Initial characterization of a position-sensitive photodiode/BGO detector for PET

The authors present initial results for a position-sensitive photodiode/BGO (bismuth germanate) detector for high-resolution, multilayer positron emission tomography (PET). Position sensitivity is achieved by dividing the 3 mm*20 mm rectangular photosensitive area along the diagonal to form two triangular segments. Each segment is individually connected to a low-noise charge amplifier. The photodiodes and crystals are cooled to -100 degrees C to reduce dark current and increase the BGO signal. With an amplifier peaking time of 17 mu s, the sum of the signals (511-keV photopeak) was 3200 electrons with a full width at half maximum (FWHM) of 750 electrons. The ratio of one signal to the sum determined the depth of interaction with a resolution of 11 mm FWHM.<
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