In the multi-crystal scintillation camera, there is an array of 294 individual scintillation detectors, 14 rows and 21 columns, as indicated in Figure 3 on the next page. Gamma-ray interactions in the individual detectors produce scintillation light; the rows and columns are monitored by 35 light pipes connected to 35 phototubes. After some complex electronic checks to discriminate against simultaneous events in other crystals, the column and row address of the event is determined, providing an x- and y-address for the scintillation event. Note that detection and localization are independent.
In the normal course of events, the multi-crystal scintillation camera sends its output to 294 scalers, where the valid counts in each crystal are collected. The contents of these scalers are scanned and presented on the face of an oscilloscope as a scintiphoto where the brightness of the oscilloscope location is a function of the number of counts in each location. In a real sense, this device is a step ahead of the Anger scintillation camera in that its output has already been digitized—the number of counts in each location is represented by a number stored in a scaler.