title: Comparing filtered backprojection and ordered-subsets expectation maximization for small-lesion detection and localization in 67Ga SPECT.
abstract: Iterative reconstruction of SPECT images has recently become clinically available as an alternative to filtered backprojection (FBP). However, there is conflicting evidence on whether iterative reconstruction, such as with the ordered-subsets expectation maximization (OSEM) algorithm, improves diagnostic performance over FBP. The study objective was to determine if the detection and localization of small lesions in simulated thoracic gallium SPECT images are better with OSEM reconstruction than with FBP, both with and without attenuation correction (AC).
  
  
  METHODS
  Images were simulated using an analytic projector acting on the mathematic cardiac torso computer phantom. Perfect scatter rejection was assumed. Lesion detection accuracy was assessed using localization receiver operating characteristic methodology. The images were read by 5 nuclear medicine physicians. For each reconstruction strategy and for each observer, data were collected in 2 viewing sessions of 100 images. Two-way ANOVA and, when indicated, the Scheffé multiple comparisons test were applied to check for significant differences.
  
  
  RESULTS
  Little difference in the accuracy of detection or localization was seen between FBP with and without AC. OSEM with AC extended the contrast range for accurate lesion detection and localization over that of the other methods investigated. Without AC, no significant difference between OSEM and FBP reconstruction was detected.
  
  
  CONCLUSIONS
  OSEM with AC may improve the detection and localization of thoracic gallium-labeled lesions over FBP reconstruction.
authors.affiliation: Division of Nuclear Medicine, University of Massachusetts Medical Center, Worcester 01655, USA.
authors.forename: R G
authors.initials: RG
authors.lastname: Wells
authors.forename: M A
authors.initials: MA
authors.lastname: King
authors.forename: P H
authors.initials: PH
authors.lastname: Simkin
authors.forename: P F
authors.initials: PF
authors.lastname: Judy
authors.forename: A B
authors.initials: AB
authors.lastname: Brill
authors.forename: H C
authors.initials: HC
authors.lastname: Gifford
authors.forename: R
authors.initials: R
authors.lastname: Licho
authors.forename: P H
authors.initials: PH
authors.lastname: Pretorius
authors.forename: P B
authors.initials: PB
authors.lastname: Schneider
authors.forename: D W
authors.initials: DW
authors.lastname: Seldin
mesh_terms: D000465:Algorithms; D019788:Fluorodeoxyglucose F18 / Q000493:pharmacokinetics; D005710:Gallium Radioisotopes / Q000493:pharmacokinetics; D006321:Heart / Q000000981:diagnostic imaging*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D009369:Neoplasms / Q000000981:diagnostic imaging*; D019047:Phantoms, Imaging; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D014018:Tissue Distribution; D015899:Tomography, Emission-Computed, Single-Photon
chemical_list: D005710:Gallium Radioisotopes; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18