title: Estimation of fan beam and parallel beam parameters in a wire mesh design.
abstract: Special collimators used in imaging systems play an important part in obtaining qualified images to improve diagnosis in medicine.
  
  
  METHODS
  The primary aim of this study was to compare resolution between fan beam and parallel beam collimators using Monte Carlo simulation in the shape of cubic holes. Also, parameters such as geometric efficiency, geometric resolution, scatter, penetration, and full width at half maximum were studied to compare their special characteristics.
  
  
  RESULTS
  The simulation results demonstrated that the geometry efficiency of a fan beam collimator increased as the angle of the slant hole increased, and the geometric resolution decreased as the angle of the slant hole increased, at a distinct distance from a monoenergetic source of γ-rays. In contrast, at a distinct angle, geometric resolution increased as the distance between the source and the collimator surface increased. For both collimators, scatter and penetration decreased as the distance increased. These results were in agreement with ADAC company data. Finally, fan beam collimators were found to have better resolution than parallel beam collimators with a cubic hole shape in a wire mesh design.
  
  
  CONCLUSIONS
  Estimation of the fan beam by parallel beam parameters as cubic holes can be suitable in collimator design to improve resolution and efficiency.
authors.affiliation: Department of Physics, Science and Research Branch, Islamic Azad University, Tehran, Iran. abkhorshidi@yahoo.com
authors.forename: Abdollah
authors.initials: A
authors.lastname: Khorshidi
authors.forename: Mansour
authors.initials: M
authors.lastname: Ashoor
authors.forename: S Hamed
authors.initials: SH
authors.lastname: Hosseini
authors.forename: Azimeh
authors.initials: A
authors.lastname: Rajaee
mesh_terms: D003952:Diagnostic Imaging / Q000295:instrumentation*; D004867:Equipment Design; D009010:Monte Carlo Method; D012542:Scattering, Radiation