Measurement of rectal dose during HDR brachytherapy using the new MOSkin dosimeter

In HDR prostate brachytherapy, post-treatment complications occur due to overdosing the rectum wall and urethra. An area of concern regarding treatment is related to how the rectal wall dose is calculated using treatment planning systems. Treatment planning systems can calculate the dose delivered to the rectal wall, assuming that the rectum is filled with water equivalent material. This assumption is not always correct, as the rectum is emptied before treatment begins. The aim of this research is to quantify the difference in the dose measured in an 'empty' rectal phantom, and in a rectal phantom filled with water equivalent material. Results indicate that the dose measured by the MOSkin and RadFET in an empty rectum is approximately 10-15% lower than the dose measured dose in a full rectum, and the dose calculated by the PLATO TPS, which assumes that the rectum is full. This could have implications on the design of HDR treatment plans. (author)