title: Ordered subset expectation maximization and wide beam reconstruction "half-time" gated myocardial perfusion SPECT functional imaging: a comparison to "full-time" filtered backprojection.
abstract: OBJECTIVE
  Compared to filtered back projection (FBP), OSEM with resolution recovery (OSEM-RR) and wide beam reconstruction (WBR)(UltraSPECT Ltd.), which resolve resolution and suppress noise simultaneously during reconstruction, have been shown to maintain/improve myocardial perfusion SPECT quality, even with low count density half-time acquisitions. We postulated that their characteristics would be advantageous for gated SPECT, where each frame is only 1/8th the count density of the summed perfusion images.
  
  
  METHODS
  An 9 mCi rest/32 mCi (333/1184 MBq) stress Tc(99m) sestamibi protocol was used. 15-min FBP, and additional 7-min OSEM-RR and WBR post-stress 8-frame/cardiac cycle SPECT scans were acquired with 90 degrees -angled dual-headed detectors equipped with high resolution collimators in 156 patients. In 82 patients (48F, 34M) (123-252 lbs) with perfusion defects gated image quality was graded visually: 1 (poor)-5 (excellent) Regional LV wall motion (WM) was scored: 0 (normal)-4 (dyskinesis) in a total of 50 vascular territories with defects. Using Myometrix software (GE Healthcare), post-stress EDV, ESV, and EF were calculated for each method. Additionally, for purposes of comparison, the FBP gated tomograms were processed with other commercially available packages, Emory Toolbox and Cedars QGS.
  
  
  RESULTS
  Despite half-time acquisitions, compared to FBP, image quality increased marginally with OSEM-RR (P = .09) but very significantly with WBR (P = 1.9 x 10(-21)). The WM score was greater only for WBR (P = 4.8 x 10(-8)). Although quantitative parameters correlated well with those determined by FBP (all EF r's > 0.85; all volume r's > 0.93), EFs were significantly lower (P = .0001 for OSEM-RR, 3.4 x 10(-14) for WBR), primarily due to a decrease in EDV with OSEM-RR (P = 7.3 x 10(-13)) and an increase in ESV with WBR (P = 9.2 x 10(-5)). However, inter-method differences in these parameters were of similar magnitude to differences encountered among the commercially available software methods.
  
  
  CONCLUSIONS
  Half-time OSEM-RR and particularly WBR improve gated SPECT diagnostic quality compared to full-time FBP due to increased resolution and reduced noise. However, these attributes, which affect endocardial edge detection, result in a systematic offset in EDV, ESV, and EF.
authors.affiliation: Department of Radiology, Division of Nuclear Medicine, St Luke's-Roosevelt Hospital, New York, NY 10025, USA. gdepuey@chpnet.org
authors.forename: E Gordon
authors.initials: EG
authors.lastname: DePuey
authors.forename: Ramesh
authors.initials: R
authors.lastname: Gadiraju
authors.forename: John
authors.initials: J
authors.lastname: Clark
authors.forename: Linda
authors.initials: L
authors.lastname: Thompson
authors.forename: Frank
authors.initials: F
authors.lastname: Anstett
authors.forename: Shuli C
authors.initials: SC
authors.lastname: Shwartz
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D003324:Coronary Artery Disease / Q000150:complications / Q000000981:diagnostic imaging*; D005260:Female; D015637:Gated Blood-Pool Imaging / Q000379:methods*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D016013:Likelihood Functions; D008297:Male; D008875:Middle Aged; D019275:Radiopharmaceuticals; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D017256:Technetium Tc 99m Sestamibi / Q000493:pharmacokinetics; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*; D018487:Ventricular Dysfunction, Left / Q000000981:diagnostic imaging* / Q000209:etiology
chemical_list: D019275:Radiopharmaceuticals; D017256:Technetium Tc 99m Sestamibi