Optimization study of range-compensating bolus for particle therapy

A noble design method has been developed to obtain an optimized single-material bolus (SM bolus) for proton beam to form a given dose distribution approximately in and around a target region. We applied this method to a two-dimensional geometrical target in water and obtained an optimized bolus with a reasonable dose distribution in and around the target. We measured 3D dose distributions in water formed by protons and carbons passing through 3D SM- and Bi-material (BM)-boluses with a segment size of 5 mm x 5 mm designed for a RTOG phantom to provide comparison data for the dose distributions for optimized boluses. In order to build a more precise calculation model of physical dose distributions for a carbon beam, we measured Bragg curves in water of mono-energetic carbon beams passing through an aluminum slab with different thicknesses instead of the ridge filter and found some regularity of the shape change. (author)