AID - A Novel Method for Improving the Imaging Resolution of a Table-Top Compton Camera

A Compton camera is usually composed of a scatterer detector and an absorber detector. The interaction position resolution of the absorber detector is the critical or limiting detector parameter that most seriously affects the imaging resolution of the table-top Compton camera currently under development in our group. Currently, it is assumed that all interactions occur at the centers of the detector segments of the absorber detector (25-segmented germanium detector), which is a simple but obviously not the best practice, considering that the interaction depths of the photons in the absorber detector, especially of low-energy photons, are not distributed uniformly. More photons have interaction in the front region of the detector due to the limited penetrating depth of the photons. Therefore, the present study developed a novel, "average interaction depth (AID)" method, which improves the imaging resolution of Compton camera by additionally considering the average interaction depth of the incident photon in the absorber detector. Simulations with Geant4 showed that the imaging resolution of the Compton camera can be significantly improved by using the AID method. For example, the resolution for a 511 keV gamma point source was improved from 9.9 mm to 7.6 mm in full width half maximum (FWRM). For a 364 keV gamma point source, the improvement was even more significant from 11.4 mm to 7.2 mm.