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Monte Carlo Evaluation of Out-Of-Field Dose in 18 Mv Pelvic Radiotherapy Using a Simplified Female Mird Phantom Publisher Pubmed



Geraily G1 ; Elmtalab S2 ; Mohammadi N3 ; Alirezaei Z4 ; Martinezovalle SA5 ; Jabbari I6 ; Vegacarrillo HR7 ; Karimi AH1
Authors
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Authors Affiliations
  1. 1. Department of Medical Physics and Biomedical Engineering, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran
  2. 2. Department of Medical Physics, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran
  3. 3. Department of Physics, Faculty of Science, Sahand University of Technology, Tabriz, Iran
  4. 4. School of Paramedicine, Bushehr University of Medical Sciences, Bushehr, Iran
  5. 5. Universidad Pedagogica y Tecnologica de Colombia, Boyaca, Tunja, Colombia
  6. 6. Department of Nuclear Engineering, Faculty of Physics, University of Isfahan, Isfahan, Iran
  7. 7. Academic Unit of Nuclear Studies, University Autonomous of Zacatecas, 10 Cipres St., Zac, Zacatecas, 98068, Mexico

Source: Biomedical Physics and Engineering Express Published:2022


Abstract

This study was devoted to determining the unwanted dose due to scattered photons to the out-of-field organs and subsequently estimate the risk of secondary cancers in the patients undergoing pelvic radiotherapy. A typical 18 MV Medical Linear Accelerator (Varian Clinac 2100 C/D) was modeled using MCNPX® code to simulate pelvic radiotherapy with four treatment fields: anterior-posterior, posterior-anterior, right lateral, left lateral. Dose evaluation was performed inside Medical Internal Radiation Dose (MIRD) revised female phantom. The average photon equivalent dose in out-of-field organs is 8.53 mSv Gy−1, ranging from 0.17 to 72.11 mSv Gy−1, respectively, for the organs far from the Planning Treatment Volume (Brain) and those close to the treatment field (Colon). Evidence showed that colon with 4.3049% and thyroid with 0.0020% have the highest and lowest risk of secondary cancer, respectively. Accordingly, this study introduced the colon as an organ with a high risk of secondary cancer which should be paid more attention in the follow-up of patients undergoing pelvic radiotherapy. The authors believe that this simple Monte Carlo (MC) model can be also used in other radiotherapy plans and mathematical phantoms with different ages (from childhood to adults) to estimate the out-of-field dose. The extractable information by this simple MC model can be also employed for providing libraries for user-friendly applications (e.g. ‘.apk’) which in turn increase the public knowledge about fatal cancer risk after radiotherapy and subsequently decrease the concerns in this regard among the public. © 2021 IOP Publishing Ltd
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