Development of a Compton camera based on 3D position-sensitive virtual Frisch-grid CZT detectors

In this study, a Compton camera was developed utilizing a 2 × 2 array of cadmium–zinc–telluride (CZT) detectors. The camera employs four CZTs, each measuring 6 mm × 6 mm × 19 mm. The virtual Frisch-grid method with a four-segment side pad was applied to ensure accurate 3D position sensing. In addition, rejection and correction methods were developed that leverage positional information to correct for non-uniform detector responses. Various isotopes were measured to evaluate the spectral performance. The energy resolutions were 3.11, 2.36, 2.00, 1.65, 1.31, and 1.50% at 356, 511, 662, 1275, and 1332 keV, respectively. In addition, to estimate depth, a comparison was made between the performance of cathode signal-based and side electrode-based methods, and their interchangeability was confirmed. Additionally, Compton imaging experiments were performed for single and multiple sources at various positions, and an iterative method was implemented for image reconstruction. Although the imaging performance varied depending on the gamma-ray direction, our system was able to accurately reconstruct the positions of single or multiple sources. The intrinsic efficiency, spatial resolution, and positional error were determined to be (1.43 ± 0.36) × 10−3, 16.42° ±7.02°, and 3.43° ±1.62°, respectively.