A plastic scintillation dosimeter for high dose rate brachytherapy.

In vivo dose verification in brachytherapy requires a small insertable dosimeter with a real-time readout capability. Fibre optic scintillation dosimeters, consisting of a plastic scintillator coupled to an optical fibre, are one of the most promising dosimeters for this application. We have developed two sizes of the BrachyFOD scintillation dosimeter which have external diameters of 2.2 mm and 1 mm and have determined their important dosimetric characteristics (depth dose relation, angular dependence, temperature dependence, energy dependence). We have shown that the background signal created by Cerenkov and fibre fluorescence does not significantly affect the performance in most clinical geometries using an (192)Ir source from an HDR brachytherapy unit. The dosimeter design enables readout at less than 0.5 s intervals. The BrachyFOD satisfies the need for a real-time in vivo brachytherapy dosimeter.