System design for a 1 mm3 resolution animal PET scanner: MicroPET II

We are currently developing microPET II, a second-generation dedicated PET scanner for small animal imaging. The design goal is to achieve ∼1 mm3 volumetric resolution, a larger axial field of view, and higher system sensitivity than our original prototype system. To minimize development time and cost, Monte Carlo simulation was used to determine appropriate dimensions for the detector crystals and for the system geometry. Simulations of the existing microPET system were compared to its measured performance to estimate errors in the simulations. Measurements from a pair of prototype detectors (12×12 array of 1×1×10 mm LSO crystals) agreed well with the simulation and provided a validation of the system design. The chosen design for microPET II has 0.975×0.975×12.5 mm LSO crystals arranged in a ring of 7.2 cm radius, and a 4.83 cm axial field of view. These specifications provide a volumetric image resolution <1.05 mm3 within 10 mm radius from the CFOV. The absolute sensitivity is estimated to be 3.6 times that of the current microPET. With 2.7 times the axial field of view, microPET II will have up to 9.7 times the total efficiency of the existing microPET system for whole body studies in mice and rats.