Journal of Computational Design and Engineering, 2022
We investigate the accuracy of direct attenuation correction (AC) in the image domain for myocard... more We investigate the accuracy of direct attenuation correction (AC) in the image domain for myocardial perfusion SPECT (single-photon emission computed tomography) imaging (MPI-SPECT) using residual (ResNet) and UNet deep convolutional neural networks. MPI-SPECT 99mTc-sestamibi images of 99 patients were retrospectively included. UNet and ResNet networks were trained using non-attenuation-corrected SPECT images as input, whereas CT-based attenuation-corrected (CT-AC) SPECT images served as reference. Chang’s calculated AC approach considering a uniform attenuation coefficient within the body contour was also implemented. Clinical and quantitative evaluations of the proposed methods were performed considering SPECT CT-AC images of 19 subjects (external validation set) as reference. Image-derived metrics, including the voxel-wise mean error (ME), mean absolute error, relative error, structural similarity index (SSI), and peak signal-to-noise ratio, as well as clinical relevant indices, ...
Renal scan is one of the common imaging requests in every nuclear medicine center (1-3). Measurem... more Renal scan is one of the common imaging requests in every nuclear medicine center (1-3). Measurement of renal function is used to make critical clinical management decisions and, as such, their reliability needs to be quality assured (4). Gamma cameras are used for renal scintigraphy which contains energy discriminators that allow only those photons within a specified energy range to be recorded (5). Periodic quality control (QC) of gamma cameras is essential to provide a reliable image. However artifacts are commonly seen in scintigraphy and nuclear physicians should be familiar with different types of artifacts to prevent misdiagnosis. We report a case of spontaneous photopeak shift during acquisition of a dynamic renal scan.
Asia Oceania Journal of Nuclear Medicine and Biology, 2018
Objective(s): In recent years, the application of radiopharmaceuticals in nuclear medicine has in... more Objective(s): In recent years, the application of radiopharmaceuticals in nuclear medicine has increased substantially. Following the diagnostic procedures performed in nuclear medicine departments, such as myocardial perfusion imaging, patients generally receive considerable doses of radiation. Normally, radiation-induced DNA damages are expected following exposure to a low-dose ionizing radiation. In order to detect molecular changes, high-sensitivity techniques must be utilized. The aim of this study was to assess the effect of a low-dose (below 10 mSv) gamma ray on gene expression using quantitative real-time polymerase chain reaction (qRT-PCR). Methods: Blood samples were obtained from 20 volunteer patients who underwent myocardial perfusion imaging. They were given various doses of Technetium-99m methoxyisobutylisonitrile (99mTc-MIBI). After that, peripheral blood mononuclear cells (PBMNs) were derived, and then total RNA was extracted and reverse-transcribed to cDNA. Finally,...
Introduction 3D reconstruction of an object from its 2D cross-sections (slices) has many applicat... more Introduction 3D reconstruction of an object from its 2D cross-sections (slices) has many applications in different fields of sciences such as medical physics and biomedical engineering. In order to perform 3D reconstruction, at first, desired boundaries at each slice are detected and then using a correspondence between points of successive slices surface of desired object is reconstructed. Materials and Methods In this study, Gradient Vector Flow (GVF) was used in order to trace the boundaries at each slice. Then, cubic Bezier Spline curves were used to approximate each of obtained contours and to approximate the corresponding points of different contours at successive slices. The reconstructed surface was a bi-cubic Bezier Spline surface which was smooth with G2 continuity. Results Our presented method was tested on SPECT data of JASZCZAK phantom and human's left ventricle. The results confirmed that the presented method was accurate, promising, applicable, and effective. Concl...
Introduction: Electronic portal imaging devices (EPIDs) provide two- and three-dimensional planar... more Introduction: Electronic portal imaging devices (EPIDs) provide two- and three-dimensional planar and volumetric cone beam images to improve the accuracy of radiation treatment delivery. Periodic quality assurance (QA) of EPIDs is essential for dosimetric verification in radiotherapy. In this study, a QA program was implemented to evaluate the function of the EPID to be confident in applying corrections for the uncertainty of patient set-up. Material and Methods: Firstly, the safety features were verified, and the uniformity of EPID response was evaluated using flat panel detector. Additionally, the contrast and spatial resolutions of the EPID were assessed using detail counting of the Los Vegas phantom images by visualization method and measuring the modulation transfer function using edge technique, respectively. Moreover, a combination of smoothing methods was used for optimal use of edge detection algorithm for the noisy portal images. Finally, the location of the central ray on...
Introduction:Gated myocardial perfusion SPECT has diagnostic and prognostic values in coronary ar... more Introduction:Gated myocardial perfusion SPECT has diagnostic and prognostic values in coronary artery disease (CAD). We tried to determine prognostic values of the left ventricular perfusion & functional indices as well as transient left ventricular dilation (TID) derived from gated myocardial perfusion SPECT. Methods: 1820patients who underwent gated myocardial perfusion SPECT (Gated SPECT) were studied. The summed stress score (SSS), summed rest score (SRS) and summed difference score (SDS) were calculated. Cardiac events considered as nonfatal myocardial infarction, cardiac death, Coronary Care Unit admission and revascularization. Mean follow-up period after Gated SPECT was 23±10 months. Results: 1599 patients didn't have any events, while from remaining 221, six patients had an acute MI, 90 patients had CCU admission, 42 patients underwent revascularization and 84 patients died. There was statistically significant difference in the cardiac events based on age, sex, SSS, SRS...
Introduction: Regular implementation of quality control (QC) program in diagnostic X-ray faciliti... more Introduction: Regular implementation of quality control (QC) program in diagnostic X-ray facilities may affect both image quality and patient radiation dose due to the changes in exposure parameters. Therefore, this study aimed to investigate the status of randomly selected conventional radiographic X-ray devices installed in radiology centers of Great Khorasan Province, Iran, to produce the data needed to formulate QC policies, which are essential to ensure the accuracy of the diagnosis while minimizing the radiation dose. Material and Methods: This cross-sectional study was performed using a calibrated Piranha multi-purpose detector to measure QC parameters in order to unify X‐ray imaging practices using international guidelines. The QC parameters included voltage accuracy, voltage reproducibility, exposure time accuracy, exposure time reproducibility, tube output linearity with time andmilliampere (mA), and tube output reproducibility. Data analysis procedures were performed base...
Introduction SPECT projections are contaminated by scatter radiation, resulting in reduced image ... more Introduction SPECT projections are contaminated by scatter radiation, resulting in reduced image contrast and quantitative errors. Backscatter constitutes a major part of the scatter contamination in lower energy windows. The current study is an evaluation of the effect of backscatter material on FWHM and image quality investigated by Monte Carlo simulation. Materials and Methods SIMIND program was used for simulation of a Siemen’s dual-head variable angle scintillation gamma camera. Planar and SPECT scanning of a 99mTc source and a Jaszczak phantom for varying thicknesses of Perspex slabs, as a backscatter media, were analyzed using the photopeak and scatter windows. Simulated planar images and reconstructed tomographic images were evaluated qualitatively, by two nuclear medicine specialists, and quantitatively, by Structural Similarity (SSIM) Index. Results In the 99mTc photopeak window, no significant change in total counts due to backscatter material was measured. In the scatter...
Introduction: The application of 3D volumetric imaging modalities in treatment planning of radiat... more Introduction: The application of 3D volumetric imaging modalities in treatment planning of radiation therapy can provide more precisely define tumor localization, and computed tomography (CT) is the most common accepted method for treatment planning. Given the lack of a CT scanner stationed in all radiotherapy departments and equipping most of the medical linear accelerators with only electronics portal imaging device (EPID) device, the use of this technology for megavoltage cone-beam computed tomography (MV-CBCT) imaging in such cases as urgent palliative radiotherapy treatments, leads to precise localization of the tumor and increases the accuracy of the beam sent to the target area. Since MV-CBCT imaging is possible using EPID, this study is aimed at conducting MV-CBCT and investigating the possibility of using these images in the treatment planning of the radiation therapy. Materials and Methods: Initially, the projection data of an anthropomorphic head phantom was acquired at 3...
During the last decades there has been an increasing interest in studying the differences between... more During the last decades there has been an increasing interest in studying the differences between males and females. These differences extend from behavioral to cognitive to micro- and macro- neuro-anatomical aspects of human biology. There have been many methods to evaluate these differences and explain their determinants. The most studied cause of this dimorphism is the prenatal sex hormones and their organizational effect on brain and behavior. However, there have been new and recent attentions to hormone’s activational influences in puberty and also the effects of genomic imprinting. In this paper, we reviewed the sex differences of brain, the evidences for possible determinants of these differences and also the methods that have been used to discover them. We reviewed the most conspicuous findings with specific attention to macro-anatomical differences based on Magnetic Resonance Imaging (MRI) data. We finally reviewed the findings and the many opportunities for future studies.
Background: With the increasing efforts to a better understanding of psychiatric diseases, detect... more Background: With the increasing efforts to a better understanding of psychiatric diseases, detection of brain morphological alterations are necessary. This study compared two methods-voxel based morphometry (VBM) and region of interest (ROI) analyses- to identify significant gray matter changes of patients with bipolar disorder type I (BP I). Methods: The structural MRI were obtained in a total of 50 subjects (25 healthy subjects with a mean age of 34.48±8.32 years as a control group and 25 patients with a mean age of 37.68±10.88 years). We compared the gray matter alteration results obtained by VBM analysis using the DARTEL approach with those obtained using ROI analysis which applies three probabilistic brain atlases namely, hammers, lpba40, and neuromorphometrics atlases. All analyses were conducted via the Computational Anatomy Toolbox (CAT12) implemented in Statistical Parametric Mapping (SPM12) software package. Results: The VBM findings suggested that gray matter reductions i...
Journal of Biomedical Physics and Engineering, 2019
Background: The present study aimed to introduce a rapid transmission dosimetry through an electr... more Background: The present study aimed to introduce a rapid transmission dosimetry through an electronic portal-imaging device (EPID) to achieve two-dimensional (2D) dose distribution for homogenous environments.Material and Methods: In this Phantom study, first, the EPID calibration curve and correction coefficients for field size were obtained from EPID and ionization chamber. Second, the EPID off-axis pixel response was measured, and the grey-scale image of the EPID was converted into portal dose image using the calibration curve. Next, the scattering contribution was calculated to obtain the primary dose. Then, by means of a verified back-projection algorithm and the Scatter-to-Primary dose ratio, a 2D dose distribution at the mid-plane was obtained.Results: The results obtained from comparing the transmitted EPID dosimetry to the calculated dose, using commercial treatment planning system with gamma function while there is 3% dose difference and 3mm distance to agreement criteria,...
Journal of Biomedical Physics and Engineering, 2019
Background: Given the importance of scattered and low doses in secondary cancer caused by radiati... more Background: Given the importance of scattered and low doses in secondary cancer caused by radiation treatment, the point dose of critical organs, which were not subjected to radiation treatment in breast cancer radiotherapy, was measured.Objective: The purpose of this study is to evaluate the peripheral dose in two techniques of breast cancer radiotherapy with two energies. Methods: Eight different plans in two techniques (conventional and conformal) and two photon energies (6 and 15 MeV) were applied to Rando Alderson Phantom’s DICOM images. Nine organs were contoured in the treatment planning system and specified on the phantom. To measure the photon dose, forty-eight thermoluminescence dosimeters (MTS700) were positioned in special places on the above nine organs and plans were applied to Rando phantom with Elekta presice linac. To obtain approximately the same dose distribution in the clinical organ volume, a wedge was used on planes with an energy of 6 MeV photon. Resul...
Journal of Computational Design and Engineering, 2022
We investigate the accuracy of direct attenuation correction (AC) in the image domain for myocard... more We investigate the accuracy of direct attenuation correction (AC) in the image domain for myocardial perfusion SPECT (single-photon emission computed tomography) imaging (MPI-SPECT) using residual (ResNet) and UNet deep convolutional neural networks. MPI-SPECT 99mTc-sestamibi images of 99 patients were retrospectively included. UNet and ResNet networks were trained using non-attenuation-corrected SPECT images as input, whereas CT-based attenuation-corrected (CT-AC) SPECT images served as reference. Chang’s calculated AC approach considering a uniform attenuation coefficient within the body contour was also implemented. Clinical and quantitative evaluations of the proposed methods were performed considering SPECT CT-AC images of 19 subjects (external validation set) as reference. Image-derived metrics, including the voxel-wise mean error (ME), mean absolute error, relative error, structural similarity index (SSI), and peak signal-to-noise ratio, as well as clinical relevant indices, ...
Renal scan is one of the common imaging requests in every nuclear medicine center (1-3). Measurem... more Renal scan is one of the common imaging requests in every nuclear medicine center (1-3). Measurement of renal function is used to make critical clinical management decisions and, as such, their reliability needs to be quality assured (4). Gamma cameras are used for renal scintigraphy which contains energy discriminators that allow only those photons within a specified energy range to be recorded (5). Periodic quality control (QC) of gamma cameras is essential to provide a reliable image. However artifacts are commonly seen in scintigraphy and nuclear physicians should be familiar with different types of artifacts to prevent misdiagnosis. We report a case of spontaneous photopeak shift during acquisition of a dynamic renal scan.
Asia Oceania Journal of Nuclear Medicine and Biology, 2018
Objective(s): In recent years, the application of radiopharmaceuticals in nuclear medicine has in... more Objective(s): In recent years, the application of radiopharmaceuticals in nuclear medicine has increased substantially. Following the diagnostic procedures performed in nuclear medicine departments, such as myocardial perfusion imaging, patients generally receive considerable doses of radiation. Normally, radiation-induced DNA damages are expected following exposure to a low-dose ionizing radiation. In order to detect molecular changes, high-sensitivity techniques must be utilized. The aim of this study was to assess the effect of a low-dose (below 10 mSv) gamma ray on gene expression using quantitative real-time polymerase chain reaction (qRT-PCR). Methods: Blood samples were obtained from 20 volunteer patients who underwent myocardial perfusion imaging. They were given various doses of Technetium-99m methoxyisobutylisonitrile (99mTc-MIBI). After that, peripheral blood mononuclear cells (PBMNs) were derived, and then total RNA was extracted and reverse-transcribed to cDNA. Finally,...
Introduction 3D reconstruction of an object from its 2D cross-sections (slices) has many applicat... more Introduction 3D reconstruction of an object from its 2D cross-sections (slices) has many applications in different fields of sciences such as medical physics and biomedical engineering. In order to perform 3D reconstruction, at first, desired boundaries at each slice are detected and then using a correspondence between points of successive slices surface of desired object is reconstructed. Materials and Methods In this study, Gradient Vector Flow (GVF) was used in order to trace the boundaries at each slice. Then, cubic Bezier Spline curves were used to approximate each of obtained contours and to approximate the corresponding points of different contours at successive slices. The reconstructed surface was a bi-cubic Bezier Spline surface which was smooth with G2 continuity. Results Our presented method was tested on SPECT data of JASZCZAK phantom and human's left ventricle. The results confirmed that the presented method was accurate, promising, applicable, and effective. Concl...
Introduction: Electronic portal imaging devices (EPIDs) provide two- and three-dimensional planar... more Introduction: Electronic portal imaging devices (EPIDs) provide two- and three-dimensional planar and volumetric cone beam images to improve the accuracy of radiation treatment delivery. Periodic quality assurance (QA) of EPIDs is essential for dosimetric verification in radiotherapy. In this study, a QA program was implemented to evaluate the function of the EPID to be confident in applying corrections for the uncertainty of patient set-up. Material and Methods: Firstly, the safety features were verified, and the uniformity of EPID response was evaluated using flat panel detector. Additionally, the contrast and spatial resolutions of the EPID were assessed using detail counting of the Los Vegas phantom images by visualization method and measuring the modulation transfer function using edge technique, respectively. Moreover, a combination of smoothing methods was used for optimal use of edge detection algorithm for the noisy portal images. Finally, the location of the central ray on...
Introduction:Gated myocardial perfusion SPECT has diagnostic and prognostic values in coronary ar... more Introduction:Gated myocardial perfusion SPECT has diagnostic and prognostic values in coronary artery disease (CAD). We tried to determine prognostic values of the left ventricular perfusion & functional indices as well as transient left ventricular dilation (TID) derived from gated myocardial perfusion SPECT. Methods: 1820patients who underwent gated myocardial perfusion SPECT (Gated SPECT) were studied. The summed stress score (SSS), summed rest score (SRS) and summed difference score (SDS) were calculated. Cardiac events considered as nonfatal myocardial infarction, cardiac death, Coronary Care Unit admission and revascularization. Mean follow-up period after Gated SPECT was 23±10 months. Results: 1599 patients didn't have any events, while from remaining 221, six patients had an acute MI, 90 patients had CCU admission, 42 patients underwent revascularization and 84 patients died. There was statistically significant difference in the cardiac events based on age, sex, SSS, SRS...
Introduction: Regular implementation of quality control (QC) program in diagnostic X-ray faciliti... more Introduction: Regular implementation of quality control (QC) program in diagnostic X-ray facilities may affect both image quality and patient radiation dose due to the changes in exposure parameters. Therefore, this study aimed to investigate the status of randomly selected conventional radiographic X-ray devices installed in radiology centers of Great Khorasan Province, Iran, to produce the data needed to formulate QC policies, which are essential to ensure the accuracy of the diagnosis while minimizing the radiation dose. Material and Methods: This cross-sectional study was performed using a calibrated Piranha multi-purpose detector to measure QC parameters in order to unify X‐ray imaging practices using international guidelines. The QC parameters included voltage accuracy, voltage reproducibility, exposure time accuracy, exposure time reproducibility, tube output linearity with time andmilliampere (mA), and tube output reproducibility. Data analysis procedures were performed base...
Introduction SPECT projections are contaminated by scatter radiation, resulting in reduced image ... more Introduction SPECT projections are contaminated by scatter radiation, resulting in reduced image contrast and quantitative errors. Backscatter constitutes a major part of the scatter contamination in lower energy windows. The current study is an evaluation of the effect of backscatter material on FWHM and image quality investigated by Monte Carlo simulation. Materials and Methods SIMIND program was used for simulation of a Siemen’s dual-head variable angle scintillation gamma camera. Planar and SPECT scanning of a 99mTc source and a Jaszczak phantom for varying thicknesses of Perspex slabs, as a backscatter media, were analyzed using the photopeak and scatter windows. Simulated planar images and reconstructed tomographic images were evaluated qualitatively, by two nuclear medicine specialists, and quantitatively, by Structural Similarity (SSIM) Index. Results In the 99mTc photopeak window, no significant change in total counts due to backscatter material was measured. In the scatter...
Introduction: The application of 3D volumetric imaging modalities in treatment planning of radiat... more Introduction: The application of 3D volumetric imaging modalities in treatment planning of radiation therapy can provide more precisely define tumor localization, and computed tomography (CT) is the most common accepted method for treatment planning. Given the lack of a CT scanner stationed in all radiotherapy departments and equipping most of the medical linear accelerators with only electronics portal imaging device (EPID) device, the use of this technology for megavoltage cone-beam computed tomography (MV-CBCT) imaging in such cases as urgent palliative radiotherapy treatments, leads to precise localization of the tumor and increases the accuracy of the beam sent to the target area. Since MV-CBCT imaging is possible using EPID, this study is aimed at conducting MV-CBCT and investigating the possibility of using these images in the treatment planning of the radiation therapy. Materials and Methods: Initially, the projection data of an anthropomorphic head phantom was acquired at 3...
During the last decades there has been an increasing interest in studying the differences between... more During the last decades there has been an increasing interest in studying the differences between males and females. These differences extend from behavioral to cognitive to micro- and macro- neuro-anatomical aspects of human biology. There have been many methods to evaluate these differences and explain their determinants. The most studied cause of this dimorphism is the prenatal sex hormones and their organizational effect on brain and behavior. However, there have been new and recent attentions to hormone’s activational influences in puberty and also the effects of genomic imprinting. In this paper, we reviewed the sex differences of brain, the evidences for possible determinants of these differences and also the methods that have been used to discover them. We reviewed the most conspicuous findings with specific attention to macro-anatomical differences based on Magnetic Resonance Imaging (MRI) data. We finally reviewed the findings and the many opportunities for future studies.
Background: With the increasing efforts to a better understanding of psychiatric diseases, detect... more Background: With the increasing efforts to a better understanding of psychiatric diseases, detection of brain morphological alterations are necessary. This study compared two methods-voxel based morphometry (VBM) and region of interest (ROI) analyses- to identify significant gray matter changes of patients with bipolar disorder type I (BP I). Methods: The structural MRI were obtained in a total of 50 subjects (25 healthy subjects with a mean age of 34.48±8.32 years as a control group and 25 patients with a mean age of 37.68±10.88 years). We compared the gray matter alteration results obtained by VBM analysis using the DARTEL approach with those obtained using ROI analysis which applies three probabilistic brain atlases namely, hammers, lpba40, and neuromorphometrics atlases. All analyses were conducted via the Computational Anatomy Toolbox (CAT12) implemented in Statistical Parametric Mapping (SPM12) software package. Results: The VBM findings suggested that gray matter reductions i...
Journal of Biomedical Physics and Engineering, 2019
Background: The present study aimed to introduce a rapid transmission dosimetry through an electr... more Background: The present study aimed to introduce a rapid transmission dosimetry through an electronic portal-imaging device (EPID) to achieve two-dimensional (2D) dose distribution for homogenous environments.Material and Methods: In this Phantom study, first, the EPID calibration curve and correction coefficients for field size were obtained from EPID and ionization chamber. Second, the EPID off-axis pixel response was measured, and the grey-scale image of the EPID was converted into portal dose image using the calibration curve. Next, the scattering contribution was calculated to obtain the primary dose. Then, by means of a verified back-projection algorithm and the Scatter-to-Primary dose ratio, a 2D dose distribution at the mid-plane was obtained.Results: The results obtained from comparing the transmitted EPID dosimetry to the calculated dose, using commercial treatment planning system with gamma function while there is 3% dose difference and 3mm distance to agreement criteria,...
Journal of Biomedical Physics and Engineering, 2019
Background: Given the importance of scattered and low doses in secondary cancer caused by radiati... more Background: Given the importance of scattered and low doses in secondary cancer caused by radiation treatment, the point dose of critical organs, which were not subjected to radiation treatment in breast cancer radiotherapy, was measured.Objective: The purpose of this study is to evaluate the peripheral dose in two techniques of breast cancer radiotherapy with two energies. Methods: Eight different plans in two techniques (conventional and conformal) and two photon energies (6 and 15 MeV) were applied to Rando Alderson Phantom’s DICOM images. Nine organs were contoured in the treatment planning system and specified on the phantom. To measure the photon dose, forty-eight thermoluminescence dosimeters (MTS700) were positioned in special places on the above nine organs and plans were applied to Rando phantom with Elekta presice linac. To obtain approximately the same dose distribution in the clinical organ volume, a wedge was used on planes with an energy of 6 MeV photon. Resul...
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