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  1. Article ; Online: Optimization of newly developed and lead shields thicknesses for protecting taxi drivers from

    Ezzati, Ahad Ollah / Mohajeri, Farzane

    Applied radiation and isotopes : including data, instrumentation and methods for use in agriculture, industry and medicine

    2021  Volume 179, Page(s) 110026

    Abstract: Presently, public members are exposed to sources of ionizing radiation, and health risks due to radiation exposures should be a concern. This study aims to calculate the whole-body cumulative radiation exposure of taxi drivers. Also, this study will ... ...

    Abstract Presently, public members are exposed to sources of ionizing radiation, and health risks due to radiation exposures should be a concern. This study aims to calculate the whole-body cumulative radiation exposure of taxi drivers. Also, this study will provide the effect of using a simple lead shield and three types of glass shield AVT6, TZN-D, and SLGC-E5, by calculating the effective annual dose of the taxi drivers that work in medical centers. Two MIRD phantoms as a driver and patient, a sample body of a taxi, pure lead, and glass sheets as a shield, were simulated using the MCNP code. We assumed that the patients had undergone the brain, liver, and kidney SPECT imaging by injecting 99mTC-HMPAO, 99mTC-sulfur colloid, and 99mTC-DMSA with the activity of 740MBq, 185MBq, and 333MBq, respectively. These shields are simulated on two sides of the driver, in the back and right side. The annual effective dose was calculated for 0-3.5 g/cm
    MeSH term(s) Automobile Driving ; Humans ; Lead ; Occupational Exposure ; Organotechnetium Compounds/administration & dosage ; Organotechnetium Compounds/therapeutic use ; Phantoms, Imaging ; Radiation Protection
    Chemical Substances Organotechnetium Compounds ; Lead (2P299V784P)
    Language English
    Publishing date 2021-11-11
    Publishing country England
    Document type Journal Article
    ZDB-ID 1142596-9
    ISSN 1872-9800 ; 0883-2889 ; 0969-8043
    ISSN (online) 1872-9800
    ISSN 0883-2889 ; 0969-8043
    DOI 10.1016/j.apradiso.2021.110026
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  2. Article: Spatial Mesh-Based Surface Source Model for the Electron Contamination of an 18 MV Photon Beams.

    Ezzati, Ahad Ollah / Studenski, Matthew T / Gohari, Masuomeh

    Journal of medical physics

    2021  Volume 45, Issue 4, Page(s) 221–225

    Abstract: Background: Source modeling is an approach to reduce computational burden in Monte Carlo simulations but at the cost of reduced accuracy. Although this method can be effective, one component of the source model that is exceptionally difficult to model ... ...

    Abstract Background: Source modeling is an approach to reduce computational burden in Monte Carlo simulations but at the cost of reduced accuracy. Although this method can be effective, one component of the source model that is exceptionally difficult to model is the electron contamination, a significant contributor to the skin and shallow dose.
    Aims and objectives: To improve the accuracy for the electron contamination component of the overall source model, we have generated a spatial mesh based surface source model.
    Methods and materials: The source model is located downstream from the flattening filter and mirror but upstream from the movable jaws. A typical phase space file uses around ten parameters per particle, but this method simplifies this number to five components. By using only the electron distance from the central axis, angles from the central axis and energy, the computational time and disk space required is greatly reduced.
    Results and conclusion: Despite the simplification in the source model, the electron contamination is still accurate to within 1.5%.
    Language English
    Publishing date 2021-02-02
    Publishing country India
    Document type Journal Article
    ZDB-ID 1193902-3
    ISSN 1998-3913 ; 0971-6203
    ISSN (online) 1998-3913
    ISSN 0971-6203
    DOI 10.4103/jmp.JMP_29_20
    Database MEDical Literature Analysis and Retrieval System OnLINE

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    Zs.B 2683: Show issues Location:
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  3. Article ; Online: Neutron damage induced in cardiovascular implantable electronic devices from a clinical 18 MV photon beam: A Monte Carlo study.

    Ezzati, Ahad Ollah / Studenski, Matthew T

    Medical physics

    2017  Volume 44, Issue 11, Page(s) 5660–5666

    Abstract: Purpose: The purpose of this study was to quantify the relative neutron damage induced in CIEDs from clinical 18 MV photon beams for varying field sizes, depths, and off axis distances.: Methods and materials: Damage was assessed using silicon damage ...

    Abstract Purpose: The purpose of this study was to quantify the relative neutron damage induced in CIEDs from clinical 18 MV photon beams for varying field sizes, depths, and off axis distances.
    Methods and materials: Damage was assessed using silicon damage response functions and ICRP neutron dose conversion factors in MCNPX. Particular attention was devoted to the modelling of the Varian 2100C/D linear accelerator to ensure accurate contamination neutron spectra. Neutron dose, fluence and relative damage to CIEDs was calculated.
    Results: CIED damage from neutrons is related to the neutron dose rather than the neutron fluence. As field size increases, the region of high damage probability extends to a greater distance beyond the edge of the field than with smaller fields. At a distance greater than 50 cm or from the central axis or a depth deeper than 10 cm, the probability of damage is less than 10% of the central axis damage probability for all field sizes.
    Conclusions: Clinically, increasing the depth or the distance from the central axis to the CIED will reduce the probability of damage from neutrons. Care must be taken when treating large fields as the overall probability of damage increase as does the distance the higher probability of damage extends beyond the field edge.
    MeSH term(s) Cardiovascular System ; Monte Carlo Method ; Neutrons/adverse effects ; Particle Accelerators ; Photons/adverse effects ; Photons/therapeutic use ; Prostheses and Implants ; Radiation Dosage
    Language English
    Publishing date 2017-11
    Publishing country United States
    Document type Journal Article
    ZDB-ID 188780-4
    ISSN 2473-4209 ; 0094-2405
    ISSN (online) 2473-4209
    ISSN 0094-2405
    DOI 10.1002/mp.12581
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  4. Article ; Online: Monte Carlo simulation of the RBE of I-131 radiation using DNA damage as biomarker.

    Ezzati, Ahad Ollah / Mahmoud-Pashazadeh, Ali / Studenski, Matthew T

    Australasian physical & engineering sciences in medicine

    2017  Volume 40, Issue 2, Page(s) 395–400

    Abstract: In general, a weighting factor of one is applied for low linear energy transfer radiations. However, several studies indicate that relative biological effectiveness (RBE) of low energy photons and electrons is greater than one. The aim of this current ... ...

    Abstract In general, a weighting factor of one is applied for low linear energy transfer radiations. However, several studies indicate that relative biological effectiveness (RBE) of low energy photons and electrons is greater than one. The aim of this current study was calculating the RBE of I-131 radiation relative to Co-60 gamma photons in 100 μm spheroid cells using Monte Carlo (MC) simulations. These calculations were compared to experimentally measured results. MCNPX2.6 was used to simulate the I-131 and Co-60 irradiation setups and calculate the secondary electron spectra at energies higher than 1 keV with varying oxygen concentrations. The electron spectra at energies lower than 1 keV were obtained by extrapolation (down to 10 eV). The calculated electron spectra were input into the MCDS micro-dosimetric Monte Carlo code to calculate the DSB induction and related RBE. The calculated RBE of I-131 radiation relative to Co-60 photons, as the reference radiation recommended by the International Commission on Radiation Protection (ICRP), was 1.06, 1.03 and 1.02 for oxygen concentrations of 0, 5 and 100%, respectively. Results of MC simulations indicate the RBE of I-131 is greater than one. This finding, despite a 10% discrepancy with the findings of the previous in vitro study of one of the authors of this paper, reemphasizes that I-131 radiation induces more severe biological damage than current ICRP recommendations.
    Language English
    Publishing date 2017-06
    Publishing country Netherlands
    Document type Journal Article
    ZDB-ID 46226-3
    ISSN 1879-5447 ; 0158-9938
    ISSN (online) 1879-5447
    ISSN 0158-9938
    DOI 10.1007/s13246-017-0544-4
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    Zs.B 2684: Show issues Location:
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  5. Article ; Online: A comprehensive procedure for characterizing arbitrary azimuthally symmetric photon beams.

    Ezzati, Ahad Ollah / Sohrabpour, Mostafa / Mahdavi, Seied Rabi / Buzurovic, Ivan / Studenski, Matthew T

    Physica medica : PM : an international journal devoted to the applications of physics to medicine and biology : official journal of the Italian Association of Biomedical Physics (AIFB)

    2014  Volume 30, Issue 2, Page(s) 191–201

    Abstract: Purpose: A new Monte Carlo (MC) source model (SM) has been developed for azimuthally symmetric photon beams.: Methods: The MC simulation tallied phase space file (PSF) is divided into two categories depending on the relationship of the particle track ...

    Abstract Purpose: A new Monte Carlo (MC) source model (SM) has been developed for azimuthally symmetric photon beams.
    Methods: The MC simulation tallied phase space file (PSF) is divided into two categories depending on the relationship of the particle track line to the beam central axis: multiple point source (MPS) and spatial mesh based surface source (SMBSS). To validate this SM, MCNPX2.6 was used to generate two PSFs for a 6 MV photon beam from a Varian 2100C/D linear accelerator.
    Results: PDDs and profiles were calculated using the SM and original PSF for different field sizes from 5 × 5 to 40 × 40 cm2. Agreement was within 2% of the maximum dose at 100 cm SSD and 2.5% of the maximum dose at 200 cm SSD for beam profiles at depths of 3.5 cm and 15 cm with respect to the original PSF. Differences between the source model and the PSF in the out-of-field regions were less than 0.5% of the profile maximum value at 100 cm SSD. Differences between measured and calculated points were less than 2% of the maximum dose or 2 mm distance to agreement (DTA) at 100 cm SSD.
    Conclusions: This SM is unique in that it accounts for a higher level of energy dependence on the particle's direction and it is independent from accelerator components, unlike other published SMs. The model can be applied to any arbitrary azimuthally symmetric beam and has source biasing capabilities that significantly increase the simulation speed up to 3300 for certain field sizes.
    MeSH term(s) Monte Carlo Method ; Particle Accelerators ; Photons/therapeutic use ; Probability ; Radiometry ; Radiotherapy Dosage ; Radiotherapy Planning, Computer-Assisted/instrumentation ; Radiotherapy Planning, Computer-Assisted/methods ; Reproducibility of Results
    Language English
    Publishing date 2014-03
    Publishing country Italy
    Document type Journal Article
    ZDB-ID 1122650-x
    ISSN 1724-191X ; 1120-1797
    ISSN (online) 1724-191X
    ISSN 1120-1797
    DOI 10.1016/j.ejmp.2013.05.040
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    Zs.B 2941: Show issues Location:
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