Development of a submillimeter resolution PET scanner with compact geometry for hybrid multi-photon/PET imaging.

For mouse brain research, multi-modal imaging techniques are important to understand neurodegenerative mechanisms with different informational aspects. The aim of this study is to develop a submillimeter resolution PET scanner of compact geometry that can be integrated with a commercial multi-photon excitation microscope. Methods: The PET scanner has ring diameter of 52.5 mm and 24.5 mm axial length. We employed 3-layer LYSO crystals (with individual crystal layer thicknesses of 4, 4 and 7 mm) with a 1 mm crystal pitch and a 4×4 silicon photomultiplier array. The physical PET performance was evaluated in line with the National Electrical Manufacturers Association NU 4-2008 protocol. In vivo mouse brain imaging was performed with 18F-FITM tracer. Main Results: The spatial resolution was 0.89 mm, and sensitivity was 0.85% at the center with an energy window of 440-560 keV. The detailed mouse brain structures were clearly resolved, although they were hardly identifiable with a commercial preclinical PET scanner. Significance: The submillimeter resolution PET scanner with the compact geometry outperformed the commercial preclinical PET scanner. In the near future, we will integrate this high-resolution PET scanner with a multi-photon microscopy system for simultaneous multi-photon/PET imaging of mouse brain. .