PERFORMANCE OF A PET DETECTOR MODULE UTILIZING AN ARRAY OF SILICON PHOTODIODES TO IDENTIFY THE CRYSTAL OF INTERACTION

We present initial performance results for a new multi-layer PET detec tor module consisting of an array of 3 mm square by 30 mm deep BGO cry stals coupled on one end to a single photomultiplier, tube and on the opposite end to an array of 3 mm square silicon photodiodes. The photo multiplier tube provides an accurate timing pulse and energy discrimin ation for the all the crystals in the module, while the silicon photod iodes identify the crystal of interaction. When a. single BGO crystal at +25-degrees-C is excited with 511 keV photons, we measure a photodi ode signal centered at 700 electrons (e-) with noise of 375 e- fwhm. W hen a four-crystal/photodiode module is excited with a collimated line source of 511 keV photons, the crystal of interaction is correctly id entified 82% of the time. The misidentification rate can be greatly re duced and an 8 x 8 crystal/photodiode module constructed by using thic ker depletion layer photodiodes or cooling to 0-degrees-C.