Investigation of SPECT/CT cardiac imaging using Geant4

The purpose of this paper is to propose a friendly computational framework able to investigate particles tracking through different compartments of the human being using dedicated numerical techniques. The main building blocks of this framework are: (i) convenient X-ray spectra calculator for different filter/anode combination, (ii) realistic voxelized computational human phantom, (iii) validated Geant4-based Monte Carlo simulation, and (iv) extendable and free image processing software. We studied the multimodality SPECT/CT cardiac imaging using specific spectrum of the Tc-99m and 120 kVp X-ray beam, for internal and external exposure, respectively. The application of the framework to quantify the loss of information between combined and simultaneous coregistration was carried out. Two main objectives were addressed: (i) an ideal geometry was simulated for educational purposes (ii) a realistic case study was carried out, for research purposes, concerning the modeling of the GE Infinia II 3/8" Gamma Camera. We compared the effect of using a Nal(Tl) and CZT crystal detector, and a LEHR and MEGP collimator with different uptake values of the heart organ (1:1, 5:1 and 50:1) for both simultaneous and combined SPECT/CT images. We confirmed the usefulness of the Nal(Tl) crystal with the LEHR collimator for such kind of study.