A device and method used in high resolution positron emission tomography
(PET) systems for digitizing gamma ray energy and characterizing peak
time and decay time constant, models a voltage pulse generated upon a PET
event detection as a fast linearly rising edge followed by a slower
exponential decay. The model includes parameters of the voltage pulse
that are relevant for PET event detection including a decay constant, a
peak voltage value, and a peak time, which are determined from time
interval measurements of the voltage pulse. The time interval
measurements are made using comparators and counters in an exemplary
electronic implementation.