Analytical model for pixellated SPECT detector concepts

Pixellated CZT detectors provide a new opportunity to improve the image quality of SPECT detector systems. Their performance has to he evaluated in terms of resolution and efficiency, in a similar way as done earlier for Nal detectors. We have developed an analytical model for spatial resolution and geometric efficiency of collimators specifically for pixellated CZT based detectors. We derive an exact description for static and rotating detector concepts, use NEMA performance criteria for detection efficiency, and adapt measures for spatial resolution of pixellated detectors, based on the sampling of the single pixel response function. Tradeoffs among resolution, efficiency, and signal-to-noise ratio (SNR) have been investigated for different applications. Our analysis shows that the concept of rotating collimators suffers from noise accumulation, except for purely hot spot imaging. We propose multi-pinhole, slat-slit or fan beam-slit collimators in a demagnification mode for optimum efficiency and image quality using pixellated solid-state detectors for SPECT cameras.