A Pre-Clinical PET Scanner Based on a Monolithic Annulus of Scintillator (AnnPET): Construction and NU4-2008 Performance Testing.

Abstract

Objective: In the past several decades, numerous PET scanners of various designs have been constructed for use in pre-clinical studies. Our group is investigating use of a monolithic annulus of scintillator, instead of the traditional arrays of discrete scintillator elements or individual detectors that utilize continuous blocks of scintillator, to construct a novel pre-clinical PET scanner. Approach: This scanner, called AnnPET, is based on a fourteen-faceted annulus of LYSO with an inner diameter of 6 cm and length of 7.2 cm. Each facet is populated with four specially constructed 4  4 arrays of 4 mm  4 mm MPPCs. To cool and temperature stabilize these devices, the scanner gantry is immersed in dielectric fluid. Positioning of events in the scintillator is accomplished with the application of deep-residual convolutional neural network. The scanner's performance was assessed using the NEMA NU4-2008 protocols. Results: Full-width-at-half-maximum (FWHM) of the images of a point source reconstructed with the single slice rebinned filtered backprojection (SSRB-FBP) algorithm at 5 mm from the center of the scanner are: 1.40 mm (radial), 1.38 mm (tangential) and 1.40 mm (axial). At 18 mm from scanner center (edge of the scanner's inner bore) the FWHMs are: 1.62 mm (radial), 1.43 mm (tangential) and 1.48 mm (axial) (FWHM). Peak detection sensitivity is 9.5% (0.086 cps/Bq). Peak noise equivalent count rate (NECR) is 234 kcps at 14.4 MBq. Significance: Overall, testing of the AnnPET system demonstrated very promising performance results for a pre-clinical PET scanner based on a single, cooled annulus of monolithic scintillator used with neural networks. Continued development of the system is planned. .