title: Noninvasive quantification of myocardial blood flow in humans. A direct comparison of the [13N]ammonia and the [15O]water techniques.
abstract: BACKGROUND
  [13N]Ammonia has been validated in dog studies as a myocardial blood flow tracer. Estimates of myocardial blood flow by [13N]ammonia were highly linearly correlated to those by the microsphere and blood sample techniques. However, estimates of myocardial blood flow with [13N]ammonia in humans have not yet been compared with those by an independent technique. This study therefore tested the hypothesis that the [13N]ammonia positron emission tomographic technique in humans gives estimates of myocardial blood flow comparable to those obtained with the [15O]water technique.
  
  
  RESULTS
  A total of 30 pairs of positron emission tomographic flow measurements were performed in 30 healthy volunteers; 15 volunteers were studied at rest and 15 during adenosine-induced hypermia. Estimates of average and of regional myocardial blood flow by the [13N]ammonia and the [15O]water approaches correlated well (y = 0.02 + 1.02x, r = .99, P < .001 SEE = 0.023 for average and y = 0.06 + 1.00x, r = .97, P < .001, SEE = 0.025 for regional values) over a flow range of 0.45 to 4.74 mL.min-1.g-1. At rest, mean myocardial blood flow was 0.64 +/- 0.09 mL.min-1.g-1 for [13N]ammonia and 0.66 +/- 0.12 mL.min-1.g-1 for [15O]water (P = NS). For adenosine-induced hyperemia, mean myocardial blood flow was 2.63 +/- 0.75 mL.min-1.g-1 for [13N]ammonia and 2.73 +/- 0.77 mL.min-1.g-1 for [15O]water (P = NS). The coefficient of variation as an index of the observed heterogeneity of myocardial blood flow averaged, for [13N]ammonia, 9 +/- 4% at rest and 12 +/- 7% during stress and, for [15O]water, 14 +/- 11% at rest and 16 +/- 9% during stress. The coefficients of variation for [15O]water were significantly higher than those for [13N]ammonia (P = .004 at rest and P = .03 during stress).
  
  
  CONCLUSIONS
  The two approaches yield comparable estimates of myocardial blood flow in humans, which supports the validity of the [13N]ammonia method in human myocardium previously shown only in animals. However, the [15O]water approach reveals a greater heterogeneity (presumably method-related), which might limit the accuracy of sectorial myocardial blood flow estimates in humans.
authors.affiliation: Department of Molecular and Medical Pharmacology, UCLA School of Medicine 90095-1735, USA.
authors.forename: E U
authors.initials: EU
authors.lastname: Nitzsche
authors.forename: Y
authors.initials: Y
authors.lastname: Choi
authors.forename: J
authors.initials: J
authors.lastname: Czernin
authors.forename: C K
authors.initials: CK
authors.lastname: Hoh
authors.forename: S C
authors.initials: SC
authors.lastname: Huang
authors.forename: H R
authors.initials: HR
authors.lastname: Schelbert
mesh_terms: D000241:Adenosine / Q000494:pharmacology; D000328:Adult; D000641:Ammonia; D000818:Animals; D003326:Coronary Circulation / Q000187:drug effects; D003331:Coronary Vessels / Q000000981:diagnostic imaging*; D004285:Dogs; D005260:Female; D006207:Half-Life; D006321:Heart / Q000000981:diagnostic imaging; D006801:Humans; D006940:Hyperemia / Q000139:chemically induced / Q000503:physiopathology; D007091:Image Processing, Computer-Assisted; D007554:Isotopes; D008297:Male; D009587:Nitrogen Isotopes; D010100:Oxygen / Q000493:pharmacokinetics; D012146:Rest; D013045:Species Specificity; D013312:Stress, Physiological / Q000503:physiopathology; D014055:Tomography, Emission-Computed; D014665:Vasodilator Agents / Q000494:pharmacology; D014867:Water
chemical_list: D007554:Isotopes; D009587:Nitrogen Isotopes; D014665:Vasodilator Agents; D014867:Water; D000641:Ammonia; D000241:Adenosine; D010100:Oxygen