A new balloon catheter device for accelerated partial breast irradiation (APBI) has been developed for the treatment of early-stage breast cancer. The purpose of this study was to investigate the dosimetric haracteristics of APBI by using microMOSFET radiation sensors. The dose investigation was carried out by using a soft tissue–equivalent cylindrical phantom. A new dosimetric system containing microMOSFET radiation sensors was used
to measure doses. Agreements between calculated and measured doses were determined. Our initial results had shown that a 15% concentration of radiographic contrast medium was sufficient to enhance the balloon volume without substantially altering the dose distribution. Good agreement was observed for surface doses between those calculated from the treatment planning system and those measured from the radiation sensors. The radiation-sensor system showed promise for immediate monitoring of skin doses during APBI.