A One-Dimensional Multigated Time-of-Flight Acquisition System

A multigated time-of-flight probe system has been developed for the simultaneous measurement of spatial and temporal modulations in the activity distribution of positron emitting radiotracers within the human body. This system consists of a pair of 4×4 cm BaF2 scintillators coupled to Amperex XP2020 Quartz photomultiplier tubes. Constant fraction discrimination provides the time pick-off of each anode signal required to start and stop a Time-to-Amplitude Converter. A slow overlap coincidence channel is used to define the dynamic range of the system and gate the TAC signal through to an ADC/LSI 11/02 microcomputer pair for data storage. A pulsewatch (LED-phototransistor pair) and the appropriate gating logic have been developed to incorporate gating capabilities into the system. A multigated TOF system can provide noninvasive alternatives to measuring blood tracer concentrations in positron emission tomography.