this evaluation, we also performed experimental measurements for cell surviving fractions and DNA rejoining kinetics of the HSGc-C5 cells irradiated by 70 MeV protons at the cyclotron facility at the National Institutes for Quantum and Radiological Science and Technology (QST). Concerning fast- and slow-DNA rejoining, the TLK model parameters were adequately optimized with the simulated initial DNA damage. The optimized DNA rejoining speeds were reasonably agreed with the experimental DNA rejoining speeds. Using the optimized TLK model, the Geant4-DNA simulation is now able to predict cell survival and DNA-rejoining kinetics for HSGc-C5 cells.
In silico nanodosimetry: New insights into nontargeted biological responses to radiation
Publisher: Hindawi Limited
Date: 2012
DOI: 10.1155/2012/147252
Abstract: The long-held view that radiation-induced biological damage must be initiated in the cell nucleus, either on or near DNA itself, is being confronted by mounting evidence to suggest otherwise. While the efficacy of cell death may be determined by radiation damage to nuclear DNA, a plethora of less deterministic biological responses has been observed when DNA is not targeted. These so-called nontargeted responses cannot be understood in the framework of DNA-centric radiobiological models what is needed are new physically motivated models that address the damage-sensing signalling pathways triggered by the production of reactive free radicals. To this end, we have conducted a series of in silico experiments aimed at elucidating the underlying physical processes responsible for nontargeted biological responses to radiation. Our simulation studies implement new results on very low-energy electromagnetic interactions in liquid water (applicable down to nanoscales) and we also consider a realistic simulation of extranuclear microbeam irradiation of a cell. Our results support the idea that organelles with important functional roles, such as mitochondria and lysosomes, as well as membranes, are viable targets for ionizations and excitations, and their chemical composition and density are critical to determining the free radical yield and ensuing biological responses.
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
The impact of sensitive volume thickness for silicon on insulator microdosimeters in hadron therapy
Publisher: IOP Publishing
Date: 24-01-2020
Abstract: Compact silicon on insulator (SOI) microdosimeters have been used to characterise the radiation field of many different hadron therapy beams. SOI devices are particularly attractive in hadron therapy fields due to their spatial resolution being well suited to the sharp dose gradients at the end of the primary beam's range. Due to the small size of SOI's sensitive volumes (SVs), which are usually ∼1-10 [Formula: see text]m thick, the fabrication of these devices can present challenges which are not as common for more conventional thickness silicon devices such as silicon spectroscopy detectors. Microdosimetry is the study of the energy deposition in micrometre sized volumes representing biological sites and is a powerful approach to estimate the biological effect of radiation on the micron-scale level, in a cell. However, cell sizes vary extensively translating in different energy deposition spectra. This work studies SV thicknesses between 1 and 100 [Formula: see text]m using Geant4 and examines the impact of SV dimensions on microdosimetric quantities. The quantities studied were the frequency mean lineal energy, [Formula: see text], and the dose mean lineal energy, [Formula: see text]. Additionally the relative biological effectiveness (RBE), estimated by the microdosimetric kinetic model (MKM), is also investigated. To study the impact of the SV thickness, SOI microdosimeters were irradiated with proton, [Formula: see text] and [Formula: see text] ion beams with ranges of ∼160 mm, with the microdosimeter being set at various positions along the Bragg curve. It was found that [Formula: see text] was influenced the least in proton beams and increased for heavier ion beams. Conversely, [Formula: see text] was impacted by the SV thickness the most in proton beams and [Formula: see text] was the least. Similar to [Formula: see text], protons were impacted the most by the SV thickness when estimating the RBE using the MKM. The cause of these differences was largely due to the different densities of the delta electron track structure for the case of [Formula: see text] and the energy transferred to the medium from the primary beam for [Formula: see text].
Microdosimetric applications in proton and heavy ion therapy using silicon microdosimeters
Publisher: Oxford University Press (OUP)
Date: 21-10-2018
DOI: 10.1093/RPD/NCX226
Abstract: Using the CMRP 'bridge' μ+ probe, microdosimetric measurements were undertaken out-of-field using a therapeutic scanning proton pencil beam and in-field using a 12C ion therapy field. These measurements were undertaken at Mayo Clinic, Rochester, USA and at HIMAC, Chiba, Japan, respectively. For a typical proton field used in the treatment of deep-seated tumors, we observed dose-equivalent values ranging from 0.62 to 0.99 mSv/Gy at locations downstream of the distal edge. Lateral measurements at depths close to the entrance and along the SOBP plateau were found to reach maximum values of 3.1 mSv/Gy and 5.3 mSv/Gy at 10 mm from the field edge, respectively, and decreased to ~0.04 mSv/Gy 120 mm from the field edge. The ability to measure the dose-equivalent with high spatial resolution is particularly relevant to healthy tissue dose calculations in hadron therapy treatments. We have also shown qualitatively and quantitively the effects critical organ motion would have in treatment using microdosimetric spectra. Large differences in spectra and RBE10 were observed for treatments where miscalculations of 12C ion range would result in critical structures being irradiated, showing the importance of motion management.
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.
Dosimetric evaluation of proton CT using a prototype proton CT scanner
Publisher: IEEE
Date: 10-2017
A novel high-resolution 2D silicon array detector for small field dosimetry with FFF photon beams
Publisher: Elsevier BV
Date: 2018
DOI: 10.1016/J.EJMP.2017.12.010
Abstract: Flattening filter free (FFF) beams are increasingly being considered for stereotactic radiotherapy (SRT). For the first time, the performance of a monolithic silicon array detector under 6 and 10 MV FFF beams was evaluated. The dosimeter, named "Octa" and designed by the Centre for Medical Radiation Physics (CMRP), was tested also under flattened beams for comparison. Output factors (OFs), percentage depth-dose (PDD), dose profiles (DPs) and dose per pulse (DPP) dependence were investigated. Results were benchmarked against commercially available detectors for small field dosimetry. The dosimeter was shown to be a 'correction-free' silicon array detector for OFs and PDD measurements for all the beam qualities investigated. Measured OFs were accurate within 3% and PDD values within 2% compared against the benchmarks. Cross-plane, in-plane and diagonal DPs were measured simultaneously with high spatial resolution (0.3 mm) and real time read-out. A DPP dependence (24% at 0.021 mGy ulse relative to 0.278 mGy ulse) was found and could be easily corrected for in the case of machine specific quality assurance applications. Results were consistent with those for monolithic silicon array detectors designed by the CMRP and previously characterized under flattened beams only, supporting the robustness of this technology for relative dosimetry for a wide range of beam qualities and dose per pulses. In contrast to its predecessors, the design of the Octa offers an exhaustive high-resolution 2D dose map characterization, making it a unique real-time radiation detector for small field dosimetry for field sizes up to 3 cm side.
SOI thin microdosimeter detectors for low-energy ions and radiation damage studies
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2019
HDR brachytherapy in vivo source position verification using a 2D diode array: A Monte Carlo study
Publisher: Wiley
Date: 06-2018
DOI: 10.1002/ACM2.12360
Teaching Monte Carlo codes at university: Development of a Geant4 course for students of schools of physics
Publisher: IEEE
Date: 08-2012
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
Simulation of cosmic radiation spectra for personal microdosimetry at the International Space Station's altitude
Publisher: IOP Publishing
Date: 2019
The dose magnifying glass quality assurance system for daily proton therapy range verification
Publisher: IOP Publishing
Date: 23-04-2021
Abstract: Proton therapy has a distinct dosimetric advantage over conventional photon therapy due to its Bragg peak profile. This allows greater accuracy in dose delivery and dose conformation to the target, however it requires greater precision in setup, delivery and for quality assurance (QA) procedures. The AAPM TG 224 report recommends daily range and spot position checks with tolerance on the order of a millimetre. Daily QA systems must therefore be efficient for daily use and be capable of sub-millimetre precision however few suitable commercial systems are available. In this work, a compact, real-time daily QA system is optimised and characterised for proton range verification using an ad-hoc Geant4 simulation. The system is comprised of a monolithic silicon diode array detector embedded in a perspex phantom. The detector is orientated at an angular offset to the incident proton beam to allow range in perspex to be determined for flat proton fields. The accuracy of the system for proton range in perspex measurements was experimentally evaluated over the full range of clinical proton energies. The mean R 100 , R 90 and R 80 ranges measured with the system were accurate within ±0.6 mm of simulated ranges in a perspex phantom for all energies assessed. This system allows real-time read-out of in idual detector channels also making it appropriate for temporal beam delivery diagnostics and for spot position monitoring along one axis. The system presented provides a suitable, economical and efficient alternative for daily QA in proton therapy.
Evaluation of silicon based microdosimetry for Boron Neutron Capture Therapy Quality Assurance
Publisher: Elsevier BV
Date: 10-2019
DOI: 10.1016/J.EJMP.2019.09.072
Abstract: The shift from reactor to accelerator based neutron production has created a renewed interested in Boron Neutron Capture Therapy (BNCT). BNCT is reliant upon the favourable uptake of
A proteomic characterization shows differences in the milk fat globule membrane of buffalo and bovine milk
Publisher: Elsevier BV
Date: 09-2017
On Monolithic Silicon Array Detectors for Small-Field Photon Beam Dosimetry
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 09-2018
Geant4 X-ray fluorescence with updated libraries
Publisher: Elsevier BV
Date: 11-2021
A Geant4 shielding design for the first US carbon multi-ion hybrid synchrotron facility
Publisher: IOP Publishing
Date: 28-02-2023
Abstract: The Mayo Clinic Florida Integrated Oncology Building will be the home of the first spot-scanning only carbon roton hybrid therapy system by Hitachi, Ltd. It will provide proton beams up to kinetic energies of 230 MeV and carbon beams up to 430 MeV n −1 for clinical deployment. To provide adequate radiation protection, the Geant4 (v10.6) Monte Carlo toolkit was utilized to quantify the ambient dose equivalent at a 10 mm depth ( H *(10)) for photons and neutrons. To perform accurate calculations of the ambient dose equivalent, three-dimensional computer-aided design files of the entire planned facility were imported into Geant4, as well as certain particle system components such as the bending magnets, fast Faraday cup, and gantry. Particle fluence was scored using 60 cm diameter spheres, which were strategically placed throughout areas of interests. Analytical calculations were performed as first-pass design checks. Major shielding slabs were optimized using Geant4 simulations iteratively, with more than 20 alternative designs evaluated within Geant4. The 430 MeV n −1 carbon beams played the most significant role in concrete thickness Requirements. The primary wall thickness for the carbon fixed beam room is 4 meters. The presence of the proton gantry structure in the simulation caused the ambient dose equivalent to increase by around 67% at the maze entrance, but a decrease in the high energy beam transport corridor. All shielding primary and secondary goals for clinical operations were met per state regulation and national guidelines.
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.
Modelling ICRP110 Adult Reference Voxel Phantoms for dosimetric applications: Development of a new Geant4 Advanced Example
Publisher: IOP Publishing
Date: 10-2020
DOI: 10.1088/1742-6596/1662/1/012021
Abstract: The reference adult male and female voxel phantoms described in the International Commission on Radiological Protection (ICRP) publication 110 have been successfully implemented in a Geant4 application named ICRP110Phantoms . The application allows users to simulate either the whole or a partial phantom, including as little as a single cross-sectional slice. The Geant4 application allows users to estimate the absorbed dose in in idual voxels and in entire organs. As ex le of application, the ICRP110Phantoms was used to estimate the dose deposited by a mono-energetic 125 MeV proton pencil beam, incident on the left breast and passing through the lungs and heart, modelled in partial chest phantoms of both male and female ICRP110 phantoms. The ICRP110Phantoms will be released in Geant4 as an Advanced Ex le to allow its use in the wider scientific community. This Geant4 Advanced Ex le application can be utilised for dosimetric studies in radiotherapy, nuclear medicine and radiation protection.
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
The investigation of prostatic calcifications using μ-PIXE analysis and their dosimetric effect in low dose rate brachytherapy treatments using Geant4
Publisher: IOP Publishing
Date: 18-05-2015
DOI: 10.1088/0031-9155/60/11/4335
Abstract: Low dose rate brachytherapy is a widely used modality for the treatment of prostate cancer. Most clinical treatment planning systems currently in use approximate all tissue to water, neglecting the existence of inhomogeneities, such as calcifications. The presence of prostatic calcifications may perturb the dose due to the higher photoelectric effect cross section in comparison to water. This study quantitatively evaluates the effect of prostatic calcifications on the dosimetric outcome of brachytherapy treatments by means of Monte Carlo simulations and its potential clinical consequences.Four pathological calcification s les were characterised with micro-particle induced x-ray emission (μ-PIXE) to determine their heavy elemental composition. Calcium, phosphorus and zinc were found to be the predominant heavy elements in the calcification composition. Four clinical patient brachytherapy treatments were modelled using Geant4 based Monte Carlo simulations, in terms of the distribution of brachytherapy seeds and calcifications in the prostate. Dose reductions were observed to be up to 30% locally to the calcification boundary, calcification size dependent. Single large calcifications and closely placed calculi caused local dose reductions of between 30-60%. In idual calculi smaller than 0.5 mm in diameter showed minimal dosimetric impact, however, the effects of small or diffuse calcifications within the prostatic tissue could not be determined using the methods employed in the study. The simulation study showed a varying reduction on common dosimetric parameters. D90 showed a reduction of 2-5%, regardless of calcification surface area and volume. The parameters V100, V150 and V200 were also reduced by as much as 3% and on average by 1%. These reductions were also found to relate to the surface area and volume of calcifications, which may have a significant dosimetric impact on brachytherapy treatment, however, such impacts depend strongly on specific factors in the patient's in idual treatment. These factors include the number, size, composition and spatial distribution of calcifications in the prostate as well as the distribution of brachytherapy seeds.
From imaging to dosimetry: GEANT4-based study on the application of Medipix to neutron dosimetry
Publisher: Elsevier BV
Date: 12-2010
CyberKnife® fixed cone and Iris™ defined small radiation fields: Assessment with a high-resolution solid-state detector array
Publisher: Wiley
Date: 12-07-2018
DOI: 10.1002/ACM2.12414
Validation of Geant4 fragmentation for Heavy Ion Therapy
Publisher: Elsevier BV
Date: 10-2017
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.
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.
Characterization of prompt gamma rays for in-vivo range verification in hadron therapy: A Geant4 simulation study
Publisher: IOP Publishing
Date: 2019
Introduction to the geant4 simulation toolkit
Publisher: AIP
Date: 2011
DOI: 10.1063/1.3576174
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
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Discovery Projects - Grant ID: DP170100967
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Amount: $300,000.00
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Amount: $430,000.00
Funder: Australian Research Council
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