title: Incremental diagnostic benefit of resolution recovery software in patients with equivocal myocardial perfusion single-photon emission computed tomography (SPECT).
abstract: BACKGROUND
  Though myocardial perfusion imaging (MPI) with single-photon emission computed tomography (SPECT) is an established diagnostic method, equivocal studies are commonly encountered. New software has been introduced that incorporates resolution recovery (RR) and noise regulation into the reconstruction algorithm and has been used to facilitate "half-dose" and "half-time" studies. Its utility with "full-time, full-dose" acquisition has not been well studied.
  
  
  OBJECTIVE
  We sought to understand the potential benefit of incorporating RR software in equivocal SPECT studies.
  
  
  METHODS
  Patients with full-time, full-dose SPECT MPI were reviewed and those with equivocal results, who subsequently underwent cardiac Rb-82 positron emission tomography (PET) scan were identified. Image reconstruction was performed with iterative reconstruction (IR), attenuation correction (IR + AC), and RR software (IR + AC + RR). Images were anonymized and read blindly by consensus of two experienced readers. All images were qualitatively assessed and semi-quantitatively graded using summed stress and summed rest scores.
  
  
  RESULTS
  45 patients were included (28 males, age = 59.6 ± 9.9 years) and the diagnostic accuracy of each of the reconstruction algorithms (IR, IR + AC, IR + AC + RR) was compared to Rb-82 PET. Agreement of clinical diagnosis of each SPECT reconstruction with Rb-PET showed incremental improvement. The agreement with PET for IR + AC + RR (κ = 0.66, CI 0.454-0.875) is significantly better than for IR (κ = 0.22, CI 0.0-0.450, P = .005) and for IR + AC (κ = 0.32, CI 0.077-0.563, P = .03). Also, IR + AC + RR improved the clinical diagnosis in 14 cases and with overall improvement of reclassification proportion of 23.5% compared to IR (P = .01). Using PET as a reference standard, ROC curves were created for IR + AC + RR, IR + AC, and IR which showed incremental value of the area under the curve of IR + AC + RR (AUC: 0.87; CI 0.76-0.98) over IR + AC (AUC: 0.75; CI 0.61-0.89, P = .078), and over IR (AUC 0.68; CI 0.52-0.84, P = .025).
  
  
  CONCLUSIONS
  The addition of RR may help in the diagnosis of patients with equivocal SPECT MPI without the need for additional testing. Further prospective studies are needed to define the role of this new software.
authors.affiliation: Department of Medicine (Cardiology), University of Ottawa Heart Institute, Ottawa, ON, Canada.
authors.forename: Mohammed A
authors.initials: MA
authors.lastname: Qutub
authors.forename: Taylor
authors.initials: T
authors.lastname: Dowsley
authors.forename: Iftikhar
authors.initials: I
authors.lastname: Ali
authors.forename: R Glenn
authors.initials: RG
authors.lastname: Wells
authors.forename: Li
authors.initials: L
authors.lastname: Chen
authors.forename: Terrence D
authors.initials: TD
authors.lastname: Ruddy
authors.forename: Benjamin J W
authors.initials: BJ
authors.lastname: Chow
mesh_terms: D000368:Aged; D000465:Algorithms; D003324:Coronary Artery Disease / Q000000981:diagnostic imaging; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008297:Male; D008875:Middle Aged; D055414:Myocardial Perfusion Imaging / Q000379:methods*; D049268:Positron-Emission Tomography / Q000379:methods; D012372:ROC Curve; D019275:Radiopharmaceuticals; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012414:Rubidium Radioisotopes / Q000737:chemistry; D012680:Sensitivity and Specificity; D012984:Software; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*
chemical_list: D019275:Radiopharmaceuticals; D012414:Rubidium Radioisotopes