Design and construction of the donner 280-crystal positron ring for dynamic transverse section emission imaging

We describe the design and construction of a medical imaging system for the rapid, accurate, three-dimensional imaging of positron-labeled compounds in the human body. Our medical research goals include quantifying blood flow and metabolism in human heart muscle and brain. The system consists of (1) a large gantry containing lead shielding and a ring of 280 NaI(T1) detectors that completely encircles the patient; (2) 280 photomultiplier tubes, preamplifiers and timing discriminators; (3) circuits that determine whenever a crystal has detected a gamma ray in time coincidence (i.e. within 12 nsec) of any of the opposing 105 crystals and determine the addresses of the crystals involved; (4) 120K words of 12 bit memory for the simultaneous acquisition of data from eight portions of the cardiac cycle; and (5) a hardwired image reconstructor capable of filtering and backprojecting data from 140 views to form a 210 ?? 210 computed transverse section image in less than 2 sec.