ORCID Profile
0000-0001-7397-0364
Current Organisations
Laurentian University
,
University of Sydney
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Publisher: Wiley
Date: 15-03-2013
DOI: 10.1118/1.4794487
Abstract: The conformity of the achieved dose distribution to the treatment plan strongly correlates with the accuracy of seed implantation in a prostate brachytherapy treatment procedure. Incorrect seed placement leads to both short and long term complications, including urethral and rectal toxicity. The authors present BrachyView, a novel concept of a fast intraoperative treatment planning system, to provide real-time seed placement information based on in-body gamma camera data. BrachyView combines the high spatial resolution of a pixellated silicon detector (Medipix2) with the volumetric information acquired by a transrectal ultrasound (TRUS). The two systems will be embedded in the same probe so as to provide anatomically correct seed positions for intraoperative planning and postimplant dosimetry. Dosimetric calculations are based on the TG-43 method using the real position of the seeds. The purpose of this paper is to demonstrate the feasibility of BrachyView using the Medipix2 pixel detector and a pinhole collimator to reconstruct the real-time 3D position of low dose-rate brachytherapy seeds in a phantom. BrachyView incorporates three Medipix2 detectors coupled to a multipinhole collimator. Three-dimensionally triangulated seed positions from multiple planar images are used to determine the seed placement in a PMMA prostate phantom in real time. MATLAB codes were used to test the reconstruction method and to optimize the device geometry. The results presented in this paper show a 3D position reconstruction accuracy of the seed in the range of 0.5-3 mm for a 10-60 mm seed-to-detector distance interval (Z direction), respectively. The BrachyView system also demonstrates a spatial resolution of 0.25 mm in the XY plane for sources at 10 mm distance from Medipix2 detector plane, comparable to the theoretical value calculated for an equivalent gamma camera arrangement. The authors successfully demonstrated the capability of BrachyView for real-time imaging (using a 3 s data acquisition time) of different brachytherapy seed configurations (with an activity of 0.05 U) throughout a 60 × 60 × 60 mm(3) Perspex prostate phantom. The newly developed miniature gamma camera component of BrachyView, with its high spatial resolution and real time capability, allows accurate 3D localization of seeds in a prostate phantom. Combination of the gamma camera with TRUS in a single probe will complete the BrachyView system.
Publisher: Oxford University Press (OUP)
Date: 10-2011
DOI: 10.1093/EJECHOCARD/JER187
Abstract: The efficacy of anthracyclines is undermined by potential life-threatening cardiotoxicity. Cardiotoxicity is dependent upon several factors and the timing to its development is variable. Moreover, as adjuvant therapy with trastuzumab often follows, a close monitoring of cardiac function in those treated with anthracyclines is mandatory. Left ventricular ejection fraction (LVEF) by echocardiography is currently used for monitoring cardiotoxicity however, LVEF has numerous limitations. Two-dimensional strain imaging may provide a more sensitive measure of altered LV systolic function, so the aim of the present study was to compare LVEF and LV systolic strain before and after anthracyclines. Fifty-two women with histologically confirmed breast cancer were prospectively studied. Echocardiographic LVEF (by Simpson's method), global and regional peak longitudinal, radial, and circumferential 2D systolic strain were measured 1 week before and 1 week after chemotherapy. Global and regional longitudinal LV systolic strain was significantly reduced after treatment global longitudinal strain decreased from -17.7 to -16.3% (P 10%. Global and regional radial LV systolic strain after treatment was also significantly reduced global radial strain dropped from 40.5 to 34.5% (P 10%. In contrast, no reduction in LVEF >10% after chemotherapy was observed. Reduced LV systolic strain immediately after anthracycline treatment may indicate early impairment of myocardial function before detectable change in LVEF.
Publisher: IEEE
Date: 10-2012
Publisher: IOP Publishing
Date: 07-06-2012
Publisher: IEEE
Date: 10-2018
Publisher: SPIE
Date: 03-03-2011
DOI: 10.1117/12.877917
Publisher: Springer Science and Business Media LLC
Date: 17-11-2015
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 1996
DOI: 10.1109/10.536903
Abstract: Whole-body positron emission tomography (PET) has recently emerged as an important imaging tool for cancer detection and staging. Initial applications of the technique have been primarily qualitative. One of the major reasons is the limits imposed by kinetically unders led data over the whole body, as opposed to the standard method of continuous dynamic s ling in one body location. In this paper, a new estimation method using weighted nonlinear least squares (WNLS) for the first bed position and Bayesian regression (BR) for subsequent positions is proposed. A general criterion for designing optimal s ling schedules which maximizes the measurement information with multiple bed positions is developed. The overall approach is illustrated with the problem of estimating the metabolic rate of glucose (MRGLu) in tumors at different axial positions (image bed positions) in the body by using computer simulations and patient data. The results show that estimates of MRGLu using sparse data and the optimized Bayesian approach are comparable with those obtained by standard methods and fully s led data. This study demonstrates the potential of the technique described for quantification where several bed positions have to be used to image all the regions of interest (ROI).
Publisher: Informa UK Limited
Date: 02-04-2016
Publisher: Elsevier
Date: 1998
Publisher: IEEE
Date: 10-2010
Publisher: IEEE
Date: 10-2010
Publisher: IOP Publishing
Date: 24-10-2005
Publisher: Springer Science and Business Media LLC
Date: 07-1997
Publisher: IEEE
Date: 2005
Publisher: MyJove Corporation
Date: 02-05-2017
DOI: 10.3791/55184
Publisher: Bentham Science Publishers Ltd.
Date: 12-2001
Abstract: Radiotracer imaging studies performed on animals have the potential to play a major role in pharmaceutical development, pharmacology studies and basic biochemistry research. Recent developments in instrumentation and imaging methodology make it possible to image and quantify the kinetics of radiolabelled pharmaceuticals in a wide range of animal models from rodents to non-human primates. This article reviews the developments which have led to the current state-of-the-art, including advances in detector technologies, image reconstruction and tracer kinetic modelling. The practical issues specific to animal imaging studies are also discussed. With appropriate instrumentation and rigorous methodology, quantitative pre-clinical imaging has an important role to play in drug development.
Publisher: IOP Publishing
Date: 09-03-2011
DOI: 10.1088/0031-9155/56/7/015
Abstract: The baboon is well suited to pre-clinical evaluation of novel radioligands for positron emission tomography (PET). We have previously demonstrated the feasibility of using a high resolution animal PET scanner for this application in the baboon brain. However, the non-homogenous distribution of tissue density within the head may give rise to photon scattering effects that reduce contrast and compromise quantitative accuracy. In this study, we investigated the magnitude and distribution of scatter contributing to the final reconstructed image and its variability throughout the baboon brain using phantoms and Monte Carlo simulated data. The scatter fraction is measured up to 36% at the centre of the brain for a wide energy window (350-650 keV) and 19% for a narrow (450-650 keV) window. We observed less than 3% variation in the scatter fraction throughout the brain and found that scattered events arising from radioactivity outside the field of view contribute less than 1% of measured coincidences. In a contrast phantom, scatter and attenuation correction improved contrast recovery compared with attenuation correction on its own and reduced bias to less than 10% at the expense of the reduced signal-to-noise ratio. We conclude that scatter correction is a necessary step for ensuring high quality measurements of the radiotracer distribution in the baboon brain with a microPET scanner, while it is not necessary to model out of field of view scatter or a spatially variant scatter function.
Publisher: IEEE
Date: 10-2009
Publisher: Public Library of Science (PLoS)
Date: 12-10-2012
Publisher: Springer Science and Business Media LLC
Date: 10-06-1997
Publisher: IOP Publishing
Date: 04-2010
DOI: 10.1088/0031-9155/55/8/015
Abstract: Assessment of the biodistribution and pharmacokinetics of radiopharmaceuticals in vivo is often performed on animal models of human disease prior to their use in humans. The baboon brain is physiologically and neuro-anatomically similar to the human brain and is therefore a suitable model for evaluating novel CNS radioligands. We previously demonstrated the feasibility of performing baboon brain imaging on a dedicated small animal PET scanner provided that the data are accurately corrected for degrading physical effects such as photon attenuation in the body. In this study, we investigated factors affecting the accuracy and reliability of alternative attenuation correction strategies when imaging the brain of a large non-human primate (papio hamadryas) using the microPET Focus 220 animal scanner. For measured attenuation correction, the best bias versus noise performance was achieved using a (57)Co transmission point source with a 4% energy window. The optimal energy window for a (68)Ge transmission source operating in singles acquisition mode was 20%, independent of the source strength, providing bias-noise performance almost as good as for (57)Co. For both transmission sources, doubling the acquisition time had minimal impact on the bias-noise trade-off for corrected emission images, despite observable improvements in reconstructed attenuation values. In a [(18)F]FDG brain scan of a female baboon, both measured attenuation correction strategies achieved good results and similar SNR, while segmented attenuation correction (based on uncorrected emission images) resulted in appreciable regional bias in deep grey matter structures and the skull. We conclude that measured attenuation correction using a single pass (57)Co (4% energy window) or (68)Ge (20% window) transmission scan achieves an excellent trade-off between bias and propagation of noise when imaging the large non-human primate brain with a microPET scanner.
Publisher: Elsevier BV
Date: 08-2012
DOI: 10.1016/J.MEDIA.2012.04.005
Abstract: Motion-compensated radiotracer imaging of fully conscious rodents represents an important paradigm shift for preclinical investigations. In such studies, if motion tracking is performed through a transparent enclosure containing the awake animal, light refraction at the interface will introduce errors in stereo pose estimation. We have performed a thorough investigation of how this impacts the accuracy of pose estimates and the resulting motion correction, and developed an efficient method to predict and correct for refraction-based error. The refraction model underlying this study was validated using a state-of-the-art motion tracking system. Refraction-based error was shown to be dependent on tracking marker size, working distance, and interface thickness and tilt. Correcting for refraction error improved the spatial resolution and quantitative accuracy of motion-corrected positron emission tomography images. Since the methods are general, they may also be useful in other contexts where data are corrupted by refraction effects.
Publisher: Springer Science and Business Media LLC
Date: 16-03-2020
DOI: 10.1007/S10560-020-00657-5
Abstract: Mindfulness-Based Interventions (MBIs) hold promise for building resilience in children/youth. We were interested in understanding why some MBIs incorporate arts-based methods, and what key findings were identified from the study of these MBIs. We used a scoping review to address our research questions. Scoping reviews can help us better understand how different types of evidence can inform practice, policy, and research. Steps include identifying research questions and relevant studies, selecting studies for analysis, charting data, and summarizing results. We identified 27 research articles for analysis. MBIs included the use of drawing, painting, sculpting, drama, music, poetry, and karate. Rationales included both the characteristics of children/youth, and the benefits of the methods. Arts-based MBIs may be more relevant and engaging especially for youth with serious challenges. Specific focus should be paid to better understanding the development and benefits of these MBIs.
Publisher: Wiley
Date: 15-08-2014
Abstract: The purpose of this work was to determine the exposure-optimised slice thickness for hepatic lesion detection with CT. A phantom containing spheres (diameter 9.5, 4.8 and 2.4 mm) with CT density 10 HU below the background (50 HU) was scanned at 125, 100, 75 and 50 mAs. Data were reconstructed at 5-, 3- and 1-mm slice thicknesses. Noise, contrast-to-noise ratio (CNR), area under the curve (AUC) as calculated using receiver operating characteristic analysis and sensitivity representing lesion detection were calculated and compared. Compared with the 125 mAs/5 mm slice thickness setting, significant reductions in AUC were found for 75 mAs (P < 0.01) and 50 mAs (P < 0.05) at 1- and 3-mm thicknesses, respectively sensitivity for the 9.5-mm sphere was significantly reduced for 75 (P < 0.05) and 50 mAs (P < 0.01) at 1-mm thickness sensitivity for the 4.8-mm sphere was significantly lower for 100, 75 and 50 mAs at all three slice thicknesses (P < 0.05). The 2.4-mm sphere was rarely detected. At each slice thickness, noise at 100, 75 and 50 mAs exposures was approximately 10, 30 and 50% higher, respectively, than that at 125 mAs exposure. CNRs decreased in an irregular manner with reductions in exposure and slice thickness. This study demonstrated no advantage to using slices below 5 mm thickness, and consequently thinner slices are not necessarily better.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 06-1999
DOI: 10.1109/23.775596
Publisher: IEEE
Date: 08-2007
Publisher: IEEE
Date: 10-2018
Publisher: IOP Publishing
Date: 10-01-2017
Abstract: In emission tomographic imaging, the stochastic origin ensembles algorithm provides unique information regarding the detected counts given the measured data. Precision in both voxel and region-wise parameters may be determined for a single data set based on the posterior distribution of the count density allowing uncertainty estimates to be allocated to quantitative measures. Uncertainty estimates are of particular importance in awake animal neurological and behavioral studies for which head motion, unique for each acquired data set, perturbs the measured data. Motion compensation can be conducted when rigid head pose is measured during the scan. However, errors in pose measurements used for compensation can degrade the data and hence quantitative outcomes. In this investigation motion compensation and detector resolution models were incorporated into the basic origin ensembles algorithm and an efficient approach to computation was developed. The approach was validated against maximum liklihood-expectation maximisation and tested using simulated data. The resultant algorithm was then used to analyse quantitative uncertainty in regional activity estimates arising from changes in pose measurement precision. Finally, the posterior covariance acquired from a single data set was used to describe correlations between regions of interest providing information about pose measurement precision that may be useful in system analysis and design. The investigation demonstrates the use of origin ensembles as a powerful framework for evaluating statistical uncertainty of voxel and regional estimates. While in this investigation rigid motion was considered in the context of awake animal PET, the extension to arbitrary motion may provide clinical utility where respiratory or cardiac motion perturb the measured data.
Publisher: CRC Press
Date: 17-02-2017
Publisher: IOP Publishing
Date: 10-1994
DOI: 10.1088/0031-9155/39/10/012
Abstract: Total-body positron emission tomography (PET) is a useful diagnostic tool for evaluating malignant disease. However, tumour detection is limited by image artefacts due to the lack of attenuation correction and noise. Attenuation correction may be possible using transmission data acquired after or simultaneously with emission data. Despite the elimination of attenuation artefacts, however, tumour detection is still h ered by noise, which is lified during image reconstruction by filtered backprojection (FBP). We have investigated, as an alternative to FBP, an accelerated expectation maximization (EM) algorithm for its potential to improve tumour detectability in total-body PET. Signal to noise ratio (SNR), calculated for a tumour with respect to the surrounding background, is used as a figure of merit. A software tumour phantom, with conditions typical of those encountered in a total-body PET study using simultaneous acquisition, is used to optimize and compare various reconstruction approaches. Accelerated EM reconstruction followed by two-dimensional filtering is shown to yield significantly higher SNR than FBP for a range of tumour sizes, concentrations and counting statistics (deltaSNR = 6.3 +/- 3.9, p < 0.001). The methods developed are illustrated by ex les derived from physical phantom and patient data.
Publisher: IEEE
Date: 10-2013
Publisher: IEEE
Date: 10-2017
Publisher: IEEE
Date: 10-2013
Publisher: IEEE
Date: 11-2016
Publisher: The Royal Society
Date: 20-06-2012
Abstract: Positron emission tomography (PET) is an important in vivo molecular imaging technique for translational research. Imaging unanaesthetized rats using motion-compensated PET avoids the confounding impact of anaesthetic drugs and enables animals to be imaged during normal or evoked behaviour. However, there is little published data on the nature of rat head motion to inform the design of suitable marker-based motion-tracking set-ups for brain imaging—specifically, set-ups that afford close to uninterrupted tracking. We performed a systematic study of rat head motion parameters for unanaesthetized tube-bound and freely moving rats with a view to designing suitable motion-tracking set-ups in each case. For tube-bound rats, using a single appropriately placed binocular tracker, uninterrupted tracking was possible greater than 95 per cent of the time. For freely moving rats, simulations and measurements of a live subject indicated that two opposed binocular trackers are sufficient (less than 10% interruption to tracking) for a wide variety of behaviour types. We conclude that reliable tracking of head pose can be achieved with marker-based optical-motion-tracking systems for both tube-bound and freely moving rats undergoing PET studies without sedation.
Publisher: Springer Science and Business Media LLC
Date: 07-2007
Publisher: IOP Publishing
Date: 21-06-2011
DOI: 10.1088/0031-9155/56/13/023
Abstract: Tomographic systems employing truncated projections have been developed for parallel and fan beam collimation and for cone beam CT but the idea has not been extensively explored in pinhole single photon emission computed tomography (SPECT). In this paper, we explore the s ling requirements and system performance of SPECT systems with asymmetric pinhole collimators and truncated projections. We demonstrate that complete 3D s ling can be achieved by using multiple detectors with truncated asymmetric pinholes, offset axially from each other, and a spiral orbit. The use of truncated projections can be exploited in the design of pinhole SPECT systems by moving the pinholes closer to the subject, resulting in increased sensitivity and improved spatial resolution. Truncated and untruncated pinhole systems were evaluated using the contrast-to-noise ratio (CNR) calculated from the linearized local impulse response as a figure of merit. The CNR for the truncated pinhole system was up to 60% greater than that for the untruncated system at matched resolution for a source voxel near the centre of a uniform phantom and 30% greater at the edge. We conclude that an object can be reconstructed from asymmetric pinholes with truncated projections, which leads to potentially important design considerations and applications in single- and multi-pinhole SPECT.
Publisher: Springer Science and Business Media LLC
Date: 14-05-2013
Publisher: Elsevier BV
Date: 11-2013
DOI: 10.1016/J.EJCA.2013.06.046
Abstract: Anthracycline agents are undermined by their cardiotoxicity. As life expectancy following treatment is greatly improved, techniques that ensure early detection and timely management of cardiotoxicity are essential. The aim of the present study was to evaluate left ventricular (LV) systolic function with LV ejection fraction (LVEF) and two-dimensional myocardial strain up to 12 months after anthracycline chemotherapy, specifically in HER2/neu negative breast cancer patients. Seventy-eight consecutive anthracycline naïve breast cancer patients were studied before and immediately after anthracycline chemotherapy. Fifty HER2/neu negative patients were studied over 12 months with serial echocardiograms at four time points. All patients were treated with standard regimens containing anthracyclines. Global systolic strain was significantly reduced immediately after, and 6 months after anthracyclines (-19.0 ± 2.3% to -17.5 ± 2.3% (P<0.001) and -18.2 ± 2.2% (P=0.01) respectively). A non-uniform reduction in strain was observed each time with relative sparing of the LV apex. LVEF remained largely unchanged at both time points. Global strain normalised by 12 months in the majority of patients. Persistently reduced strain was observed in 16% (n=8) these patients had a greater reduction in strain at 6 months (≤ -17.2%), and had received higher cumulative anthracycline doses. Myocardial strain imaging is more sensitive than LVEF for the early detection and intermediate term monitoring of LV systolic function following anthracycline chemotherapy in HER2/neu negative breast cancer patients, and may aid in the development of improved monitoring protocols.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 10-2013
Publisher: IOP Publishing
Date: 23-08-2016
Publisher: Springer-Verlag
Date: 1991
DOI: 10.1007/BFB0033740
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 10-2002
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 02-2016
Publisher: Elsevier BV
Date: 06-2000
DOI: 10.1016/S0969-8051(00)00105-0
Abstract: We investigated the influence of tomograph sensitivity on reliability of parameter estimation in positron emission tomography studies of the rat brain. The kinetics of two tracers in rat striatum and cerebellum were simulated. A typical injected dose of 10 MBq and a reduced dose of 1 MBq were assumed. Kinetic parameters were estimated using a region of interest (ROI) analysis and two pixel-by-pixel analyses. Striatal binding potential was estimated as a function of effective tomograph sensitivity (S(eff)) using a simplified reference tissue model. A S(eff) value of > or =1% was required to ensure reliable parameter estimation for ROI analysis and a S(eff) of 3-6% was required for pixel-by-pixel analysis. We conclude that effective tomograph sensitivity of 3% may be an appropriate design goal for rat brain imaging.
Publisher: Elsevier BV
Date: 04-2005
DOI: 10.1016/J.BRAINRESREV.2004.12.010
Abstract: Within the diseased brain, glial cells and in particular, microglia, express a multimeric protein complex termed "peripheral benzodiazepine binding sites (PBBS)" or "peripheral benzodiazepine receptor (PBR)". The expression of the PBBS is dependent on the functional state of the cell and in glial cells is triggered by a wide range of activating stimuli. In the healthy brain, the PBBS are nearly absent with the notable exception of the choroid plexus, ependymal layer, perivascular cells, central canal, possibly certain nuclei in the brainstem and layers in the cerebellum where a constitutive presence of the PBBS is found. Likewise, areas that due to the absence of the blood-brain barrier contain more active glial cells, such as the pituitary gland, or the area postrema at floor of the 4th ventricle show a degree of constitutive expression. The tight correlation of the parenchymal de novo expression of the PBBS with the presence of activated glial cells, that in turn are usually only found in tissue affected by progressive disease, establishes the PBBS as a generic marker for the detection and measurement of active disease processes in the brain. Specific radioligands of the PBBS for use in positron emission tomography (PET) may thus provide a sensitive in vivo index of neuropathological activity. Whilst prototype ligands for the PBBS are available, future research needs to focus on the development of new ligands with improved pharmacodynamic properties and the ability to discriminate between the different, still insufficiently understood functional states of the peripheral benzodiazepine receptor complex.
Publisher: IEEE
Date: 10-2008
Publisher: SPIE
Date: 19-03-2014
DOI: 10.1117/12.2043962
Publisher: Elsevier BV
Date: 03-2019
DOI: 10.1016/J.NEUROIMAGE.2018.11.051
Abstract: A comprehensive understanding of how the brain responds to a changing environment requires techniques capable of recording functional outputs at the whole-brain level in response to external stimuli. Positron emission tomography (PET) is an exquisitely sensitive technique for imaging brain function but the need for anaesthesia to avoid motion artefacts precludes concurrent behavioural response studies. Here, we report a technique that combines motion-compensated PET with a robotically-controlled animal enclosure to enable simultaneous brain imaging and behavioural recordings in unrestrained small animals. The technique was used to measure in vivo displacement of [
Publisher: Elsevier BV
Date: 09-2015
DOI: 10.1016/J.NEUROIMAGE.2015.06.029
Abstract: Quantitative measurements in dynamic PET imaging are usually limited by the poor counting statistics particularly in short dynamic frames and by the low spatial resolution of the detection system, resulting in partial volume effects (PVEs). In this work, we present a fast and easy to implement method for the restoration of dynamic PET images that have suffered from both PVE and noise degradation. It is based on a weighted least squares iterative deconvolution approach of the dynamic PET image with spatial and temporal regularization. Using simulated dynamic [(11)C] Raclopride PET data with controlled biological variations in the striata between scans, we showed that the restoration method provides images which exhibit less noise and better contrast between emitting structures than the original images. In addition, the method is able to recover the true time activity curve in the striata region with an error below 3% while it was underestimated by more than 20% without correction. As a result, the method improves the accuracy and reduces the variability of the kinetic parameter estimates calculated from the corrected images. More importantly it increases the accuracy (from less than 66% to more than 95%) of measured biological variations as well as their statistical detectivity.
Publisher: Springer Science and Business Media LLC
Date: 1990
DOI: 10.1007/BF00998184
Abstract: In the operative treatment of spinal injuries, the reconstruction of the anterior column of the thoracolumbar spine is still controversial. We conducted a prospective clinical study to investigate the clinical and radiological outcome of 50 patients treated with a vertebral body replacement of adjustable height (Synex). Fifty consecutive patients were evaluated during in-patient treatment and at 12 and 20 months post-operatively in clinical notes and radiographs. 38/50 patients were operated for traumatic fractures. Out of 50 patients 45 attended the follow-up clinic 1 year post-operatively and 39 of these patients were examined after 20 months. Twenty-five patients returned to pre-injury activities within 1 year. This number increased to 29/39 patients at 20 months. Seventy-three percent of the patients returned to their job. After 1 year 25/45 patients complained of little or no back pain and 6 months later six patients were limited in their back function. At 1 year only three patients complained of surgical site pain which was improved at their final follow-up at 20 months. In idual satisfaction was determined using a score on a visual analog scale containing 19 questions on back pain, and functional limitation of the spine that has to be filled in by the patients at three different points of time. The score decreased from 87/100 pre-operatively to 65/100 at 1 year follow-up (P<0.001). The average permanent correction of the injured vertebra was 16.8 degrees (88%) including 2.3 degrees (12%) loss of correction at 12 months after operation. Bony integration was obtained in 83%. Early and intermediate outcome with the Synex vertebral replacement device for reconstruction of the anterior column appears promising. The loss of correction or reduction was only minimal. On the basis of our results we recommend the Synex implant as an alternative for the fixation and stabilisation of thoracolumbar fractures. However, long-term results and a clinically random control study are still required.
Publisher: IOP Publishing
Date: 25-01-2021
Abstract: The quality of reconstructed dynamic PET images, as well as the statistical reliability of the estimated pharmacokinetic parameters is often compromised by high levels of statistical noise, particularly at the voxel level. Many denoising strategies have been proposed, both in the temporal and spatial domain, which substantially improve the signal to noise ratio of the reconstructed dynamic images. However, although most filtering approaches are fairly successful in reducing the spatio-temporal inter-voxel variability, they may also average out or completely eradicate the critically important temporal signature of a transient neurotransmitter activation response that may be present in a non-steady state dynamic PET study. In this work, we explore an approach towards temporal denoising of non-steady state dynamic PET images using an artificial neural network, which was trained to identify the temporal profile of a time-activity curve, while preserving any potential activation response. We evaluated the performance of a feed-forward perceptron neural network to improve the signal to noise ratio of dynamic [ 11 C]raclopride activation studies and compared it with the widely used highly constrained back projection (HYPR) filter. Results on both simulated Geant4 Application for Tomographic Emission data of a realistic rat brain phantom and experimental animal data of a freely moving animal study showed that the proposed neural network can efficiently improve the noise characteristics of dynamic data in the temporal domain, while it can lead to a more reliable estimation of voxel-wise activation response in target region. In addition, improvements in signal-to-noise ratio achieved by denoising the dynamic data using the proposed neural network led to improved accuracy and precision of the estimated model parameters of the lp-ntPET model, compared to the HYPR filter. The performance of the proposed denoising approach strongly depends on the amount of noise in the dynamic PET data, with higher noise leading to substantially higher variability in the estimated parameters of the activation response. Overall, the feed-forward network led to a similar performance as the HYPR filter in terms of spatial denoising, but led to notable improvements in terms of temporal denoising, which in turn improved the estimation activation parameters.
Publisher: Informa UK Limited
Date: 11-2013
Publisher: Elsevier BV
Date: 08-2014
DOI: 10.1016/J.NEUROIMAGE.2014.04.010
Abstract: Positron emission tomography (PET) with [(11)C]Raclopride is an important tool for studying dopamine D2 receptor expression in vivo. [(11)C]Raclopride PET binding experiments conducted using the Partial Saturation Approach (PSA) allow the estimation of receptor density (B(avail)) and the in vivo affinity appK(D). The PSA is a simple, single injection, single scan experimental protocol that does not require blood s ling, making it ideal for use in longitudinal studies. In this work, we generated a complete Monte Carlo simulated PET study involving two groups of scans, in between which a biological phenomenon was inferred (a 30% decrease of B(avail)), and used it in order to design an optimal data processing chain for the parameter estimation from PSA data. The impact of spatial smoothing, noise removal and image resolution recovery technique on the statistical detection was investigated in depth. We found that image resolution recovery using iterative deconvolution of the image with the system point spread function associated with temporal data denoising greatly improves the accuracy and the statistical reliability of detecting the imposed phenomenon. Before optimisation, the inferred B(avail) variation between the two groups was underestimated by 42% and detected in 66% of cases, while a false decrease of appK(D) by 13% was detected in more than 11% of cases. After optimisation, the calculated B(avail) variation was underestimated by only 3.7% and detected in 89% of cases, while a false slight increase of appK(D) by 3.7% was detected in only 2% of cases. We found during this investigation that it was essential to adjust a factor that accounts for difference in magnitude between the non-displaceable ligand concentrations measured in the target and in the reference regions, for different data processing pathways as this ratio was affected by different image resolutions.
Publisher: IEEE
Date: 10-2011
Publisher: IEEE
Date: 10-2010
Publisher: IEEE
Date: 10-2011
Publisher: IEEE
Date: 10-2013
Publisher: IEEE
Date: 10-2011
Publisher: IOP Publishing
Date: 24-11-2009
DOI: 10.1088/0031-9155/54/24/009
Abstract: The incorporation of accurately aligned anatomical information as a prior to guide reconstruction and noise regularization in positron emission tomography (PET) has been suggested in many previous studies. However, the advantages of this approach can only be realized if the exact lesion outline is also available. In practice, the anatomical imaging modality may be unable to differentiate between normal and pathological tissues, and thus the edges of lesions seen in the anatomical image may not correspond to functional boundaries in the emission image. In this study, we explored an alternative approach to incorporating an anatomical prior into PET image reconstruction. Of particular interest was the realistic situation where lesions are apparent in the emission images but not in the corresponding anatomical images. In the proposed method, regional information obtained from the anatomical prior was used to estimate an anatomically adaptive anisotropic median-diffusion filtering (AAMDF) prior. This smoothing prior was determined and applied adaptively to each anatomical region on the emission image and then assembled to form a prior image for the next iteration in the reconstruction process. We formulated a two-step joint estimation reconstruction scheme to update the estimated image and prior image iteratively. The proposed AAMDF prior was evaluated and compared with maximum a posteriori (MAP) reconstruction methods with and without anatomical side information. In experiments using synthetic and physical phantom data, the AAMDF prior yielded overall higher lesion-to-background contrast and less error in lesion estimation than other algorithms for a comparable level of background noise. We conclude that lesion contrast and quantification can be improved using an anatomically derived smoothing prior without requiring knowledge of the lesion boundary. This may have important implications in clinical PET/CT, where lesion boundaries are often not obtainable from CT images.
Publisher: IOP Publishing
Date: 28-07-2015
DOI: 10.1088/0031-9155/60/15/6087
Abstract: Radium-223 dichloride ((223)Ra) is an alpha particle emitter and a natural bone-seeking radionuclide that is currently used for treating osteoblastic bone metastases associated with prostate cancer. The stochastic nature of alpha emission, hits and energy deposition poses some challenges for estimating radiation damage. In this paper we investigate the distribution of hits to cells by multiple alpha particles corresponding to a typical clinically delivered dose using a Monte Carlo model to simulate the stochastic effects. The number of hits and dose deposition were recorded in the cytoplasm and nucleus of each cell. Alpha particle tracks were also visualized. We found that the stochastic variation in dose deposited in cell nuclei ([Formula: see text]40%) can be attributed in part to the variation in LET with pathlength. We also found that [Formula: see text]18% of cell nuclei receive less than one sigma below the average dose per cell ([Formula: see text]15.4 Gy). One possible implication of this is that the efficacy of cell kill in alpha particle therapy need not rely solely on ionization clustering on DNA but possibly also on indirect DNA damage through the production of free radicals and ensuing intracellular signaling.
Publisher: IEEE
Date: 10-2018
Publisher: IOP Publishing
Date: 13-07-2017
Abstract: 'Open-field' PET, in which an animal is free to move within an enclosed space during imaging, is a very promising advance for neuroscientific research. It provides a key advantage over conventional imaging under anesthesia by enabling functional changes in the brain to be correlated with an animal's behavioural response to environmental or pharmacologic stimuli. Previously we have demonstrated the feasibility of open-field imaging of rats using motion compensation techniques applied to a commercially available PET scanner. However, this approach of 'retro-fitting' motion compensation techniques to an existing system is limited by the inherent geometric and performance constraints of the system. The goal of this project is to develop a purpose-built PET scanner with geometry, motion tracking and imaging performance tailored and optimised for open-field imaging of the mouse brain. The design concept is a rail-based sliding tomograph which moves according to the animal's motion. Our specific aim in this work was to evaluate candidate scanner designs and characterise the performance of a depth-of-interaction detector module for the open-field system. We performed Monte Carlo simulations to estimate and compare the sensitivity and spatial resolution performance of four scanner geometries: a ring, parallel plate, and two box variants. Each system was based on a detector block consisting of a 23 × 23 array of 0.785 × 0.785 × 20 mm
Publisher: Elsevier BV
Date: 2011
DOI: 10.1016/J.HLC.2010.09.007
Abstract: Refinements to conventional treatment and the development of new therapies have led to significant improvements in cancer survival. Yet, many frontline cancer treatments continue to be hindered by their significant side effects, amongst which cardiotoxicity is particularly important. Therefore, the focus of cancer management has changed treatment is no longer aimed solely at overcoming malignancy, but emphasises early identification and treatment of potential side effects. In this regard, the cardiotoxic potential of certain anticancer agents mandate close monitoring of cardiac function, and the method of choice for monitoring is transthoracic echocardiography. Whilst this method has its limitations, a newer echocardiographic technique called myocardial strain imaging has the potential to detect early sub-clinical changes in cardiac function due to cardiotoxicity. Strain analysis has been the subject of several recent studies to evaluate its potential in monitoring cardiotoxicity, and this article reviews the recent literature and explores the potential role of myocardial strain imaging in cancer management and avenues for future research.
Publisher: IEEE
Date: 10-2016
Publisher: SAGE Publications
Date: 07-2023
DOI: 10.1177/21582440231192111
Abstract: Research exploring the benefits of Mindfulness-Based Interventions (MBIs) with youth is emerging and promising for the improvement of resiliencies. We developed an arts-based mindfulness intervention to make learning mindfulness accessible for children who had experienced trauma. Arts-based methods are engaging, enjoyable, and developmentally relevant. Previously, we found benefits of participating in this MBI for children aged 8 to 12 years. Herein we discuss research in which we explored the benefits of this MBI for adolescents who were experiencing challenges with schooling 146 youth completed the program. Our research question asked whether the MBI was beneficial and/or effective for these youth and, if so, what were these benefits and how did these benefits assist youth to cope? Benefits were explored via reflexive thematic analysis (TA) of pre ost-intervention, and follow-up in idual interviews with youth. Effectiveness was assessed by analyzing pre- and post-intervention scores on youth self-report inventories measuring mindfulness and resilience, as well as responses from caregiver assessments of behavior/coping. To assess if there were changes in responses across timeperiods, a series of repeated measures ANOVA were employed. Quantitative findings were mixed in that the youths’ self-report scores measuring resilience showed limited improvement while mindfulness showed no significant change. However, parents’ perceptions regarding their child’s behaviors indicated significant improvements in social competence and both internalizing/externalizing behaviors. Similarly, the thematic analysis suggested improvements in youths’ self-awareness, self-judgment, thinking, mood, ability to make choices, social skills, coping, and emotion regulation. The results are promising and warrant further investigation of arts-based approaches to facilitating mindfulness with youth.
Publisher: IEEE
Date: 10-2009
Publisher: IOP Publishing
Date: 05-04-2011
DOI: 10.1088/0031-9155/56/9/001
Abstract: Accurate attenuation correction is important for quantitative positron emission tomography (PET) studies. When performing transmission measurements using an external rotating radioactive source, object motion during the transmission scan can distort the attenuation correction factors computed as the ratio of the blank to transmission counts, and cause errors and artefacts in reconstructed PET images. In this paper we report a compensation method for rigid body motion during PET transmission measurements, in which list mode transmission data are motion corrected event-by-event, based on known motion, to ensure that all events which traverse the same path through the object are recorded on a common line of response (LOR). As a result, the motion-corrected transmission LOR may record a combination of events originally detected on different LORs. To ensure that the corresponding blank LOR records events from the same combination of contributing LORs, the list mode blank data are spatially transformed event-by-event based on the same motion information. The number of counts recorded on the resulting blank LOR is then equivalent to the number of counts that would have been recorded on the corresponding motion-corrected transmission LOR in the absence of any attenuating object. The proposed method has been verified in phantom studies with both stepwise movements and continuous motion. We found that attenuation maps derived from motion-corrected transmission and blank data agree well with those of the stationary phantom and are significantly better than uncorrected attenuation data.
Publisher: American Psychological Association (APA)
Date: 09-2009
Publisher: IEEE
Date: 10-2008
Publisher: IEEE
Date: 2007
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 02-2002
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 02-1997
DOI: 10.1109/23.554827
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 06-2018
Publisher: Oxford University Press (OUP)
Date: 10-07-2012
DOI: 10.1093/EHJCI/JES139
Abstract: The benefits from anthracycline chemotherapy are undermined by potentially life-threatening cardiotoxicity. Transthoracic echocardiography is the most commonly used method for monitoring cardiotoxicity, and centres on the measurement of left ventricular systolic function. The aim of this study was to utilize two-dimensional speckle tracking echocardiography (2DSTE) at baseline and immediately after anthracycline chemotherapy to investigate whether patients with significant changes in systolic function after anthracycline therapy would also develop alterations in diastolic parameters. Fifty-two women with histologically confirmed breast cancer were prospectively recruited. Echocardiograms were performed 1 week prior to and 1 week following chemotherapy (always before adjuvant trastuzumab or thoracic radiotherapy). Conventional Doppler, tissue velocity imaging (TVI), and 2DSTE were used to measure diastolic function. 2DSTE measurements included longitudinal diastolic strain, early (E-Sr), and late (A-Sr) myocardial strain rate. 2DSTE and left ventricular ejection fraction (LVEF) were used to measure longitudinal systolic function. Altered LV diastolic function (including E-Sr) was observed in the entire cohort after chemotherapy, with a differential reduction in participants with a post therapy LVEF <55%. Pre-chemotherapy systolic strain was found to predict reduced E-Sr post therapy (P = 0.04). Univariate predictors of E-Sr were LVEF post therapy (P = 0.049) and systolic strain post-therapy (P = 0.01). In a multivariate analysis, systolic strain after chemotherapy was the strongest independent predictor (P = 0.001). Altered LV diastolic function was observed immediately after the administration of therapeutic doses of anthracycline chemotherapy. Furthermore, our analysis indicates that the changes in diastolic function are associated with reduced systolic function.
Publisher: IOP Publishing
Date: 18-07-2019
Abstract: Although PET is routinely evaluated using NEMA NU2 as standard in the clinic, standard methodology for evaluating the performance of quantitative SPECT systems has not been established. In this study, the quantitative performance of the Symbia Intevo SPECT/CT was evaluated for two common isotopes (
Publisher: Springer Science and Business Media LLC
Date: 10-1996
DOI: 10.1007/BF01367584
Abstract: The paper is devoted to optimal vaccination scheduling during a pandemic to minimize the probability of infection. The recent COVID-19 pandemic showed that the international community is not properly prepared to manage a crisis of this scale. Just after the vaccines had been approved by medical agencies, the policymakers needed to decide on the distribution strategy. To successfully fight the pandemic, the key is to find the equilibrium between the vaccine distribution schedule and the available supplies caused by limited production capacity. This is why society needs to be ided into stratified groups whose access to vaccines is prioritized. Herein, we present the problem of distributing protective actions (i.e., vaccines) and formulate two mixed-integer programs to solve it. The problem of distributing protective actions (PDPA) aims at finding an optimal schedule for a given set of social groups with a constant probability of infection. The problem of distributing protective actions with a herd immunity threshold (PDPAHIT) also includes a variable probability of infection, i.e., the situation when herd immunity is obtained. The results of computational experiments are reported and the potential of the models is illustrated with ex les.
Publisher: IEEE
Date: 10-2018
Publisher: IEEE
Date: 2007
Publisher: Springer Science and Business Media LLC
Date: 07-1998
Abstract: The aim of this study was to investigate the feasibility of evaluating the pharmacokinetics of radiolabeled anti-cancer drugs using spectral analysis, a non-compartmental tracer kinetic modeling technique, and positron emission tomography (PET). Dynamic PET studies were performed on patients receiving tracer doses of 5-fluorouracil (5-[18F]-FU) and two developmental drugs [11C]-temozolomide and [11C]-acridine carboxamide. Spectral analysis was then used to (a) determine in idual and group average pharmacokinetics, (b) predict tumour handling in response to different drug administration regimens, and (c) produce functional parametric images describing regional pharmacokinetics. Spectral analysis could distinguish tumour kinetics from normal tissue kinetics in an in idual [11C]-temozolomide study and demonstrated a markedly greater volume of distribution (VD) in glioma than in normal brain, although there was no appreciable difference in mean residence time. Analysis of pooled acridine carboxamide data (n = 22) revealed a relatively large VD (and prolonged retention) in the liver and spleen and a markedly lower VD (and initial uptake) in the brain. Continuous infusion of 5-[18F]-FU was predicted to achieve a concentration in colorectal metastases in liver approximately 10 times that achieved in plasma at 10 h after commencement of the infusion. We conclude that spectral analysis provides important pharmacokinetic information about radiolabeled anti-cancer drugs with relatively few model assumptions.
Publisher: Public Library of Science (PLoS)
Date: 07-2011
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 06-2002
Publisher: IEEE
Date: 10-2012
Publisher: IEEE
Date: 10-2012
Publisher: Society of Nuclear Medicine
Date: 05-09-2013
DOI: 10.2967/JNUMED.112.117572
Abstract: The Inveon small-animal SPECT system comes with several types of multipinhole collimator plates. We evaluate here the performance measurements of the Inveon SPECT system using 6 different collimators: 3 dedicated for mouse imaging and 3 for rat imaging. The measured performance parameters include the sensitivity, the spatial resolution using line sources, the ultra-micro Derenzo phantom, the recovery coefficient and the noise measurements using the National Electrical Manufacturers Association NU-4 image quality phantom, obtained with the 2 reconstruction algorithms available with the Inveon Acquisition Workplace, version 1.5-the 3-dimensional ordered-subset expectation maximization (3DOSEM) and the 3-dimensional maximum a posteriori (3DMAP). Further, the overall performance of the system is illustrated by an animal experiment. The results show that the Inveon SPECT scanner offers a spatial resolution, measured at the center of the field of view, ranging from 0.6 to 1 mm with the collimator plates dedicated to mouse imaging and from 1.2 to less than 2 mm with rat collimator plates. The system sensitivity varies from 29 to 404 cps/MBq for mouse collimators and from 53 to 175 cps/MBq for rat collimators. The image quality study showed that 3DMAP allows better noise reduction while preserving the recovery coefficient, compared with other regularization strategies such as the premature termination of the 3DOSEM reconstruction or 3DOSEM followed by gaussian filtering. The acquisition parameters, such as the collimator set and the radius of rotation, offer a wide range of possibilities to apply to a large number of biologic studies. However, special care must be taken because this increase in sensitivity can be offset by image degradation, such as image artifacts caused by projection overlap and statistical noise due to a higher number of iterations required for convergence. 3DMAP allowed better noise reduction while maintaining relatively constant recovery coefficients, as compared with other reconstruction strategies.
Publisher: Elsevier BV
Date: 2007
DOI: 10.1016/J.NEUROIMAGE.2006.10.002
Abstract: Molecular brain imaging using positron emission tomography (PET) has evolved into a vigorous academic field and is progressively gaining importance in the clinical arena. Significant progress has been made in the design of high-resolution three-dimensional (3-D) PET units dedicated to brain research and the development of quantitative imaging protocols incorporating accurate image correction techniques and sophisticated image reconstruction algorithms. However, emerging clinical and research applications of molecular brain imaging demand even greater levels of accuracy and precision and therefore impose more constraints with respect to the quantitative capability of PET. It has long been recognized that photon attenuation in tissues is the most important physical factor degrading PET image quality and quantitative accuracy. Quantitative PET image reconstruction requires an accurate attenuation map of the object under study for the purpose of attenuation compensation. Several methods have been devised to correct for photon attenuation in neurological PET studies. Significant attention has been devoted to optimizing computational performance and to balancing conflicting requirements. Approximate methods suitable for clinical routine applications and more complicated approaches for research applications, where there is greater emphasis on accurate quantitative measurements, have been proposed. The number of scientific contributions related to this subject has been increasing steadily, which motivated the writing of this review as a snapshot of the dynamically changing field of attenuation correction in cerebral 3D PET. This paper presents the physical and methodological basis of photon attenuation and summarizes state of the art developments in algorithms used to derive the attenuation map aiming at accurate attenuation compensation of brain PET data. Future prospects, research trends and challenges are identified and directions for future research are discussed.
Publisher: IOP Publishing
Date: 11-11-2011
DOI: 10.1088/0031-9155/56/23/010
Abstract: Multiple pinholes are advantageous for maximizing the use of the available field of view (FOV) of compact small animal single photon emission computed tomography (SPECT) detectors. However, when the pinholes are aligned axially to optimize imaging of extended objects, such as rodents, multiplexing of the pinhole projections can give rise to inconsistent data which leads to 'ghost point' artefacts in the reconstructed volume. A novel four pinhole collimator with a baffle was designed and implemented to eliminate these inconsistent projections. Simulation and physical phantom studies were performed to investigate artefacts from axially aligned pinholes and the efficacy of the baffle in removing inconsistent data and, thus, reducing reconstruction artefacts. SPECT was performed using a Defrise phantom to investigate the impact of collimator design on FOV utilization and axial blurring effects. Multiple pinhole SPECT acquired with a baffle had fewer artefacts and improved quantitative accuracy when compared to SPECT acquired without a baffle. The use of four pinholes positioned in a square maximized the available FOV, increased acquisition sensitivity and reduced axial blurring effects. These findings support the use of a baffle to eliminate inconsistent projection data arising from axially aligned pinholes and improve small animal SPECT reconstructions.
Publisher: IEEE
Date: 10-2009
Publisher: Springer Science and Business Media LLC
Date: 1997
DOI: 10.1007/BF01728302
Abstract: This retrospective, cross-sectional study aimed to assess the pharyngeal airway dimensions of patients with juvenile idiopathic arthritis (JIA) and moderate/severe JIA-related dentofacial deformity (mandibular retrognathia/micrognathia), and compare the results with JIA patients with a normal mandibular appearance and a group of non-JIA patients. Seventy-eight patients were retrospectively included in a 1:1:1 manner as specified below. All patients had previously been treated at the Section of Orthodontics, Aarhus University, Denmark. All had a pretreatment cone beam computed tomography (CBCT). Group 1 (JIA+) 26 JIA patients with severe arthritis-related dentofacial deformity and mandibular retrognathia/micrognathia. Group 2 (JIA-) 26 JIA patients with normal mandibular morphology osition. Group 3 (Controls) 26 non-JIA subjects. Dentofacial morphology and upper airway dimensions, excluding the nasal cavity, were assessed in a validated three-dimensional (3D) fashion. Assessment of dentofacial deformity comprised six morphometric measures. Assessment of airway dimensions comprised nine measures. Five morphometric measures of dentofacial deformity were significantly deviating in the JIA+ group compared with the JIA- and control groups: Posterior mandibular height, anterior facial height, mandibular inclination, mandibular occlusal inclination, and mandibular sagittal position. Five of the airway measurements showed significant inter-group differences: JIA+ had a significantly smaller nasopharyngeal airway dimension (ad2-PNS), a smaller velopharyngeal volume, a smaller minimal cross-sectional area and a smaller minimal hydraulic diameter than JIA- and controls. No significant differences in upper airway dimensions were seen between JIA- and controls. JIA patients with severe arthritis-related dentofacial deformity and mandibular micrognathia had significantly restricted upper airway dimensions compared with JIA patients without dentofacial deformity and controls. The restrictions of upper airway dimension seen in the JIA+ group herein were previously associated with sleep-disordered breathing in the non-JIA background population. Further studies are needed to elucidate the role of dentofacial deformity and restricted airways in the development of sleep-disordered breathing in JIA.
Publisher: IEEE
Date: 10-2009
Publisher: IEEE
Date: 10-2016
Publisher: Springer Science and Business Media LLC
Date: 03-1996
DOI: 10.1007/BF00837632
Abstract: The clinical syndromes of Progressive Supranuclear Palsy (PSP) may be mediated by abnormal temporal dynamics of brain networks, due to the impact of atrophy, synapse loss and neurotransmitter deficits. We tested the hypothesis that alterations in signal complexity in neural networks influence short-latency state transitions. Ninety-four participants with PSP and 64 healthy controls were recruited from two independent cohorts. All participants underwent clinical and neuropsychological testing and resting-state functional MRI. Network dynamics were assessed using hidden Markov models and neural signal complexity measured in terms of multiscale entropy. In both cohorts, PSP increased the proportion of time in networks associated with higher cognitive functions. This effect correlated with clinical severity as measured by the PSP-rating-scale, and with reduced neural signal complexity. Regional atrophy influenced abnormal brain-state occupancy, but abnormal network topology and dynamics were not restricted to areas of atrophy. Our findings show that the pathology of PSP causes clinically relevant changes in neural temporal dynamics, leading to a greater proportion of time in inefficient brain-states.
Publisher: IEEE
Date: 2007
Publisher: IOP Publishing
Date: 17-05-2018
Abstract: Motion-compensated brain imaging can dramatically reduce the artifacts and quantitative degradation associated with voluntary and involuntary subject head motion during positron emission tomography (PET), single photon emission computed tomography (SPECT) and computed tomography (CT). However, motion-compensated imaging protocols are not in widespread clinical use for these modalities. A key reason for this seems to be the lack of a practical motion tracking technology that allows for smooth and reliable integration of motion-compensated imaging protocols in the clinical setting. We seek to address this problem by investigating the feasibility of a highly versatile optical motion tracking method for PET, SPECT and CT geometries. The method requires no attached markers, relying exclusively on the detection and matching of distinctive facial features. We studied the accuracy of this method in 16 volunteers in a mock imaging scenario by comparing the estimated motion with an accurate marker-based method used in applications such as image guided surgery. A range of techniques to optimize performance of the method were also studied. Our results show that the markerless motion tracking method is highly accurate (<2 mm discrepancy against a benchmarking system) on an ethnically erse range of subjects and, moreover, exhibits lower jitter and estimation of motion over a greater range than some marker-based methods. Our optimization tests indicate that the basic pose estimation algorithm is very robust but generally benefits from rudimentary background masking. Further marginal gains in accuracy can be achieved by accounting for non-rigid motion of features. Efficiency gains can be achieved by capping the number of features used for pose estimation provided that these features adequately s le the range of head motion encountered in the study. These proof-of-principle data suggest that markerless motion tracking is amenable to motion-compensated brain imaging and holds good promise for a practical implementation in clinical PET, SPECT and CT systems.
Publisher: Wiley
Date: 03-2012
DOI: 10.1111/J.1540-8175.2011.01645.X
Abstract: A 45-year-old female breast cancer patient developed heart failure during adjuvant trastuzumab therapy. Her initial left ventricular ejection fraction (LVEF) was 39% and corresponding global longitudinal and circumferential systolic strain measurements were also significantly reduced. Trastuzumab was ceased and supportive cardiac therapy commenced. The ensuing LVEF and systolic strain measurements showed consistent improvement so that trastuzumab was recommenced (while supportive cardiac therapy continued). At this point, reduced circumferential systolic strain with preserved LVEF was observed. Subsequent echocardiograms revealed further reductions in circumferential and longitudinal systolic strain without reductions in LVEF.
Publisher: IOP Publishing
Date: 05-09-2014
DOI: 10.1088/0031-9155/59/19/5651
Abstract: Attenuation correction in positron emission tomography brain imaging of freely moving animals is a very challenging problem since the torso of the animal is often within the field of view and introduces a non negligible attenuating factor that can degrade the quantitative accuracy of the reconstructed images. In the context of unrestrained small animal imaging, estimation of the attenuation correction factors without the need for a transmission scan is highly desirable. An attractive approach that avoids the need for a transmission scan involves the generation of the hull of the animal's head based on the reconstructed motion corrected emission images. However, this approach ignores the attenuation introduced by the animal's torso. In this work, we propose a virtual scanner geometry which moves in synchrony with the animal's head and discriminates between those events that traversed only the animal's head (and therefore can be accurately compensated for attenuation) and those that might have also traversed the animal's torso. For each recorded pose of the animal's head a new virtual scanner geometry is defined and therefore a new system matrix must be calculated leading to a time-varying system matrix. This new approach was evaluated on phantom data acquired on the microPET Focus 220 scanner using a custom-made phantom and step-wise motion. Results showed that when the animal's torso is within the FOV and not appropriately accounted for during attenuation correction it can lead to bias of up to 10% . Attenuation correction was more accurate when the virtual scanner was employed leading to improved quantitative estimates (bias < 2%), without the need to account for the attenuation introduced by the extraneous compartment. Although the proposed method requires increased computational resources, it can provide a reliable approach towards quantitatively accurate attenuation correction for freely moving animal studies.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 05-1997
DOI: 10.1097/00004728-199705000-00028
Abstract: We evaluated the impact of simultaneous emission and transmission (SET) measurements of quantification and noise in neurological PET studies. Bias in SET was measured as a function of emission count rate and used to predict distortion in simulated FDG tissue curves and its effect on model parameter estimates. Studies were performed on a brain phantom and a patient to verify predicted bias and examine the effect of SET on noise. In static imaging, SET underestimated tracer concentration by approximately 2%. In kinetic studies, tracer concentration was overestimated initially and underestimated during the mid to late part of the study, but bias in measurement of glucose metabolic rate was < 5% by simulation and < 10% in the patient study. SET imaging takes 10% longer than the emission part of a conventional scan to achieve comparable statistics. Accurate neurological PET studies can be performed with SET. The relatively small bias can be predicted and potentially corrected.
Publisher: Elsevier BV
Date: 02-2001
DOI: 10.1016/S0969-8051(00)00206-7
Abstract: To quantify changes in neuronal nAChR binding in vivo, quantitative dynamic SPECT studies were performed with 5-[(123)I]-iodo-A-85380 in baboons pre and post chronic treatment with (-)-nicotine or saline control. Infusion of (-)-nicotine at a dose of 2.0 mg/kg/24h for 14 days resulted in plasma (-)-nicotine levels of 27.3 ng/mL. This is equivalent to that found in an average human smoker (20 cigarettes a day). In the baboon brain the regional distribution of 5-[(123)I]-iodo-A-85380 was consistent with the known densities of nAChRs (thalamus > frontal cortex > cerebellum). Changes in nAChR binding were estimated from the volume of distribution (V(d) ) and binding potential (BP) derived from 3-compartment model fits. In the (-)-nicotine treated animal V(d) was significantly increased in the thalamus (52%) and cerebellum (50%) seven days post cessation of (-)-nicotine treatment, suggesting upregulation of nAChRs. The observed 33% increase in the frontal cortex failed to reach significance. A significant increase in BP was seen in the thalamus. In the saline control animal no changes were observed in V(d) or BP under any experimental conditions. In this preliminary study, we have demonstrated for the first time in vivo upregulation of neuronal nAChR binding following chronic (-)-nicotine treatment.
Publisher: Elsevier BV
Date: 12-2016
DOI: 10.1016/J.EJMP.2016.09.019
Abstract: A Geant4 model of a novel, water-equivalent electronic portal imaging device (EPID) prototype for radiotherapy imaging and dosimetry utilising an array of plastic scintillating fibres (PSFs) has been developed. Monte Carlo (MC) simulations were performed to quantify the PSF-EPID imaging performance and to investigate design aspects affecting performance for optimisation. Using the Geant4 model, the PSF-EPID's imaging performance for 6 MV photon beams was quantified in terms of its modulation transfer function (MTF), noise power spectrum (NPS) and detective quantum efficiency (DQE). Model parameters, including fibre dimensions, optical cladding reflectivity and scintillation yield, were varied to investigate impact on imaging performance. The MC-calculated DQE(0) for the reference PSF-EPID geometry employing 30mm fibres was approximately nine times greater than values reported for commercial EPIDs. When using 10mm long fibres, the PSF-EPID DQE(0) was still approximately three times greater than that of a commercial EPID. Increased fibre length, cladding reflectivity and scintillation yield produced the greatest decreases in NPS and increases in DQE. The potential to develop an optimised next-generation water-equivalent EPID with MV imaging performance at least comparable to commercial EPIDs has been demonstrated. Factors most important for optimising prototype design include fibre length, cladding reflectivity and scintillation yield.
Publisher: American Psychological Association (APA)
Date: 05-2022
DOI: 10.1037/SPY0000289
Publisher: IEEE
Date: 10-2012
Publisher: IEEE
Date: 10-2012
Publisher: IOP Publishing
Date: 30-09-2008
DOI: 10.1088/0031-9155/53/20/019
Abstract: We have tested the performance of an Optotrak Certus system, which optically tracks multiple markers, in both position and time. To do this, we have developed custom code which enables a range of testing protocols, and make this code available to the community. We find that the Certus' positional accuracy is very high, around 20 microm at a distance of 2.8 m. In contrast, we find that its timing accuracy is typically no better than around 5-10% for typical data rates, whether one is using an ethernet connection or a dedicated SCSI link from the system to a host computer. However, with our code we are able to attach very accurate timest s to the data frames, and in cases where regularly-spaced data are not an absolute requirement, this will be more than adequate.
Publisher: Springer Science and Business Media LLC
Date: 10-10-2013
DOI: 10.1007/S13246-013-0222-0
Abstract: Imaging the brain of a freely moving small animal using positron emission tomography (PET) while simultaneously observing its behaviour is an important goal for neuroscience. While we have successfully demonstrated the use of line-of-response (LOR) rebinning to correct the head motion of confined animals, a large proportion of events may need to be discarded because they either 'miss' the detector array after transformation or fall out of the acceptance range of a sinogram. The proportion of events that would have been measured had motion not occurred, so-called 'lost events', is expected to be even larger for freely moving animals. Moreover, the data acquisition in the case of a freely moving animal is further complicated by a complex attenuation field. The aims of this study were (a) to characterise the severity of the 'lostevents' problem for the freely moving animal scenario, and(b) to investigate the relative impact of attenuation correction errors on quantitative accuracy of reconstructed images. A phantom study was performed to simulate the uncorrelated motion of a target and non-target sourcevolume. A small animal PET scanner was used to acquirelist-mode data for different sets of phantom positions. The list-mode data were processed using the standard LOR rebinning approach, and multiple frame variants of this designed to reduce discarded events. We found that LOR rebinning caused up to 86 % 'lost events', and artifacts that we attribute to incomplete projections, when applied to a freely moving target. This fraction was reduced by up to 18 % using the variant approaches, resulting in slightly reduced image artifacts. The effect of the non-target compartment on attenuation correction of the target volume was surprisingly small. However, for certain poses where the target and non-target volumes are aligned transaxially in the field-of-view, the attenuation problem becomes more complex and sophisticated correction methods will be required. We conclude that there are limitations with the LOR rebinning approach and simplified attenuation correction for freely moving animals requiring the development and validation of more sophisticated approaches.
Publisher: Elsevier BV
Date: 06-2006
DOI: 10.1016/J.DDTEC.2006.05.001
Abstract: Molecular imaging has emerged as a powerful approach for studying drug interactions with cellular targets noninvasively in animal models and humans. Most large pharmaceutical companies are now building capacity for molecular imaging or seeking partnerships with research facilities. Therefore, it is timely to review the features and capabilities of the key technologies - single photon emission computed tomography (SPECT), positron emission tomography (PET) and magnetic resonance imaging (MRI). Owing to the differences in the information they convey and the time scales on which they are able to measure the kinetics of labelled drugs, they form a highly complementary set of technologies.:
Publisher: IEEE
Date: 10-2017
Publisher: IEEE
Date: 2004
Publisher: British Institute of Radiology
Date: 03-2013
DOI: 10.1259/BJR.20120500
Publisher: IEEE
Date: 2004
Publisher: IEEE
Date: 11-2016
Publisher: Elsevier BV
Date: 11-2011
DOI: 10.1016/J.BMCL.2011.09.028
Abstract: N-(2-Benzofuranylmethyl)-N'-[4-(2-fluoroethoxy)benzyl]piperazine (6, σ(1)K(i)=2.6 nM) was radiolabeled with fluorine-18 to provide a potential σ(1) receptor radioligand for use in positron emission tomography (PET). Radiofluorination of the appropriate tosylate precursor furnished [(18)F]6 with a specific activity of 45 GBq/μmol, in an average radiochemical yield of 18% and greater than 98% radiochemical purity. MicroPET imaging in Papio hamadryas baboon brain revealed [(18)F]6 uptake consistent with σ receptor distribution, and specificity for σ receptors was demonstrated in a haloperidol pre-treated animal. [(18)F]6 possesses suitable properties for PET imaging of σ(1) receptors, and further investigation of this σ(1) receptor tracer is warranted.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 06-2005
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 03-2014
Publisher: IEEE
Date: 09-2025
Publisher: Informa UK Limited
Date: 14-05-2018
Publisher: Springer US
Date: 2005
Publisher: Public Library of Science (PLoS)
Date: 25-01-2012
Publisher: IOP Publishing
Date: 20-05-2021
Abstract: Aims. We describe an intuitive, easy to use method called PET-ABC that enables full Bayesian statistical inference from single subject dynamic PET data. The performance of PET-ABC was compared with weighted non-linear least squares (WNLS) in terms of reliability of kinetic parameter estimation and statistical power for model selection. Methods. Dynamic PET data based on 1-tissue and 2-tissue compartmental models were simulated with 2 noise models and 3 noise levels. PET-ABC was used to evaluate the reliability of parameter estimates under each condition. It was also used to perform model selection for a simulated noisy dataset composed of a mixture of 1- and 2-tissue compartment kinetics. Finally, PET-ABC was used to analyze a non-steady state dynamic [ 11 C] raclopride study performed on a fully conscious rat administered either 2 mg.kg −1 hetamine or saline 20 min after tracer injection. Results. PET-ABC yielded posterior point estimates for model parameters with smaller variance than WNLS, as well as probability density functions indicating confidence intervals for those estimates. It successfully identified the superiority of a 2-tissue compartment model to fit the simulated mixed model data. For the drug challenge study, the post observation probability of striatal displacement of the PET signal was 0.9 for hetamine and approximately 0 for saline, indicating a high probability of hetamine-induced endogenous dopamine release in the striatum. PET-ABC also demonstrated superior statistical power to WNLS (0.87 versus 0.09) for selecting the correct model in a simulated ligand displacement study. Conclusions. PET-ABC is a simple and intuitive method that provides complete Bayesian statistical analysis of single subject dynamic PET data, including the extent to which model parameter estimates and model choice are supported by the data. Software for PET-ABC is freely available as part of the PETabc package grazian/PETabc .
Publisher: IOP Publishing
Date: 29-04-2008
DOI: 10.1088/0031-9155/53/10/014
Abstract: High-resolution positron emission tomography (PET) imaging of conscious, unrestrained laboratory animals presents many challenges. Some form of motion correction will normally be necessary to avoid motion artefacts in the reconstruction. The aim of the current work was to develop and evaluate a motion tracking system potentially suitable for use in small animal PET. This system is based on the commercially available stereo-optical MicronTracker S60 which we have integrated with a Siemens Focus-220 microPET scanner. We present measured performance limits of the tracker and the technical details of our implementation, including calibration and synchronization of the system. A phantom study demonstrating motion tracking and correction was also performed. The system can be calibrated with sub-millimetre accuracy, and small lightweight markers can be constructed to provide accurate 3D motion data. A marked reduction in motion artefacts was demonstrated in the phantom study. The techniques and results described here represent a step towards a practical method for rigid-body motion correction in small animal PET. There is scope to achieve further improvements in the accuracy of synchronization and pose measurements in future work.
Publisher: American Astronomical Society
Date: 10-09-2008
DOI: 10.1086/590400
Publisher: Elsevier BV
Date: 11-2005
DOI: 10.1016/J.BMC.2005.06.030
Abstract: The novel pyrazolopyrimidine ligand, N,N-diethyl-2-[2-(4-methoxyphenyl)-5,7-dimethyl-pyrazolo[1,5-a]pyrimidin-3-yl]-acetamide 1 (DPA-713), has been reported as a potent ligand for the peripheral benzodiazepine receptor (PBR) displaying an affinity of K(i)=4.7 nM. In this study, 1 was successfully synthesised and demethylated to form the phenolic derivative 6 as precursor for labelling with carbon-11 (t(1/2) = 20.4 min). [11C]1 was prepared by O-alkylation of 6 with [11C]methyl iodide. The radiochemical yield of [(11)C]1 was 9% (non-decay corrected) with a specific activity of 36 GBq/micromol at the end of synthesis. The average time of synthesis including formulation was 13.2 min with a radiochemical purity >98%. In vivo assessment of [11C]1 was performed in a healthy Papio hamadryas baboon using positron emission tomography (PET). Following iv administration of [11C]1, significant accumulation was observed in the baboon brain and peripheral organs. In the brain, the radioactivity peaked at 20 min and remained constant for the duration of the imaging experiment. Pre-treatment with the PBR-specific ligand, PK 11195 (5 mg/kg), effectively reduced the binding of [11C]1 at 60 min by 70% in the whole brain, whereas pre-treatment with the central benzodiazepine receptor ligand, flumazenil (1mg/kg), had no inhibitory effect on [11C]1 uptake. These results indicate that accumulation of [11C]1 in the baboon represents selective binding to the PBR. These exceptional in vivo binding properties suggest that [11C]1 may be useful for imaging the PBR in disease states. Furthermore, [11C]1 represents the first ligand of its pharmacological class to be labelled for PET studies and therefore has the potential to generate new information on the pathological role of the PBR in vivo.
Publisher: IEEE
Date: 10-2017
Publisher: IEEE
Date: 10-2008
Publisher: IEEE
Date: 10-2012
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 02-2002
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 10-2010
Publisher: IOP Publishing
Date: 26-10-2007
DOI: 10.1088/0031-9155/52/22/005
Abstract: The neuroanatomy and physiology of the baboon brain closely resembles that of the human brain and is well suited for evaluating promising new radioligands in non-human primates by PET and SPECT prior to their use in humans. These studies are commonly performed on clinical scanners with 5 mm spatial resolution at best, resulting in sub-optimal images for quantitative analysis. This study assessed the feasibility of using a microPET animal scanner to image the brains of large non-human primates, i.e. papio hamadryas (baboon) at high resolution. Factors affecting image accuracy, including scatter, attenuation and spatial resolution, were measured under conditions approximating a baboon brain and using different reconstruction strategies. Scatter fraction measured 32% at the centre of a 10 cm diameter phantom. Scatter correction increased image contrast by up to 21% but reduced the signal-to-noise ratio. Volume resolution was superior and more uniform using maximum a posteriori (MAP) reconstructed images (3.2-3.6 mm(3) FWHM from centre to 4 cm offset) compared to both 3D ordered subsets expectation maximization (OSEM) (5.6-8.3 mm(3)) and 3D reprojection (3DRP) (5.9-9.1 mm(3)). A pilot (18)F-2-fluoro-2-deoxy-d-glucose ([(18)F]FDG) scan was performed on a healthy female adult baboon. The pilot study demonstrated the ability to adequately resolve cortical and sub-cortical grey matter structures in the baboon brain and improved contrast when images were corrected for attenuation and scatter and reconstructed by MAP. We conclude that high resolution imaging of the baboon brain with microPET is feasible with appropriate choices of reconstruction strategy and corrections for degrading physical effects. Further work to develop suitable correction algorithms for high-resolution large primate imaging is warranted.
Publisher: IEEE
Date: 10-2012
Publisher: IEEE
Date: 10-2011
Publisher: IEEE
Date: 10-2010
Publisher: IEEE
Date: 10-2016
Publisher: Wiley
Date: 18-08-2014
DOI: 10.1118/1.4892931
Abstract: Single photon emission computed tomography (SPECT) brain imaging of freely moving small animals would allow a wide range of important neurological processes and behaviors to be studied, which are normally inhibited by anesthetic drugs or precluded due to the animal being restrained. While rigid body motion of the head can be tracked and accounted for in the reconstruction, activity in the torso may confound brain measurements, especially since motion of the torso is more complex (i.e., nonrigid) and not well correlated with that of the head. The authors investigated the impact of mispositioned events and attenuation due to the torso on the accuracy of motion corrected brain images of freely moving mice. Monte Carlo simulations of a realistic voxelized mouse phantom and a dual compartment phantom were performed. Each phantom comprised a target and an extraneous compartment which were able to move independently of each other. Motion correction was performed based on the known motion of the target compartment only. Two SPECT camera geometries were investigated: a rotating single head detector and a stationary full ring detector. The effects of motion, detector geometry, and energy of the emitted photons (hence, attenuation) on bias and noise in reconstructed brain regions were evaluated. The authors observed two main sources of bias: (a) motion-related inconsistencies in the projection data and (b) the mismatch between attenuation and emission. Both effects are caused by the assumption that the orientation of the torso is difficult to track and model, and therefore cannot be conveniently corrected for. The motion induced bias in some regions was up to 12% when no attenuation effects were considered, while it reached 40% when also combined with attenuation related inconsistencies. The detector geometry (i.e., rotating vs full ring) has a big impact on the accuracy of the reconstructed images, with the full ring detector being more advantageous. Motion-induced inconsistencies in the projection data and attenuation/emission mismatch are the two main causes of bias in reconstructed brain images when there is complex motion. It appears that these two factors have a synergistic effect on the qualitative and quantitative accuracy of the reconstructed images.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 11-2020
Publisher: SPIE
Date: 02-03-2006
DOI: 10.1117/12.652898
Publisher: SPIE
Date: 23-02-2012
DOI: 10.1117/12.910452
Publisher: European Respiratory Society (ERS)
Date: 04-1996
DOI: 10.1183/09031936.96.09040725
Abstract: Hyperosmolarity of the airway surface liquid (ASL) has been proposed as the stimulus for hyperpnoea-induced asthma. We found previously that mucociliary clearance (MCC) was increased after isocapnic hyperventilation (ISH) with dry air, and we proposed that the increase related to transient hyperosmolarity of the ASL. We investigated the effect of increasing the osmolarity of the ASL on MCC, by administering an aerosol of concentrated salt solution. MCC was measured using 99mTc-sulphur colloid, gamma camera and computer analysis in 12 asthmatic and 10 healthy subjects on three separate days, involving administration of each of the following: 1) ultrasonically nebulized 14.4% saline 2) ultrasonically nebulized 0.9% saline and 3) no aerosol intervention (control). The (mean +/- SD) volume of nebulized 14.4% saline was 2.2 +/- 1.2 mL for asthmatics and 3.2 +/- 0.7 mL for healthy subjects. This volume was delivered over a period of 5.4 +/- 1.3 and 6.4 +/- 0.7 min for asthmatic and healthy subjects, respectively. The airway response to 14.4% saline was assessed on a separate visit and the fall in forced expiratory volume in one second (FEV1) was 22 +/- 4% in the asthmatic and 3 +/- 2% in the healthy subjects. Compared to the MCC with the 0.9% saline and control, the hypertonic aerosol increased MCC in both groups. In asthmatic subjects, MCC of the whole right lung in 1 h was 68 +/- 10% with 14.4% saline vs 44 +/- 14% with 0.9% saline and 39 +/- 13% with control. In healthy subjects, MCC of the whole right lung in 1 h was 53 +/- 12% with 14.4% saline vs 41 +/- 15% with 0.9% saline and 36 +/- 13% with control. We conclude that an increase in osmolarity of the airway surface liquid increases mucociliary clearance both in asthmatic and healthy subjects. These findings are in keeping with our previous suggestion that the increase in mucociliary clearance after isotonic hyperventilation with dry air is due to a transient hyperosmolarity of the airway surface liquid.
Publisher: Springer New York
Date: 2014
Publisher: American Thoracic Society
Date: 02-1997
DOI: 10.1164/AJRCCM.155.2.9032213
Abstract: Absence of a maximal dose-response plateau and mathematical modeling suggest that asthmatic airways close during bronchoconstriction. Finding segmental areas affected by closure would be important in understanding asthmatic airway function. The aim of this study was to evaluate single-photon emission computed tomography (SPECT) as a method of investigating airway closure. Simultaneous SPECT transmission and emission studies were performed on a thoracic phantom to develop analysis methodology, and on 13 normal subjects after they inhaled a Technegas bolus from residual volume (RV), to measure airway closure. Single-breath nitrogen test values and lung volumes were measured. Airway closure was defined as the percent of Technegas-free lung volume (LVclosed). The mean error +/- 95% CI of the error, as determined by transmission scan, was 1.1 ml +/- 165 ml (0.8% +/- 15% lung volume) in the phantom studies, and 112 ml +/- 419 ml (4% +/- 31% of supine functional residual capacity [FRC]) in the human studies. LVclosed correlated with closing capacity (r = 0.86, p < 0.01 ) and closing volume (r = 0.86, p < 0.01), but not with RV/total lung capacity (TLC). This study indicates that simultaneous SPECT emission and transmission scans, using a Technegas bolus, are a valid method of measuring airway closure in vivo, with the added advantage of providing three-dimensional data that allow the detection of small, discrete areas of airway closure and determination of their volumes and shapes.
Publisher: IEEE
Date: 2007
Publisher: IOP Publishing
Date: 18-08-2009
DOI: 10.1088/0031-9155/54/17/016
Abstract: Line of response (LOR) rebinning is an event-based motion-correction technique for positron emission tomography (PET) imaging that has been shown to compensate effectively for rigid motion. It involves the spatial transformation of LORs to compensate for motion during the scan, as measured by a motion tracking system. Each motion-corrected event is then recorded in the sinogram bin corresponding to the transformed LOR. It has been shown previously that the corrected event must be normalized using a normalization factor derived from the original LOR, that is, based on the pair of detectors involved in the original coincidence event. In general, due to data compression strategies (mashing), sinogram bins record events detected on multiple LORs. The number of LORs associated with a sinogram bin determines the relative contribution of each LOR. This paper provides a thorough treatment of event-based normalization during motion correction of PET data using LOR rebinning. We demonstrate theoretically and experimentally that normalization of the corrected event during LOR rebinning should account for the number of LORs contributing to the sinogram bin into which the motion-corrected event is binned. Failure to account for this factor may cause artifactual slice-to-slice count variations in the transverse slices and visible horizontal stripe artifacts in the coronal and sagittal slices of the reconstructed images. The theory and implementation of normalization in conjunction with the LOR rebinning technique is described in detail, and experimental verification of the proposed normalization method in phantom studies is presented.
Publisher: IEEE
Date: 10-2013
Publisher: IEEE
Date: 10-2018
Publisher: IOP Publishing
Date: 13-04-2017
Abstract: Awake and/or freely moving small animal single photon emission imaging allows the continuous study of molecules exhibiting slow kinetics without the need to restrain or anaesthetise the animals. Estimating motion free projections in freely moving small animal planar imaging can be considered as a limited angle tomography problem, except that we wish to estimate the 2D planar projections rather than the 3D volume, where the angular s ling in all three axes depends on the rotational motion of the animal. In this study, we hypothesise that the motion corrected planar projections estimated by reconstructing an estimate of the 3D volume using an iterative motion compensating reconstruction algorithm and integrating it along the projection path, will closely match the true, motion-less, planar distribution regardless of the object motion. We tested this hypothesis for the case of rigid motion using Monte-Carlo simulations and experimental phantom data based on a dual opposed detector system, where object motion was modelled with 6 degrees of freedom. In addition, we investigated the quantitative accuracy of the regional activity extracted from the geometric mean of opposing motion corrected planar projections. Results showed that it is feasible to estimate qualitatively accurate motion-corrected projections for a wide range of motions around all 3 axes. Errors in the geometric mean estimates of regional activity were relatively small and within 10% of expected true values. In addition, quantitative regional errors were dependent on the observed motion, as well as on the surrounding activity of overlapping organs. We conclude that both qualitatively and quantitatively accurate motion-free projections of the tracer distribution in a rigidly moving object can be estimated from dual opposed detectors using a correction approach within an iterative reconstruction framework and we expect this approach can be extended to the case of non-rigid motion.
Publisher: SPIE
Date: 19-03-2014
DOI: 10.1117/12.2043403
Publisher: Elsevier BV
Date: 2007
DOI: 10.1016/J.EJPHAR.2006.10.020
Abstract: Trishomocubane analogues TC1 (N-(3'-fluorophenyl)ethyl-4-azahexacyclo [5.4.1.0(2,6).0(3,10).0(5,9).0(8,11)]dodecan-3-ol) and TC4 (N-(3'-fluorophenyl)methyl-4-azahexacyclo [5.4.1.0(2,6).0(3,10).0(5,9).0(8,11)]dodecan-3-ol) were evaluated for their modulatory effects on locomotor activity as well as interactions with cocaine-induced responses. TC1 and TC4 have high affinity and moderate to high selectivity for sigma(1) (Ki=10 nM, sigma1/sigma2=0.03) and sigma2 (Ki=20 nM, sigma1/sigma2=7.6) receptor subtypes respectively. Both compounds have negligible affinity for the dopamine (DAT), serotonin (SERT), and norepinephrine (NET) transporters. In behavioural studies, TC1 produced a dose-related inhibition in spontaneous locomotor activity measured in a Digiscan apparatus. TC1 attenuated the stimulatory locomotor effect of 20 mg/kg cocaine with a half-maximal depressant activity (ID50) of 38.6 mg/kg. TC1 (dose range of 25 to 100 mg/kg) also partially substituted for the effect of cocaine (10 mg/kg) in a discriminative stimulus task, involving the trained discrimination between cocaine and saline using a two-lever choice method. Following a dose of 50 mg/kg TC1, a maximum of 31% substitution was reached. The response rate was reduced to 56% of vehicle control following a TC1 dose of 100 mg/kg. These behavioural effects suggest that TC1 can act as an antagonist via the sigma1 receptor. In contrast to TC1, TC4 produced a stimulant effect in locomotor activity with the ED50 estimated at 0.94 mg/kg. In addition, TC4 failed to inhibit cocaine-induced stimulation neither did it substitute for the discriminative stimulus effects of cocaine. TC4 thus appears to interact predominantly with the sigma2 receptor subtype (sigma1/sigma2=7.6) which may result in dopamine stimulation independent of the effects of cocaine. The differential effect of TC1 and TC4 warrants further study of the mechanism of these actions. Present data also suggests a potential role for trishomocubane analogues in developing medication or research tools for cocaine addiction.
Publisher: IEEE
Date: 10-2013
Publisher: IEEE
Date: 10-2010
Publisher: Springer Science and Business Media LLC
Date: 05-11-2011
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 10-2008
Publisher: IOP Publishing
Date: 11-04-2018
Publisher: IEEE
Date: 10-2012
Publisher: Springer Science and Business Media LLC
Date: 18-05-2016
DOI: 10.1007/S00125-016-3993-5
Abstract: Type 2 diabetes is characterised by decreased HDL levels, as well as the level of apolipoprotein A-I (apoA-I), the main apolipoprotein of HDLs. Pharmacological elevation of HDL and apoA-I levels is associated with improved glycaemic control in patients with type 2 diabetes. This is partly due to improved glucose uptake in skeletal muscle. This study used kinetic modelling to investigate the impact of increasing plasma apoA-I levels on the metabolism of glucose in the db/db mouse model. Treatment of db/db mice with apoA-I for 2 h significantly improved both glucose tolerance (AUC 2574 ± 70 mmol/l × min vs 2927 ± 137 mmol/l × min, for apoA-I and PBS, respectively p < 0.05) and insulin sensitivity (AUC 388.8 ± 23.8 mmol/l × min vs 194.1 ± 19.6 mmol/l × min, for apoA-I and PBS, respectively p < 0.001). ApoA-I treatment also increased glucose uptake by skeletal muscle in both an insulin-dependent and insulin-independent manner as evidenced by increased uptake of fludeoxyglucose ([(18)F]FDG) from plasma into gastrocnemius muscle in apoA-I treated mice, both in the absence and presence of insulin. Kinetic modelling revealed an enhanced rate of insulin-mediated glucose phosphorylation (k 3) in apoA-I treated mice (3.5 ± 1.1 × 10(-2) min(-1) vs 2.3 ± 0.7 × 10(-2) min(-1), for apoA-I and PBS, respectively p < 0.05) and an increased influx constant (3.7 ± 0.6 × 10(-3) ml min(-1) g(-1) vs 2.0 ± 0.3 × 10(-3) ml min(-1) g(-1), for apoA-I and PBS, respectively p < 0.05). Treatment of L6 rat skeletal muscle cells with apoA-I for 2 h indicated that increased hexokinase activity mediated the increased rate of glucose phosphorylation. These findings indicate that apoA-I improves glucose disposal in db/db mice by improving insulin sensitivity and enhancing glucose phosphorylation.
Publisher: IEEE
Date: 2007
Publisher: IEEE
Date: 10-2010
Publisher: IEEE
Date: 11-2016
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 11-2014
Publisher: IEEE
Date: 2007
Publisher: Elsevier BV
Date: 03-1996
DOI: 10.1016/0735-1097(95)00497-1
Abstract: We examined the utility of the 32-point QRS score from the 12-lead electrocardiogram (ECG) for measurement of the ischemic risk region and infarct size in patients receiving thrombolytic therapy. The QRS score offers a means of evaluating the therapeutic benefit of thrombolytic therapy by comparing final infarct size with the initial extent of ischemic myocardium. The study included 38 patients (34 men, 4 women mean [+/-SD] age 54 +/- 10 years) with a first infarction (18 anterior, 20 inferior). The maximal potential QRS score (QRS0) was assigned to all leads with >/= 100-microV ST elevation on the initial ECG. The QRS scores were calculated at 7 and 30 days after infarction. Left ventricular ejection fraction was measured by radionuclide ventriculography at 1 month. Twenty-eight patients had thallium (Tl)-201 and technetium (Tc)-99m pyrophosphate tomographic measurement of the ischemic region and infarct size. The QRS0 was 10.3 +/- 3.1 (mean +/- SD) for anterior and 10.4 +/- 3.5 for inferior infarcts. The QRS scores were similar at 7 and 30 days for both anterior (5.6 +/- 3.4 vs. 5.5 +/- 3.4) and inferior infarcts (3.7 +/- 2.6 vs. 2.9 +/- 2.2). The day 7 QRS score and ejection fraction at 1 month were inversely correlated (r = -0.74, p < 0.01). The Tl-201 perfusion defect was 34 +/- 11% of the left ventricle for anterior and 32 +/- 7% for inferior infarcts. Subsequent Tc-99m pyrophosphate infarct size was 15 +/- 9% of the left ventricle for anterior and 17 +/- 9% for inferior infarcts. The QRS0 was correlated with the extent of the Tl-201 perfusion defect (r = 0.79, p < 0.001), and the day 7 QRS score was correlated with Tc-99m pyrophosphate infarct size (r = 0.79, p < 0.005). The 32-point QRS score can provide useful immediate measurements of the ischemic risk region and subsequent infarct size.
Publisher: Hindawi Limited
Date: 08-2006
DOI: 10.1111/J.1600-0404.2006.00694.X
Abstract: Evidence from numerous neuropathological observations and in vivo clinical imaging studies suggests a prominent role of activated microglia, the main effector cell of the brain's innate immune system, in Alzheimer's disease and other neurodegenerative diseases. Though the comprehensive molecular definition of the microglial activation process is still incomplete, the de novo expression of 'peripheral benzodiazepine-binding sites (PBBS)' by activated but not resting microglia has been established as a useful descriptor of functional state changes in microglia. As microglial transformation to an activated state is closely linked to progressive changes in brain disease, the detection of activated microglia can provide information about disease distribution and rate of disease progression. Positron emission tomography (PET) and [(11)C](R)-PK11195, a specific ligand of the PBBS, have been used to study systematically microglial activation in vivo. Significant microglial activation is present in the brains of patients with neurodegenerative dementia even at early and possibly preclinical stages of the disease with a spatial distribution reflecting different clinical phenotypes. We review some of the posited functions of activated microglia in the pathophysiology of dementia and speculate on the relationship between increased regional [(11)C](R)-PK11195 signals and the ensuing changes in brain volume. Finally, we provide a brief outlook on the development of new radioligands for the PBBS.
Publisher: Elsevier BV
Date: 02-2009
DOI: 10.1016/J.BRAINRESBULL.2008.08.006
Abstract: Positron emission tomography (PET) is a sensitive and specific non-invasive molecular imaging technique providing quantitative images and data on biochemical pathways, molecular interactions, drug pharmacokinetics and pharmacodynamics. The PET measurement of regional biochemical functions requires a rational design of the radiolabelled probes employed. When choosing a drug to radiolabel there are many considerations, the most important being the potential of the drug to provide the information that is required in vivo. For ex le, when developing a radiolabelled probe for measuring the regional concentration of a neurotransmitter receptor the affinity and selectivity of the drug need to be considered. Other factors which influence a decision about which drug to radiolabel include the ability of the drug to reach its target, drug lipophilicity and metabolism, toxicity and the amenability to radiolabelling. PET has been applied in studies of Parkinson's disease (PD) and has provided important information on disease on-set and progression. This brief overview aims to outline the challenges and capabilities of PET and the more commonly used molecular probes in PD studies.
Publisher: Springer Science and Business Media LLC
Date: 07-01-2011
Publisher: IOP Publishing
Date: 30-06-2023
Abstract: Positron emission tomography (PET) molecular biomarkers and diffusion magnetic resonance imaging (dMRI) derived information show associations and highly complementary information in a number of neurodegenerative conditions, including Alzheimer’s disease. Diffusion MRI provides valuable information about the microstructure and structural connectivity (SC) of the brain which could guide and improve the PET image reconstruction when such associations exist. However, this potental has not been previously explored. In the present study, we propose a CONNectome-based non-local means one-atep late maximum a posteriori (CONN-NLM-OSLMAP) method, which allows diffusion MRI-derived connectivity information to be incorporated into the PET iterative image reconstruction process, thus regularising the estimated PET images. The proposed method was evaluated using a realistic tau-PET/MRI simulated phantom, demonstrating more effective noise reduction and lesion contrast improvement, as well as the lowest overall bias compared with both a median filter applied as an alternative regulariser and CONNectome-based non-local means as a post-reconstruction filter. By adding complementary SC information from diffusion MRI, the proposed regularisation method offers more useful and targeted denoising and regularisation, demonstrating the feasibility and effectiveness of integrating connectivity information into PET image reconstruction.
Publisher: Springer Science and Business Media LLC
Date: 06-1997
DOI: 10.1007/BF00841411
Abstract: Background Virtual tumor board (VTB) platforms are an important aspect of cancer management. They enable easier access to a multidisciplinary team of experts. To deliver high-quality cancer care, it is necessary to coordinate numerous therapies and providers, share technical knowledge, and maintain open lines of communication among all professionals involved. The VTB is an essential tool in the diagnosis and treatment of brain cancer. For patients with glioma and brain metastases, multidisciplinary tumor board guidelines should guide diagnosis and therapy throughout the course of the illness. VTBs are an emerging resource across various cancer care networks in the United States. Methodology We performed a systematic search of all VTBs incorporating a platform designed for this specific role. We reviewed the records of the Genomet VTB, the Medical University of South Carolina (MUSC) VTB, and Xcures VTB. Summary data examined included the year of launch, demographics, characteristics of cases, average response time, advantages, and how they handle protected health information. Results Overall, 30% of VTBs examined were launched in 2017. All had a Health Insurance Portability and Accountability Act-compliant online environment. On a review of Xcures records, the median age of the female patients was 57 years and the median age of the male patients was 55 years. The data showed that 44% (4.4 out of every 10 patients) with a confirmed treatment chose the VTB integrated option. Overall, 76% of patients in the Xcures registry had primary central nervous system tumors, with at least 556 patients in the tumor registry which included 46% glioblastoma cases (96% primary, 4% secondary). In the MUSC VTB project, 112 thoracic tumor cases and nine neuro-oncology cases were reviewed. The tumor board met weekly, and the average response time was within 24 hours of case review and presentation. The Genomet VTB de-identifies all patient information this is a virtual platform primarily focused on neuro-oncology cases. Cases involved a median of five specialists most commonly neuro-oncologists, neurosurgeons, radiation oncologists, molecular pathologists, and neuroradiologists. The case review revealed an age range of six months to 84 years (mean age = 44.5 years), with 69.6% males and 30.4% females, 43.5% glioblastomas, 8.7% adenocarcinomas, and 8.7% infratentorial tumors. The average response time observed in all cases was ≤24 hours. Conclusions VTBs allow for quicker expert analysis of cases. This has resulted in an accelerated number of cases reviewed with a shortened communication time. More studies are needed to gain additional insights into user engagement metrics.
Publisher: Elsevier BV
Date: 05-2012
DOI: 10.1016/J.NEUROIMAGE.2012.02.032
Abstract: Accurate quantification of PET imaging data is required for a useful interpretation of the measured radioactive tracer concentrations. The partial volume effect (PVE) describes signal dilution and mixing due to spatial resolution and s ling limitations, which introduces bias in quantitative results. In the present study we investigated the magnitude of PVE for volumes of interest (VOIs) in the rat brain and the effect of positron range. In simulated (11)C-raclopride studies we examined the influence of PVE on time activity curves in striatal and cerebellar VOIs and binding potential estimation. The performance of partial volume correction (PVC) was studied using the region-based geometric transfer matrix (GTM) method including the question of whether a spatially variant point spread function (PSF) is necessary for PVC of a rat brain close to the centre of the field of view. Furthermore, we determined the effect of spillover from activity outside the brain. The results confirmed that PVE is significant in rat brain PET and showed that positron range is an important factor that needs to be included in the PSF. There was considerable bias in time activity curves for the simulated (11)C-raclopride studies and significant underestimation of binding potential even for very small centred VOIs. Good activity recovery was achieved with the GTM PVC using a spatially invariant simulated PSF when no activity was present outside the brain. PVC using a simple Gaussian fit point spread function was not sufficiently accurate. Spillover from regions outside the brain had a significant impact on measured activity concentrations and reduced the accuracy of PVC with the GTM method using rat brain regions alone, except for the smallest VOI size but at the cost of increased noise. Voxel-based partial volume correction methods which inherently compensate for spillover from outside the brain might be a more suitable choice.
Publisher: IOP Publishing
Date: 12-03-2021
Abstract: Positron emission tomography (PET) plays an increasingly important role in research and clinical applications, catalysed by remarkable technical advances and a growing appreciation of the need for reliable, sensitive biomarkers of human function in health and disease. Over the last 30 years, a large amount of the physics and engineering effort in PET has been motivated by the dominant clinical application during that period, oncology. This has led to important developments such as PET/CT, whole-body PET, 3D PET, accelerated statistical image reconstruction, and time-of-flight PET. Despite impressive improvements in image quality as a result of these advances, the emphasis on static, semi-quantitative ‘hot spot’ imaging for oncologic applications has meant that the capability of PET to quantify biologically relevant parameters based on tracer kinetics has not been fully exploited. More recent advances, such as PET/MR and total-body PET, have opened up the ability to address a vast range of new research questions, from which a future expansion of applications and radiotracers appears highly likely. Many of these new applications and tracers will, at least initially, require quantitative analyses that more fully exploit the exquisite sensitivity of PET and the tracer principle on which it is based. It is also expected that they will require more sophisticated quantitative analysis methods than those that are currently available. At the same time, artificial intelligence is revolutionizing data analysis and impacting the relationship between the statistical quality of the acquired data and the information we can extract from the data. In this roadmap, leaders of the key sub-disciplines of the field identify the challenges and opportunities to be addressed over the next ten years that will enable PET to realise its full quantitative potential, initially in research laboratories and, ultimately, in clinical practice.
Publisher: Wiley
Date: 08-05-2023
DOI: 10.1002/JMRS.686
Abstract: Recently developed Long (≥100 cm) axial field of view (AFOV) PET/CT scanners are capable of producing images with higher signal‐to‐noise ratio, or performing faster whole‐body acquisitions, or scanning with lower radiation dose to the patient, compared with conventional PET/CT scanners. These benefits, which arise due to their substantially higher, by more than an order of magnitude, geometric efficiency, have been well described in the recent literature. The introduction of Long AFOV PET/CT technology into the clinic also has important implications for the design and workflow of PET/CT facilities and their effects on radiation exposure to staff and patients. Maximising the considerable benefits of this technology requires a thorough understanding of the relationships between these factors to optimise workflows while appropriately managing radiation exposure. This article reviews current knowledge on PET/CT facility design, workflows and their effects on radiation exposure, identifies gaps in the literature and discusses the challenges that need to be considered with the introduction of Long AFOV PET/CT into the clinic.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 06-2001
DOI: 10.1109/23.940169
Publisher: IOP Publishing
Date: 10-05-2011
DOI: 10.1088/0031-9155/56/11/009
Abstract: Monte Carlo simulation codes that model positron interactions along their tortuous path are expected to be accurate but are usually slow. A simpler and potentially faster approach is to model positron range from analytical annihilation density distributions. The aims of this paper were to efficiently implement and validate such a method, with the addition of medium heterogeneity representing a further challenge. The analytical positron range model was evaluated by comparing annihilation density distributions with those produced by the Monte Carlo simulator GATE and by quantitatively analysing the final reconstructed images of Monte Carlo simulated data. In addition, the influence of positronium formation on positron range and hence on the performance of Monte Carlo simulation was investigated. The results demonstrate that 1D annihilation density distributions for different isotope-media combinations can be fitted with Gaussian functions and hence be described by simple look-up-tables of fitting coefficients. Together with the method developed for simulating positron range in heterogeneous media, this allows for efficient modelling of positron range in Monte Carlo simulation. The level of agreement of the analytical model with GATE depends somewhat on the simulated scanner and the particular research task, but appears to be suitable for lower energy positron emitters, such as (18)F or (11)C. No reliable conclusion about the influence of positronium formation on positron range and simulation accuracy could be drawn.
Publisher: IOP Publishing
Date: 03-1998
DOI: 10.1088/0031-9155/43/3/016
Abstract: Spectral analysis is a general modelling approach that enables calculation of parametric images from reconstructed tracer kinetic data independent of an assumed compartmental structure. We investigated the validity of applying spectral analysis directly to projection data motivated by the advantages that: (i) the number of reconstructions is reduced by an order of magnitude and (ii) iterative reconstruction becomes practical which may improve signal-to-noise ratio (SNR). A dynamic software phantom with typical 2-[11C]thymidine kinetics was used to compare projection-based and image-based methods and to assess bias-variance trade-offs using iterative expectation maximization (EM) reconstruction. We found that the two approaches are not exactly equivalent due to properties of the non-negative least-squares algorithm. However, the differences are small (< 5%) and mainly affect parameters related to early and late time points on the impulse response function (K1 and, to a lesser extent, VD). The optimal number of EM iteration was 15-30 with up to a two-fold improvement in SNR over filtered back projection. We conclude that projection-based spectral analysis with EM reconstruction yields accurate parametric images with high SNR and has potential application to a wide range of positron emission tomography ligands.
Publisher: Laurentian University Library
Date: 05-01-2021
Abstract: Mindfulness-based interventions (MBIs) teach practices that encourage the development of present moment awareness through paying attention on purpose and non-judgmentally to one’s experiences, feelings, thoughts, and behaviors. We describe three graduate student research thesis projects that explored the suitability and benefits of an arts-based MBI with three different populations teachers, university students, and women survivors of intimate partner violence. These three populations have been identified as experiencing heightened levels of stress and in need of resilience building supports. All three projects were qualitative pilot studies that explored whether participants would experience increased understanding and development of mindfulness-based skills, and improved coping with stress through participating in the program. Pre- and post-MBI group interviews were conducted, and interview data was analyzed using thematic analysis. Across the three projects, the student researchers found self-reported benefits with no adverse effects. Developing mindfulness-based skills helped the participants to build their self-awareness/understanding which in turn helped to develop emotion regulation. This is consistent with our understanding of how MBIs can build people’s capacity to make conscious choices about their feelings rather than reacting to emotional triggers. Improved coping with stress was also reported in all three projects. Developing present-moment awareness and mindfulness can help people appreciate life’s moments, and cope better with daily life stressors. Also important was the growth of self-compassion and acceptance. The results are promising and indicate that further exploration with these populations is warranted. Future research could explore an arts-based approach to facilitating mindfulness with larger numbers of participants and using control and/or comparison groups.
Publisher: Springer Science and Business Media LLC
Date: 03-2004
DOI: 10.1007/BF03190567
Publisher: IEEE
Date: 2007
Publisher: IEEE
Date: 10-2010
Publisher: Informa UK Limited
Date: 04-02-2019
Publisher: IEEE
Date: 10-2010
Publisher: IEEE
Date: 10-2007
Publisher: IOP Publishing
Date: 02-08-2006
DOI: 10.1088/0031-9155/51/16/008
Abstract: An accurate, low noise estimate of photon attenuation in the subject is required for quantitative microPET studies of molecular tracer distributions in vivo. In this work, several transmission-based measurement techniques were compared, including coincidence mode with and without rod windowing, singles mode with two different energy sources ((68)Ge and (57)Co), and postinjection transmission scanning. In addition, the effectiveness of transmission segmentation and the propagation of transmission bias and noise into the emission images were examined. The (57)Co singles measurements provided the most accurate attenuation coefficients and superior signal-to-noise ratio, while (68)Ge singles measurements were degraded due to scattering from the object. Scatter correction of (68)Ge transmission data improved the accuracy for a 10 cm phantom but over-corrected for a mouse phantom. (57)Co scanning also resulted in low bias and noise in postinjection transmission scans for emission activities up to 20 MBq. Segmentation worked most reliably for transmission data acquired with (57)Co but the minor improvement in accuracy of attenuation coefficients and signal-to-noise may not justify its use, particularly for small subjects. We conclude that (57)Co singles transmission scanning is the most suitable method for measured attenuation correction on the microPET Focus 220 animal scanner.
Publisher: IEEE
Date: 2007
Publisher: IEEE
Date: 2005
Publisher: SAGE Publications
Date: 12-02-2019
Abstract: We facilitated an arts-based mindfulness group program with youths who were receiving short-term in-patient mental health supports within hospital. We aimed to explore the challenges and benefits these marginalized youths experienced through their exposure to the group intervention. Forty pregroup and 24 postgroup interviews were analyzed using a thematic analysis framework. The qualitative findings are presented using creative nonfiction in the form of a composite vignette. The composite vignette portrays the content within the themes, creatively telling a more compelling story that illustrates key points and themes within the data set. The vignette shows how mental health challenges created problems in the youths’ lives. Although most of the youths were initially nervous about participating in the program, the strengths and arts-based nature of the program helped them to connect with others in the group and express themselves. All of the youths reported that the group program was enjoyable and beneficial. They learned to identify what they were feeling/thinking and to express these feelings/thoughts using creative means of expression. Making art helped them to develop their self-awareness and created enjoyment in the group and with the group methods. Also, learning about mindfulness helped them to think in different ways, and to focus and relax more. The results of this pilot project warrant further investigation into the benefits of creative strengths-based mindfulness-based interventions for in-patient youths experiencing mental health challenges. The composite vignette centers the youths’ voices and provides a comprehensive account of their experiences.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 08-2001
DOI: 10.1109/23.958754
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 03-2001
DOI: 10.1109/4233.908397
Abstract: Dynamic imaging with positron emission tomography (PET) is widely used for the in vivo measurement of regional cerebral metabolic rate for glucose (rCMRGlc) with [18F]fluorodeoxy-D-glucose (FDG) and is used for the clinical evaluation of neurological disease. However, in addition to the acquisition of dynamic images, continuous arterial blood s ling is the conventional method to obtain the tracer time-activity curve in blood (or plasma) for the numeric estimation of rCMRGlc in mg glucose/100-g tissue/min. The insertion of arterial lines and the subsequent collection and processing of multiple blood s les are impractical for clinical PET studies because it is invasive, has the remote, but real potential for producing limb ischemia, and it exposes personnel to additional radiation and risks associated with handling blood. In this paper, based on our previously proposed method for extracting kinetic parameters from dynamic PET images, we developed a modified version (post-estimation method) to improve the numerical identifiability of the parameter estimates when we deal with data obtained from clinical studies. We applied both methods to dynamic neurologic FDG PET studies in three adults. We found that the input function and parameter estimates obtained with our noninvasive methods agreed well with those estimated from the gold standard method of arterial blood s ling and that rCMRGlc estimates were highly correlated (r = 0.973). More importantly, no significant difference was found between rCMRGlc estimated by our methods and the gold standard method (P > 0.16). We suggest that our proposed noninvasive methods may offer an advance over existing methods.
Publisher: IOP Publishing
Date: 03-1994
DOI: 10.1088/0031-9155/39/3/009
Abstract: 3D acquisition and reconstruction in positron emission tomography (PET) produce data with improved signal-to-noise ratios compared with conventional 2D slice-oriented methods. However, the sensitivity increase is accompanied by an increase in the number of scattered photons and random coincidences detected. This paper presents a scatter correction technique for 3D PET data where an estimate of the scattered photon distribution is subtracted from the data before reconstruction. The scatter distribution is estimated by iteratively convolving the photopeak projections with a mono-exponential kernel. The method accounts for the 3D acquisition geometry and nature of scatter by performing the scatter estimation on 2D projections. The assumptions of the method have been investigated by measuring the variation in the scatter fraction and the scatter function at different positions in a cylinder. Both parameters were found to vary by up to 50% from the centre to the edge of a large water-filled cylinder. Despite this, in a uniform cylinder containing water with different concentrations of radioactivity, scatter was reduced from 25% in a non-radioactive region to less than 5% using the convolution-subtraction method. In addition, the relative concentration of a cylinder containing an increased concentration, which was underestimated by almost 50% without scatter correction, was within 5% of the true concentration after correction.
Publisher: Springer Science and Business Media LLC
Date: 08-2008
DOI: 10.1007/S11307-008-0157-0
Abstract: The purpose of the study is to investigate the feasibility of an event driven motion correction method for neurological microPET imaging of small laboratory animals in the fully awake state. A motion tracking technique was developed using an optical motion tracking system and light (<1g) printed targets. This was interfaced to a microPET scanner. Recorded spatial transformations were applied in software to list mode events to create a motion-corrected sinogram. Motion correction was evaluated in microPET studies, in which a conscious animal was simulated by a phantom that was moved during data acquisition. The motion-affected scan was severely distorted compared with a reference scan of the stationary phantom. Motion correction yielded a nearly distortion-free reconstruction and a marked reduction in mean squared error. This work is an important step towards motion tracking and motion correction in neurological studies of awake animals in the small animal PET imaging environment.
No related grants have been discovered for Steven Meikle.