Accurately Positioning and Incorporating Tissue-Scattered Photons into PET Image Reconstruction

We are developing cadmium zinc telluride detectors with three-dimensional positioning capabilities for high-resolution PET imaging. These detectors exhibit high spatial resolution (1 mm), energy resolution (2.5% full width at half maximum for 511 keV photons), and the ability to identify the 3-D coordinates of individual Compton and photoelectric interactions within the detector. These detectors can operate in conventional PET mode measuring photons in coincidence and as a Compton camera for single photon events. In this work, we show how the capabilities of this detector can be used to reconstruct tissue-scatter coincidence events. We present a scatter projector function for positioning tissue-scatter coincidence events in the field of view. Using Monte Carlo simulated data generated by GATE (Geant4), we showed that this new approach might be used to increase the number of usable counts in PET.