Papers by Alireza sadremomtaz
Iranian Journal of Medical Physics, 2018
Introduction: Neutrons have many applications in various fields, such as medicine. The important ... more Introduction: Neutrons have many applications in various fields, such as medicine. The important application of neutron in medical science is in Boron Neutron Capture Therapy (BNCT). Because of this, determination of neutron dose and flux is critical for the health maintaining of workers and patients exposed to this beam. The neutron radioisotope sources produce gamma rays in addition to the neutrons, and the neutron fields around these sources are mixed-field neutron-gamma fields. Since the separation of the dose of each radiation component in the compound field is difficult, the gamma-neutron mixed field dosimetry is a major challenge. International Commission on Radiation and Units (ICRU) recommends the use of a dosimeter pair for mixed-field dosimetry that have different responses to each component of radiation. One of the effective methods of neutron dosimetry is the use of the TLD-600/700 dosimeter pair. TLD-600 is 6Li enriched and TLD-700 is 7Li enriched. These dosimeters hav...
Journal of Cancer Research and Therapeutics, 2018
Purpose: GATE/GEANT is a Monte Carlo code dedicated to nuclear medicine that allows calculation o... more Purpose: GATE/GEANT is a Monte Carlo code dedicated to nuclear medicine that allows calculation of the dose to organs (bone and bone marrow) of voxel phantoms. On the other hand, Medical Internal Radiation Dose (MIRD) is a well-developed system for estimation of the dose to human organs. In this study, results obtained from GATE/GEANT using leg of Snyder phantom is compared to published MIRD data. Materials and Methods: For this, the mathematical leg of Snyder phantom was discretized and converted to a digital phantom of 100 × 100 × 200 voxels. The activity was considered uniformly distributed within bone and bone marrow. The GATE/GEANT Monte Carlo code was used to calculate the dose to the bone and bone marrow of the leg phantom from mono-energetic photons of 10, 15, 20, 30, 50, 100, 200, 500, and 1000 keV. The dose was converted into a specific absorbed fraction (SAF) and the results were compared to the corresponding published MIRD data. Results: On average, there was a good correlation between the two series of data for self-absorption (r 2 = 0.99) and for cross-irradiation (r 2 = 0.99). However, the GATE/GEANT data were on average 1.01 ± 0.79% higher than the corresponding MIRD data for self-absorption. As for cross-irradiation, the GATE/GEANT data were on average 8.11 ± 7.95% higher than the MIRD data. Conclusion: In this study, the SAF values derived from GATE/GEANT and the corresponding MIRD published data were compared. On average, the SAF values derived with GATE/GEANT showed an acceptable correlation and agreement with the MIRD data for the photon energies of 50–1000 keV. For photons of 10–30 keV, there was an only poor agreement between the GATE/GEANT results and MIRD data.
Single photon emission computed tomography (SPECT) is an important diagnostic tool in nuclear med... more Single photon emission computed tomography (SPECT) is an important diagnostic tool in nuclear medicine, which is practical in imaging of organs. Usage of SPECT imaging systems in the diagnosis of pulmonary diseases is developing. In this paper, lesions with different sizes in lungs are studied. These pulmonary lesions were created in ZUBAL torso phantom by MATLAB. Then, new phantom transferred to SIMIND program and the lung images with their lesions were simulated. The planar and SPECT simulated images were evaluated. The evaluation of simulation results is based on the observer. The results are reported in two diagrams according to probability parameters. In the case of the peripheral lesions, planar images are effective but they were not enough to represent all sizes of the pulmonary nodules involved the inside and in some situation the surface of the organ tissue. However, SPECT by reconstruction of images can represent different sizes of lesions.
International Journal of Scientific & Technology Research, 2015
In liver scintigraphy, radioactive tracers, in addition to liver, are accumulated in other organs... more In liver scintigraphy, radioactive tracers, in addition to liver, are accumulated in other organs such as spleen. It leads to the presence of secondary source, which affects image quality. Therefore, knowing the influence of the noise arising from the secondary source and trying to reduce the additional data is necessary. In nuclear medicine imaging, using of energy window is a useful way to reduce the noise. In this paper, we try to find an optimum energy window to reduce the noise for two different low energy collimators. Liver scintigraphy images with and without activity in spleen were simulated by SIMIND software with different energy window percentages and with Low-Energy High-Resolution (LEHR) and Low-Energy General-Purpose (LEGP) collimators. We used Tc m 99 with activity of 190 MBq. Spleen was outside of the camera field of view so that just its noise effects on the liver image is examined. Finally, the images of liver with activity in spleen were compared with that without...
Iranian Journal of Medical Physics, 2018
Introduction: Thyroid cancer is at the ninth from ten of common malignant cancer. A man has highe... more Introduction: Thyroid cancer is at the ninth from ten of common malignant cancer. A man has higher risk to get Thyroid cancer that a woman has. This organ is lain near human neck. The use of radioactive I-131, I-123 and Tc-99m for diagnosis of thyroid cancer has a risk where other organs around Thyroid will accept dose of radiation. One of the risks is large dose which is accepted by brain, skin and lung. Large dose accepted those organs will make a high defect at those organs. To reduce that problem, we have to know the problem dose which is accepted by cell cancer and the organs. One of is to make a simulation of interaction of radiation particle with organ. The simulation used to determine the intermine the interaction of radiation particles and matter is a Monte Carlo method. One of Monte Carlo software is MCNPX (Monte Carlo N-Particle) made by a team from Los Alamos National Laboratory. It can simulate particles interaction with real situation. The use of Monte Carlo in radiati...
iranian journal of nuclear medicine, 2017
Introduction:The use of beta emitters is one of the effective methods for palliation of bone meta... more Introduction:The use of beta emitters is one of the effective methods for palliation of bone metastasis. The risk of normal tissue toxicity should be evaluated in the bone pain palliation treatment. Methods: In this study, the Monte Carlo simulation code MCNPX was used for simulation a bone phantom model consisted of bone marrow, bone and soft tissue. Specific absorbed fractions were calculated for monoenergetic electrons, photons and eight betaemitters: 32P, 89Sr, 90Y, 153Sm, 166Ho, 177Lu, 186Re and 188Re. Beta and gamma S-factor, absorbed dose and cumulative dose of mentioned radionuclides were obtained to the selection of radionuclides with optimal radiation characteristics. Results: The results show 177Lu gives a higher local dose to source organ. 177Lu has fewer side effects on critical organ including bone marrow in comparison with other radionuclides such as 89Sr, 32P and 90Y. Cumulative dose versus time shows after a long time, long half-life radionuclides delivering a highe...
Iranian Journal of Medical Physics, 2018
Introduction: In recent years, the use of neutrons has increased in various fields such as medici... more Introduction: In recent years, the use of neutrons has increased in various fields such as medicine and industry. One of the important applications of neutrons is in medical research. Neutrons have greater linear energy transfer than gamma rays and are considered more dangerous radiation. Hence, the detection and determination of neutron dose is a very important and vital issue. For determination of neutron dose, measurement of its intensity or flux is essential. One of the ways of neutron flux determination is using of gold foil activation method. In this method, the activity of the irradiated foil is proportional to the neutron flux. The gold foil is activated by reaction 197Au (n,γ) 198Au because of the thermal neutron capture,. In the decay of activated gold, a gamma radiation of 411.8 keV is released with a probability of more than 95%, that By measuring the area below the peak associated with this energy, by the NaI(Tl) detector, the activity of gold and then the neutron flux ...
Biomedical Physics & Engineering Express, 2018
In the present work, Monte Carlo code MCNPX was used to determine the cellular dosimetric paramet... more In the present work, Monte Carlo code MCNPX was used to determine the cellular dosimetric parameter; cellular S-values for frequently used radionuclides in targeted radionuclide therapy including 32P, 89Sr, 90Y, 117mSn, 153Sm, 166Ho, 170Tm, 177Lu, 186Re and 188Re. We considered the effect of some factors such as cell size, radiation subcellular localization and chemical composition on cellular S-values. The cells were defined as two concentric spheres and the radionuclides were assumed to be uniformly distributed in one of the cell compartments including cell surface (CS), cytoplasm (Cy), and nucleus (N). A comparison between MCNPX results with obtained MIRDcell values was performed. Deviations between MCNPX and MIRDcell were found to be less than ~15% for self-absorption, in the cases of S(C ← C) and S(N ← N) values whereas discrepancies in S-values increased up to ~22% for C ← CS and ~28% for N ← Cy and N ← CS. The results showed a significant change with increasing the cell and cell nucleus size. For a given radionuclide, with increasing radii, S-values decreased in all compartments. For a given radius of the cell and nucleus, low energy radionuclides had higher S-values. For all source-target combinations, 153Sm and 90Y had the highest and lowest S-values, respectively.
Nuclear Medicine and Molecular Imaging, 2018
Purpose This study aims to compare Monte Carlo-based codes' characteristics in the determination ... more Purpose This study aims to compare Monte Carlo-based codes' characteristics in the determination of the basic parameters of a high-resolution single photon emission computed tomography (HiReSPECT) scanner. Methods The geometry of this dual-head gamma camera equipped with a pixelated CsI(Na) scintillator and lead hexagonal hole collimator were accurately described in the GEANT4 Application for the Tomographic Emission (GATE), Monte Carlo N-particle extended (MCNP-X), and simulation of imaging nuclear detectors (SIMIND) codes. We implemented simulation procedures similar to the experimental test for calculation of the energy spectra, spatial resolution, and sensitivity of HiReSPECT by using 99m Tc sources. Results The energy resolutions simulated by SIMIND, MCNP-X, and GATE were 17.53, 19.24, and 18.26%, respectively, while it was calculated at 19.15% in experimental test. The average spatial resolutions of the HiReSPECT camera at 2.5 cm from the collimator surface simulated by SIMIND, MCNP-X, and GATE were 3.18, 2.9, and 2.62 mm, respectively, while this parameter was reported at 2.82 mm in the experiment test. The sensitivities simulated by SIMIND, MCNP-X, and GATE were 1.44, 1.27, and 1.38 cps/μCi, respectively, on the collimator surface. Conclusions Comparison between simulation and experimental results showed that among these MC codes, GATE enabled to accurately model realistic SPECT system and electromagnetic physical processes, but it required more time and hardware facilities to run simulations. SIMIND was the most flexible and user-friendly code to simulate a SPECT camera, but it had limitations in defining the non-conventional imaging device. The most important characteristics like time and speed of simulation, preciseness of results, and user-friendliness should be considered during simulations.
Journal of Medical Imaging and Radiation Sciences, 2019
INTRODUCTION The α- and β-emitter radionuclides are used for palliative treatment of bone metasta... more INTRODUCTION The α- and β-emitter radionuclides are used for palliative treatment of bone metastasis. Our objective was to compare the dosimetric parameters of radionuclides used in bone pain palliation therapy. METHODS Monte Carlo code, MCNPX, was used to simulate radiation transport. Dosimetric calculations were performed for monoenergetic electrons with energies of 0.1-3 MeV, α-particles with energies of 3-10 MeV, and several radionuclides 32P, 89Sr, 153Sm, 177Lu, 223Ra, and its progeny. The simulated phantom consisted of bone marrow, an endosteal layer, bone, and soft tissue. Source tissues included bone marrow, endosteal layer, and bone. Absorbed fractions and specific absorbed fractions were calculated for target regions. Absorbed doses were calculated for investigated radionuclides. RESULTS The obtained results demonstrated that the dosimetric parameters vary depending on the source or target size, particle energy, and location of the source. The β-emitter radionuclides were able to penetrate the bone marrow region, whereas the α-emitter radionuclides gave a higher and localized dose to the bone and endosteal layer in comparison. CONCLUSION 223Ra and 177Lu have fewer side effects on the bone marrow, and they may be a better choice for use in bone pain palliation radiotherapy.
Annals of Nuclear Medicine, 2019
Objective Bone-seeking radiopharmaceuticals have the main role in the treatment of painful bone m... more Objective Bone-seeking radiopharmaceuticals have the main role in the treatment of painful bone metastases. The aim of this study was to dosimetrically compare radiopharmaceuticals in use for bone pain palliation therapy and bone scan. Methods The MCNPX code was used to simulate the radiation transport in a vertebral phantom. Absorbed fractions were calculated for monoenergetic electrons, photons and alpha particles. S values were obtained for radionuclides 32 P, 33 P, 89 Sr, 90 Y, 99m Tc, 117m Sn, 153 Sm, 166 Ho, 169 Er, 177 Lu, 186 Re, 188 Re, 223 Ra, 224 Ra and their progenies for target regions including the active marrow and the bone endosteum. Results The results demonstrated the dependence of dosimetric parameters on the source or target size, particle energy and location of the source. The electron emitters including 33 P, 117m Sn, 169 Er and 177 Lu and 223 Ra as an α-emitter gave the lower absorbed dose to the active marrow. These radionuclides gave the highest values of the Relative Advantage Factor (RAF). Conclusions According to the results, 33 P, 117m Sn, 169 Er, 177 Lu and 223 Ra have fewer side effects on the active marrow than other investigated radionuclides. Therefore, these radionuclides may be a better choice for use in palliative radiotherapy.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2019
Small animal imaging has been widely considered for the development and evaluation of new radioph... more Small animal imaging has been widely considered for the development and evaluation of new radiopharmaceuticals. For this purpose, simulations are primarily used for the design and optimization of new and existing imaging devices, the assessment of acquisition and processing protocols. In this paper, the methodology follows two basic steps: (I) A validation of a small animal SPECT scanner which is based on CsI(Na) pixelated scintillator detector and a lead hexagonal parallel-hole collimator. In this phase, experimentally obtained results were directly compared to Geant4 Toolkit for Emission Tomography (GATE) simulation data. (II) The optimization studies with different collimator and semiconductor materials by using GATE simulation. The simulated and experimental planar sensitivities of the system were obtained 51.06 and 48.65 cps/MBq on the collimator surface, respectively. The difference between simulated spatial resolution and experimental value at 2.5 cm distance from the collimator surface was 3.27 %. Also, sensitivity of lead collimator was 18, 63.37, and 65.21 % higher than tantalum, tungsten and gold collimators, respectively but gold collimator had the best spatial resolution. CdTe semiconductor detector usually has some superiority to the other semiconductors in energy resolution, spatial resolution, sensitivity, and detection efficiency. Very good agreement between GATE simulation and experimental results indicates that the GATE Monte Carlo simulation is appropriate and reliable tool for simulating imaging systems. Also, HiReSPECT has high resolution and sensitivity for imaging of small animals such as mice and rats. In the following, our study highlights that the collimator and crystal materials can significantly affect the camera performance. As well as developments in semiconductor detector technology can provide an appropriate substitution for scintillation detectors according to high sensitivity, better energy resolution, and also high spatial resolution.
Indian Journal of Physics, 2012
ABSTRACT We have studied the effect of staggered Dzyaloshinsky–Moria (DM) interaction on the grou... more ABSTRACT We have studied the effect of staggered Dzyaloshinsky–Moria (DM) interaction on the ground state phase diagram of the Ising model using variational matrix product state and numerical Lanczos methods. Variational matrix product state results show that the ground state phase diagram of the model consists of two ferromagnetic (FM) and staggered spiral phases in FM case. The quantum corrections of the staggered DM interaction on the ground state phase diagram are determined by a very accurate numerical method and its results confirm our analytic prediction.
Nuclear Engineering and Technology, 2017
Gel dosimeters have unique advantages in comparison with other dosimeters. Until now, these gels ... more Gel dosimeters have unique advantages in comparison with other dosimeters. Until now, these gels have been used in different radiotherapy techniques as a reliable dosimetric tool. Because dose distribution measurement is an important factor for appropriate treatment planning in different radiotherapy techniques, in this study, we evaluated the ability of the N-isopropylacrylamide (NIPAM) polymer gel to record the dose distribution resulting from the mixed neutron-gamma field of boron neutron capture therapy (BNCT). In this regard, a head phantom containing NIPAM gel was irradiated using the Tehran Research Reactor BNCT beam line, and then by a magnetic resonance scanner. Eventually, the R 2 maps were obtained in different slices of the phantom by analyzing T2-weighted images. The results show that NIPAM gel has a suitable potential for recording threedimensional dose distribution in mixed neutron-gamma field dosimetry.
British Journal of Applied Science & Technology, 2013
Aims: Wavelet transform is the powerful mathematical tool used for image processing and noise sup... more Aims: Wavelet transform is the powerful mathematical tool used for image processing and noise suppression applications in different area of science and engineering. In this technique,selecting optimal threshold for de -noising is still an area of thrust for the researchers. In this paper, we have focused on the de -noising of planar nuclear medicine
Journal of Cancer Research and Therapeutics, 2016
Determination of in-phantom quality factors of Tehran research reactor (TRR) boron neutron captur... more Determination of in-phantom quality factors of Tehran research reactor (TRR) boron neutron capture therapy (BNCT) beam. The doses from thermal neutron reactions with 14N and 10B are calculated by kinetic energy released per unit mass approach, after measuring thermal neutron flux using neutron activation technique. Gamma dose is measured using TLD-700 dosimeter. Different dose components have been measured in a head phantom which has been designed and constructed for BNCT purpose in TRR. Different in-phantom beam quality factors have also been determined. This study demonstrates that the TRR BNCT beam line has potential for treatment of superficial tumors.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2016
Recently, the configuration of the Tehran Research Reactor (TRR) thermal column has been modified... more Recently, the configuration of the Tehran Research Reactor (TRR) thermal column has been modified and a proper thermal neutron beam for preclinical Boron Neutron Capture Therapy (BNCT) has been obtained. In this study, simulations and experimental measurements have been carried out to identify the BNCT beam parameters including the beam uniformity, the distribution of the thermal neutron dose, boron dose, gamma dose in a phantom and also the Therapeutic Gain (TG). To do this, the entire TRR structure including the reactor core, pool, the thermal column and beam tubes have been modeled using MCNPX Monte Carlo code. To measure in-phantom dose distribution a special head phantom has been constructed and foil activation techniques and TLD700 dosimeter have been used. The results show that there is enough uniformity in TRR thermal BNCT beam. TG parameter has the maximum value of 5.7 at the depth of 1 cm from the surface of the phantom, confirming that TRR thermal neutron beam has potential for being used in treatment of superficial brain tumors. For the purpose of a clinical trial, more modifications need to be done at the reactor, as, for example design, and construction of a treatment room at the beam exit which is our plan for future. To date, this beam is usable for biological studies and animal trials. There is a relatively good agreement between simulation and measurement especially within a diameter of 10 cm which is the dimension of usual BNCT beam ports. This relatively good agreement enables a more precise prediction of the irradiation conditions needed for future experiments.
Measurement, 2016
Abstract Boron Neutron Capture Therapy (BNCT) project in Tehran Research Reactor (TRR) is current... more Abstract Boron Neutron Capture Therapy (BNCT) project in Tehran Research Reactor (TRR) is currently ongoing and an appropriate neutron beam for BNCT has been provided by modification of TRR thermal column. In order to measure the neutron beam characteristics inside of a phantom, a standard phantom is needed. The present paper describes details of the head phantom construction and its different potential. The constructed head phantom permits us to put different dosimeters with different sizes in many locations of the phantom volume. Foils, wires, TLDs and ion chamber can be placed inside of its volume. Gel dosimeter can also be poured into the phantom volume and removed from it easily.
Global Journal of Health Science, 2015
Interventional procedures, cine acquisitions and operation of fluoroscopic equipment in high-dose... more Interventional procedures, cine acquisitions and operation of fluoroscopic equipment in high-dose fluoroscopic modes, involve long fluoroscopic times which can lead to high staff doses. Also, Coronary angiography (CA) procedures require the cardiologist and assisting personnel to remain close to the patient, which is the main source of scattered radiation. Thus, radiation exposure is a significant concern for radiation workers and it is important to measure the radiation doses received by personnel and evaluate the parameters concerning total radiation burden. In this research, we investigated radiation doses to 10 cardiologists performing 120 CA procedures. Using thermo luminescent dosimeters doses to the wrists, thyroid and eyes per procedure were measured. Based on the measured dose values, maximum doses to the Left wrist, Right wrist, thyroid and eyes of cardiologist were measured 241.45 µSv, 203.17 µSv, 78.21 µSv and 44.58 µSv, respectively. The results of this study indicate that distance from the source, use of protective equipment's, procedure complexity, equipment performance, and cardiologist experience are the principal exposure-determining variables. It can be conclude that if adequate radiation protection approaches have been implemented, occupational dose levels to cardiologists would be within the regulated acceptable dose limits.
Indian Journal of Science and Technology, 2015
In myocardial perfusion single Photon Emission Computed Tomography (SPECT), images are degraded b... more In myocardial perfusion single Photon Emission Computed Tomography (SPECT), images are degraded by photon attenuation, distance-dependent collimator, detector response. The filters in reconstruction process can greatly affect the quality of the SPECT images. The purpose of this study is to make quantitative and qualitative evaluation of the acquired SPECT images of similar defects which are located in the different regions of myocardial phantom under implementation of different filters. Herein, rectangular defects with the same thickness were inserted on the different regions of on the inner wall of the myocardial phantom. Myocardial perfusion study was performed with meta-stable Technetium with a dual head SPECT system. Raw data was reconstructed by filter back projection method with some filters. Then, results of implementation of various filters with different parameters on the contrast, signal to noise ratio and size of defects images in transverse, coronal and sagittal views of the phantom have been studied. The results show that contrast, signal to noise ratio and size of defects images are depending on the defect locations, type of filters and the selection of view which is examined for specified defect.
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Papers by Alireza sadremomtaz