Optical fiber dosimeter for real-time in-vivo dose monitoring during LDR brachytherapy

An optical fiber sensor for monitoring low dose radiation is presented. The sensor, based on radiation sensitive scintillation material, terbium doped gadolinium oxysulphide (Gd₂O₂S:Tb), is embedded in a cavity of 700µm diameter within a 1mm plastic optical fiber. The sensor is compared with the treatment planning system for repeatability, angular dependency, distance and accumulated radiation activity. The sensor demonstrates a high sensitivity of 152 photon counts/Gy with a temporal resolution of 0.1 seconds, with the largest repeatability error of 4.1%, to 0.361mCi of Iodine-125 the radioactive source most commonly used in LDR brachytherapy for treating prostate cancer.