Reconstruction of detector scattered events to improve PET sensitivity

Abstract

The sensitivity of a PET scanner is a function of the solid angle of coverage from the scintillation material to the object being scanned and the stopping power of the scintillation material being used. PET scanners also operate with an energy window centered on the 511 keV annihilation photons, wide enough to account for the energy resolution of the scanner's scintillator. The energy window reduces the amount of object scatter accepted, but also eliminates detector scatter events that do not experience object scatter. By adding lower energy windows, an un-scattered, full energy deposition event can be put in coincidence with a lower energy event, creating a high angle scatter line of response, or a detector scattered event that represents an object un-scattered line of response. Using a normalization specifically calculated for the coincidences with the new, lower energy windows and scatter correction of the high angle object scattered events, the data is reconstructed separately from the simultaneously collected PET data acquired with the traditional energy windows. Preliminary results showed that multi energy data reconstruction images can be created, recovering unscattered true events present across all data.