A Modular SPECT Camera Combining PMTs and SiPMs

Abstract

In this work, novel modular gamma camera concepts for SPECT imaging systems were investigated. The camera designs included curved scintillation crystal to address parallax errors and 3D position resolution In addition, fiber optics plates as a light guides to transfer scintillation light from the curved exit face of the scintillation crystal to the planar light sensors for readout. The estimated intrinsic spatial resolution of the cameras averaged over the detector volumes were used as the figures of merit for comparisons. Spatial resolution was estimated using the Cramér-Rao lower bound condition from Fisher Information Matrices. The components of the Fisher Information Matrices were derived under an assumption of Poisson statistics by finding mean detector response function using a custom Monte-Carlo photon transport code written in Swift and Metal. All the designs were candidates for the AdaptiSPECT-C system, and ultimately a camera design using a hybrid combination of silicon photomultipliers and photomultiplier tubes balanced cost and performance goals for this system. The addition of curvature into modular gamma cameras did not significantly change the intrinsic spatial resolution of the cameras but does improve the point spread function for oblique rays from a single pinhole collimator. The addition of fiber optic plates as light guides does offer a path to improved 3D positioning that is worth exploring with a prototype camera and point-spread-function measurements.