Development of a prototype Compton camera consisting of high-resolution scintillator detectors

A prototype Compton camera composed of two high resolution scintillator detectors is presented in this work. The scatterer detector consists of a 21 × 21 gadolinium aluminum gallium garnet (GAGG) crystal array with a crystal size of 0.6 × 0.6 × 2 mm³. The absorber detector consists of a 23 × 23 lutetium yttrium orthosilicate (LYSO) crystal array with a crystal size of 1.0 × 1.0 × 20 mm³. A simple back-projection image reconstruction method was developed. The energy of the scatterer detector was accurately calibrated using the 55, 202, 307 keV gamma-rays from the LYSO natural background and the 511 keV gamma-ray from a ²²Na point source. The scatterer detector provides a performance with all crystals clearly resolved even at an energy window of 30-120 keV and an average crystal energy resolution of 10.4% at 511 keV. The absorber detector provides a performance with all crystals clearly resolved, an average crystal depth of interaction resolution of ~ 2 mm and an average crystal energy resolution of 19.4% at 511 keV. An average spatial resolution of 2.5 mm was obtained and 9 point sources of 3 mm apart were well resolved at an image plane 7.5 mm from the front of the scatterer detector by using the 511 keV gamma-rays from a ²²Na point sources. Furthermore, iterative reconstruction using the maximum-likelihood expectation maximization (MLEM) algorithm achieved a spatial resolution of ~ 1 mm at a plane 7.5 mm from the front of the scatterer detector. Compared with the simple back-projection method, the MLEM reconstruction significantly enhanced the image contrast and effectively suppressed the background artifacts.