Monte-Carlo Simulation Based Estimation of NECR, Sensitivity, and Spatial Resolution of a Novel Preclinical PET Insert for MR

The Small Animal Fast Insert for mRi (SAFIR) will be a PET insert for the Bruker BioSpin 70/30. It aims at applications where fast processes such as blood perfusion in the rodent brain are to be monitored comprehensively and non-invasively. Employing electronics originally designed for time-of-flight applications, coincidence resolving times of less than a nanosecond can be achieved allowing for short coincidence time windows. Consequently, random contributions to the coincidence events are suppressed, making short acquisition frames with very high tracer concentrations possible. This will allow collecting sufficient count statistics in a few seconds. Geant4-based Monte Carlo simulations were used to characterize the performance of the reference design consisting of polished LSO-like crystals, one-to-one coupled to Silicon Photomultipliers. The crystals are grouped into 8 x 8 matrices, which are arranged into 24 modules and 10 rings. Similar methods as described in the NEMA NU 4-2008 standard were employed. The simulation results on NECR, sensitivity, and spatial resolution will be presented. Most notably, the NECR at 500 MBq is almost nine times higher than at 50 MBq for the given scanner. Combined with a very high sensitivity, this allows for short acquisition times using these very high injected doses. In addition, essentially random-free measurements at standard activities below 50 MBq are possible.