Evaluation of a multistage CdZnTe Compton camera for prompt y imaging for proton therapy

摘要

A new detector system, Polaris J from H3D, has been evaluated for its potential application as a Compton camera (CC) imaging device for prompt γ rays (PGs) emitted during proton radiation therapy (RT) for the purpose of dose range verification. This detector system consists of four independent CdZnTe detector stages and a coincidence module, allowing the user to construct a Compton camera in different geometrical configurations and to accept both double and triple scatter events. Energy resolution for the 662 keV line from ~(137)Cs was found to be 9.7 keV FWHM. The raw absolute efficiencies for double and triple scatter events were 2.2 × 10~(-5) and 5.8 × 10~(-7), respectively, for γs from a ~(60)Co source. The position resolution for the reconstruction of a point source from the measured CC data was about 2 mm. Overall, due to the low efficiency of the Polaris J CC, the current system was deemed not viable for imaging PGs emitted during proton RT treatment delivery. However, using a validated Monte Carlo model of the CC, we found that by increasing the size of the detectors and placing them in a two stage configuration, the efficiency could be increased to a level to make PG imaging possible during proton RT.