title: An improved model for the measurement of myocardial perfusion in human beings using N-13 ammonia.
abstract: BACKGROUND
  Oxygen 15 water and nitrogen 13 ammonia are widely used for the quantitative measurement of myocardial perfusion with positron emission tomography. However, blood flow obtained with N-13 ammonia by use of the conventional 2-compartment model frequently underestimates flow by 30% to 50% compared with O-15 water. We hypothesized that this discrepancy is a result of the model configuration of N-13 ammonia and investigated changes to the mathematical model to determine whether more accurate measurements of perfusion could be obtained.
  
  
  RESULTS
  Twelve healthy volunteers were sequentially studied with O-15 water and N-13 ammonia at rest and during maximal coronary vasodilation with adenosine. Perfusion measurements obtained with the conventional and modified models were compared with values obtained with O-15 water. The conventional N-13 ammonia model underestimated flow by 37% +/- 16% at rest and by 20% +/- 24% with stress when compared with flows obtained with O-15 water. The modified model yielded flow values closer to the line of identity than the conventional model (y = 1.07x + 0.04 vs y = 0.69x + 0.08; respectively; P < .01).
  
  
  CONCLUSIONS
  Model changes made N-13 ammonia myocardial blood flow estimates more comparable to those obtained with O-15 and may allow for better comparison of flows obtained with these two tracers in the future. Further efforts are warranted to evaluate the accuracy of flow models in human subjects.
authors.affiliation: Department of Medicine, Division of Cardiology, College of Physicians & Surgeons of Columbia University, New York, NY 10032, USA. kt2hickey@aol.com
authors.forename: Kathleen T
authors.initials: KT
authors.lastname: Hickey
authors.forename: Robert R
authors.initials: RR
authors.lastname: Sciacca
authors.forename: Ru-Ling
authors.initials: RL
authors.lastname: Chou
authors.forename: Oswaldo
authors.initials: O
authors.lastname: Rodriguez
authors.forename: Sabahat
authors.initials: S
authors.lastname: Bokhari
authors.forename: Steven R
authors.initials: SR
authors.lastname: Bergmann
mesh_terms: D000328:Adult; D000465:Algorithms; D000641:Ammonia; D001783:Blood Flow Velocity / Q000502:physiology*; D003198:Computer Simulation; D003326:Coronary Circulation / Q000502:physiology*; D003331:Coronary Vessels / Q000000981:diagnostic imaging*; D005080:Exercise Test; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008297:Male; D008955:Models, Cardiovascular; D009590:Nitrogen Radioisotopes; D010104:Oxygen Radioisotopes; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014867:Water
chemical_list: D009590:Nitrogen Radioisotopes; D010104:Oxygen Radioisotopes; D019275:Radiopharmaceuticals; D014867:Water; D000641:Ammonia