title: A New Positioning Algorithm for Position-Sensitive Avalanche Photodiodes.
abstract: We are using a novel position sensitive avalanche photodiode (PSAPD) for the construction of a high resolution positron emission tomography (PET) camera. Up to now most researchers working with PSAPDs have been using an Anger-like positioning algorithm involving the four corner readout signals of the PSAPD. This algorithm yields a significant non-linear spatial "pin-cushion" distortion in raw crystal positioning histograms. In this paper, we report an improved positioning algorithm, which combines two diagonal corner signals of the PSAPD followed by a 45° rotation to determine the X or Y position of the interaction. We present flood positioning histogram data generated with the old and new positioning algorithms using a 3 × 4 array of 2 × 2 × 3 mm3and a 3 × 8 array of 1 × 1 × 3 mm3of LSO crystals coupled to 8 × 8 mm2PSAPDs. This new algorithm significantly reduces the pin-cushion distortion in raw flood histogram image.
authors.affiliation: Department of Radiology and Molecular Imaging Program, Stanford University, Stanford, CA 94305 USA.
authors.forename: Jin
authors.initials: J
authors.lastname: Zhang
authors.forename: Peter D
authors.initials: PD
authors.lastname: Olcott
authors.forename: Craig S
authors.initials: CS
authors.lastname: Levin
keywords: Avalanche photodiode; positioning algorithm; positron emission tomography