A new silicon detector for microdosimetry applications in proton therapy

A silicon-on-insulator diode array with a sensitive depth of 10 microns has been developed for microdosimetry in proton therapy. The detector was coup led to a radiation-hard charge sensitive amplifier with the probe assembly capable of measuring-an LET down to 1.2 keV/mu m. The device has been succe ssfully tested at two proton therapy centers: The 230 MeV Northeastern Prot on Therapy Center, Boston and the 250 MeV Proton Medical Research Center at Tsukuba, Japan. The:device offers much improved spatial resolution compare d with a-proportional gas counter particularly in the critical high dose re gion around the proton Bragg peak. Due to its small cross-sectional area (0 .04 cm(2)) measurements may also be made in facilities with short high inte nsity beams.