Abstract-GATE, the Geant4 Application for Tomographic Emission, is a simulation platform developed for PET and SPECT. It combines a powerful simulation core (the Geant4 toolkit) and a large range of developments dedicated to nuclear medicine. In particular, it models the passing of time during real acquisitions, allowing to handle dynamic systems such as decaying source distributions or moving detectors. We present several series of results that illustrate the possibilities of this new platform. The simulation of decaying sources is illustrated on a dual-isotope acquisition with multiple time-frames. Count rate curves taking into account random coincidences and dead-time are shown for a dual-crystal set-up and for a small-animal PET scanner configuration. Simulated resolution curves and reconstructed images are shown for rotating PET scanners. Lastly, we present comparisons of simulated point-spread functions and spectra with experimental results obtained from a small-animal gamma camera prototype.
The Clear-PEM device is a Positron Emission Mammography (PEM) unit based on planar detectors and is currently under development. We have developed a 2D Algebraic Reconstruction Technique (ART) algorithm using linograms to reconstruct Clear-PEM data. In this work we evaluate three different methods of calculating the system matrix used by the ART algorithm, which we designate as the pixel-, ray-and tubedriven methods, respectively. The methods were tested using Monte Carlo simulated data. The results obtained show that ART algorithm allows, for these cases, accurate image reconstruction and indicate that a more accurate modeling of the image system matrix using Tubes of Response (TORs) provides the best image evaluation indexes.
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