GATE Simulation of the Biograph 2 PET/CT Scanner

Abstract

GATE is advanced open source software dedicated to numerical simulations in medical imaging and radiotherapy. It currently supports simulations of Emission Tomography (Positron Emission Tomography -PET and Single Photon Emission Computed Tomography -SPECT), Computed Tomography (CT) and Radiotherapy experiments. This work focused on the commercial Biograph 6 PET/CT scanner. The study targeted to (a) port previously developed and validated GATE codes to the currently available stable version GATE v.6.1, (b) evaluate model's validity detecting sources of bias (c) investigate differentiations imposed if different sources were employed, namely F-18 (Fluorine-18), O-15 (Oxygen-15) and C-11 (Carbon-11). The geometry of the system components was described in GATE, including detector ring, crystal blocks, PMTs etc. Energy and spatial resolution were taken into account. The GATE results were compared to experimental data obtained according to the NEMA NU-2-2001 protocol, Analysis was limited to scatter fraction, count looses and randoms. Good agreement was achieved between experimental and GATE results. Significant sources of bias were the (a) dead time value, (b) dead-time mode (paralysable-nonparalysable), (c) modelled activity (d) modelled source, (e) additional dead time values adopted in GATE modules.