Gamma camera system

An improved gamma camera system comprises a circuit for performing digital dynamic compression wherein the circuit is readily modifiable to accept different compression procedures and the input and output signals are in digital form. The system further includes a photomultiplier tube (PMT) channel amplification integration circuit having multiple separate and independently triggerable integrators. In addition, the system comprises circuitry for generating spatially variant photomultiplier cluster based on a peak photomultiplier and for generating spatially variant weights for photomultipliers of the cluster depending on a cluster type signal. Further, the system includes a system for correcting and maintaining the baseline offset signal value of a PMT channel of a scintillation detector at a predetermined value. The correction system utilizes an event driven mode wherein the correction is performed based on detected gamma interactions and a second mode, software driven correction, wherein false triggers are inserted into the processing logic to initiate sampling of the baseline offset signal value and "simulate" gamma interactions. The system further comprises an automatic gain calibration system for PMTs operable during periods when a collimator is installed to the scintillation detector. The system calibrates PMTs located along the periphery of the detector having surfaces that are partially or totally obscured by the solid lead edge regions of the installed collimator and adjusts the preamplification gain associated with each channel to maintain the effective gain of each PMT in response to long term variations in the characteristic gain of each PMT.