title: Comparison of multi-ray and point-spread function based resolution recovery methods in pinhole SPECT reconstruction.
abstract: OBJECTIVE
  Statistical reconstruction methods allow resolution recovery in tomographic reconstruction. Even though resolution recovery has the potential to improve overall image quality, pinhole SPECT images are still often reconstructed using simplified models of the acquisition geometry in order to reduce reconstruction time. This paper investigates the benefits of two resolution recovery methods, multi-ray and point-spread function based, in pinhole SPECT by comparing them to uncorrected reconstruction.
  
  
  METHODS
  Resolution recovery was incorporated into ordered subsets expectation maximization reconstruction algorithm. The first of the correction methods used a simple but very fast multiple projection ray approach, whereas the second, much slower, method modelled the acquisition geometry more accurately using the analytical point-spread function of the pinhole collimator. Line source, Jaszczak and contrast phantom studies were performed and used for comparison.
  
  
  RESULTS
  Resolution recovery improved resolution, contrast and visual quality of the images when compared to reconstructions without it. The method based on the point-spread function performed slightly better, but was almost 50 times slower than the much simpler multi-ray approach.
  
  
  CONCLUSIONS
  The multiple projection ray approach is a promising method for very fast and easy resolution recovery in pinhole SPECT. It has a profound effect on image quality and can markedly improve the resolution-sensitivity trade-off.
authors.affiliation: National Cardiovascular Center Research Institute, Suita City, Osaka, Japan. antti@ri.ncvc.go.jp
authors.forename: Antti
authors.initials: A
authors.lastname: Sohlberg
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Watabe
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Zeniya
authors.forename: Hidehiro
authors.initials: H
authors.lastname: Iida
mesh_terms: D000465:Algorithms; D000818:Animals; D003287:Contrast Media / Q000494:pharmacology; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional; D023421:Models, Animal; D015233:Models, Statistical; D008962:Models, Theoretical; D019047:Phantoms, Imaging; D012680:Sensitivity and Specificity; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*
chemical_list: D003287:Contrast Media