title: Comparison of myocardial perfusion 82Rb PET performed with CT- and transmission CT-based attenuation correction.
abstract: CT-based attenuation correction (AC) for myocardial perfusion PET studies is challenging because of respiratory motion. Our study aimed to compare the transmission CT (TCT)-based and CT-based AC for myocardial perfusion PET/CT images with a direct semiquantitative approach comparing differences in segmental count distribution.
  
  
  METHODS
  Stress and rest (82)Rb PET scans from 54 consecutive patients acquired on a PET/CT scanner with dual CT-based and TCT-based AC were considered. TCT- and CT-based AC images were automatically registered to each other, and direct voxel-based and American Heart Association segment-based estimation of positive and negative changes between these scans was performed. Additionally, visual quality control (QC) of CT map alignment with PET emission data was performed by 2 expert observers, and studies with significant (>/=5 mm) misalignment were reprocessed with corrected CT alignment.
  
  
  RESULTS
  We used the 17-segment American Heart Association model for TCT-to-CT regional change analysis in all patients and found that 4 segments on rest and 4 segments on stress scans differed more than 3% between CT- and TCT-corrected images for studies without significant misalignments (<5 mm); only 1 differed by more than 5%. In cases with significant misalignment of greater than or equal to 3% TCT-CT AC, changes were observed on 14 rest and 10 stress segments; after alignment, these differences were still seen in 13 rest segments and 11 stress segments. Visual QC revealed that 46% of rest and 54% of stress PET scans were misaligned by greater than or equal to 5 mm with the CT maps acquired during normal breathing. The range of the reported PET/CT misalignment was 0-15 mm in x, 0-16 mm in y, and 0-20 mm in z directions. The overall agreement in visual QC of PET/CT alignment between the observers was 72.2%
  
  
  CONCLUSIONS
  There are significant differences between TCT and CT AC applied to cardiac PET/CT studies, which remain after alignment of CT maps to emission data.
authors.affiliation: Department of Imaging and Medicine, Cedars-Sinai Medical Center, Los Angeles, California, USA. Piotr.Slomka@cshs.org
authors.forename: Piotr J
authors.initials: PJ
authors.lastname: Slomka
authors.forename: Ludovic
authors.initials: L
authors.lastname: Le Meunier
authors.forename: Sean W
authors.initials: SW
authors.lastname: Hayes
authors.forename: Wanda
authors.initials: W
authors.lastname: Acampa
authors.forename: Muneo
authors.initials: M
authors.lastname: Oba
authors.forename: Gillian G
authors.initials: GG
authors.lastname: Haemer
authors.forename: Daniel S
authors.initials: DS
authors.lastname: Berman
authors.forename: Guido
authors.initials: G
authors.lastname: Germano
mesh_terms: D000368:Aged; D000465:Algorithms; D016477:Artifacts; D003324:Coronary Artery Disease / Q000150:complications / Q000175:diagnosis*; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals; D015203:Reproducibility of Results; D012414:Rubidium Radioisotopes; D012680:Sensitivity and Specificity; D013382:Subtraction Technique; D014057:Tomography, X-Ray Computed / Q000379:methods*; D018487:Ventricular Dysfunction, Left / Q000150:complications / Q000175:diagnosis*
chemical_list: D019275:Radiopharmaceuticals; D012414:Rubidium Radioisotopes