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Papers by John Gillam

Early Intervention in Psychiatry, 2019

Where a licence is displayed above, please note the terms and conditions of the licence govern yo... more Where a licence is displayed above, please note the terms and conditions of the licence govern your use of this document. When citing, please reference the published version. Take down policy While the University of Birmingham exercises care and attention in making items available there are rare occasions when an item has been uploaded in error or has been deemed to be commercially or otherwise sensitive.

Schizophrenia Bulletin, 2018

Results: All participants in both groups (n=31) completed the study. Because of such a small samp... more Results: All participants in both groups (n=31) completed the study. Because of such a small sample size (n=28) and a pilot nature of the study we were restricted to use descriptive statistics. The quantitative data suggest that DMT and SC were not equally effective in enhancing primary outcomes. Analysis of the PANSS mean score changes showed a slight increase in the negative symptom in the DMT from 28.33 ± 4.76 to 29.00 ± 4.10, and slight decrease in the SC from 28.92 ± 5.72 to 27.08 ± 5.64. BNSS scores indicate that both groups improved. SC participants reported grater reduction on BNSS overal score from 53.31 ± 11.48 to 47.77 ± 8.10 in comparison to DMT from 53.07 ± 7.27 to 51.93 ± 6.18. However, DMT participants reported reduction of symptoms in distress, antisocial activity, avolition and verbal expression. Analysis of WHO-DAS suggests that DMT was effective in reduction of disability severity compared to SC. DMT participants reported grater improvement in cognition, mobility, self-care, and getting along. Both groups reported reduction of the impact of difficulties on daily functioning on SDS, however DMT participants reported a greater reduction in days during which they were completely unable to perform or had to limit their usual activities or work due to symptoms. In the SC, the results suggest a reduction in the number of days lost and days of lower productivity. Qualitative findings identified participants' experiences and the most important themes related to benefits of the DMT intervention: enhanced activation, motivation, socialization, and self-awareness. Discussion: Results of this study contribute to knowledge about bodybased interventions for schizophrenia and indicate that DMT had an effect on participants psychosocial functioning and coping with negative symptoms. Integration of quantitative and qualitative data provides a wider perspective by gaining a better understanding of the treatment outcomes and explaining inconclusive results. Findings of this study set the stage for larger fully powered research, examining intervention methods and procedures, as well as treatment effects, more thoroughly.

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2014

A two-body fully relativistic three-dimensional scattering framework has been utilised to develop... more A two-body fully relativistic three-dimensional scattering framework has been utilised to develop an alternative Compton scattering computational model to those adapted from Ribberfors' work for Monte Carlo modelling of Compton scattering. Using a theoretical foundation that ensures the conservation of energy and momentum in the relativistic impulse approximation, this new model, the Monash University Compton scattering model, develops energy and directional algorithms for both the scattered photon and ejected Compton electron from first principles. The Monash University Compton scattering model was developed to address the limitation of the Compton electron directionality algorithms of other computational models adapted from Ribberfors' work. Here the development of the Monash University Compton scattering model, including its implementation in a Geant4 low energy electromagnetic physics class, G4LowEPComptonModel, is outlined. Assessment of the performance of G4LowEPComptonModel was undertaken in two steps: (1) comparison with respect to the two standard Compton scattering classes of Geant4 version 9.5, G4LivermoreComptonModel and G4PenelopeComptonModel, and (2) experimental comparison with respect to Compton electron kinetic energy spectra obtained from the Compton scattering of 662 keV photons off the K-shell of gold. Both studies illustrate that the Monash University Compton scattering model, and in turn G4LowEPComptonModel, is a viable replacement for the majority of computational models that have been adapted from Ribberfors' work. It was also shown that the Monash University Compton scattering model is able to reproduce the Compton scattering triply differential cross-section Compton electron kinetic energy spectra of 662 keV photons K-shell scattering off of gold to within experimental uncertainty.

2009 IEEE Nuclear Science Symposium Conference Record (NSS/MIC), 2009

ABSTRACT A proof-of-principle single photon emission imaging (SPEI) system is being constructed a... more ABSTRACT A proof-of-principle single photon emission imaging (SPEI) system is being constructed and validated against Geant4 Monte-Carlo simulations, with the intention of determining the optimal detector configuration for imaging the evolution of induced matastices in small animals. This device consists of a Compton-camera situated behind a mechanical modulator. The combination of mechanical and electronic (hybrid) collimation should provide optimal detection characteristics over a broad spectral range (30 keV to 511 keV), through a reduction in the sensitivity-resolution trade-off, inherent in conventional mechanically collimated configurations. The Phase I imager has been constructed from a combination of off-the-shelf detectors and custom electronics to allow the experimental architecture and data processing algorithms to be tested. This paper presents the designs and preliminary results from the simulations.

2011 IEEE Nuclear Science Symposium Conference Record, 2011

ABSTRACT Simulated One Pass List-mode is a means of image-reconstruction that distributes on-the-... more ABSTRACT Simulated One Pass List-mode is a means of image-reconstruction that distributes on-the-fly calculations of the full system matrix across multiple iterations during Maximum Likelihood-Expectation Maximization image reconstruction. On the fly list-mode processing of coincidence data provides a very flexible approach to image reconstruction that can be applied to many novel systems for Positron Emission Tomography. However, in addition to standard on-the-fly calculation and list-mode methods, Simulated One Pass List-mode provides for extra possibilities during image reconstruction. Two possibilities are investigated here: system modeling accuracy can be altered at each iteration and enhanced modeling can be conduced only for specific Regions of Interest. In this investigation simulated data from a simple two dimensional PET system is used to demonstrate these two advantages of Simulated One Pass List-mode image reconstruction for Positron Emission Tomography.

IEEE Nuclear Science Symposuim & Medical Imaging Conference, 2010

Page 1. GPU Acceleration of Compton Reconstruction for the PEDRO Matthew R. Dimmock*, Dmitri A. N... more Page 1. GPU Acceleration of Compton Reconstruction for the PEDRO Matthew R. Dimmock*, Dmitri A. Nikulin*, Jeremy MC Brown, Chuong V. Nguyen, and John E. Gillam Abstract—Compton reconstruction requires the computation ...

2006 IEEE Nuclear Science Symposium Conference Record, 2006

... We considered a dual layer camera geometry containing two SmartPET detectors [4], and employe... more ... We considered a dual layer camera geometry containing two SmartPET detectors [4], and employed Geant4 [5] to simulate the response to 662 keV photons. A cone-intersection algorithm [6] is utilised to reconstruct the activity distribution. The major findings are as follows. ...

Physics in medicine and biology, Jan 21, 2014

A high-resolution silicon detector probe, in coincidence with a conventional PET scanner, is expe... more A high-resolution silicon detector probe, in coincidence with a conventional PET scanner, is expected to provide images of higher quality than those achievable using the scanner alone. Spatial resolution should improve due to the finer pixelization of the probe detector, while increased sensitivity in the probe vicinity is expected to decrease noise. A PET-probe prototype is being developed utilizing this principle. The system includes a probe consisting of ten layers of silicon detectors, each a 80 × 52 array of 1 × 1 × 1 mm(3) pixels, to be operated in coincidence with a modern clinical PET scanner. Detailed simulation studies of this system have been performed to assess the effect of the additional probe information on the quality of the reconstructed images. A grid of point sources was simulated to study the contribution of the probe to the system resolution at different locations over the field of view (FOV). A resolution phantom was used to demonstrate the effect on image reso...

IEEE Symposium Conference Record Nuclear Science 2004.

... Australia (telephone +61-3-9905-9765, email: toby.beveridge@spme.monash.edu.au) JE Gillam is ... more ... Australia (telephone +61-3-9905-9765, email: toby.beveridge@spme.monash.edu.au) JE Gillam is with the School of Physics and Materials Engineering, Monash University, Clayton, Victoria, 3800, Australia (telephone +61-3-9905-9765, email: john.gillam@spme.monash.edu ...

Increased sensitivity is one of the major challenges in novel detector development. While pixelat... more Increased sensitivity is one of the major challenges in novel detector development. While pixelated crystals are standard, the use of continuous crystals can provide increased active volume and thus sensitivity. Accurate estimation of the interaction positions of photons in continuous crystals requires a sophisticated algorithm. Additionally, including depth of interaction (Dol) in the reconstruction process can mitigate parallax effects near the edges of field of view, therefore Dol estimation is highly desirable. In this work, the interaction position coordinates in 3D are estimated adapting an already existing analytical model to our system with no additional hardware, training data sets or Monte Carlo simulations. The algorithm is implemented in a two-detector-head system comprised of continuous crystals coupled to SiPM arrays. Acquired data is stored in list-mode where the continuous nature of the interaction position is preserved. For image reconstruction, since the crystal is...

2012 IEEE Nuclear Science Symposium and Medical Imaging Conference Record (NSS/MIC), 2012

ABSTRACT Hadron-therapy exploits ions to treat tumors by maximizing the dose released to the targ... more ABSTRACT Hadron-therapy exploits ions to treat tumors by maximizing the dose released to the target and sparing healthy tissues. With hadrons, the dose distribution rises sharply at the end of the range, providing the characteristic Bragg peak, and drops quickly thereafter to a negligible value. During hadron-therapy, short-lived β+-emitters are produced along the beam path. Following positron annihilation, two photons are emitted, which can be detected using a PET scanner. The low yield of β+-emitters and the washout from the target region make the use of PET a few minutes after hadron-irradiation a challenging application. In-beam PET represents a potential candidate to measure the produced β+-emitters during irradiation, at the cost of truncation effects and degraded image quality due to the partial-rings of the PET scanner. Time-of-Flight (ToF) information can potentially be used to enhance image contrast and to compensate for truncation effects. However, the highly demanding timing performance that detectors require to be used in ToF-PET makes this option very costly. Alternatively, including total variation (TV) as prior information in the MAP reconstruction produces images with low noise, without degrading spatial resolution. In this work we compare ML-EM with ToF information and MAP using TV as prior from data acquired with a complete and a partial-rings of Gemini TF, of simulated proton-beams interacting in a PMMA target. Results show that MAP-TV, in the absence of ToF information, produces lower noise and higher correlation coefficients compared to ML-EM with ToF information (in the order of 400-600 ps). Moreover, MAP-TV outperforms MLEM with a ToF of 200 ps in some cases.

2012 IEEE Nuclear Science Symposium and Medical Imaging Conference Record (NSS/MIC), 2012

ABSTRACT Image reconstruction for Compton camera data can be problematic due to the common trade-... more ABSTRACT Image reconstruction for Compton camera data can be problematic due to the common trade-off between physically realistic models and speed of computation. In this investigation a novel method of system matrix calculation - Simulated One-Pass Listmode (SOPL) - is extended to incorporate Compton camera data. The method reduces the Cone Surface Response for the Compton camera to an ensemble of Siddon-rays and is conducted in two stages. As part of the ENVISION project for monitoring in hadron therapy, a continuous-crystal Lanthanum Bromide Compton camera has been developed and experimental data acquired. Continuous detection geometries are particularly susceptible to variation in both spatial and spectral resolution over the detection volume and so accurate yet flexible models of detection are particularly important. The SOPL-Compton method was applied via the Maximum Likelihood - Expectation Maximization algorithm to experimental data taken using the prototype device. In this investigation, detection modeling using SOPL-Compton in a two interaction Compton camera is validated and the incorporation of a shift-invariant image-space model confirmed as a useful modification to reduce computational expense. Finally experimental data taken using the prototype LaBr3 Compton camera provide confirmation of the SOPL-Compton approach to system modeling. Results indicate a fast, flexible and accurate algorithm that can easily be extended to alternate and novel detection geometries.

2012 IEEE Nuclear Science Symposium and Medical Imaging Conference Record (NSS/MIC), 2012

ABSTRACT A Compton telescope prototype for dose monitoring in hadron therapy is under development... more ABSTRACT A Compton telescope prototype for dose monitoring in hadron therapy is under development. It will consist of three detector layers and each layer will be made of a continuous LaBr3 crystal coupled to four Silicon Photomultiplier (SiPM) arrays. As a first test, a small prototype made of only two detectors layers has been assembled. The camera is based on continuous LaBr3 and LYSO crystals coupled to a SiPM arrays for gamma-ray detection and readout. The setup consists of a 16×18×5 mm3 LaBr3 crystal coupled to a SiPM array as the first layer of the telescope, and a 16×18×5 mm3 LYSO crystal coupled to another SiPM array as the second layer. The SPIROCI ASIC is employed in the readout electronics. The first coincidence tests have been successfully carried out, using a 22Na source placed at different positions, and allow the reconstruction of a point-like source, encouraging the development and the improvement of the prototype to a full imaging system.

2011 IEEE Nuclear Science Symposium Conference Record, 2011

In hadron therapy particulate radiation is used to treat regions in close proximity to vital orga... more In hadron therapy particulate radiation is used to treat regions in close proximity to vital organs or tissue. Protons, or Carbon ions, provide enhanced treatment due to the characteristic Bragg peak structure of dose deposition, which constrains maximum dose deposition to a small volume of the patient. However, as there is no transmitted beam novel methods of beam monitoring must

Medical Imaging 2011: Physics of Medical Imaging, 2011

Hadron therapy, a subject of study by the ENVISION project, promises to provide enhanced accuracy... more Hadron therapy, a subject of study by the ENVISION project, promises to provide enhanced accuracy in the treatment of cancer. The Bragg-peak, characteristic of the hadron-beam structure provides larger dose to the tumor while being able to spare surrounding tissue - even tissues in the ...

International journal of biomedical imaging, 2012

Statistical iterative methods are a widely used method of image reconstruction in emission tomogr... more Statistical iterative methods are a widely used method of image reconstruction in emission tomography. Traditionally, the image space is modelled as a combination of cubic voxels as a matter of simplicity. After reconstruction, images are routinely filtered to reduce statistical noise at the cost of spatial resolution degradation. An alternative to produce lower noise during reconstruction is to model the image space with spherical basis functions. These basis functions overlap in space producing a significantly large number of non-zero elements in the system response matrix (SRM) to store, which additionally leads to long reconstruction times. These two problems are partly overcome by exploiting spherical symmetries, although computation time is still slower compared to non-overlapping basis functions. In this work, we have implemented the reconstruction algorithm using Graphical Processing Unit (GPU) technology for speed and a precomputed Monte-Carlo-calculated SRM for accuracy. The reconstruction time achieved using spherical basis functions on a GPU was 4.3 times faster than the Central Processing Unit (CPU) and 2.5 times faster than a CPU-multi-core parallel implementation using eight cores. Overwriting hazards are minimized by combining a random line of response ordering and constrained atomic writing. Small differences in image quality were observed between implementations.

Nuclear Instruments & Methods in Physics Research Section a-Accelerators Spectrometers Detectors and Associated Equipment, 2013

2011 IEEE Nuclear Science Symposium Conference Record, 2011

This is a preliminary study on the feasibility of using Resistive-Plate-Chambers (RPC) based Posi... more This is a preliminary study on the feasibility of using Resistive-Plate-Chambers (RPC) based Positron Emission Tomography (PET) for hadron-therapy monitoring. The imaging capabilities of the RPC gas detector are being investigated for PET. Their main advantages are excellent timing resolution, low cost and Depth Of Interaction information (DOI) due to their layered structure. Hadron-therapy (HT) aims at treating tumors by

2013 3rd International Conference on Advancements in Nuclear Instrumentation, Measurement Methods and their Applications (ANIMMA), 2013

A Compton telescope for dose delivery monitoring in hadron therapy is under development at IFIC V... more A Compton telescope for dose delivery monitoring in hadron therapy is under development at IFIC Valencia within the European project ENVISION. The telescope will consist of three detector planes, each one composed of a LaBr3 continuous scintillator crystal coupled to four silicon photomultiplier (SiPM) arrays. After the development of a first prototype which served to assess the principle, a second prototype with larger crystals has been assembled and is being tested. The current version of the prototype consists of two detector layers, each one composed of a 32.5 × 35 mm2 crystal coupled to four SiPM arrays. The VATA64HDR16 ASIC has been employed as front-end electronics. The readout system consists of a custom made data acquisition board. Tests with point-like sources have been carried out in the laboratory, assessing the correct functioning of the device. The system optimization is ongoing.

Early Intervention in Psychiatry, 2019

Where a licence is displayed above, please note the terms and conditions of the licence govern yo... more Where a licence is displayed above, please note the terms and conditions of the licence govern your use of this document. When citing, please reference the published version. Take down policy While the University of Birmingham exercises care and attention in making items available there are rare occasions when an item has been uploaded in error or has been deemed to be commercially or otherwise sensitive.

Schizophrenia Bulletin, 2018

Results: All participants in both groups (n=31) completed the study. Because of such a small samp... more Results: All participants in both groups (n=31) completed the study. Because of such a small sample size (n=28) and a pilot nature of the study we were restricted to use descriptive statistics. The quantitative data suggest that DMT and SC were not equally effective in enhancing primary outcomes. Analysis of the PANSS mean score changes showed a slight increase in the negative symptom in the DMT from 28.33 ± 4.76 to 29.00 ± 4.10, and slight decrease in the SC from 28.92 ± 5.72 to 27.08 ± 5.64. BNSS scores indicate that both groups improved. SC participants reported grater reduction on BNSS overal score from 53.31 ± 11.48 to 47.77 ± 8.10 in comparison to DMT from 53.07 ± 7.27 to 51.93 ± 6.18. However, DMT participants reported reduction of symptoms in distress, antisocial activity, avolition and verbal expression. Analysis of WHO-DAS suggests that DMT was effective in reduction of disability severity compared to SC. DMT participants reported grater improvement in cognition, mobility, self-care, and getting along. Both groups reported reduction of the impact of difficulties on daily functioning on SDS, however DMT participants reported a greater reduction in days during which they were completely unable to perform or had to limit their usual activities or work due to symptoms. In the SC, the results suggest a reduction in the number of days lost and days of lower productivity. Qualitative findings identified participants' experiences and the most important themes related to benefits of the DMT intervention: enhanced activation, motivation, socialization, and self-awareness. Discussion: Results of this study contribute to knowledge about bodybased interventions for schizophrenia and indicate that DMT had an effect on participants psychosocial functioning and coping with negative symptoms. Integration of quantitative and qualitative data provides a wider perspective by gaining a better understanding of the treatment outcomes and explaining inconclusive results. Findings of this study set the stage for larger fully powered research, examining intervention methods and procedures, as well as treatment effects, more thoroughly.

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2014

A two-body fully relativistic three-dimensional scattering framework has been utilised to develop... more A two-body fully relativistic three-dimensional scattering framework has been utilised to develop an alternative Compton scattering computational model to those adapted from Ribberfors' work for Monte Carlo modelling of Compton scattering. Using a theoretical foundation that ensures the conservation of energy and momentum in the relativistic impulse approximation, this new model, the Monash University Compton scattering model, develops energy and directional algorithms for both the scattered photon and ejected Compton electron from first principles. The Monash University Compton scattering model was developed to address the limitation of the Compton electron directionality algorithms of other computational models adapted from Ribberfors' work. Here the development of the Monash University Compton scattering model, including its implementation in a Geant4 low energy electromagnetic physics class, G4LowEPComptonModel, is outlined. Assessment of the performance of G4LowEPComptonModel was undertaken in two steps: (1) comparison with respect to the two standard Compton scattering classes of Geant4 version 9.5, G4LivermoreComptonModel and G4PenelopeComptonModel, and (2) experimental comparison with respect to Compton electron kinetic energy spectra obtained from the Compton scattering of 662 keV photons off the K-shell of gold. Both studies illustrate that the Monash University Compton scattering model, and in turn G4LowEPComptonModel, is a viable replacement for the majority of computational models that have been adapted from Ribberfors' work. It was also shown that the Monash University Compton scattering model is able to reproduce the Compton scattering triply differential cross-section Compton electron kinetic energy spectra of 662 keV photons K-shell scattering off of gold to within experimental uncertainty.

2009 IEEE Nuclear Science Symposium Conference Record (NSS/MIC), 2009

ABSTRACT A proof-of-principle single photon emission imaging (SPEI) system is being constructed a... more ABSTRACT A proof-of-principle single photon emission imaging (SPEI) system is being constructed and validated against Geant4 Monte-Carlo simulations, with the intention of determining the optimal detector configuration for imaging the evolution of induced matastices in small animals. This device consists of a Compton-camera situated behind a mechanical modulator. The combination of mechanical and electronic (hybrid) collimation should provide optimal detection characteristics over a broad spectral range (30 keV to 511 keV), through a reduction in the sensitivity-resolution trade-off, inherent in conventional mechanically collimated configurations. The Phase I imager has been constructed from a combination of off-the-shelf detectors and custom electronics to allow the experimental architecture and data processing algorithms to be tested. This paper presents the designs and preliminary results from the simulations.

2011 IEEE Nuclear Science Symposium Conference Record, 2011

ABSTRACT Simulated One Pass List-mode is a means of image-reconstruction that distributes on-the-... more ABSTRACT Simulated One Pass List-mode is a means of image-reconstruction that distributes on-the-fly calculations of the full system matrix across multiple iterations during Maximum Likelihood-Expectation Maximization image reconstruction. On the fly list-mode processing of coincidence data provides a very flexible approach to image reconstruction that can be applied to many novel systems for Positron Emission Tomography. However, in addition to standard on-the-fly calculation and list-mode methods, Simulated One Pass List-mode provides for extra possibilities during image reconstruction. Two possibilities are investigated here: system modeling accuracy can be altered at each iteration and enhanced modeling can be conduced only for specific Regions of Interest. In this investigation simulated data from a simple two dimensional PET system is used to demonstrate these two advantages of Simulated One Pass List-mode image reconstruction for Positron Emission Tomography.

IEEE Nuclear Science Symposuim & Medical Imaging Conference, 2010

Page 1. GPU Acceleration of Compton Reconstruction for the PEDRO Matthew R. Dimmock*, Dmitri A. N... more Page 1. GPU Acceleration of Compton Reconstruction for the PEDRO Matthew R. Dimmock*, Dmitri A. Nikulin*, Jeremy MC Brown, Chuong V. Nguyen, and John E. Gillam Abstract—Compton reconstruction requires the computation ...

2006 IEEE Nuclear Science Symposium Conference Record, 2006

... We considered a dual layer camera geometry containing two SmartPET detectors [4], and employe... more ... We considered a dual layer camera geometry containing two SmartPET detectors [4], and employed Geant4 [5] to simulate the response to 662 keV photons. A cone-intersection algorithm [6] is utilised to reconstruct the activity distribution. The major findings are as follows. ...

Physics in medicine and biology, Jan 21, 2014

A high-resolution silicon detector probe, in coincidence with a conventional PET scanner, is expe... more A high-resolution silicon detector probe, in coincidence with a conventional PET scanner, is expected to provide images of higher quality than those achievable using the scanner alone. Spatial resolution should improve due to the finer pixelization of the probe detector, while increased sensitivity in the probe vicinity is expected to decrease noise. A PET-probe prototype is being developed utilizing this principle. The system includes a probe consisting of ten layers of silicon detectors, each a 80 × 52 array of 1 × 1 × 1 mm(3) pixels, to be operated in coincidence with a modern clinical PET scanner. Detailed simulation studies of this system have been performed to assess the effect of the additional probe information on the quality of the reconstructed images. A grid of point sources was simulated to study the contribution of the probe to the system resolution at different locations over the field of view (FOV). A resolution phantom was used to demonstrate the effect on image reso...

IEEE Symposium Conference Record Nuclear Science 2004.

... Australia (telephone +61-3-9905-9765, email: toby.beveridge@spme.monash.edu.au) JE Gillam is ... more ... Australia (telephone +61-3-9905-9765, email: toby.beveridge@spme.monash.edu.au) JE Gillam is with the School of Physics and Materials Engineering, Monash University, Clayton, Victoria, 3800, Australia (telephone +61-3-9905-9765, email: john.gillam@spme.monash.edu ...

Increased sensitivity is one of the major challenges in novel detector development. While pixelat... more Increased sensitivity is one of the major challenges in novel detector development. While pixelated crystals are standard, the use of continuous crystals can provide increased active volume and thus sensitivity. Accurate estimation of the interaction positions of photons in continuous crystals requires a sophisticated algorithm. Additionally, including depth of interaction (Dol) in the reconstruction process can mitigate parallax effects near the edges of field of view, therefore Dol estimation is highly desirable. In this work, the interaction position coordinates in 3D are estimated adapting an already existing analytical model to our system with no additional hardware, training data sets or Monte Carlo simulations. The algorithm is implemented in a two-detector-head system comprised of continuous crystals coupled to SiPM arrays. Acquired data is stored in list-mode where the continuous nature of the interaction position is preserved. For image reconstruction, since the crystal is...

2012 IEEE Nuclear Science Symposium and Medical Imaging Conference Record (NSS/MIC), 2012

ABSTRACT Hadron-therapy exploits ions to treat tumors by maximizing the dose released to the targ... more ABSTRACT Hadron-therapy exploits ions to treat tumors by maximizing the dose released to the target and sparing healthy tissues. With hadrons, the dose distribution rises sharply at the end of the range, providing the characteristic Bragg peak, and drops quickly thereafter to a negligible value. During hadron-therapy, short-lived β+-emitters are produced along the beam path. Following positron annihilation, two photons are emitted, which can be detected using a PET scanner. The low yield of β+-emitters and the washout from the target region make the use of PET a few minutes after hadron-irradiation a challenging application. In-beam PET represents a potential candidate to measure the produced β+-emitters during irradiation, at the cost of truncation effects and degraded image quality due to the partial-rings of the PET scanner. Time-of-Flight (ToF) information can potentially be used to enhance image contrast and to compensate for truncation effects. However, the highly demanding timing performance that detectors require to be used in ToF-PET makes this option very costly. Alternatively, including total variation (TV) as prior information in the MAP reconstruction produces images with low noise, without degrading spatial resolution. In this work we compare ML-EM with ToF information and MAP using TV as prior from data acquired with a complete and a partial-rings of Gemini TF, of simulated proton-beams interacting in a PMMA target. Results show that MAP-TV, in the absence of ToF information, produces lower noise and higher correlation coefficients compared to ML-EM with ToF information (in the order of 400-600 ps). Moreover, MAP-TV outperforms MLEM with a ToF of 200 ps in some cases.

2012 IEEE Nuclear Science Symposium and Medical Imaging Conference Record (NSS/MIC), 2012

ABSTRACT Image reconstruction for Compton camera data can be problematic due to the common trade-... more ABSTRACT Image reconstruction for Compton camera data can be problematic due to the common trade-off between physically realistic models and speed of computation. In this investigation a novel method of system matrix calculation - Simulated One-Pass Listmode (SOPL) - is extended to incorporate Compton camera data. The method reduces the Cone Surface Response for the Compton camera to an ensemble of Siddon-rays and is conducted in two stages. As part of the ENVISION project for monitoring in hadron therapy, a continuous-crystal Lanthanum Bromide Compton camera has been developed and experimental data acquired. Continuous detection geometries are particularly susceptible to variation in both spatial and spectral resolution over the detection volume and so accurate yet flexible models of detection are particularly important. The SOPL-Compton method was applied via the Maximum Likelihood - Expectation Maximization algorithm to experimental data taken using the prototype device. In this investigation, detection modeling using SOPL-Compton in a two interaction Compton camera is validated and the incorporation of a shift-invariant image-space model confirmed as a useful modification to reduce computational expense. Finally experimental data taken using the prototype LaBr3 Compton camera provide confirmation of the SOPL-Compton approach to system modeling. Results indicate a fast, flexible and accurate algorithm that can easily be extended to alternate and novel detection geometries.

2012 IEEE Nuclear Science Symposium and Medical Imaging Conference Record (NSS/MIC), 2012

ABSTRACT A Compton telescope prototype for dose monitoring in hadron therapy is under development... more ABSTRACT A Compton telescope prototype for dose monitoring in hadron therapy is under development. It will consist of three detector layers and each layer will be made of a continuous LaBr3 crystal coupled to four Silicon Photomultiplier (SiPM) arrays. As a first test, a small prototype made of only two detectors layers has been assembled. The camera is based on continuous LaBr3 and LYSO crystals coupled to a SiPM arrays for gamma-ray detection and readout. The setup consists of a 16×18×5 mm3 LaBr3 crystal coupled to a SiPM array as the first layer of the telescope, and a 16×18×5 mm3 LYSO crystal coupled to another SiPM array as the second layer. The SPIROCI ASIC is employed in the readout electronics. The first coincidence tests have been successfully carried out, using a 22Na source placed at different positions, and allow the reconstruction of a point-like source, encouraging the development and the improvement of the prototype to a full imaging system.

2011 IEEE Nuclear Science Symposium Conference Record, 2011

In hadron therapy particulate radiation is used to treat regions in close proximity to vital orga... more In hadron therapy particulate radiation is used to treat regions in close proximity to vital organs or tissue. Protons, or Carbon ions, provide enhanced treatment due to the characteristic Bragg peak structure of dose deposition, which constrains maximum dose deposition to a small volume of the patient. However, as there is no transmitted beam novel methods of beam monitoring must

Medical Imaging 2011: Physics of Medical Imaging, 2011

Hadron therapy, a subject of study by the ENVISION project, promises to provide enhanced accuracy... more Hadron therapy, a subject of study by the ENVISION project, promises to provide enhanced accuracy in the treatment of cancer. The Bragg-peak, characteristic of the hadron-beam structure provides larger dose to the tumor while being able to spare surrounding tissue - even tissues in the ...

International journal of biomedical imaging, 2012

Statistical iterative methods are a widely used method of image reconstruction in emission tomogr... more Statistical iterative methods are a widely used method of image reconstruction in emission tomography. Traditionally, the image space is modelled as a combination of cubic voxels as a matter of simplicity. After reconstruction, images are routinely filtered to reduce statistical noise at the cost of spatial resolution degradation. An alternative to produce lower noise during reconstruction is to model the image space with spherical basis functions. These basis functions overlap in space producing a significantly large number of non-zero elements in the system response matrix (SRM) to store, which additionally leads to long reconstruction times. These two problems are partly overcome by exploiting spherical symmetries, although computation time is still slower compared to non-overlapping basis functions. In this work, we have implemented the reconstruction algorithm using Graphical Processing Unit (GPU) technology for speed and a precomputed Monte-Carlo-calculated SRM for accuracy. The reconstruction time achieved using spherical basis functions on a GPU was 4.3 times faster than the Central Processing Unit (CPU) and 2.5 times faster than a CPU-multi-core parallel implementation using eight cores. Overwriting hazards are minimized by combining a random line of response ordering and constrained atomic writing. Small differences in image quality were observed between implementations.

Nuclear Instruments & Methods in Physics Research Section a-Accelerators Spectrometers Detectors and Associated Equipment, 2013

2011 IEEE Nuclear Science Symposium Conference Record, 2011

This is a preliminary study on the feasibility of using Resistive-Plate-Chambers (RPC) based Posi... more This is a preliminary study on the feasibility of using Resistive-Plate-Chambers (RPC) based Positron Emission Tomography (PET) for hadron-therapy monitoring. The imaging capabilities of the RPC gas detector are being investigated for PET. Their main advantages are excellent timing resolution, low cost and Depth Of Interaction information (DOI) due to their layered structure. Hadron-therapy (HT) aims at treating tumors by

2013 3rd International Conference on Advancements in Nuclear Instrumentation, Measurement Methods and their Applications (ANIMMA), 2013

A Compton telescope for dose delivery monitoring in hadron therapy is under development at IFIC V... more A Compton telescope for dose delivery monitoring in hadron therapy is under development at IFIC Valencia within the European project ENVISION. The telescope will consist of three detector planes, each one composed of a LaBr3 continuous scintillator crystal coupled to four silicon photomultiplier (SiPM) arrays. After the development of a first prototype which served to assess the principle, a second prototype with larger crystals has been assembled and is being tested. The current version of the prototype consists of two detector layers, each one composed of a 32.5 × 35 mm2 crystal coupled to four SiPM arrays. The VATA64HDR16 ASIC has been employed as front-end electronics. The readout system consists of a custom made data acquisition board. Tests with point-like sources have been carried out in the laboratory, assessing the correct functioning of the device. The system optimization is ongoing.