Irene Espallardo | Hospital Universitario y politécnico La FE de Valencia (original) (raw)
Papers by Irene Espallardo
Nuclear Medicine and Molecular Imaging
![Research paper thumbnail of Same-day comparative protocol PET/CT-PET/MRI [68 Ga]Ga-DOTA-TOC in paragangliomas and pheochromocytomas: an approach to personalized medicine](https://attachments.academia-assets.com/97486665/thumbnails/1.jpg)
](Cancer Imaging
Background PET/MRI is an emerging imaging modality which enables the evaluation and quantificatio... more Background PET/MRI is an emerging imaging modality which enables the evaluation and quantification of biochemical processes in tissues, complemented with accurate anatomical information and low radiation exposure. In the framework of theragnosis, PET/MRI is of special interest due to its ability to delineate small lesions, adequately quantify them, and therefore to plan targeted therapies. The aim of this study was to validate the diagnostic performance of [68 Ga]Ga-DOTA-TOC PET/MRI compared to PET/CT in advanced disease paragangliomas and pheochromocytomas (PGGLs) to assess in which clinical settings, PET/MRI may have a greater diagnostic yield. Methods We performed a same-day protocol with consecutive acquisition of a PET/CT and a PET/MRI after a single [68 Ga]Ga-DOTA-TOC injection in 25 patients. Intermodality agreement, Krenning Score (KS), SUVmax (Standard Uptake Value), target-to-liver-ratio (TLR), clinical setting, location, and size were assessed. Results The diagnostic accu...
Journal of Medical Systems
Nuclear Medicine and Molecular Imaging, 2022
Positron Emission Tomography (PET) is a non invasive imaging technique that provides three-dimens... more Positron Emission Tomography (PET) is a non invasive imaging technique that provides three-dimensional (3D) tomographic images of radiotracer distribution within a living subject (1). Molecular probes can be labeled with positron-emitting
Purpose The purpose of this project is to develop and externally validate a Deep Learning (DL) FD... more Purpose The purpose of this project is to develop and externally validate a Deep Learning (DL) FDG PET imaging algorithm able to identify patients with Alzheimer's Disease (AD), Frontotemporal Degeneration (FTD) and Dementia with Lewy Bodies (DLB) among a group of patients with Mild Cognitive Impairment (MCI). Methods A 3D Convolutional neural network, trained using images from the Alzheimer's Disease Neuroimaging Initiative (ADNI) database, was implemented. The ADNI dataset used for training and testing the model consisted of 822 subjects (472 AD and 350 MCI). The external validation was performed on an independent dataset from our hospital. The hospital real world dataset contains 90 subjects with MCI: 71 patients that developed a neurodegenerative disease (64 AD, 4 FTD and 3 DLB) and 19 subjects without associated neurodegenerative disease. Results The ADNI model had 79% accuracy, 88% sensitivity and 71% specificity in the identification of patients with neurodegenerative...
Bajo el título Reconstrucción de la Imagen y Correcciones para MADPET-II usando Técnicas de Monte... more Bajo el título Reconstrucción de la Imagen y Correcciones para MADPET-II usando Técnicas de Montecarlo hemos englobado diversos temas relacionados con la obtención de imágenes y correcciones necesarias para obtener información cuantitativa del escáner ...
Revista espanola de medicina nuclear e imagen molecular, Jan 23, 2016
Therapy with radiolabelled somatostatin analogue peptides is a promising new therapy to treat neu... more Therapy with radiolabelled somatostatin analogue peptides is a promising new therapy to treat neuroendocrine tumours. The aim of this preliminary study is to present our experience with (177)Lu-DOTATATE therapy, and evaluate tolerability and short-term efficacy in patients with tumours expressing somatostatin receptors. A total of 7 patients with metastatic neuroendocrine tumours were treated, each with 4 doses of (177)Lu-DOTATATE. The treatment response was evaluated in the form of biochemical response (tumour markers), imaging methods (somatostatin receptor scintigraphy, computed tomography, and magnetic resonance), and functional and quality of life responses using the Karnofsky performance status scale. Treatment toxicity was also evaluated. The results obtained were as follows: Biochemical response: 60% of patients showed tumour marker levels returning to normal, while they decreased significantly in the remaining 40%. Imaging response: 85.7% had a partial response, while 14.3%...
2013 IEEE Nuclear Science Symposium and Medical Imaging Conference (2013 NSS/MIC), 2013
Hadron-therapy (HT) aims to treat tumors by maximizing the dose released to the target and sparin... more Hadron-therapy (HT) aims to treat tumors by maximizing the dose released to the target and sparing the dose to normal tissues. For a successful outcome it is very important to determine where the maximum dose is deposited; therefore range verification is necessary for treatment optimization and patient safety. Secondary positron emitting isotopes and prompt gamma radiation are produced after the hadron beam passage. This secondary radiation coming from tissue activation could be used for quality control of treatment, provided that it can be detected and employed to reconstruct the beam path using imaging techniques. This is one of the main goals of the ENVISION project: to evaluate and develop on-line monitoring devices for HT, like PET for detecting the annihilation photons from positrons and Compton Cameras (CCs) for prompt gamma radiation detection. In both technologies high sensitivity is required to increase the signal-to-noise ratio of the reconstructed image for a given thera...
Revista de Física Médica
La imagen PET es crucial en la dosimetría de tratamientos de radioembolización hepática con Y90. ... more La imagen PET es crucial en la dosimetría de tratamientos de radioembolización hepática con Y90. Sin embargo, dada la limitada resolución espacial de estos escáneres, la distribución real de actividad se difumina. Suele argumentarse que este difuminado es mayor que el debido a la convolución con un kernel de dosis (algoritmo VSV) de tal modo que el método de deposición local (LDM) proporciona resultados suficientemente precisos. En este trabajo hemos comparado los resultados dosimétricos de LDM, VSV y Monte Carlo en imágenes PET generadas matemáticamente a las cuales se les ha aplicado difuminados que simulan la resolución espacial del PET.
International Journal of Radiation Biology
Physics in medicine and biology, Jul 21, 2016
In order to exploit the advantages of ion-beam therapy in a clinical setting, delivery verificati... more In order to exploit the advantages of ion-beam therapy in a clinical setting, delivery verification techniques are necessary to detect deviations from the planned treatment. Efforts are currently oriented towards the development of devices for real-time range monitoring. Among the different detector concepts proposed, Compton cameras are employed to detect prompt gammas and represent a valid candidate for real-time range verification. We present the first on-beam test of MACACO, a Compton telescope (multi-layer Compton camera) based on lanthanum bromide crystals and silicon photo-multipliers. The Compton telescope was first characterized through measurements and Monte Carlo simulations. The detector linearity was measured employing (22)Na and Am-Be sources, obtaining about 10% deviation from linearity at 3.44 MeV. A spectral image reconstruction algorithm was tested on synthetic data. Point-like sources emitting gamma rays with energy between 2 and 7 MeV were reconstructed with 3-5 ...
Physics in medicine and biology, Jan 17, 2015
Particle therapy is a highly conformal radiotherapy technique which reduces the dose deposited to... more Particle therapy is a highly conformal radiotherapy technique which reduces the dose deposited to the surrounding normal tissues. In order to fully exploit its advantages, treatment monitoring is necessary to minimize uncertainties related to the dose delivery. Up to now, the only clinically feasible technique for the monitoring of therapeutic irradiation with particle beams is Positron Emission Tomography (PET). In this work we have compared a Resistive Plate Chamber (RPC)-based PET scanner with a scintillation-crystal-based PET scanner for this application. In general, the main advantages of the RPC-PET system are its excellent timing resolution, low cost, and the possibility of building large area systems. We simulated a partial-ring scanner based on an RPC prototype under construction within the Fondazione per Adroterapia Oncologica (TERA). For comparison with the crystal-based PET scanner we have chosen the geometry of a commercially available PET scanner, the Philips Gemini TF...
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, a proton or carbon ion beam interacts with the tissue and prompt gamma rays ar... more In hadron therapy, a proton or carbon ion beam interacts with the tissue and prompt gamma rays are emitted from the excited nuclei that can be employed for dose monitoring. A Compton telescope makes it possible to locate the origin of these photons, allowing an indirect estimation of the delivered dose. The telescope prototype being developed at IFIC-Valencia within the
Physics in Medicine and Biology, 2015
Compton Cameras emerged as an alternative for real-time dose monitoring techniques for Particle T... more Compton Cameras emerged as an alternative for real-time dose monitoring techniques for Particle Therapy (PT), based on the detection of prompt-gammas. As a consequence of the Compton scattering process, the gamma origin point can be restricted onto the surface of a cone (Compton cone). Through image reconstruction techniques, the distribution of the gamma emitters can be estimated, using cone-surfaces backprojections of the Compton cones through the image space, along with more sophisticated statistical methods to improve the image quality. To calculate the Compton cone required for image reconstruction, either two interactions, the last being photoelectric absorption, or three scatter interactions are needed. Because of the high energy of the photons in PT the first option might not be adequate, as the photon is not absorbed in general. However, the second option is less efficient. That is the reason to resort to spectral reconstructions, where the incoming γ energy is considered as a variable in the reconstruction inverse problem. Jointly with prompt gamma, secondary neutrons and scattered photons, not strongly correlated with the dose map, can also reach the imaging detector and produce false events. These events deteriorate the image quality. Also, high intensity beams can produce particle accumulation in the camera, which lead to an increase of random coincidences, meaning events which gather measurements from different incoming particles. The noise scenario is expected to be different if double or triple events are used, and consequently, the reconstructed images can be affected differently by spurious data. The aim of the present work is to study the effect of false events in the reconstructed image, evaluating their impact in the determination of the beam particle ranges. A simulation study that includes misidentified events (neutrons and random coincidences) in the final image of a Compton Telescope for PT monitoring is presented. The complete chain of detection, from the beam particle entering a phantom to the event classification, is simulated using FLUKA. The range determination is later estimated from the reconstructed image obtained from a two and three-event algorithm based on Maximum Likelihood Expectation Maximization. The neutron background and random coincidences due to a therapeutic-like time structure are analyzed for mono-energetic proton beams. The time structure of the beam is included in the simulations, which will affect the rate of particles entering the detector.
Nuclear Medicine and Molecular Imaging
Cancer Imaging
Background PET/MRI is an emerging imaging modality which enables the evaluation and quantificatio... more Background PET/MRI is an emerging imaging modality which enables the evaluation and quantification of biochemical processes in tissues, complemented with accurate anatomical information and low radiation exposure. In the framework of theragnosis, PET/MRI is of special interest due to its ability to delineate small lesions, adequately quantify them, and therefore to plan targeted therapies. The aim of this study was to validate the diagnostic performance of [68 Ga]Ga-DOTA-TOC PET/MRI compared to PET/CT in advanced disease paragangliomas and pheochromocytomas (PGGLs) to assess in which clinical settings, PET/MRI may have a greater diagnostic yield. Methods We performed a same-day protocol with consecutive acquisition of a PET/CT and a PET/MRI after a single [68 Ga]Ga-DOTA-TOC injection in 25 patients. Intermodality agreement, Krenning Score (KS), SUVmax (Standard Uptake Value), target-to-liver-ratio (TLR), clinical setting, location, and size were assessed. Results The diagnostic accu...
Journal of Medical Systems
Nuclear Medicine and Molecular Imaging, 2022
Positron Emission Tomography (PET) is a non invasive imaging technique that provides three-dimens... more Positron Emission Tomography (PET) is a non invasive imaging technique that provides three-dimensional (3D) tomographic images of radiotracer distribution within a living subject (1). Molecular probes can be labeled with positron-emitting
Purpose The purpose of this project is to develop and externally validate a Deep Learning (DL) FD... more Purpose The purpose of this project is to develop and externally validate a Deep Learning (DL) FDG PET imaging algorithm able to identify patients with Alzheimer's Disease (AD), Frontotemporal Degeneration (FTD) and Dementia with Lewy Bodies (DLB) among a group of patients with Mild Cognitive Impairment (MCI). Methods A 3D Convolutional neural network, trained using images from the Alzheimer's Disease Neuroimaging Initiative (ADNI) database, was implemented. The ADNI dataset used for training and testing the model consisted of 822 subjects (472 AD and 350 MCI). The external validation was performed on an independent dataset from our hospital. The hospital real world dataset contains 90 subjects with MCI: 71 patients that developed a neurodegenerative disease (64 AD, 4 FTD and 3 DLB) and 19 subjects without associated neurodegenerative disease. Results The ADNI model had 79% accuracy, 88% sensitivity and 71% specificity in the identification of patients with neurodegenerative...
Bajo el título Reconstrucción de la Imagen y Correcciones para MADPET-II usando Técnicas de Monte... more Bajo el título Reconstrucción de la Imagen y Correcciones para MADPET-II usando Técnicas de Montecarlo hemos englobado diversos temas relacionados con la obtención de imágenes y correcciones necesarias para obtener información cuantitativa del escáner ...
Revista espanola de medicina nuclear e imagen molecular, Jan 23, 2016
Therapy with radiolabelled somatostatin analogue peptides is a promising new therapy to treat neu... more Therapy with radiolabelled somatostatin analogue peptides is a promising new therapy to treat neuroendocrine tumours. The aim of this preliminary study is to present our experience with (177)Lu-DOTATATE therapy, and evaluate tolerability and short-term efficacy in patients with tumours expressing somatostatin receptors. A total of 7 patients with metastatic neuroendocrine tumours were treated, each with 4 doses of (177)Lu-DOTATATE. The treatment response was evaluated in the form of biochemical response (tumour markers), imaging methods (somatostatin receptor scintigraphy, computed tomography, and magnetic resonance), and functional and quality of life responses using the Karnofsky performance status scale. Treatment toxicity was also evaluated. The results obtained were as follows: Biochemical response: 60% of patients showed tumour marker levels returning to normal, while they decreased significantly in the remaining 40%. Imaging response: 85.7% had a partial response, while 14.3%...
2013 IEEE Nuclear Science Symposium and Medical Imaging Conference (2013 NSS/MIC), 2013
Hadron-therapy (HT) aims to treat tumors by maximizing the dose released to the target and sparin... more Hadron-therapy (HT) aims to treat tumors by maximizing the dose released to the target and sparing the dose to normal tissues. For a successful outcome it is very important to determine where the maximum dose is deposited; therefore range verification is necessary for treatment optimization and patient safety. Secondary positron emitting isotopes and prompt gamma radiation are produced after the hadron beam passage. This secondary radiation coming from tissue activation could be used for quality control of treatment, provided that it can be detected and employed to reconstruct the beam path using imaging techniques. This is one of the main goals of the ENVISION project: to evaluate and develop on-line monitoring devices for HT, like PET for detecting the annihilation photons from positrons and Compton Cameras (CCs) for prompt gamma radiation detection. In both technologies high sensitivity is required to increase the signal-to-noise ratio of the reconstructed image for a given thera...
Revista de Física Médica
La imagen PET es crucial en la dosimetría de tratamientos de radioembolización hepática con Y90. ... more La imagen PET es crucial en la dosimetría de tratamientos de radioembolización hepática con Y90. Sin embargo, dada la limitada resolución espacial de estos escáneres, la distribución real de actividad se difumina. Suele argumentarse que este difuminado es mayor que el debido a la convolución con un kernel de dosis (algoritmo VSV) de tal modo que el método de deposición local (LDM) proporciona resultados suficientemente precisos. En este trabajo hemos comparado los resultados dosimétricos de LDM, VSV y Monte Carlo en imágenes PET generadas matemáticamente a las cuales se les ha aplicado difuminados que simulan la resolución espacial del PET.
International Journal of Radiation Biology
Physics in medicine and biology, Jul 21, 2016
In order to exploit the advantages of ion-beam therapy in a clinical setting, delivery verificati... more In order to exploit the advantages of ion-beam therapy in a clinical setting, delivery verification techniques are necessary to detect deviations from the planned treatment. Efforts are currently oriented towards the development of devices for real-time range monitoring. Among the different detector concepts proposed, Compton cameras are employed to detect prompt gammas and represent a valid candidate for real-time range verification. We present the first on-beam test of MACACO, a Compton telescope (multi-layer Compton camera) based on lanthanum bromide crystals and silicon photo-multipliers. The Compton telescope was first characterized through measurements and Monte Carlo simulations. The detector linearity was measured employing (22)Na and Am-Be sources, obtaining about 10% deviation from linearity at 3.44 MeV. A spectral image reconstruction algorithm was tested on synthetic data. Point-like sources emitting gamma rays with energy between 2 and 7 MeV were reconstructed with 3-5 ...
Physics in medicine and biology, Jan 17, 2015
Particle therapy is a highly conformal radiotherapy technique which reduces the dose deposited to... more Particle therapy is a highly conformal radiotherapy technique which reduces the dose deposited to the surrounding normal tissues. In order to fully exploit its advantages, treatment monitoring is necessary to minimize uncertainties related to the dose delivery. Up to now, the only clinically feasible technique for the monitoring of therapeutic irradiation with particle beams is Positron Emission Tomography (PET). In this work we have compared a Resistive Plate Chamber (RPC)-based PET scanner with a scintillation-crystal-based PET scanner for this application. In general, the main advantages of the RPC-PET system are its excellent timing resolution, low cost, and the possibility of building large area systems. We simulated a partial-ring scanner based on an RPC prototype under construction within the Fondazione per Adroterapia Oncologica (TERA). For comparison with the crystal-based PET scanner we have chosen the geometry of a commercially available PET scanner, the Philips Gemini TF...
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, a proton or carbon ion beam interacts with the tissue and prompt gamma rays ar... more In hadron therapy, a proton or carbon ion beam interacts with the tissue and prompt gamma rays are emitted from the excited nuclei that can be employed for dose monitoring. A Compton telescope makes it possible to locate the origin of these photons, allowing an indirect estimation of the delivered dose. The telescope prototype being developed at IFIC-Valencia within the
Physics in Medicine and Biology, 2015
Compton Cameras emerged as an alternative for real-time dose monitoring techniques for Particle T... more Compton Cameras emerged as an alternative for real-time dose monitoring techniques for Particle Therapy (PT), based on the detection of prompt-gammas. As a consequence of the Compton scattering process, the gamma origin point can be restricted onto the surface of a cone (Compton cone). Through image reconstruction techniques, the distribution of the gamma emitters can be estimated, using cone-surfaces backprojections of the Compton cones through the image space, along with more sophisticated statistical methods to improve the image quality. To calculate the Compton cone required for image reconstruction, either two interactions, the last being photoelectric absorption, or three scatter interactions are needed. Because of the high energy of the photons in PT the first option might not be adequate, as the photon is not absorbed in general. However, the second option is less efficient. That is the reason to resort to spectral reconstructions, where the incoming γ energy is considered as a variable in the reconstruction inverse problem. Jointly with prompt gamma, secondary neutrons and scattered photons, not strongly correlated with the dose map, can also reach the imaging detector and produce false events. These events deteriorate the image quality. Also, high intensity beams can produce particle accumulation in the camera, which lead to an increase of random coincidences, meaning events which gather measurements from different incoming particles. The noise scenario is expected to be different if double or triple events are used, and consequently, the reconstructed images can be affected differently by spurious data. The aim of the present work is to study the effect of false events in the reconstructed image, evaluating their impact in the determination of the beam particle ranges. A simulation study that includes misidentified events (neutrons and random coincidences) in the final image of a Compton Telescope for PT monitoring is presented. The complete chain of detection, from the beam particle entering a phantom to the event classification, is simulated using FLUKA. The range determination is later estimated from the reconstructed image obtained from a two and three-event algorithm based on Maximum Likelihood Expectation Maximization. The neutron background and random coincidences due to a therapeutic-like time structure are analyzed for mono-energetic proton beams. The time structure of the beam is included in the simulations, which will affect the rate of particles entering the detector.