Abstract: In a gamma camera system, means are provided for correcting nonuniformity or lack of correspondence between the positions of scintillations and their calculated and displayed x-y coordinates. In an accumulation mode, pulse counts corresponding with scintillations in various areas of the radiation field are stored in memory locations corresponding with their locations in the radiation field. A uniform radiation source is presented to the detectors during the accumulation mode. When a predetermined maximum number of counts is reached in several memory locations, accumulation is interrupted at which time other locations have fewer counts in them. In the run mode, counts are stored in corresponding locations of a memory and these counts are compared continuously with those stored in the accumulation mode.

Abstract: In a gamma camera system having an array of photomultiplier tubes for detecting scintillation events and preamplifiers connecting each tube to a weighting resistor matrix for determining the position coordinates of the events, means are provided for summing the signals from all photomultipliers to obtain the total energy of each event. In one embodiment, at least two different percentages of the summed voltage are developed and used to change the gain of the preamplifiers as a function of total energy when energies exceed specific levels to thereby obtain more accurate correspondence between the true coordinates of the event and its coordinates in a display.

Abstract: In a gamma camera system a computer calculates the x and y coordinates of scintillations and a pulse height analyzer determines if they are within the proper amplitude limits for being displayed on a cathode ray tube at corresponding coordinates. Means are provided for correcting nonuniformity or lack of correspondence between the positions of the scintillations and their calculated coordinates. In an accumulation mode, a first memory matrix stores pulse counts for incremental areas of the radiation field when a uniform source is presented to the detectors. When a predetermined maximum number of counts is reached in at least one memory location accumulation is interrupted at which time other locations have fewer counts in them. In the run mode counts are stored in corresponding locations in a second memory matrix and these counts are compared continuously with those in locations in the first memory.

Abstract: In a scintillation camera system, the output pulse signals from an array of photomultiplier tubes are coupled to the inputs of individual preamplifiers. The preamplifier output signals are coupled to circuitry for computing the x and y coordinates of the scintillations. A cathode ray oscilloscope is used to form an image corresponding with the pattern in which radiation is emitted by a body. Means for improving the uniformity and resolution of the scintillations are provided. The means comprise biasing means coupled to the outputs of selected preamplifiers so that output signals below a predetermined amplitude are not suppressed and signals falling within increasing ranges of amplitudes are increasingly suppressed. In effect, the biasing means make the preamplifiers non-linear for selected signal levels.