Historically, patient datasets have been used to develop and validate various reconstruction algo... more Historically, patient datasets have been used to develop and validate various reconstruction algorithms for PET/MRI and PET/CT. To enable such algorithm development, without the need for acquiring hundreds of patient exams, in this paper we demonstrate a deep learning technique to generate synthetic but realistic whole-body PET sinograms from abundantly-available whole-body MRI. Specifically, we use a dataset of 56 18 F-FDG-PET/MRI exams to train a 3D residual UNet to predict physiologic PET uptake from whole-body T1-weighted MRI. In training we implemented a balanced loss function to generate realistic uptake across a large dynamic range and computed losses along tomographic lines of response to mimic the PET acquisition. The predicted PET images are forward projected to produce synthetic PET time-of-flight (ToF) sinograms that can be used with vendor-provided PET reconstruction algorithms, including using CT-based attenuation correction (CTAC) and MR-based attenuation correction (MRAC). The resulting synthetic data recapitulates physiologic 18 F-FDG uptake, e.g. high uptake localized to the brain and bladder, as well as uptake in liver, kidneys, heart and muscle. To simulate abnormalities with high uptake, we also insert synthetic lesions. We demonstrate that this synthetic PET data can be used interchangeably with real PET data for the PET quantification task of comparing CT and MRbased attenuation correction methods, achieving ≤ 7.6% error in mean-SUV compared to using real data. These results together show that the proposed synthetic PET data pipeline can be reasonably used for development, evaluation, and validation of PET/MRI reconstruction methods.
Histopathological analysis of whole-slide images is the gold standard technique for diagnosis of ... more Histopathological analysis of whole-slide images is the gold standard technique for diagnosis of lung cancer and classifying it into types and subtypes by specialized pathologists. This labor-based approach is time and effort consuming, which led to development of automatic approaches to assist in reducing the time and effort. Deep learning is a supervised classification approach that is well adapted for automatic classification of histopathological images. We aimed to develop a deep learning-based approach for lung adenocarcinoma pattern classification and generalize the proposed approach to the classification of the major non-small cell lung cancer types. Three publicly available datasets were used in this study. A deep learning approach for histopathological image analysis using convolutional neural networks was developed and incorporated into automatic pipelines to accurately classify the predominant patterns on the whole-slide images level and non-small cell lung cancer types o...
A novel technique, called augmented whole-body scanning via magnifying PET (AWSM-PET), that impro... more A novel technique, called augmented whole-body scanning via magnifying PET (AWSM-PET), that improves the sensitivity and lesion detectability of a PET scanner for whole-body imaging is proposed and evaluated. A Siemens Biograph Vision PET/CT scanner equipped with one or two high-resolution panel-detectors was simulated to study the effectiveness of AWSM-PET technology. The detector panels are located immediately outside the scanner's axial field-of-view (FOV). A detector panel contains 2 × 8 detector modules each consisting of 32 × 64 LSO crystals (1.0 × 1.0 × 10.0 mm 3 each). A 22 Na point source was stepped across the scanner's FOV axially to measure sensitivity profiles at different locations. An elliptical torso phantom containing 7 × 9 spherical lesions was imaged at different axial locations to mimic a multi-bed-position whole-body imaging protocol. Receiver operating characteristic (ROC) curves were analyzed to evaluate the improvement in lesion detectability by the AWSM-PET technology. Experimental validation was conducted using an existing flat-panel detector integrated with a Siemens Biograph 40 PET/CT scanner to image a torso phantom containing spherical lesions with diameters ranging from 3.3 to 11.4 mm. The contrast-recovery-coefficient (CRC) of the lesions was evaluated for the scanner with or without the AWSM-PET technology. Monte Carlo simulation shows 36%-42% improvement in system sensitivity by a dual-panel AWSM-PET device. The area under the ROC curve is 0.962 by a native scanner for the detection of 4 mm diameter
Computerized medical imaging and graphics : the official journal of the Computerized Medical Imaging Society, 2018
Monte Carlo (MC) simulation is widely recognized as an important technique to study the physics o... more Monte Carlo (MC) simulation is widely recognized as an important technique to study the physics of particle interactions in nuclear medicine and radiation therapy. There are different codes dedicated to dosimetry applications and widely used today in research or in clinical application, such as MCNP, EGSnrc and Geant4. However, such codes made the physics easier but the programming remains a tedious task even for physicists familiar with computer programming. In this paper we report the development of a new interface GEANT4 Dose And Radiation Interactions (G4DARI) based on GEANT4 for absorbed dose calculation and for particle tracking in humans, small animals and complex phantoms. The calculation of the absorbed dose is performed based on 3D CT human or animal images in DICOM format, from images of phantoms or from solid volumes which can be made from any pure or composite material to be specified by its molecular formula. G4DARI offers menus to the user and tabs to be filled with v...
Please cite this article in press as: Hamdi M, et al. Impact of X-ray energy on absorbed dose ass... more Please cite this article in press as: Hamdi M, et al. Impact of X-ray energy on absorbed dose assessed with Monte Carlo simulations in a mouse tumor and in nearest organs irradiated with kilovoltage X-ray beams. Cancer Radiother (2017),
Australasian physical & engineering sciences in medicine, 2017
Small animal CT imaging and dosimetry usually rely on X-ray radiation produced by X-ray tubes. Th... more Small animal CT imaging and dosimetry usually rely on X-ray radiation produced by X-ray tubes. These X-rays typically cover a large energy range. In this study, we compared poly-energetic X-ray spectra against estimated equivalent (effective) mono-energetic beams with the same number of simulated photons for small animal CT imaging and dosimetry applications. Two poly-energetic X-ray spectra were generated from a tungsten anode at 50 and 120 kVp. The corresponding effective mono-energetic beams were established as 36 keV for the 50 kVp spectrum and 49.5 keV for the 120 kVp spectrum. To assess imaging applications, we investigated the spatial resolution by a tungsten wire, and the contrast-to-noise ratio in a reference phantom and in a realistic mouse phantom. For dosimetry investigation, we calculated the absorbed dose in a segmented digital mouse atlas in the skin, fat, heart and bone tissues. Differences of 2.1 and 2.6% in spatial resolution were respectively obtained between the ...
2015 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC), 2015
In this study, we compared the X-ray energy spectra against its estimated effective energy for sm... more In this study, we compared the X-ray energy spectra against its estimated effective energy for small animal CT imaging and dosimetry applications. Two realistic Monte Carlo energy spectra were generated by means of an X-ray source at 50 kVp and 120 kVp, and validated against published spectra. The mono-energetic beam energies were 33 keV and 44 keV considered as the effective energies of the energy spectra of 50 kVp and 120 kVp, respectively. The effective energy was estimated regarding to the ASTM standards. For imaging application, we investigated the spatial resolution and contrast using a needle phantom and a uniform water cylinder with 4 sub-cylinders made of bone, brain tissue, fat and air. For dosimetry investigations, the mono- and the poly-energetic beam absorbed dose to a targeted lung tumor and to other organs was evaluated during small animal external beam radiotherapy treatment using Digimouse phantom. The results showed slight differences in the spatial resolution of 2.90% and -4.10% between the mono-(33 keV and 44 keV) and their respective poly-energetic beams (50 kVp and 120 kVp). The contrast depended on the materials: for 50 kVp and its effective energy 33 keV, the difference in the brain tissue was 1.17% and in bone tissue it was 13.48%. For 120 kVp and 44 keV, it was 1.84% and 10.16% in the brain and bone tissues respectively. In the case of bone, the lowest is the energy, the highest is the difference between the mono- and the poly-energetic contrast. The dose induced by mono-energetic beams was found higher than their counterparts poly-energetic beams in all tissues in the Digimouse phantom, and they showed the same behavior in terms of absorbed dose to neighboring organs relatively the tumor dose.
2015 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC), 2015
The aim of the present work was to investigate the absorbed dose in a target lung tumor, in its s... more The aim of the present work was to investigate the absorbed dose in a target lung tumor, in its surrounding tissues and in neighboring organs not traversed by radiation beams during a small animal X-rays radiotherapy treatment by means of Monte Carlo simulations (MCS). A digital mouse phantom was irradiated by 7 X-ray spectral beams targeting the tumor with energies of 50, 100, 150, 200, 250, 350 and 450 kVp. Each energy beam was directed towards the tumor from 7 different angles to reduce energy deposit in normal tissue. To examine dose behavior, 10 volumes of interest (VOIs) were considered in the lung tumor and its surrounding tissues, in the lungs, the heart, the spinal bone and spinal cord. The results showed that by raising beam energy, the tumor as well as the other VOIs had similar absorbed dose behavior. The absorbed dose was high at 50 kVp and started decreasing until 150 kVp, then it uniformly increased until 450 kVp, except for the spinal cord where the absorbed dose was continuously decreasing from 50 to 450 kVp. The absorbed dose calculated here depended on the whole body of the mouse as the photons interacted in the heterogeneous body of the mouse before energy deposit in a VOI. In conclusion, MCS present a useful tool for small animal radiotherapy treatment planning allowing the optimization of the absorbed dose in the target and in the secondary organs as function of beam energy and of incident beam angles.
Purpose: This study evaluated the safety, dosimetry, and characteristics of 11C-CS1P1, a radiotra... more Purpose: This study evaluated the safety, dosimetry, and characteristics of 11C-CS1P1, a radiotracer targeting sphingosine-1-phoshate receptor 1. Sphingosine-1-phoshate receptor 1 is of clinical interest because of its role in multiple sclerosis (and other conditions) with an expanding class of sphingosine-1-phosphate receptor modulators approved for relapsing multiple sclerosis. 11C-CS1P1 binds sphingosine-1-phosphate receptor 1 with high specificity and has shown promise in animal models of inflammatory diseases. Procedures: 11C-CS1P1 was injected into 5 male and 6 female healthy participants. Ten participants were imaged with positron emission tomography using a multi-pass whole-body continuous-bed-motion acquisition and one had dedicated head and neck positron emission tomography and magnetic resonance imaging. Participants were continuously monitored for safety events. Organ time activity data were collected, integrated and normalized to the injected activity. Organ radiation doses as well as effective dose were computed using the adult male and female model in OLINDA v2.2. SUV images were evaluated for qualitative biodistribution. Results: No adverse events were observed following the dose, including no bradycardia. The liver was the critical organ from dosimetry analysis (mean ± st. dev; Female: 23.12 ± 5.19 μSv/MBq; Male: 21.06 ± 1.63 μSv/MBq). The whole-body effective dose (as defined by ICRP103) was 4.18 ± 0.30 μSv/MBq in females and 3.54 ± 0.14 μSv/MBq in males. Using a maximum delivered dose of 740 MBq (20 mCi), the effective dose for females would be 3.1 mSv (0.31 rem) with a liver dose of 17.1 mSv (1.7 rem); the effective dose for males would be 2.6 mSv (0.26 rem) with a liver dose of 15.6 mSv (1.56 rem). Brain uptake was predominantly seen in gray matter and correlated with regional sphingosine-1-phosphate receptor 1 RNA expression (r = 0.84). Conclusion: These results support the safety of 11C-CS1P1 for evaluation of inflammation in human clinical populations. Dosimetry permits repeated measures in the same participants. Brain uptake correlates well with known target topography.
This paper presents a novel PET geometry for breast cancer imaging. The scanner consists of a ‘st... more This paper presents a novel PET geometry for breast cancer imaging. The scanner consists of a ‘stadium’ (a rectangle with two semi-circles on opposite sides) shaped ring, along with anterior and posterior panels to provide high sensitivity and high spatial resolution for an imaging field-of-view (FOV) that include both breasts, mediastinum and axilla. We simulated this total-breast PET system using GATE and reconstructed the coincidence events using a GPU-based list-mode image reconstruction implementing maximum likelihood expectation-maximization (ML-EM) algorithm. The rear-panel is made up of a single layer of LSO crystals (3.2 × 3.2 × 20 mm3 each), while the ‘stadium’-shaped elongated ring and the anterior panel are made with dual-layered LSO crystals (1.6 × 1.6 × 6 mm3 each). The energy resolution and coincidence resolving time of all detectors are assumed to be 12% and 250 ps full-width-at-half-maximum, respectively. Various sized simulated lesions (4, 5, 6 mm) having 4:1, 5:1,...
2017 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC), 2017
There are several computer programs or combination of programs for radiation tracking, imaging an... more There are several computer programs or combination of programs for radiation tracking, imaging and dosimetry in phantoms and inliving tissues. Among these some are based on GEANT4 programs whichare provided as classes that can be incorporated in C++ codes to achieve differenttasks in radiation interactionswith matter. GEANT4 made the physics easier but the programming remains a tedious task even for physicists familiar with computer programming while it is obviously out of reach of biological and clinical researchers. The aim of the present work was to report the design and development of a new interface GEANT4 Dose And Radiation Interactions (G4DARI) for absorbed dose calculation and for particle tracking in humans, small animals and phantoms. The calculation of the absorbed dose can be performed based on 3D CT images in DICOM format, from images of phantoms or from solid volumes which can be made from any pure or composite material to be specified by its molecular formula. As appl...
2018 IEEE Nuclear Science Symposium and Medical Imaging Conference Proceedings (NSS/MIC), 2018
We developed a graphical user interface based on GEANT4 and GATE to calculate particle interactio... more We developed a graphical user interface based on GEANT4 and GATE to calculate particle interactions and absorbed dose estimates in phantoms and small animals such as mice. In the present work, we extended the interface to absorbed dose calculation and particle interactions in humans based on 3D CT images and radiation beam definition in a clinical setting. The images of the subject and of the beams were supplied in DICOM format. All the parameters needed to calculate the absorbed dose were obtained from these DICOM images. In this work, images of a human brain with glioblastoma were used together with the parameters of five photon beams defined in the clinic. The DICOM file of the beams contained several parameter values such as beam energy, in this case 6 MV, the dose to be deposited in the tumor as a total of 60 Gy, and the 5 beams orientation. Based on the 3D CT images of the patient brain, the whole patient head was rebuilt from the voxel intensity and size providing the real di...
Purpose: One major challenge facing simultaneous positron emission tomography (PET)/ magnetic res... more Purpose: One major challenge facing simultaneous positron emission tomography (PET)/ magnetic resonance imaging (MRI) is PET attenuation correction (AC) measurement and evaluation of its accuracy. There is a crucial need for the evaluation of current and emergent PET AC methodologies in terms of absolute quantitative accuracy in the reconstructed PET images. Approach: To address this need, we developed and evaluated a lesion insertion tool for PET/MRI that will facilitate this evaluation process. This tool was developed for the Biograph mMR and evaluated using phantom and patient data. Contrast recovery coefficients (CRC) from the NEMA IEC phantom of synthesized lesions were compared to measurements. In addition, SUV biases of lesions inserted in human brain and pelvis images were assessed from PET images reconstructed with MRI-based AC (MRAC) and CT-based AC (CTAC). Results: For cross-comparison PET/MRI scanners AC evaluation, we demonstrated that the developed lesion insertion too...
2015 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC), 2015
– In this study, we compared the X-ray energy spectra against its estimated effective energy for ... more – In this study, we compared the X-ray energy spectra against its estimated effective energy for small animal CT imaging and dosimetry applications. Two realistic Monte Carlo energy spectra were generated by means of an X-ray source at 50 kVp and 120 kVp, and validated against published spectra. The mono-energetic beam energies were 33 keV and 44 keV considered as the effective energies of the energy spectra of 50 kVp and 120 kVp, respectively. The effective energy was estimated regarding to the ASTM standards. For imaging application, we investigated the spatial resolution and contrast using a needle phantom and a uniform water cylinder with 4 sub-cylinders made of bone, brain tissue, fat and air. For dosimetry investigations, the mono-and the poly-energetic beam absorbed dose to a targeted lung tumor and to other organs was evaluated during small animal external beam radiotherapy treatment using Digimouse phantom. The results showed slight differences in the spatial resolution of 2.90% and-4.10% between the mono-(33 keV and 44 keV) and their respective poly-energetic beams (50 kVp and 120 kVp). The contrast depended on the materials: for 50 kVp and its effective energy 33 keV, the difference in the brain tissue was 1.17% and in bone tissue it was 13.48%. For 120 kVp and 44 keV, it was 1.84% and 10.16% in the brain and bone tissues respectively. In the case of bone, the lowest is the energy, the highest is the difference between the mono-and the poly-energetic contrast. The dose induced by mono-energetic beams was found higher than their counterparts poly-energetic beams in all tissues in the Digimouse phantom, and they showed the same behavior in terms of absorbed dose to neighboring organs relatively the tumor dose.
brain and bone were respectively −2.9, −0.2, 11.2 and −4.8%, and similarly between the 120 kVp an... more brain and bone were respectively −2.9, −0.2, 11.2 and −4.8%, and similarly between the 120 kVp and its effective energy 49.5 keV: −11.3, −20.2, −4.2 and −13.5%. Concerning the absorbed dose, for the lower X-ray beam energies, 50 kVp against 36 keV, the poly-energetic radiation doses were higher than the mono-energetic doses. Instead, for the higher X-ray beam energies, 120 kVp and 49.5 keV, the absorbed dose to the bones and lungs were higher for the mono-energetic 49.5 keV. The intensity and energy of the X-ray beam spectrum have an impact on both imaging and dosimetry in small animal studies. Simulations with mono-energetic beams should take into account these differences in order to study biological effects or to be compared to experimental data.
– In this study, we compared the X-ray energy spectra against its estimated effective energy for ... more – In this study, we compared the X-ray energy spectra against its estimated effective energy for small animal CT imaging and dosimetry applications. Two realistic Monte Carlo energy spectra were generated by means of an X-ray source at 50 kVp and 120 kVp, and validated against published spectra. The mono-energetic beam energies were 33 keV and 44 keV considered as the effective energies of the energy spectra of 50 kVp and 120 kVp, respectively. The effective energy was estimated regarding to the ASTM standards. For imaging application, we investigated the spatial resolution and contrast using a needle phantom and a uniform water cylinder with 4 sub-cylinders made of bone, brain tissue, fat and air. For dosimetry investigations, the mono-and the poly-energetic beam absorbed dose to a targeted lung tumor and to other organs was evaluated during small animal external beam radiotherapy treatment using Digimouse phantom. The results showed slight differences in the spatial resolution of 2.90% and-4.10% between the mono-(33 keV and 44 keV) and their respective poly-energetic beams (50 kVp and 120 kVp). The contrast depended on the materials: for 50 kVp and its effective energy 33 keV, the difference in the brain tissue was 1.17% and in bone tissue it was 13.48%. For 120 kVp and 44 keV, it was 1.84% and 10.16% in the brain and bone tissues respectively. In the case of bone, the lowest is the energy, the highest is the difference between the mono-and the poly-energetic contrast. The dose induced by mono-energetic beams was found higher than their counterparts poly-energetic beams in all tissues in the Digimouse phantom, and they showed the same behavior in terms of absorbed dose to neighboring organs relatively the tumor dose.
– The aim of the present work was to investigate the absorbed dose in a target lung tumor, in its... more – The aim of the present work was to investigate the absorbed dose in a target lung tumor, in its surrounding tissues and in neighboring organs not traversed by radiation beams during a small animal X-rays radiotherapy treatment by means of Monte Carlo simulations (MCS). A digital mouse phantom was irradiated by 7 X-ray spectral beams targeting the tumor with energies of 50, 100, 150, 200, 250, 350 and 450 kVp. Each energy beam was directed towards the tumor from 7 different angles to reduce energy deposit in normal tissue. To examine dose behavior, 10 volumes of interest (VOIs) were considered in the lung tumor and its surrounding tissues, in the lungs, the heart, the spinal bone and spinal cord. The results showed that by raising beam energy, the tumor as well as the other VOIs had similar absorbed dose behavior. The absorbed dose was high at 50 kVp and started decreasing until 150 kVp, then it uniformly increased until 450 kVp, except for the spinal cord where the absorbed dose was continuously decreasing from 50 to 450 kVp. The absorbed dose calculated here depended on the whole body of the mouse as the photons interacted in the heterogeneous body of the mouse before energy deposit in a VOI. In conclusion, MCS present a useful tool for small animal radiotherapy treatment planning allowing the optimization of the absorbed dose in the target and in the secondary organs as function of beam energy and of incident beam angles.
Historically, patient datasets have been used to develop and validate various reconstruction algo... more Historically, patient datasets have been used to develop and validate various reconstruction algorithms for PET/MRI and PET/CT. To enable such algorithm development, without the need for acquiring hundreds of patient exams, in this paper we demonstrate a deep learning technique to generate synthetic but realistic whole-body PET sinograms from abundantly-available whole-body MRI. Specifically, we use a dataset of 56 18 F-FDG-PET/MRI exams to train a 3D residual UNet to predict physiologic PET uptake from whole-body T1-weighted MRI. In training we implemented a balanced loss function to generate realistic uptake across a large dynamic range and computed losses along tomographic lines of response to mimic the PET acquisition. The predicted PET images are forward projected to produce synthetic PET time-of-flight (ToF) sinograms that can be used with vendor-provided PET reconstruction algorithms, including using CT-based attenuation correction (CTAC) and MR-based attenuation correction (MRAC). The resulting synthetic data recapitulates physiologic 18 F-FDG uptake, e.g. high uptake localized to the brain and bladder, as well as uptake in liver, kidneys, heart and muscle. To simulate abnormalities with high uptake, we also insert synthetic lesions. We demonstrate that this synthetic PET data can be used interchangeably with real PET data for the PET quantification task of comparing CT and MRbased attenuation correction methods, achieving ≤ 7.6% error in mean-SUV compared to using real data. These results together show that the proposed synthetic PET data pipeline can be reasonably used for development, evaluation, and validation of PET/MRI reconstruction methods.
Histopathological analysis of whole-slide images is the gold standard technique for diagnosis of ... more Histopathological analysis of whole-slide images is the gold standard technique for diagnosis of lung cancer and classifying it into types and subtypes by specialized pathologists. This labor-based approach is time and effort consuming, which led to development of automatic approaches to assist in reducing the time and effort. Deep learning is a supervised classification approach that is well adapted for automatic classification of histopathological images. We aimed to develop a deep learning-based approach for lung adenocarcinoma pattern classification and generalize the proposed approach to the classification of the major non-small cell lung cancer types. Three publicly available datasets were used in this study. A deep learning approach for histopathological image analysis using convolutional neural networks was developed and incorporated into automatic pipelines to accurately classify the predominant patterns on the whole-slide images level and non-small cell lung cancer types o...
A novel technique, called augmented whole-body scanning via magnifying PET (AWSM-PET), that impro... more A novel technique, called augmented whole-body scanning via magnifying PET (AWSM-PET), that improves the sensitivity and lesion detectability of a PET scanner for whole-body imaging is proposed and evaluated. A Siemens Biograph Vision PET/CT scanner equipped with one or two high-resolution panel-detectors was simulated to study the effectiveness of AWSM-PET technology. The detector panels are located immediately outside the scanner's axial field-of-view (FOV). A detector panel contains 2 × 8 detector modules each consisting of 32 × 64 LSO crystals (1.0 × 1.0 × 10.0 mm 3 each). A 22 Na point source was stepped across the scanner's FOV axially to measure sensitivity profiles at different locations. An elliptical torso phantom containing 7 × 9 spherical lesions was imaged at different axial locations to mimic a multi-bed-position whole-body imaging protocol. Receiver operating characteristic (ROC) curves were analyzed to evaluate the improvement in lesion detectability by the AWSM-PET technology. Experimental validation was conducted using an existing flat-panel detector integrated with a Siemens Biograph 40 PET/CT scanner to image a torso phantom containing spherical lesions with diameters ranging from 3.3 to 11.4 mm. The contrast-recovery-coefficient (CRC) of the lesions was evaluated for the scanner with or without the AWSM-PET technology. Monte Carlo simulation shows 36%-42% improvement in system sensitivity by a dual-panel AWSM-PET device. The area under the ROC curve is 0.962 by a native scanner for the detection of 4 mm diameter
Computerized medical imaging and graphics : the official journal of the Computerized Medical Imaging Society, 2018
Monte Carlo (MC) simulation is widely recognized as an important technique to study the physics o... more Monte Carlo (MC) simulation is widely recognized as an important technique to study the physics of particle interactions in nuclear medicine and radiation therapy. There are different codes dedicated to dosimetry applications and widely used today in research or in clinical application, such as MCNP, EGSnrc and Geant4. However, such codes made the physics easier but the programming remains a tedious task even for physicists familiar with computer programming. In this paper we report the development of a new interface GEANT4 Dose And Radiation Interactions (G4DARI) based on GEANT4 for absorbed dose calculation and for particle tracking in humans, small animals and complex phantoms. The calculation of the absorbed dose is performed based on 3D CT human or animal images in DICOM format, from images of phantoms or from solid volumes which can be made from any pure or composite material to be specified by its molecular formula. G4DARI offers menus to the user and tabs to be filled with v...
Please cite this article in press as: Hamdi M, et al. Impact of X-ray energy on absorbed dose ass... more Please cite this article in press as: Hamdi M, et al. Impact of X-ray energy on absorbed dose assessed with Monte Carlo simulations in a mouse tumor and in nearest organs irradiated with kilovoltage X-ray beams. Cancer Radiother (2017),
Australasian physical & engineering sciences in medicine, 2017
Small animal CT imaging and dosimetry usually rely on X-ray radiation produced by X-ray tubes. Th... more Small animal CT imaging and dosimetry usually rely on X-ray radiation produced by X-ray tubes. These X-rays typically cover a large energy range. In this study, we compared poly-energetic X-ray spectra against estimated equivalent (effective) mono-energetic beams with the same number of simulated photons for small animal CT imaging and dosimetry applications. Two poly-energetic X-ray spectra were generated from a tungsten anode at 50 and 120 kVp. The corresponding effective mono-energetic beams were established as 36 keV for the 50 kVp spectrum and 49.5 keV for the 120 kVp spectrum. To assess imaging applications, we investigated the spatial resolution by a tungsten wire, and the contrast-to-noise ratio in a reference phantom and in a realistic mouse phantom. For dosimetry investigation, we calculated the absorbed dose in a segmented digital mouse atlas in the skin, fat, heart and bone tissues. Differences of 2.1 and 2.6% in spatial resolution were respectively obtained between the ...
2015 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC), 2015
In this study, we compared the X-ray energy spectra against its estimated effective energy for sm... more In this study, we compared the X-ray energy spectra against its estimated effective energy for small animal CT imaging and dosimetry applications. Two realistic Monte Carlo energy spectra were generated by means of an X-ray source at 50 kVp and 120 kVp, and validated against published spectra. The mono-energetic beam energies were 33 keV and 44 keV considered as the effective energies of the energy spectra of 50 kVp and 120 kVp, respectively. The effective energy was estimated regarding to the ASTM standards. For imaging application, we investigated the spatial resolution and contrast using a needle phantom and a uniform water cylinder with 4 sub-cylinders made of bone, brain tissue, fat and air. For dosimetry investigations, the mono- and the poly-energetic beam absorbed dose to a targeted lung tumor and to other organs was evaluated during small animal external beam radiotherapy treatment using Digimouse phantom. The results showed slight differences in the spatial resolution of 2.90% and -4.10% between the mono-(33 keV and 44 keV) and their respective poly-energetic beams (50 kVp and 120 kVp). The contrast depended on the materials: for 50 kVp and its effective energy 33 keV, the difference in the brain tissue was 1.17% and in bone tissue it was 13.48%. For 120 kVp and 44 keV, it was 1.84% and 10.16% in the brain and bone tissues respectively. In the case of bone, the lowest is the energy, the highest is the difference between the mono- and the poly-energetic contrast. The dose induced by mono-energetic beams was found higher than their counterparts poly-energetic beams in all tissues in the Digimouse phantom, and they showed the same behavior in terms of absorbed dose to neighboring organs relatively the tumor dose.
2015 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC), 2015
The aim of the present work was to investigate the absorbed dose in a target lung tumor, in its s... more The aim of the present work was to investigate the absorbed dose in a target lung tumor, in its surrounding tissues and in neighboring organs not traversed by radiation beams during a small animal X-rays radiotherapy treatment by means of Monte Carlo simulations (MCS). A digital mouse phantom was irradiated by 7 X-ray spectral beams targeting the tumor with energies of 50, 100, 150, 200, 250, 350 and 450 kVp. Each energy beam was directed towards the tumor from 7 different angles to reduce energy deposit in normal tissue. To examine dose behavior, 10 volumes of interest (VOIs) were considered in the lung tumor and its surrounding tissues, in the lungs, the heart, the spinal bone and spinal cord. The results showed that by raising beam energy, the tumor as well as the other VOIs had similar absorbed dose behavior. The absorbed dose was high at 50 kVp and started decreasing until 150 kVp, then it uniformly increased until 450 kVp, except for the spinal cord where the absorbed dose was continuously decreasing from 50 to 450 kVp. The absorbed dose calculated here depended on the whole body of the mouse as the photons interacted in the heterogeneous body of the mouse before energy deposit in a VOI. In conclusion, MCS present a useful tool for small animal radiotherapy treatment planning allowing the optimization of the absorbed dose in the target and in the secondary organs as function of beam energy and of incident beam angles.
Purpose: This study evaluated the safety, dosimetry, and characteristics of 11C-CS1P1, a radiotra... more Purpose: This study evaluated the safety, dosimetry, and characteristics of 11C-CS1P1, a radiotracer targeting sphingosine-1-phoshate receptor 1. Sphingosine-1-phoshate receptor 1 is of clinical interest because of its role in multiple sclerosis (and other conditions) with an expanding class of sphingosine-1-phosphate receptor modulators approved for relapsing multiple sclerosis. 11C-CS1P1 binds sphingosine-1-phosphate receptor 1 with high specificity and has shown promise in animal models of inflammatory diseases. Procedures: 11C-CS1P1 was injected into 5 male and 6 female healthy participants. Ten participants were imaged with positron emission tomography using a multi-pass whole-body continuous-bed-motion acquisition and one had dedicated head and neck positron emission tomography and magnetic resonance imaging. Participants were continuously monitored for safety events. Organ time activity data were collected, integrated and normalized to the injected activity. Organ radiation doses as well as effective dose were computed using the adult male and female model in OLINDA v2.2. SUV images were evaluated for qualitative biodistribution. Results: No adverse events were observed following the dose, including no bradycardia. The liver was the critical organ from dosimetry analysis (mean ± st. dev; Female: 23.12 ± 5.19 μSv/MBq; Male: 21.06 ± 1.63 μSv/MBq). The whole-body effective dose (as defined by ICRP103) was 4.18 ± 0.30 μSv/MBq in females and 3.54 ± 0.14 μSv/MBq in males. Using a maximum delivered dose of 740 MBq (20 mCi), the effective dose for females would be 3.1 mSv (0.31 rem) with a liver dose of 17.1 mSv (1.7 rem); the effective dose for males would be 2.6 mSv (0.26 rem) with a liver dose of 15.6 mSv (1.56 rem). Brain uptake was predominantly seen in gray matter and correlated with regional sphingosine-1-phosphate receptor 1 RNA expression (r = 0.84). Conclusion: These results support the safety of 11C-CS1P1 for evaluation of inflammation in human clinical populations. Dosimetry permits repeated measures in the same participants. Brain uptake correlates well with known target topography.
This paper presents a novel PET geometry for breast cancer imaging. The scanner consists of a ‘st... more This paper presents a novel PET geometry for breast cancer imaging. The scanner consists of a ‘stadium’ (a rectangle with two semi-circles on opposite sides) shaped ring, along with anterior and posterior panels to provide high sensitivity and high spatial resolution for an imaging field-of-view (FOV) that include both breasts, mediastinum and axilla. We simulated this total-breast PET system using GATE and reconstructed the coincidence events using a GPU-based list-mode image reconstruction implementing maximum likelihood expectation-maximization (ML-EM) algorithm. The rear-panel is made up of a single layer of LSO crystals (3.2 × 3.2 × 20 mm3 each), while the ‘stadium’-shaped elongated ring and the anterior panel are made with dual-layered LSO crystals (1.6 × 1.6 × 6 mm3 each). The energy resolution and coincidence resolving time of all detectors are assumed to be 12% and 250 ps full-width-at-half-maximum, respectively. Various sized simulated lesions (4, 5, 6 mm) having 4:1, 5:1,...
2017 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC), 2017
There are several computer programs or combination of programs for radiation tracking, imaging an... more There are several computer programs or combination of programs for radiation tracking, imaging and dosimetry in phantoms and inliving tissues. Among these some are based on GEANT4 programs whichare provided as classes that can be incorporated in C++ codes to achieve differenttasks in radiation interactionswith matter. GEANT4 made the physics easier but the programming remains a tedious task even for physicists familiar with computer programming while it is obviously out of reach of biological and clinical researchers. The aim of the present work was to report the design and development of a new interface GEANT4 Dose And Radiation Interactions (G4DARI) for absorbed dose calculation and for particle tracking in humans, small animals and phantoms. The calculation of the absorbed dose can be performed based on 3D CT images in DICOM format, from images of phantoms or from solid volumes which can be made from any pure or composite material to be specified by its molecular formula. As appl...
2018 IEEE Nuclear Science Symposium and Medical Imaging Conference Proceedings (NSS/MIC), 2018
We developed a graphical user interface based on GEANT4 and GATE to calculate particle interactio... more We developed a graphical user interface based on GEANT4 and GATE to calculate particle interactions and absorbed dose estimates in phantoms and small animals such as mice. In the present work, we extended the interface to absorbed dose calculation and particle interactions in humans based on 3D CT images and radiation beam definition in a clinical setting. The images of the subject and of the beams were supplied in DICOM format. All the parameters needed to calculate the absorbed dose were obtained from these DICOM images. In this work, images of a human brain with glioblastoma were used together with the parameters of five photon beams defined in the clinic. The DICOM file of the beams contained several parameter values such as beam energy, in this case 6 MV, the dose to be deposited in the tumor as a total of 60 Gy, and the 5 beams orientation. Based on the 3D CT images of the patient brain, the whole patient head was rebuilt from the voxel intensity and size providing the real di...
Purpose: One major challenge facing simultaneous positron emission tomography (PET)/ magnetic res... more Purpose: One major challenge facing simultaneous positron emission tomography (PET)/ magnetic resonance imaging (MRI) is PET attenuation correction (AC) measurement and evaluation of its accuracy. There is a crucial need for the evaluation of current and emergent PET AC methodologies in terms of absolute quantitative accuracy in the reconstructed PET images. Approach: To address this need, we developed and evaluated a lesion insertion tool for PET/MRI that will facilitate this evaluation process. This tool was developed for the Biograph mMR and evaluated using phantom and patient data. Contrast recovery coefficients (CRC) from the NEMA IEC phantom of synthesized lesions were compared to measurements. In addition, SUV biases of lesions inserted in human brain and pelvis images were assessed from PET images reconstructed with MRI-based AC (MRAC) and CT-based AC (CTAC). Results: For cross-comparison PET/MRI scanners AC evaluation, we demonstrated that the developed lesion insertion too...
2015 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC), 2015
– In this study, we compared the X-ray energy spectra against its estimated effective energy for ... more – In this study, we compared the X-ray energy spectra against its estimated effective energy for small animal CT imaging and dosimetry applications. Two realistic Monte Carlo energy spectra were generated by means of an X-ray source at 50 kVp and 120 kVp, and validated against published spectra. The mono-energetic beam energies were 33 keV and 44 keV considered as the effective energies of the energy spectra of 50 kVp and 120 kVp, respectively. The effective energy was estimated regarding to the ASTM standards. For imaging application, we investigated the spatial resolution and contrast using a needle phantom and a uniform water cylinder with 4 sub-cylinders made of bone, brain tissue, fat and air. For dosimetry investigations, the mono-and the poly-energetic beam absorbed dose to a targeted lung tumor and to other organs was evaluated during small animal external beam radiotherapy treatment using Digimouse phantom. The results showed slight differences in the spatial resolution of 2.90% and-4.10% between the mono-(33 keV and 44 keV) and their respective poly-energetic beams (50 kVp and 120 kVp). The contrast depended on the materials: for 50 kVp and its effective energy 33 keV, the difference in the brain tissue was 1.17% and in bone tissue it was 13.48%. For 120 kVp and 44 keV, it was 1.84% and 10.16% in the brain and bone tissues respectively. In the case of bone, the lowest is the energy, the highest is the difference between the mono-and the poly-energetic contrast. The dose induced by mono-energetic beams was found higher than their counterparts poly-energetic beams in all tissues in the Digimouse phantom, and they showed the same behavior in terms of absorbed dose to neighboring organs relatively the tumor dose.
brain and bone were respectively −2.9, −0.2, 11.2 and −4.8%, and similarly between the 120 kVp an... more brain and bone were respectively −2.9, −0.2, 11.2 and −4.8%, and similarly between the 120 kVp and its effective energy 49.5 keV: −11.3, −20.2, −4.2 and −13.5%. Concerning the absorbed dose, for the lower X-ray beam energies, 50 kVp against 36 keV, the poly-energetic radiation doses were higher than the mono-energetic doses. Instead, for the higher X-ray beam energies, 120 kVp and 49.5 keV, the absorbed dose to the bones and lungs were higher for the mono-energetic 49.5 keV. The intensity and energy of the X-ray beam spectrum have an impact on both imaging and dosimetry in small animal studies. Simulations with mono-energetic beams should take into account these differences in order to study biological effects or to be compared to experimental data.
– In this study, we compared the X-ray energy spectra against its estimated effective energy for ... more – In this study, we compared the X-ray energy spectra against its estimated effective energy for small animal CT imaging and dosimetry applications. Two realistic Monte Carlo energy spectra were generated by means of an X-ray source at 50 kVp and 120 kVp, and validated against published spectra. The mono-energetic beam energies were 33 keV and 44 keV considered as the effective energies of the energy spectra of 50 kVp and 120 kVp, respectively. The effective energy was estimated regarding to the ASTM standards. For imaging application, we investigated the spatial resolution and contrast using a needle phantom and a uniform water cylinder with 4 sub-cylinders made of bone, brain tissue, fat and air. For dosimetry investigations, the mono-and the poly-energetic beam absorbed dose to a targeted lung tumor and to other organs was evaluated during small animal external beam radiotherapy treatment using Digimouse phantom. The results showed slight differences in the spatial resolution of 2.90% and-4.10% between the mono-(33 keV and 44 keV) and their respective poly-energetic beams (50 kVp and 120 kVp). The contrast depended on the materials: for 50 kVp and its effective energy 33 keV, the difference in the brain tissue was 1.17% and in bone tissue it was 13.48%. For 120 kVp and 44 keV, it was 1.84% and 10.16% in the brain and bone tissues respectively. In the case of bone, the lowest is the energy, the highest is the difference between the mono-and the poly-energetic contrast. The dose induced by mono-energetic beams was found higher than their counterparts poly-energetic beams in all tissues in the Digimouse phantom, and they showed the same behavior in terms of absorbed dose to neighboring organs relatively the tumor dose.
– The aim of the present work was to investigate the absorbed dose in a target lung tumor, in its... more – The aim of the present work was to investigate the absorbed dose in a target lung tumor, in its surrounding tissues and in neighboring organs not traversed by radiation beams during a small animal X-rays radiotherapy treatment by means of Monte Carlo simulations (MCS). A digital mouse phantom was irradiated by 7 X-ray spectral beams targeting the tumor with energies of 50, 100, 150, 200, 250, 350 and 450 kVp. Each energy beam was directed towards the tumor from 7 different angles to reduce energy deposit in normal tissue. To examine dose behavior, 10 volumes of interest (VOIs) were considered in the lung tumor and its surrounding tissues, in the lungs, the heart, the spinal bone and spinal cord. The results showed that by raising beam energy, the tumor as well as the other VOIs had similar absorbed dose behavior. The absorbed dose was high at 50 kVp and started decreasing until 150 kVp, then it uniformly increased until 450 kVp, except for the spinal cord where the absorbed dose was continuously decreasing from 50 to 450 kVp. The absorbed dose calculated here depended on the whole body of the mouse as the photons interacted in the heterogeneous body of the mouse before energy deposit in a VOI. In conclusion, MCS present a useful tool for small animal radiotherapy treatment planning allowing the optimization of the absorbed dose in the target and in the secondary organs as function of beam energy and of incident beam angles.
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Papers by Mahdjoub Hamdi