Addressing of the 294 Crystal Mosaic of the Digital Autofluoroscope

A camera-type device, the Digital Autofluoroscope*, recently developed for organ visualization and other applications in the nuclear field is described. The detection head of the Autofluoroscope consists of a 6 × 9 inch rectangular array of discrete 1-1/2 inch long NaI(T1) crystals. The array is made up of 294 crystals forming a grid of 14 × 21 crystals. Each row and column is optically coupled to separate photomultiplier tubes. Pulses that occur simultaneously in any pair of photomultiplier tubes uniquely identify the crystal in which the interaction occurred. Anticoincidence logic is provided to inhibit all pulses arising simultaneously in more than one crystal. The optical coupling between the 294 crystal mosaic and the 35 photomultiplier tubes is accomplished by means of total internal reflection to achieve efficient light conduction in plexiglass light-pipe array. The parameters that govern uniformity and transmission along with the calibration of the instrument are discussed.