Scintillation event localization in hemi-ellipsoid detector for SPECT, a simulation study using Geant4 Monte-Carlo

A high sensitivity Cardiac SPECT system using curved crystals with pinhole collimation was proposed previously (Dey, IEEE TNS 2012, Bhusal et al, Med. Phys. 2019). Here, we hypothesize that a curvature hemi-ellipsoid detector results in measurable differences light distribution from events at different depths the crystal. This tested by analyzing scintillation Monte-Carlo (Geant4) and evaluation of both localization error back-projected errors object-space. We used Geant4 to simulate propagation monolithic hemi-ellipsoidal CsI look-up table (LUT) created map points inside crystal expected pattern on surface Geant4. In thirteen zones across crystal, gamma-rays were simulated resulting scintillator intensity captured, serving as our experimental interactions. Poisson-statistics-based algorithm developed limit search gamma-ray event locations into small regions LUT fine-tuned interpolating between selected comparing gamma interactions patterns. The localized individually object mid-plane, recorded. Excluding some outliers (up 2%), averaged over all 0.71 (+/-0.44) mm worse case 1.36 (+/-0.67) apex. When midplane for SPECT, <1mm average 0.4(+/-0.22) mm, due magnification afforded detector. Thus, system, also able achieve resolution, assuming perfect collimator resolution recovery application.