Gamma-Ray Imaging Using Cherenkov Cone Detection from Energetic Compton Electrons

A novel detection concept for higher energetic gamma-rays (E≥1MeV) is introduced using the coincident detection of Cherenkov photons from Compton-electrons in an optically transparent radiator material. Such detection capability would facilitate imaging of the distribution of certain targeted alpha-emitter therapies and also could be applicable in range verification for proton therapy, which are both connected to prompt gamma emission. For a proof of concept a coincident detection of the Cherenkov photons created in PMMA by the energetic electrons from a collimated strontium source was performed. Using a 8x8 silicon photomultiplier (SiPM) array and fast FPGA-based read-out electronics, a timing resolution of 242ps could be achieved. The measured number of photons and their distribution from accumulated events is in good agreement with theoretical predictions. The data exhibit the expected variation with source position and radiator thickness. A measurement of Cherenkov light from Compton and photo electrons was performed as well and the number of detected photons could be counted. The goal is the ability to use the number of photons and the detected pattern on the array for a reconstruction of momentum and energy of individual Compton-scattered electrons.