title: Design and performance evaluation of a new high energy parallel hole collimator for radioiodine planar imaging by gamma cameras: Monte Carlo simulation study.
abstract: OBJECTIVE
  In addition to the trade-off between resolution and sensitivity which is a common problem among all types of parallel hole collimators (PCs), obtained images by high energy PCs (HEPCs) suffer from hole-pattern artifact (HPA) due to further septa thickness. In this study, a new design on the collimator has been proposed to improve the trade-off between resolution and sensitivity and to eliminate the HPA.
  
  
  METHODS
  A novel PC, namely high energy extended PC (HEEPC), is proposed and is compared to HEPCs. In the new PC, trapezoidal denticles were added upon the septa in the detector side. The performance of the HEEPCs were evaluated and compared to that of HEPCs using a Monte Carlo-N-particle version5 (MCNP5) simulation. The point spread functions (PSF) of HEPCs and HEEPCs were obtained as well as the various parameters such as resolution, sensitivity, scattering, and penetration ratios, and the HPA of the collimators was assessed. Furthermore, a Picker phantom study was performed to examine the effects of the collimators on the quality of planar images.
  
  
  RESULTS
  It was found that the HEEPCDwith an identical resolution to that of HEPCCincreased sensitivity by 34.7%, and it improved the trade-off between resolution and sensitivity as well as to eliminate the HPA. In the picker phantom study, the HEEPCDindicated the hot and cold lesions with the higher contrast, lower noise, and higher contrast to noise ratio (CNR).
  
  
  CONCLUSIONS
  Since the HEEPCs modify the shaping of PSFs, they are able to improve the trade-off between the resolution and sensitivity; consequently, planar images can be achieved with higher contrast resolutions. Furthermore, because the HEEPCSreduce the HPA and produce images with a higher CNR, compared to HEPCs, the obtained images by HEEPCs have a higher quality, which can help physicians to provide better diagnosis.
authors.affiliation: Nuclear Science and Technology Research Institute, AEOI, P.O. Box: 113653486, Tehran, Iran. vmoslemi@gmail.com.
authors.forename: Vahid
authors.initials: V
authors.lastname: Moslemi
authors.affiliation: Nuclear Science and Technology Research Institute, AEOI, P.O. Box: 113653486, Tehran, Iran.
authors.forename: Mansour
authors.initials: M
authors.lastname: Ashoor
mesh_terms: D016477:Artifacts; D003198:Computer Simulation; D004867:Equipment Design; D015902:Gamma Cameras; D009010:Monte Carlo Method; D019047:Phantoms, Imaging; D017785:Photons; D011877:Radionuclide Imaging / Q000295:instrumentation*; D012542:Scattering, Radiation
keywords: High energy extended parallel hole collimator; Hole-pattern artifact; Resolution; Sensitivity