Accurate Monte Carlo modeling and performance assessment of the X-PET ™ subsystem of the FLEX Triumph ™ preclinical PET/CT scanner
Kamali-Asl Alireza R.
Purpose: X PET ™ is a commercial small animal PET scanner incorporating several innovative designs to achieve improved performance. It is employed as a PET subsystem in the FLEX Triumph ™ preclinical PET/CT scanner the first commercial small animal PET/CT scanner worldwide. The authors report on a novel Monte Carlo (MC) model designed for the evaluation of performance parameters of the X PET ™. Methods: The Geant4 Application for Tomographic Emission (GATE) MC code was used as a simulation tool. The authors implemented more accurate modeling of the geometry of detector blocks and associated electronic chains including dead time and time independent parameters compared to previously presented MC models of the X PET ™ scanner. Validation of the MC model involved comparison between simulated and measured performance parameters of the X PET ™ including spatial resolution sensitivity and noise equivalent count rate (NECR). Thereafter various simulations were performed to assess scanner performance parameters according to NEMA NU 4 2008 standards with the aim to present a reliable Monte Carlo platform for small animal PET scanner design optimization. Results: The average differences between simulated and measured results were 11.2 33.3 and 9.1 for spatial resolution sensitivity and NECR respectively. The average system absolute sensitivity was 2.7. Furthermore the peak true count rate peak NECR and scatter fraction were 2050 kcps 1520 kcps and 4.7 respectively for a mouse phantom and 1017 kcps 469 kcps and 18.2 respectively for a rat phantom. Spatial resolution was also measured in ten different positions at two axial locations. The radial tangential and axial FWHM ranged from 1.31 to 1.96 mm 1.17 to 2.11 mm and 1.77 to 2.44 mm respectively as the radial position varied from 0 to 25 mm at the centre of the axial field of view. Conclusions: The developed MC simulation platform provides a reliable tool for performance evaluation of small animal PET scanners and has the potential to be used in other applications such as detector design optimization correction of image degrading factors such as randoms scatter intercrystal scatter parallax error and partial volume effect. © 2011 American Association of Physicists in Medicine.