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Evaluation of Various Boluses in Dose Distribution for Electron Therapy of the Chest Wall With an Inward Defect Publisher



Mahdavi H1 ; Jabbari K2 ; Roayaei M1
Authors
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Authors Affiliations
  1. 1. Department of Radiotherapy, Seyed al-Shohada Hospital, Isfahan University of Medical Sciences, Isfahan, Iran
  2. 2. Department of Medical Physics and Engineering, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran

Source: Journal of Medical Physics Published:2016


Abstract

Delivering radiotherapy to the postmastectomy chest wall can be achieved using matched electron fields. Surgical defects of the chest wall change the dose distribution of electrons. In this study, the improvement of dose homogeneity using simple, nonconformal techniques of thermoplastic bolus application on a defect is evaluated. The proposed phantom design improves the capability of film dosimetry for obtaining dose profiles of a patient's anatomical condition. A modeled electron field of a patient with a postmastectomy inward surgical defect was planned. High energy electrons were delivered to the phantom in various settings, including no bolus, a bolus that filled the inward defect (PB0), a uniform thickness bolus of 5 mm (PB1), and two 5 mm boluses (PB2). A reduction of mean doses at the base of the defect was observed by any bolus application. PB0 increased the dose at central parts of the defect, reduced hot areas at the base of steep edges, and reduced dose to the lung and heart. Thermoplastic boluses that compensate a defect (PB0) increased the homogeneity of dose in a fixed depth from the surface; adversely, PB2 increased the dose heterogeneity. This study shows that it is practical to investigate dose homogeneity profiles inside a target volume for various techniques of electron therapy. © 2016 Journal of Medical Physics Published by Wolters Kluwer - Medknow.
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