A very-high resolution SPECT system based on the energy-resolved photon counting CdTe detectors

This paper presents preliminary experimental results obtained with a prototype SPECT system for small animal studies. This system is based on novel energy-resolved photon counting (ERPC) detectors we have recently developed for gamma ray imaging applications. The ERPC detector has basic modular configuration that offers an overall detection area of 4.5 cm × 4.5 cm, comprising of eight CdTe/CMOS detector hybrids. Each hybrid has a CdTe detector of 11 mm × 22 mm bump-bonded onto a dedicated readout ASIC that has 32 × 64 readout pixels with 350 μm pitch size. The 1 mm and 2 mm thickness CdTe detector have both been developed. This configuration offers a very-high spatial resolution of around 350 μm and an excellent energy resolution of around 3~4 keV at 140 keV. The prototype SPECT system that consists of two or four ERPC detectors is mounted on a system gantry rotating around a horizontal axis. The detectors are coupled to apertures with differently sized pinholes. In order to utilize the imaging information provided by the ERPC detector, we have developed a comprehensive system modelling and calibration method that accounts for the irregular shapes and physical details in the collimation apertures. Detailed system design and experimental procedures will be described in this paper.