Fast and accurate Monte Carlo-based system response modeling for a digital whole-body PET

Recently, we have developed a digital whole-body PET scanner based on multi-voltage threshold (MVT) digitizers. To mitigate the impact of resolution degrading factors, an accurate system response is calculated by Monte Carlo simulation, which is computationally expensive. To address the problem, here we improve the method of using symmetries by simulating an axial wedge region. This approach takes full advantage of intrinsic symmetries in the cylindrical PET system without significantly increasing the computation cost in the process of symmetries. A total of 4224 symmetries are exploited. It took 17 days to generate the system maxtrix on 160 cores of Xeon 2.5 GHz. Both simulation and experimental data are used to evaluate the accuracy of system response modeling. The simulation studies show the full-width-half-maximum of a line source being 2.1 mm and 3.8 mm at the center of FOV and 200 mm at the center of FOV. Experimental results show the 2.4 mm rods in the Derenzo phantom image, which can be well distinguished.