title: Quantitative myocardial perfusion-SPECT: algorithm-specific influence of reorientation on calculation of summed stress score.
abstract: OBJECTIVE
  Myocardial perfusion SPECT (MPS) with software-assisted determination of summed stress score (SSS) is of established importance for diagnosis/therapy planning in coronary artery disease. Differences in contour finding suggest algorithm-specific influence on quantification if heart axes are chosen incorrectly. Thus, this study quantified the influence of heart-axis tilt on SSS calculation using Quantitative Perfusion SPECT and 4D-MSPECT.
  
  
  METHODS
  Stress MPS of 50 men acquired on a triple-head gamma camera were correctly reoriented by experienced technologists (R0) and then tilted by 5 degrees/10 degrees/15 degrees/20 degrees/30 degrees/45 degrees along both long axes (R5-R45). SPECT images were quantified for SSS using QPS and 4D-MSPECT. SSS values for R0 and R5-R45 were analyzed using correlation analysis. Weighted kappa values (κ) were calculated to measure agreement regarding perfusion abnormality severity (4-step SSS rating: 0-3, 4-8, 9-13, and ≥14).
  
  
  RESULTS
  For QPS SSS correlation, R0 vs. tilted datasets remained very high (R > 0.97) up to 20 degrees, but degraded for higher tilts (R = 0.895/0.780 for 30 degrees/45 degrees). 4D-MSPECT showed comparable SSS correlation only up to 10 degrees (R > 0.95) and strong deterioration thereafter (R = 0.863-0.347 for 15-45 degrees). Deviation in severity class from R0 increased from 6/50 (R5; κ = 0.914) to 25/50 (R45; κ = 0.252) using QPS and from 7/50 (R5; κ = 0.899) to 33/50 (R45; κ = 0.065) using 4D-MSPECT.
  
  
  CONCLUSIONS
  For tilted MPS datasets, considerable differences in SSS calculation emerge using QPS and 4D-MSPECT. QPS showed more stable results than 4D-MSPECT.
authors.affiliation: Department of Nuclear Medicine, Kliniken Maria Hilf, Viersener Str. 450, Mönchengladbach, Germany. Daniela.Knollmann@mariahilf.de
authors.forename: Daniela
authors.initials: D
authors.lastname: Knollmann
authors.forename: Mardjan
authors.initials: M
authors.lastname: Raptis
authors.forename: Philipp T
authors.initials: PT
authors.lastname: Meyer
authors.forename: Oliver H
authors.initials: OH
authors.lastname: Winz
authors.forename: Thomas
authors.initials: T
authors.lastname: Krohn
authors.forename: Wolfgang M
authors.initials: WM
authors.lastname: Schaefer
mesh_terms: D000328:Adult; D000368:Aged; D000465:Algorithms; D006321:Heart / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D055414:Myocardial Perfusion Imaging / Q000379:methods*; D012984:Software; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*