Gate Intro

GATE, the Geant4 Application for Emission Tomography, incorporates the Geant4 libraries in a modular, versatile, and scripted simulation toolkit which is adapted to the field of nuclear medicine. In addition, GATE allows the accurate description of time-dependent phenomena such as source or detector movement and source decay kinetics. The ability to synchronize all time-dependent components allows a coherent description of the acquisition process and is one of the most innovative features of GATE. It makes it possible to perform realistic simulations of data acquisitions in time. The example below shows the simulation of the decay of O-15 (in green) and C-11 (in blue) sources throughout 3 time frames with the GATE: 0-2 min (left), 7-9 min (centre), and 14-16 min (right). On all frames, one detector has been hidden (gap in the detector ring) to illustrate the scanner rotation steps.

In addition to the timing features, a dedicated scripting mechanism extends the native command interpreter of Geant4 and allows to perform and control the Monte Carlo simulation in an intuitive manner. Moreover, the Geant4 interaction histories or hits can be further processed to realistically mimic detector output pulses. This digitization of the hits allows for the modeling of the detector response by using a chain of processing modules designed by the user. In the example below, GATE has been used to study the effect of detector dead-time (DT) and coincidence time window duration (CW) on the Noise Equivalent Count (NEC) rate of a prospective small animal PET scanner design. Detector electronic response was modeled including detector cross-talk, transfer efficiency of the scintillation photons to the photodetector, quantum efficiency of the photodetector, detector energy resolution, and trigger efficiency.