Studies on sensitivity, resolution, and Doppler broadening in gamma-ray imaging with pixellated semiconductor detectors

We studied the Doppler broadening effect which is one of the major issues pertaining to overall imaging quality in Compton cameras. For the study of Doppler broadening due to the pre-collision electron momentum, we used a collimated beam of 662-keV gamma rays and selected events corresponding to the 90degrees Compton scattering using a Compton spectrometer, consisting of a 25-fold segmented germanium detector and a coaxial germanium detector shielded with a bismuth germanate (BGO) scintillator. Comparison of the energy spread due to Doppler broadening between a silicon and a germanium detector was made with the Monte Carlo simulation. To see the effect of Doppler broadening on the image resolution, we performed the Monte Carlo simulation in a simple backprojection method.