GATE Simulation of the Biograph 2 PET/CT Scanner

Nikolopoulos D Michail C

doi:10.4172/2155-9619.1000201

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.

Highlights

Positron emission tomography (PET) is a medical diagnostic method to observe metabolism, blood flow, neurotransmission and important biochemical entities [1]
Simulated scatter coincidences count rates seem to be very sensitive to changes of dead-time in electronics and activity values inserted in the GATE codes
Simulation data have been scaled to offset sensitivity mismatches to achieve close agreement with experimental results [10,22,31,32]. The risk with these approaches is that the methods used to develop and validate the simulation models may not scale with confidence beyond the exact scanner configuration used in the validation, and may result in larger errors when used for performance prediction [1]

Summary

Introduction

Positron emission tomography (PET) is a medical diagnostic method to observe metabolism, blood flow, neurotransmission and important biochemical entities [1]. PET/CT systems, eliminate lengthy PET transmission scans and generate complex three dimensional images within few minutes This improves count-rate, spatial resolution and signal-to-noise ratio (SNR) [2,3,13]. As the current technology becomes more widespread, it is likely that there will be a demand for PET designs of better performance and less cost [1,3] This intensifies the interest for investigations on already employed PET systems [5,7,11,14,15,16,17,18,19,20,21,22] and in seeking applicability of new detector concepts. GATE (GEANT4 Application for Tomographic Emission) is more frequently employed in PET due to its flexibility for Tomographic simulations [16]

Methods

Results

Conclusion