Comparison of LSO and BGO block detectors for prompt gamma imaging in ion beam therapy

A major weakness of ion beam therapy is the absence of applicable tools for verifying the particle range in clinical routine. The application of the Compton camera concept for the imaging of prompt gamma rays, a by-product of the irradiation correlated to the dose distribution, is a promising approach for range assessment and even two-dimensional in vivo dosimetry. Multiple position sensitive gamma ray detectors arranged in scatter and absorber planes, together with an imaging algorithm, are required to reconstruct the prompt gamma emission density map. Conventional block detectors deployed in Positron Emission Tomography (PET), which are based on Lu2SiO5:Ce (LSO) and Bi4Ge3O12 (BGO) scintillators, are suitable candidates for the Absorber of a Compton camera due to their high density and absorption efficiency even for the prompt Gamma energy range (several MeV). We compare experimentally LSO and BGO block detectors in clinical-like radiation fields in Terms of energy, spatial and time resolution. The high energy range compensates for the low light yield of the BGO material and boosts significantly its performance compared to the PET scenario. Notwithstanding the overall superiority of LSO, BGO catches up in the field of prompt gamma Imaging and can be considered as a competitive alternative to LSO for the absorber plane due to its lower price and the lack of intrinsic radioactivity.