Compact hybrid gamma camera with a coded aperture for investigation of nuclear materials

Mechanical collimation commonly uses the photoelectric effect to reconstruct radiation images. Electronic collimation (i.e. Compton camera) using Compton scattering has been developed to reconstruct radiation images without utilizing mechanical collimators. Generally, for radiation imaging, electronic and mechanical collimation methods are used individually. In order to increase the quality of imaging and the efficiency of radiation detection, we combined both collimation methods in a single system. Our compact hybrid gamma camera comprised a modified uniformly redundant array (MURA) and a Compton camera, and the information from each modality was obtained simultaneously. The entire system formed a radial shape with detector modules which comprising CsI(Na) scintillators coupled with position-sensitive photomultiplier tubes (PSPMTs) whose anodes were connected to custom-made circuits. For various energy sources, the reconstructed images produced using this hybrid method were obtained and compared with reconstructed images from the two aforementioned methods. The maximum likelihood expectation maximization (MLEM) algorithm was applied for the reconstruction method. Compared with individual imagers at intermediate energies, the hybrid imager showed equal or better performance.