Construction and performance evaluation of a buildup bolus for breast intraoperative electron radiotherapy

Abstract

The under-dosage of the target surface in breast intraoperative electron radiotherapy (IOERT) is one of the main concerns which can be compensated through employing a buildup bolus. The aim of this study is to design and introduce a new buildup bolus for breast IOERT to improve both surface dose and dose uniformity within the target. PLA (Polylactic Acid) material was selected to construct the flat panel bolus. Two different infill percentages of 60 and 100 were considered for bolus printing and their dosimetric characteristics were evaluated through Monte Carlo simulation and based on the closer matching to those of water, the best filling percentage was selected. Then, the bolus was constructed by a Diane K36-S 3D printer and its dosimetric performance in intraoperative electron beam was evaluated through ionometric dosimetry inside the developed bolus. All of the irradiations were performed by LIAC12 dedicated IOERT accelerator and the dosimetric data were obtained by Advanced Markus dosimeter. The results showed that the PLA bolus with 100 infill percentage would have the best performance as a buildup bolus. The measured PDD curves inside the constructed PLA bolus at different energies had desirable accordance with those measured inside the water. Based on the obtained results, it can be concluded that the dosimetric characteristics of designed PLA bolus would be satisfactorily in breast IOERT. This toxic-free PLA based bolus can be considered for surface dose enhancement and dose uniformity improvement during breast IOERT. © 2020 Elsevier Lt