Digital peak detector for radiation detection systems

Abstract

A subject ( ) is disposed adjacent a detector array ( ) of a nuclear camera. The subject ( ) is injected with a radioactive isotope ( ) and &ggr;-ray emissions indicative of nuclear decay are detected at the detector array ( ). Individual detectors ( ) are monitored in groups of 64. When one of them detects a nuclear event, it produces an electrical spike that is filtered into a Gaussian with about a 1.2 &mgr;sec peaking time. A 10 bit analog to digital converter ( ) 10 repeatedly digitizes the amplitude of the Gaussian pulse, e.g. at a 20 MHz clock rate. The 10 bit digitized pulse amplitudes are monitored by a 10 bit comparitor ( ), which monitors consecutive values of the digitized signal, looking for the peak value, e.g. for the amplitude to stop rising. When the peak is detected, the most recent four digital pulse amplitudes contiguous to the peak are summed in a 12 bit accumulator ( ) to generate a 12 bit peak amplitude value. A series of 12-bit peak values and the corresponding pixel addresses are stored in a buffer memory of the event analyzer ( ). A reconstruction processor ( ) reconstructs the identifications of the &ggr;-ray receiving detectors, or other indicators of event detection location, and the digital peak values to generate an image representation.