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dosimetry
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Evaluation of dosimetric characteristics of graphene oxide/PVC nanocomposite for gamma radiation applications
, Article Radiochimica Acta ; Volume 105, Issue 2 , 2017 , Pages 161-170 ; 00338230 (ISSN) ; Malekie, S ; Rahighi, R ; Tayyebi, A ; Ziaie, F ; Sharif University of Technology
Walter de Gruyter GmbH
2017
Abstract
Graphene oxide-polyvinyl chloride composite was prepared using tetrahydrofuran solvent-assisted dispersion of characterized nano flakes of graphene oxide in polymer matrix. Electrical percolation threshold of GO/PVC nanocomposite was determined via a finite element simulation method with a 2D model and compared with experimental results. A conductive cell with two silver coated walls was designed and fabricated for exploring dosimetric properties of the composite. Some characteristics of the new nanocomposite such as linearity of dose response, repeatability, sensitivity and angular dependence are investigated. According to 2D proposed method, obtained data associated to electrical...
Dosimetric evaluation of a newly developed radiochromic film for radiation processing
, Article Iranian Journal of Science and Technology, Transaction A: Science ; Volume 31, Issue 4 , 2007 , Pages 397-401 ; 10286276 (ISSN) ; Sohrabpour, M ; Sharifzadeh, M ; Sharif University of Technology
Shiraz University
2007
Abstract
In order to improve the performance of a newly developed radiochromic film, GIC-79, some dosimetric characteristics of this film have been studied based on relevant standard practice. The present study describes some parameters that may affect the dosimeter response before, during, and after irradiation. The effect of absorbed dose rate on dosimeter response was determined by irradiating dosimeters at low absorbed dose rates with gamma rays. Calibration irradiations of dosimeters were performed with both gamma rays and also electrons to determine the effect of large difference absorbed dose rates on dosimeter response. In addition, post irradiation stability was obtained and also the...
EPR Dosimetry based on Monte Carlo Method (Simulation and Measuring Dose with EPR Method)
, M.Sc. Thesis Sharif University of Technology ; Hosseini, Abolfazl (Supervisor) ; Mohammadzadeh, Mohammad (Co-Advisor)
Abstract
The Electron Paramagnetic Resonance(EPR) is a retrospective and accurate dosimetry method to measure irradiated-induced radical population in the matter for determination the induced dose in the matter. The dose uncertainties will be about 1 percent. in the first stage of the present research, the response of EPR system to a reference sample has been measured. Then, responses due to the other samples has been compared with it and the secondary sample dose has been calculated. The reference sample usually is alanine. Unlike the perturbation theory forecast,the EPR signal intensity response to dose for alanine is not linear. In this thesis, first, the alanine samples (with pellet form) have...
The Effect of GPU for Radiation Transport of Photons and Electrons for dose Calculation
, M.Sc. Thesis Sharif University of Technology ; Sohrabpour, Mostafa (Supervisor) ; Vosoughi, Naser (Co-Advisor)
Abstract
In radiotherapy, dose calculation is one of the most important stages that should be carefully done for patient treatment planning. Dose calculation methods have been developed from early dose algorithms that used analytical methods to relatively recent high precision monte carlo methods.Monte carlo methods while very accurate in dose estimations usually suffer from long computation time. In the recent time the emphasis for reduction of the computation time has been focused on software techniques as well as on hardware technology development. One example of hardware development has been graphic processing unit (GPU) which was introduced in 2006 by the Nvidia to accelerate the processing and...
Dose Simulation in Different Body Parts in Radiotherapy Using Fluka Monte Carlo Code on Human Phantom and Benchmarking with TL Dosimetry
, M.Sc. Thesis Sharif University of Technology ; Sohrabpour, Mostafa (Supervisor) ; Mahdavi, Rabi (Supervisor)
Abstract
Radiation therapy is a treatment modality that is used in treatment of most newly diagnosed cancer patients. In this method the interaction of radiation with matter and their biological effects is used for cancer treatment. The energy and intensity of the radiation in radiotherapy should be considered in order to have a lethal effect on tumors. Linear accelerators are substitutes for previous methods of radiotherapy in all over the world. These machines can work in both electron and photon mode. The Monte Carlo technique has become ubiquitous in medical physics in the last 50 years. The range of applications is very broad in medical physics. The increased use of Monte Carlo techniques is...
Estimation of Genetically Significant Dose to the Iranian Population from Diagnostic Radiology Procedures
, M.Sc. Thesis Sharif University of Technology ; Sohrabpour, Mostafa (Supervisor) ; Sharifzadeh, Monireh (Co-Advisor)
Abstract
Genetic significant dose to the Iranian population from diagnostic radiology procedures has been measured. A survey of 26500 radiology patients has radiological tests, age and sex distribution. A second survey has produced the radiological operational parameters, including kV, mAs, FTD, field size, filtration, film number & body orientation. Statistical demographic data have been obtained and from which child expectancy number have been calculated. A Rando phantom has been used for dosimetry phase of the gonad doses using TLD. Combining all of the above data a new GSD of 10.5 mrem/year has been calculated which is 14% higher than the previous number measured in 1980
Organ Body Dose Simulation Using Monte Carlo Code EGS5 and Human Phantom and Bench-Marking with TL Dosimetry
, M.Sc. Thesis Sharif University of Technology ; Sohrabpour, Mostafa (Supervisor) ; Mahdavi, Rabie (Supervisor)
Abstract
Varian Clinac 2100 accelerator head was simulated using EGS5 Monte Carlo code. Phase space method was applied to this simulation. Two phase space plates were used in these simulations; one was inserted before the moveable jaws and the other one was placed after the jaws. The first plate was simulated for energy. And the second plate was to simulate each field size at the set energy. In the phase space method used in the EGS5 code one extracts the particle parametric information from a file as opposed to following the original particles that start at the source point. It is expected that this file to be a replica of the particles that pass the plate and further it should not add any...
Monte Carlo Simulation of Ir-192 Brachytherapy System for Intracavity Applicators and Benchmarking the Result with TLD and EDR2 Dosimeters
, M.Sc. Thesis Sharif University of Technology ; Sohrabpour, Mostafa (Supervisor) ; Mahdavi, Rabi (Supervisor)
Abstract
The main aim in radiotherapy is to destroy tumor while keeping the normal tissue in a safe condition. Brachytherapy is a method of radiotherapy in which sealed radioactive sources are used to deliver radiation at a short distance. With this mode of therapy, a high radiation dose can be delivered locally to the tumor with rapid dose fall-off in the surrounding normal tissue. Brachytherapy is usually used for cancer treatment such as breast, brain, liver, ovary, uterine cervix and prostate. In clinical application, the treatment plan is typically acquired from the planning softwares. Dose calculation in these softwares is based upon the published recommendations of AAPM TG-43 in which...
Simulation of Active Proton Therapy Scanning System with GATE Simulator in Order to Reduce the Dose Reached to the Patient
, M.Sc. Thesis Sharif University of Technology ; Hosseini, Abolfazl (Supervisor) ; Vosoughi, Naser (Supervisor)
Abstract
Validation of dosimetry accuracy in the context of advanced methods for radiotherapy, including proton therapy for ensure the accuracy of treatment plan is nessecory. One of the reasons for using MC code is the modeling of PT systems and the support of more accurate computation of dose distribution in clinical tarin. The purpose of this project is to validate the modeling of a spot scanning proton therapy system using a GATE MC code. In this study, the dose distribution calculated in the calibration process of the device and syno TPS is used as a criterion and the dose distribution obtained from the GATE MC code is calculated and validated with it. For this purpose, a water phantom was used...
Individual virtual phantom reconstruction for organ dosimetry based on standard available phantoms
, Article Iranian Journal of Radiation Research ; Volume 7, Issue 4 , 2010 , Pages 201-206 ; 23223243 (ISSN) ; Aghaeizadeh Zoroofi, R ; Tehrani Fard, A. A ; Akhlaghpoor, S ; Chen, Y. W ; Sato, Y ; Sharif University of Technology
Novim Medical Radiation Institute
2010
Abstract
Background: In nuclear medicine application often it is required to use computational methods for evaluation of organ absorbed dose. Monte Carlo simulation and phantoms have been used in many works before. The shape, size and volume in organs are varied, and this variation will produce error in dose calculation if no correction is applied. Materials and Methods: A computational framework for constructing individual phantom for dosimetry was performed on five liver CT scan data sets of Japanese normal individuals. The Zubal phantom was used as an original phantom to be adjusted by each individual data set. This registration was done by Spherical Harmonics (SH) and Thin-Plate Spline methods....
SAR thresholds for electromagnetic exposure using functional thermal dose limits
, Article International Journal of Hyperthermia ; Volume 34, Issue 8 , 2018 , Pages 1248-1254 ; 02656736 (ISSN) ; Paulides, M. M ; Van Rhoon, G. C ; Sharif University of Technology
Taylor and Francis Ltd
2018
Abstract
Background and purpose: To protect against any potential adverse effects to human health from localised exposure to radio frequency (100 kHz–3 GHz) electromagnetic fields (RF EMF), international health organisations have defined basic restrictions on specific absorption rate (SAR) in tissues. These exposure restrictions incorporate safety factors which are generally conservative so that exposures that exceed the basic restrictions are not necessarily harmful. The magnitude of safety margin for various exposure scenarios is unknown. This shortcoming becomes more critical for medical applications where the safety guidelines are required to be relaxed. The purpose of this study was to quantify...
Development of a novel analytical method for calculating the dose equivalent rate as a case study of fields which obey the inverse square law
, Article Journal of Instrumentation ; Volume 14, Issue 9 , 2019 ; 17480221 (ISSN) ; Sharif University of Technology
Institute of Physics Publishing
2019
Abstract
The field of any point source which is broadened equally in all directions without any limitation to its range is within category of the inverse square law (ISL). As a case study, the dose equivalent (DE) rate is calculated. For calculating the DE rate, the radiation source can be divided into multiple layers and each layer is fractionated to multiple rectangular surfaces. Each rectangular surface can be replaced with three types of sectors. The DE rate of a source on a target is then sum of DE rates of sectors. The developed method is independent of the target position relative to the source and is used for the dose calculation of any arbitrary arrangement of source and target. As an...
Influence of ridge filter material on the beam efficiency and secondary neutron production in a proton therapy system
, Article Zeitschrift fur Medizinische Physik ; Volume 22, Issue 3 , September , 2012 , Pages 231-240 ; 09393889 (ISSN) ; Afarideh, H ; Sadighi-Bonabi, R ; Sharif University of Technology
Elsevier
2012
Abstract
In this work, the 3D proton dose profile is calculated in a homogenous water phantom using a Monte Carlo application developed with the Geant4 toolkit. The effect of the ridge filter material (for SOBP widths of 6, 9 and 12 cm) on the homogeneity of the dose distribution, secondary neutron production and beam efficiency are investigated in a single ring wobbling irradiation system. The energy spectrum of secondary neutrons per primary proton at various locations around the phantom surface is calculated. The simulation revealed that most of the produced neutrons are released at slight angles which enable them to reach the patient and consequently to be hazardous. Also, the homogeneity of the...
Megavoltage dose enhancement of gold nanoparticles for different geometric set-ups: Measurements and monte carlo simulation
, Article International Journal of Radiation Research ; Volume 10, Issue 3-4 , 2012 , Pages 183-186 ; 23223243 (ISSN) ; Shirazi, A ; Mahdavi, S. R ; Ezzati, A ; Mofid, B ; Khoei, S ; Zarrinfard, M. A ; Sharif University of Technology
2012
Abstract
Background: Gold nanoparticles (GNPs) have been shown as a good radiosensitizer. In combination with radiotherapy, several studies with orthovoltage X-rays have shown considerable dose enhancement effects. This paper reports the dose enhancement factor (DEF) due to GNPs in 18 megavoltage (MV) beams. Materials and Methods: Different geometrical 50-nm GNPs configurations at a concentration of 5 mg/ml were used by both experimental and Monte Carlo (MC) simulation in a deep-seated tumor-like insertion within a phantom. Using MCNP repeated structure capability; a large number of gold nanospheres with a semi-random distribution were applied to simulate this phantom based study. Thermoluminescence...
Mamsim: A computational software platform for measuring and optimizing imaging and dosimetry parameters in screen-film and digital mammography systems
, Article 15th IEEE International Symposium on Medical Measurements and Applications, MeMeA 2020, 1 June 2020 through 3 June 2020 ; July , 2020 ; Vahdat, B. V ; Ebrahimi Khankook, A ; Noorvand, M ; IEEE; IEEE Instrumentation and Measurement Society; IEEE Sensors Council Italy Chapter; Politecnica di Bari; Politecnico di Torino; Societa Italiana di Analisi del Movimento in Clinica ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2020
Abstract
The aim of this work is to develop a mammography Monte Carlo MCNP-FBSM based simulation platform called 'MamSim' that is able to model the detailed geometry and physics of commercial screen-film and digital mammography units. This simulation platform is designed to enable the virtual assessment and optimization of mammography protocols and parameters for obtaining the desired image quality while diminishing radiation dose to the patient in both contact and magnification modes. A graphical user interface generates MCNP-FBSM input files for simulating mammography units under various geometries and imaging protocols. We considered the full simulation of all components of mammography procedure...
Comparative assessment of passive scattering and active scanning proton therapy techniques using Monte Carlo simulations
, Article Journal of Instrumentation ; Volume 17, Issue 9 , 2022 ; 17480221 (ISSN) ; Hosseini, S. A ; Akhavanallaf, A ; Vosoughi, N ; Zaidi, H ; Sharif University of Technology
Institute of Physics
2022
Abstract
Background: in this study, two proton beam delivery designs, i.e. passive scattering proton therapy (PSPT) and pencil beam scanning (PBS), were quantitatively compared in terms of dosimetric indices. The GATE Monte Carlo (MC) particle transport code was used to simulate the proton beam system; and the developed simulation engines were benchmarked with respect to the experimental measurements. Method: A water phantom was used to simulate system energy parameters using a set of depth-dose data in the energy range of 120-235 MeV. To compare the performance of PSPT against PBS, multiple dosimetric parameters including Bragg peak width (BP W50), peak position, range, peak-To-entrance dose ratio,...