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This is a front end electronic design for a PET camera with 8 arrays of position sensitive detectors. Each array has 16 BGO blocks (each block is composed of 49 crystals). The design goals are component and space reduction. Each PMT has its fast amplifier and triggered integrator. Nine flash ADCs serve an array of 27 PMTs and 784 crystals. The fast signals from one or more PMT clusters are summed. The fast summed signals are thresholded and sent to a programmable logic to determines the probable scintillation zone (4 blocks) and to turn on the associated 9 PMT integrators. After integration, the logic also drives a set of ultra-fast analog switches to connect the flash ADC set to the PMT integration channels in the scintillation zone. The 9 ADC outputs (integrated pulses with good photon statistics) are latched and compared. The comparator result determines which block in the zone is firing and the appropriate 4 ADCs are selected and bused into a position decoder. The decoder outputs the image-slice address and the crystal address. The circuit is pipelined and driven by a 250 MHz master clock.

A prototype PET camera has been designed and is being constructed to test the concept, and develop the engineering design and production methodology for a variable field PET camera. The long term goal of the design is to develop a lower cost, high resolution PET camera. The camera has eight detector heads which form a closely packed octagon detector ring with an average diameter of 44cm for brain/breast and animal model imaging. The heads can be translated radially to a maximum ring diameter of 70cm for whole body imaging. In the larger diameter modes, the camera rotates 45 [degrees] during imaging. The camera heads can be set to intermediate positions to fit the camera to the subject size to maximize detection sensitivity and sampling uniformity. Special design features for imaging the breast and the axillary metastases have been incorporated. The detector design implemented is the quadrant sharing photomultiplier (PMT) design using circular 19mm PMT. The BGO detector pitch size is 2.7x2.7mm. The prototype camera images 27 slices simultaneously with an axial field of view (FOV) of 39mm. The prototype's limited axial FOV, which is appropriate for testing the camera concept, would be expanded in a next-generation clinical camera implementation. Preliminary simulation studies have been performed to evaluate the resolution, sensitivity, and sampling uniformity.