Dose build up characteristics with eXaSkin bolus during 6MV radiotherapy: MOSkin dosimetry results

Skin dose evaluation is important to ensure adequate dose to the superficial target volume and to avoid severe skin toxicity. The purpose of this study is to investigate the build-up dose characteristics of eXaSkin bolus for 6MV photon beams and evaluate this material for use in skin tumor treatment. Using a 6MV Varian LINAC with field size of 10x10cm 2 , the surface and build up dose characteristics of eXaSkin (thickness = 3, 5, 8, 10, 15 and 26 mm) was investigated in comparison with solid water (thickness = 2, 5, 15, 20 and 26 mm). Dose measurements were performed using a MOSkin dosimeter and advanced Markus chamber. Additionally, the percentage surface dose measurements for various oblique incident beams with 3mm thick of both bolus was investigated. Measurements were performed using MOSkin dosimeter and compared with advanced Markus chamber. D max of eXaSkin for 6MV was approximately 0.9 cm that is consistent with the higher density of this material (ρSW = 1.04 g/cm 3 ρeXa = 1.7± 0.03 g/cm 3 ). This bolus also exhibits higher dose in the build-up region between 2-10 mm depths and higher dose at oblique incident beams than solid water. Preliminary results suggest that eXaSkin is a promising candidate for use in the treatment of superficial tumors without producing excessive skin reaction.