Sub-0.5 mm Resolution PET Scanner with 3-Layer DOI Detectors for Rodent Neuroimaging

Spatial resolution is the most important parameter for preclinical positron emission tomography (PET) to visualize mouse brain function with high quantification accuracy. However, the spatial resolution of PET has been limited to over 0.5 mm, which causes a substantial partial volume effect especially for small mouse brain structures. In this study, we present the initial results of a mouse brain dedicated PET scanner that can achieve sub-0.5 mm resolution. The ring diameter and axial coverage of the PET scanner are 48 mm and 23.4 mm. To encode depth-of-interaction (DOI) information, 3-layers of lutetium yttrium oxyorthosilicate crystals were stacked in a staggered configuration and coupled to a 5×5 array of silicon photomultipliers having a pixel pitch of 2.4 mm. The crystal pitch and total thickness are 0.8 mm and 11 mm. The PET performance was characterized according to the National Electrical Manufacturers Association NU4-2008 standard. In vivo mouse brain imaging was carried out with ¹⁸F-FITM and ¹⁸F-FDG tracers. The average radial resolution from the center to 10 mm offset was 0.67±0.06 mm with filtered back projection. The 0.45 mm diameter rods were identified clearly with an iterative reconstruction algorithm. To the best of our knowledge, this is the first separate identification of the hypothalamus, amygdala, and cerebellar nuclei of mouse brain. The developed PET scanner achieved sub-0.5 mm resolution thereby visualizing small mouse brain structures with high quantification accuracy.