Monte Carlo simulation for the ECAT HRRT using GATE

The ECAT HRRT (High Resolution Research Tomograph, CPS Innovations, Knoxville, TN, U.S.A.) is a 3D-only brain positron tomograph made of height flat panels using LSO and LVSO scintillators. This dual-layer octagonal geometry allows the scanner to measure depth-of-interaction, preserving the good spatial resolution toward the edge of the transverse field-of-view. With the objective of optimizing protocols and acquisition parameters, we used the GATE (Geant4 Application for Tomographic Emission) Monte Carlo simulation platform to build a realistic model of this scanner. The aim of this paper is to compare the performance of the model against the real system. In order to remain the comparison being independent on the reconstruction scheme used, we generated the simulation data as the HRRT native 64-bit list-mode format before software histogramming and rebinning into sinograms. We performed for the comparison three sets of experiments: intrinsic spatial resolution, scatter fraction and count rates. Real and simulated data were found to be in good agreement. To illustrate the use of this model we evaluated the crystal thickness influence for a single layer HRRT on spatial resolution and sensitivity.