Evaluation of Single-Field Electron Beams for Postmastectomy Radiotherapy
Keywords:Electron irradiation, chest wall, postmastectomy, radiotherapy, Monte Carlo, EGSnrc, DICOM, CT-scans, XSTING, dose-volume histograms
Introduction:electron beams have been extensively used in postmastectomy radiotherapy due to its homogenous dose at the surface followed by sharp fall-off sparing the underlying tissue. Multiple electron fields or electron photon mix were the techniques commonly used. An old study reported the successful use of single-field electron beams with beam energy of 20 MeV. Yet the potential risks of the organs at risk were not clearly shown.
Objectives:the objectives of this study were to assess the possibility of applying single-field electron beams in postmastectomy radiotherapy in terms of: the dose distribution in the target, the volume of organs that receive a certain threshold dose and the volume of organs that receive low doses of radiation.
Materials and Methods: the Monte Carlo codes of EGSnrc were used to simulate electron beams of different energies and gantry angles. The resulting dose files were used by XSTING to generate dose volume histograms, which were used for evaluation.
Results and Discussions: the target coverage was quite poor in most of the studied scenarios. Improving the target coverage was at the expense of irradiating the lung and heart with unacceptable dose values.
Conclusion and Recommendations: Single field electron beams cannot be used for postmastectomy radiotherapy. Multiple electron fields or photon electron mix are necessary and need to be assessed.
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