Gamma-ray tracking for high energy gamma-ray imaging in pixelated CdZnTe

Sequencing gamma-ray interactions within a detector system is an integral component of Compton imaging. In detectors with poor timing resolution compared to the time interval of successive interactions, algorithms which order gamma-ray interactions must be implemented using only energy and position information. This work examines previous algorithms and inspects interaction kinematics to increase the sequencing algorithm's speed and effectiveness. The proposed method, in which the first interaction is assumed to deposit the largest energy, has improved sequencing performance by greater than 20% for full energy gamma ray depositions larger than 1 MeV that do not contain pair-production. In addition, the algorithm shows a decrease in computational costs for sequence reconstruction to allow for better real time reconstruction. Experimental results show an almost twofold increase in the signal to noise ratio (SNR) for simple backprojection images of a Na-22 source. Additional measurements of the 2.2 MeV gamma rays from H-1(n, gamma)D-2 neutron capture demonstrates the proposed algorithm's superior performance.