title: Monte Carlo-based assessment of the trade-off between spatial resolution, field-of-view and scattered radiation in the variable resolution X-ray CT scanner.
abstract: OBJECTIVE
  The purpose of this work is to evaluate the impact of optimization of magnification on performance parameters of the variable resolution X-ray (VRX) CT scanner.
  
  
  METHODS
  A realistic model based on an actual VRX CT scanner was implemented in the GATE Monte Carlo simulation platform. To evaluate the influence of system magnification, spatial resolution, field-of-view (FOV) and scatter-to-primary ratio of the scanner were estimated for both fixed and optimum object magnification at each detector rotation angle. Comparison and inference between these performance parameters were performed angle by angle to determine appropriate object position at each opening half angle.
  
  
  RESULTS
  Optimization of magnification resulted in a trade-off between spatial resolution and FOV of the scanner at opening half angles of 90°-12°, where the spatial resolution increased up to 50% and the scatter-to-primary ratio decreased from 4.8% to 3.8% at a detector angle of about 90° for the same FOV and X-ray energy spectrum. The disadvantage of magnification optimization at these angles is the significant reduction of the FOV (up to 50%). Moreover, magnification optimization was definitely beneficial for opening half angles below 12° improving the spatial resolution from 7.5 cy/mm to 20 cy/mm. Meanwhile, the FOV increased by more than 50% at these angles.
  
  
  CONCLUSIONS
  It can be concluded that optimization of magnification is essential for opening half angles below 12°. For opening half angles between 90° and 12°, the VRX CT scanner magnification should be set according to the desired spatial resolution and FOV.
authors: Division of Nuclear Medicine and Molecular Imaging, Geneva University Hospital, CH-1211, Geneva, Switzerland.
authors: Hossein
authors: H
authors: Arabi
authors: Department of Radiation Medicine, Shahid Beheshti University, 1983963113, Tehran, Iran.
authors: Ali Reza
authors: AR
authors: Kamali Asl
authors: Research Centre for Molecular and Cellular Imaging, Tehran University of Medical Sciences, Tehran, Iran; Department of Medical Physics and Biomedical Engineering, Tehran University of Medical Sciences, Tehran, Iran.
authors: Mohammad Reza
authors: MR
authors: Ay
authors: Division of Nuclear Medicine and Molecular Imaging, Geneva University Hospital, CH-1211, Geneva, Switzerland; Geneva Neuroscience Center, Geneva University, CH-1205, Geneva, Switzerland; Department of Nuclear Medicine and Molecular Imaging, University of Groningen, University Medical Center Groningen, 9700, RB Groningen, Netherlands. Electronic address: habib.zaidi@hcuge.ch.
authors: Habib
authors: H
authors: Zaidi
mesh_terms: D009010:Monte Carlo Method; D012399:Rotation; D012542:Scattering, Radiation; D059629:Signal-To-Noise Ratio; D015898:Tomography Scanners, X-Ray Computed
keywords: Monte Carlo; Scattered radiation; Spatial resolution; Variable resolution X-ray CT