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

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 ¿s. 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.