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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 the Compton scattering event and scattering photon absorption event, which results in erroneous image reconstruction. In this paper, 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 137Cs 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 angle of effective Compton scattering events and imaging of the radioactive source are reconstructed using the simple back-projection algorithm which is a suitable image reconstruction algorithm for real-time imaging scenes. The effect of event sequence reconstruction on the imaging resolution and its improvement are investigated. The results show that the impact of incorrect sequence events on imaging is mainly in the region within 30° from the source position, resulting in a decrease in the density of the image point distribution at the source position. Incorrect reconstructed image points are generated near the source position and form a ring at 26°. The percentage of correctly sequenced events increase to 82% using Compton edge test and simple comparison method based on the deposited energy for sequencing events. The density of the image point distribution 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 results provide support for the design of Compton camera and the optimization of image reconstruction.
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Keywords:
- Compton camera /
- GEANT4 /
- sequence reconstruction /
- imaging resolution
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