Objective: A quantitative study on the performance of cadmium zinc telluride, thallium-doped sodium iodide and germanium detectors as potential Compton camera absorbers.
Methods: The GEANT4 toolkit was used to model the performance of these materials over the nuclear medicine energy range. The metrics of analyses were the materials’ intrinsic efficiency, multiple scattering occurrence and spatial resolution. An evaluation of the detector effects of a Compton camera system based on the most suitable absorber material on image resolution was then carried out.
Results: Cadmium zinc telluride and germanium demonstrate the highest and lowest efficiencies respectively. Although the best spatial resolution was attained for germanium, its lowest ratio of single photoelectric to multiple interactions suggests that it is most prone to inter-pixel cross-talk. In contrast, cadmium zinc telluride, which demonstrates the least positioning error due to multiple interactions, has a comparable spatial resolution with germanium. Interestingly, finite spatial resolution of our Compton camera model which accounted for the least image degradation at 140.5 keV became the dominant degrading factor at 511 keV, indicating that the absorber parameters play significant roles at higher gamma ray energies.
Conclusions: Our results suggest that cadmium zinc telluride is the most suitable Compton camera absorber, and that reducing its pad size would improve image resolution at higher gamma ray energies.