Construction and performance of a dose-verification scintillation-fiber detector for proton therapy

A multilayer scintillation-fiber detector has been developed for precision measurement of time-dependent dose verification in proton therapy. In order to achieve the time and position sensitivity required for the precision dose measurements, a prototype detector was constructed with double-clad 1-mm-thick scintillation fibers and 128-channel silicon photodiodes. The hole charges induced in each channel of the silicon photodiodes were amplified and processed with a charge-integration mode. The detector was tested with 45-MeV proton beams provided by the MC50 cyclotron at the Korea Institute of Radiological and Medical Science (KIRAMS). The detector response for a 45-MeV proton beam was agreed fairly well with the predicted by GEANT4 simulations. Furthermore, the quantitative accuracy appearing in the spatial distribution of the detector response measured for 20 s is in the order of 1%, whose accuracy is satisfactory to verify beam-induced dose in proton therapy. We anticipate that the detector composed of scintillation fibers and operating in the charge-integration mode allows us to perform quality measurement of dynamic therapeutic beams.