Design simulation of a rotating dual-headed PET/CT scanner for breast imaging

A PET system based on a pair of opposing LSO detectors for breast imaging has previously been described by Doshi et al (IEEE Trans. Nucl. Sci. 48: 811-815, 2001). This system has undergone some modifications in geometry and electronics and is being integrated into a dedicated breast CT system. In this work we perform a design simulation of the new system with a view to determining areas for future improvements. Simulations were performed using the public domain GATE software, based on the GEANT 4 particle simulation engine. The NURBS-based NCAT phantom was used to create an anthropomorphic activity and attenuation distribution. We show that activity outside of the field of view has a major impact on singles-to-trues ratios and is an important design constraint. The coincidence time window width and system dead-time both have a significant effect on noise equivalent count-rates, and efforts to reduce them on a future prototype are likely to be worthwhile.