Influence of event sequence reconstruction on imaging resolution of Compton camera

The Compton camera for γ-ray imaging has the advantages of light weight, high detection efficiency, and wide imaging energy range. However, it is difficult for the detection system to distinguish between the Compton scattering event and scattering photon absorption event, which results in erroneous image reconstruction. In this work, a simulation model of Compton camera based on a three-dimensional position-sensitive CdZnTe detector is constructed using GEANT4 program. The detection of characteristic γ-ray from a far-field <sup>137</sup>Cs point-like source is simulated. The location of the interaction and energy deposition in the detector are recorded by means of event-by-event. The Compton scattering angles of effective Compton scattering events and imaging of the radioactive source are reconstructed using a simple back-projection algorithm which is an image reconstruction algorithm suitable for real-time imaging scenes. The influences of event sequence reconstruction on the imaging resolution and its improvement are investigated. The results show that the influence of incorrect sequence events on imaging resolution is mainly in the area within 30° deviation from the source position, resulting in a decrease in the density of the image points distributed at the source position. Incorrectly reconstructed image points are generated near the source position and form a ring at 26°. The percentage of correctly sequenced events increases to 82% by using Compton edge test and simple comparison method based on the deposited energy for sequencing events. The density of image points distributed at the source location is improved by 47%, and the incorrect reconstruction of the image point distribution near the source location is greatly suppressed, resulting in an improved imaging resolution. The research results provide support for designing Compton camera and optimizing image reconstruction.