title: Reproducibility and accuracy of quantitative myocardial blood flow assessment with (82)Rb PET: comparison with (13)N-ammonia PET.
abstract: (82)Rb cardiac PET allows the assessment of myocardial perfusion with a column generator in clinics that lack a cyclotron. There is evidence that the quantitation of myocardial blood flow (MBF) and coronary flow reserve (CFR) with dynamic (82)Rb PET is feasible. The objectives of this study were to determine the accuracy and reproducibility of MBF estimates from dynamic (82)Rb PET by using our methodology for generalized factor analysis (generalized factor analysis of dynamic sequences [GFADS]) and compartment analysis.
  
  
  METHODS
  Reproducibility was evaluated in 22 subjects undergoing dynamic rest and dipyridamole stress (82)Rb PET studies at a 2-wk interval. The inter- and intraobserver variability of MBF quantitation with dynamic (82)Rb PET was assessed with 4 repeated estimations by each of 4 observers. Accuracy was evaluated in 20 subjects undergoing dynamic rest and dipyridamole stress PET studies with (82)Rb and (13)N-ammonia, respectively. The left ventricular and right ventricular blood pool and left ventricular tissue time-activity curves were estimated by GFADS. MBF was estimated by fitting the blood pool and tissue time-activity curves to a 2-compartment kinetic model for (82)Rb and to a 3-compartment model for (13)N-ammonia. CFR was estimated as the ratio of peak MBF to baseline MBF.
  
  
  RESULTS
  The reproducibility of the MBF estimates in repeated (82)Rb studies was very good at rest and during peak stress (R(2)= 0.935), as was the reproducibility of the CFR estimates (R(2) = 0.841). The slope of the correlation line was very close to one for the estimation of MBF (0.986) and CFR (0.960) in repeated (82)Rb studies. The intraobserver reliability was less than 3% for the estimation of MBF at rest and during peak stress as well as for the estimation of CFR. The interobserver reliabilities were 0.950 at rest and 0.975 at peak stress. The correlation between myocardial flow estimates obtained at rest and those obtained during peak stress in (82)Rb and (13)N-ammonia studies was very good (R(2) = 0.857). Bland-Altman plots comparing CFR estimated with (82)Rb and CFR estimated with (13)N-ammonia revealed an underestimation of CFR with (82)Rb compared with (13)N-ammonia; the underestimation was within +/-1.96 SD.
  
  
  CONCLUSIONS
  MBF quantitation with GFADS and dynamic (82)Rb PET demonstrated excellent reproducibility as well as intra- and interobserver reliability. The accuracy of the absolute quantitation of MBF with factor and compartment analyses and dynamic (82)Rb PET was very good, compared with that achieved with (13)N-ammonia, for MBF of up to 2.5 mL/g/min.
authors.affiliation: Division of Nuclear Medicine and Molecular Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA. elfakhri@pet.mgh.harvard.edu
authors.forename: Georges
authors.initials: G
authors.lastname: El Fakhri
authors.forename: Arash
authors.initials: A
authors.lastname: Kardan
authors.forename: Arkadiusz
authors.initials: A
authors.lastname: Sitek
authors.forename: Sharmila
authors.initials: S
authors.lastname: Dorbala
authors.forename: Nathalie
authors.initials: N
authors.lastname: Abi-Hatem
authors.forename: Youmna
authors.initials: Y
authors.lastname: Lahoud
authors.forename: Alan
authors.initials: A
authors.lastname: Fischman
authors.forename: Martha
authors.initials: M
authors.lastname: Coughlan
authors.forename: Tsunehiro
authors.initials: T
authors.lastname: Yasuda
authors.forename: Marcelo F
authors.initials: MF
authors.lastname: Di Carli
mesh_terms: D000641:Ammonia; D001783:Blood Flow Velocity; D002247:Carbon Isotopes; D003324:Coronary Artery Disease / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D003326:Coronary Circulation; D005260:Female; D006801:Humans; D008875:Middle Aged; D055420:Perfusion Imaging / Q000379:methods*; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals; D015203:Reproducibility of Results; D012414:Rubidium Radioisotopes; D012680:Sensitivity and Specificity
chemical_list: D002247:Carbon Isotopes; D019275:Radiopharmaceuticals; D012414:Rubidium Radioisotopes; D000641:Ammonia