Comparative evaluation of three microPET series systems using Monte Carlo simulation: sensitivity and scatter fraction

SIEMENS Inveon is newly released fully multi-modality animal dedicated PET incorporated with SPECT and CT scanner. In this study, Monte Carlo simulation model for the Inveon PET scanner was developed and the preliminary GATE simulation studies were performed to predict the absolute sensitivity and scatter fraction of this scanner. The results of simulations were compared to those of microPET R4 and Focus 120 (F120). PET geometry and physical component such as photoelectric effect, Compton and Rayleigh interactions were simulated. Simulation for sensitivity and scatter fraction were repeated under four different conditions (energy window: 250~750 keV or 350~650 keV, coincidence window: 6 ns or 10 ns). "NEMA-like" rat and mouse phantoms were simulated for calculating scatter fraction. Sensitivity of R4, F120, and Inveon were 5.7, 6.4, and 9.8% within an energy window of 250~750 keV and coincidence window of 10 ns. Scatter fraction of mouse simulating phantom of R4, F120, and Inveon were 19.6, 18.7 and 19.3% within the same energy window and coincidences window. This paper presents the results of Monte Carlo simulation for the R4, F120, and newly released Inveon PET systems. The results of the simulation of F120 were comparable to measured data, which shows the feasibility of performing a comprehensive simulation study of the R4, F120, and Inveon using GATE. The simulation results also show that the improvement in sensitivity of Inveon over the F120 was more than 50%. This improvement would be mainly due to the increased axial length of the detector system. Scatter fractions were similar to those of the previous scanners.