Effects of reflectors on the imaging performance of a mouse brain PET scanner with staggered 3-layer DOI detectors

For mouse brain positron emission tomography (PET), good spatial resolution and depth-of-interaction (DOI) information are necessary. Spatial and DOI resolutions of PET systems are highly affected by reflector materials. Nevertheless, the effects of reflector materials on the imaging performance have not been investigated in PET system levels.

Here, we systematically investigate the effects of reflector materials on the imaging performance of a mouse brain PET scanner using staggered 3-layer DOI detectors.

We separately constructed mouse brain PET scanners with two reflector materials of barium sulfate (BaSO₄) powder and enhanced specular reflector (ESR) film. The PET inner diameter (53 mm), crystal pitch (1 mm), and crystal layer thickness (4/4/7 mm) were the same for BaSO₄ and ESR. Physical and imaging performance of the PET scanners were evaluated with the same silicon photomultipliers and front-end electronics.

The system coincidence timing resolution with ESR (3.6 ns) was twice as good as that with BaSO₄. (7.0 ns). However, the average radial resolution with BaSO₄ (0.96 mm) was 0.2 mm better than that with ESR (1.16 mm) because of the reduced crystal decoding error. A narrow energy window (440-560 keV) effectively improved the valley-to-peak ratio of submillimeter rod structures, especially for BaSO₄ due to the reduced inter-crystal scattering events, although at the expense of sensitivity.

We found BaSO₄ provided better spatial resolution and imaging performance over ESR for the mouse brain PET scanner with staggered 3-layer DOI detectors.