Performance optimization of continuous detector modules using Cramer-Rao theory combined with Monte Carlo simulations

We are currently investigating the possibility of using continuous scintillator blocks as detectors for small animal PET. These block detectors consist of a few cm³ of scintillating material, read out by one or two APD arrays. The entry point of an incoming gamma photon is reconstructed from the distribution of the scintillation light over the APD pixels. To optimize the detector design, the influence of different parameters is investigated using simulations. As a measure of detector performance that is independent of the reconstruction algorithm used, the Cramer-Rao lower bound on the reconstruction of the coordinates of a point source of light inside the crystal is calculated. Results are presented for different detector designs, surface finishes and pixel sizes. A comparison with resolutions obtained from simulations involving beams of 511 keV annihilation photons indicates that this approach gives valid results.