Initial Characterization of a Bgo-Photodiode Detector for High Resolution Positron Emission Tomography

Abstract

Spatial resolution in positron emission tomography is currently limited by the resolution of the detectors. This work presents the initial characterization of a detector design using small bismuth germanate (BGO) crystals individually coupled to silicon photodiodes (SPOs) for crystal identification, and coupled in groups to phototubes (PMTs) for coincidence timing. A 3 mm × 3 mm × 3 mm BGO crystal coupled only to a SPD can achieve a 511 keV photopeak resolution of 8.7% FWHM at -150°C, using a pulse peaking time of 10 μs. When two 3 mm × 3 mm × 15 mm BGO crystals are coupled individually to SPDs and also coupled to a common 14 mm diam PMT, the SPDs detect the 511 keV photopeak with a resolution of 30% FWHM at -76°C. In coincidence with an opposing 3 mm wide BGO crystal, the SPDs are able to identify the crystal of interaction with good signal-to-noise ratio, and the detector pair resolution is 2 mm FWHM.