Mohammad Reza Ay
Department of Medical Physics and Biomedical Engineering, Tehran University of Medical Sciences, Tehran, Iran|Research Center for Molecular and Cellular Imaging, Tehran University of Medical Sciences, Tehran, Iran
[ 1 ] - The influence of using different reconstruction algorithms on sensitivity of quantitative 18F-FDG-PET volumetric measures to background activity variation
Introduction: This study aims to investigate the influence of background activity variation on image quantification in differently reconstructed PET/CT images. Methods: Measurements were performed on a Discovery-690 PET/CT scanner using a custom-built NEMA-like phantom. A background activity level of 5.3 and 2.6 kBq/ml 18F-FDG were applied. Ima...
[ 2 ] - An alternative mathematical modeling of the scintillation camera and framework for performance analysis of gamma-ray positioning algorithms
Introduction: Substantive amount of work has been done in modeling and analyzing the scintillation camera system processes including positioning and image formation. The goal of this work is to develop a framework for analyzing performance of nonlinear positioning methods upon construction of a mathematical model of the system. In this study, the photodetector array counts are ...
[ 3 ] - Is correction for metallic artefacts mandatory in cardiac SPECT/CT imaging in the presence of pacemaker and implantable cardioverter defibrillator leads?
Introduction: Metallic artifacts due to pacemaker/ implantable cardioverter defibrillator (ICD) leads in CT images can produce artifactual uptake in cardiac SPECT/CT images. The aim of this study was to determine the influence of the metallic artifacts due to pacemaker and ICD leads on myocardial SPECT/CT imaging. Methods: The study included 9 patients wh...
[ 4 ] - Collimator-detector response compensation in molecular SPECT reconstruction using STIR framework
Introduction:It is well-recognized that collimator-detector response (CDR) is the main image blurring factor in SPECT. In this research, we compensated the images for CDR in molecular SPECT by using STIR reconstruction framework. Methods: To assess resolution recovery capability of the STIR, a phantom containing five point sources along with a micro Derenzo p...
[ 5 ] - New approach for calibration of pixelated scintillation detectors of intraoperative gamma cameras
Introduction:SURGEOSIGHT is a dedicated intra-operative hand-held gamma camera designed and manufactured by our team to be used for lymphoscintigraphy. Although conventional gamma cameras are widely used, they lack the capability of the sentinel lymph node (SLN) imaging in the operation room. Like conventional gamma cameras it is necessary to calibrate SURGEOSIGHT for linearity...
[ 6 ] - Monte Carlo estimation of electron contamination in a 18 MV clinical photon beam
Background: The electron contamination may reduce or even diminish the skin sparing property of the megavoltage beam. The detailed characteristics of contaminant electrons are presented for different field sizes and cases. Materials and Methods: The Monte Carlo code, MCNPX, has been used to simulate 18 MV photon beam from a Varian Linac-2300 accelerator. All dose measurements were car...
[ 7 ] - Monte Carlo-based optimization of a gamma probe system for sentinel lymph node mapping
Introduction: Sentinel lymph node biopsy (SLNB) is a standard surgical technique to identify sentinel lymph node (SLN) for the staging of early breast cancer. Nowadays, two methods are used for the identification of SLN: blue dye method aiding visually and radioactive dye using gamma detector. A wide range of gamma probe systems with different design and performance are used in...
[ 8 ] - Design and performance evaluation of spheroid geometry for brain PET scanner using Monte Carlo modeling
Introduction: There has been a curiosity about the spheroid geometry for PET scanners developments since several years ago, therefore in this study, we are aiming to evaluate the performance of this geometry and compare its performance with cylindrical geometry using Monte Carlo simulation. Methods: We simulated a spheroid geometry with a radius of 199 mm...
[ 9 ] - Fast System Matrix Calculation in CT Iterative Reconstruction
Introduction: Iterative reconstruction techniques provide better image quality and have the potential for reconstructions with lower imaging dose than classical methods in computed tomography (CT). However, the computational speed is major concern for these iterative techniques. The system matrix calculation during the forward- and back projection is one of the most time- cons...
[ 10 ] - Conventional Voxel in Tomographic Reconstruction Based upon Plane-Integral Projections – Use It or Lose It?
Introduction: While the necessity of replacing voxels with blobs in conventional tomographic reconstruction based upon line-integrals is clear, it is not however well-investigated in plane- integral-based reconstruction. The problem is more challenging in convergent-plane projection reconstruction. In this work, we are aiming at utilizing blobs as alternative to voxels. <stron...
[ 11 ] - Evaluation of effect of gold nanorods and spherical gold nanoparticles of different sizes on X-ray attenuation in computed tomography
Introduction: To date, gold nanoparticles (GNPs) have been demonstrated to have great potential as contrast agent for CT imaging and therapeutics. This study was designed to evaluate any effect on X-ray attenuation that might result from using GNPs with a variety of size, surface chemistries and shapes. Materials and Methods: Spherical GNPs and gold nanorod...
[ 12 ] - Evaluation of multifunctional targeted gold nanoparticles on X-ray attenuation in nasopharyngeal cancer cells by X- ray imaging
Introduction: Head-and-neck cancer is the sixth most common cancer worldwide with the number of cases consistently increasing in developing countries. Successful development of effective, safe and cost effective nanoprobes for head-and-neck cancer targeting imaging is a big challenge. This study is aimed to develop cysteamine-folate conjugated gold nanoparticles (F-Cys-AuNPs) a...
[ 13 ] - Advantages and disadvantages of removed flattening filter Linac: A Monte Carlo study on full quantitative dosimetric data of 18 MV-Varian Linac
Introduction: During intensity modulated radiation therapy (IMRT) technique, theoretically, presence of flattening filter (FF) across the beamline of clinical linear accelerator (linac) is not essential to obtain uniform lateral profiles due to intensity modulation of photon beams by multileaf collimators (MLCs). The aim of this study was to investigate the dosimetrical propert...
[ 14 ] - The influence of misregistration between CT and SPECT images on the accuracy of CT-based attenuation correction of cardiac SPECT/CT imaging: Phantom and clinical studies
Introduction: Integration of single photon emission computed tomography (SPECT) and computed tomography (CT) scanners into SPECT/CT hybrid systems permit detection of coronary artery disease in myocardial perfusion imaging (MPI). Misregistration between CT and emission data can produce some errors in uptake value of SPECT images. The aim of this study was evaluate the influence...
[ 15 ] - A novel approach to automatic position calibration for pixelated crystals in gamma imaging
Introduction: The position estimation in gamma detection system will have constant misplacements which can be corrected in the calibration procedure. In the pixelated crystal uniformly irradiation of detector will produce irregular shape due to position estimation errors. This image is called flood field image and is used to calibrate the position estimation. In this work we pr...
[ 16 ] - Molecular imaging approaches in the diagnosis of breast cancer: A systematic review and meta-analysis
Introduction:The accuracy of positron emission tomography with computed tomography (PET/CT), positron emission mammography (PEM), and breast specific-gamma imaging (BSGI) in diagnosing breast cancer has never been systematically assessed, the present systematic review was aimed to address this issue. Methods:PubMed, Scopus and EMBASE were searched for st...
[ 17 ] - Validation and evaluation of a GATE model for MAMMI PET scanner
Introduction:MAMMI is a dedicated PET based on high resolution detectors placed close to the breast. In this study, we presented a GATE model for the simulation of MAMMI scanner and model its performance of the MAMMI based on an adaptation of the NU 4-2008 NEMA standard. Methods:A detailed of geometry MAMMI system that uses scintillation crystals coupled...
[ 18 ] - Introducing a novel Polyvinyl chloride/Tungsten composites for shielding against gamma and X-ray radiations
Introduction: This study introduces a novel polyvinyl chloride (PVC)/tungsten composites with characterization of their shielding properties by employing different techniques. Methods: The PVC/tungsten composites were produced by employing various weight fractions of tungsten micro-particles including 0, 20, and 40 % wt via melt blending method. In the next st...
Co-Authors