Measurement of regional myocardial blood flow with N-13 ammonia and positron-emission tomography in intact dogs

Abstract

N-13 ammonia mimics certain properties of microspheres. It rapidly clears from blood into myocardium where it becomes fixed in proportion to myocardial blood flow. Used with positron emission tomography as a means for quantifying in vivo myocardial indicator concentrations, N-13 ammonia may be useful for noninvasive determination of myocardial blood flow with the arterial reference sampling technique. This possibility was examined in 27 experiments in 10 chronically instrumented dogs at control, high and low blood flows. Myocardial blood flow was calculated in vivo from the myocardial N-13 tissue activity concentrations derived from serial cross-sectional images of the heart, the 2 minute arterial input function and the withdrawal rate of arterial blood. These calculations were compared with blood flow determined by the standard microsphere technique. Blood flow determined in vivo with N-13 ammonia and positron emission tomography correlated with microsphere blood flow by y = -36.2 + 1.53x -0.0027x2 (r = 0.94 with a standard error of the estimate of 16 ml/min per 100 g). For flows from 44 to 200 ml/min per 100 g, the relation between in vivo and in vitro measured myocardial blood flow was nearly linear but reached a plateau at flows higher than 200 ml/min per 100 g. These results indicate that in dogs, blood flow in the physiologic range can be quantified in vivo with N-13 ammonia and positron emission tomography.

Relation between geometric dimensions of coronary artery stenoses and myocardial perfusion reserve in man.

“…Positron-emitting radiotracers have decay characteristics that permit quantification of regional myocardial activity in vivo (12). Regional myocardial perfusion can be estimated using N-13 ammonia or Rb-82 by direct measurement of tracer uptake (13)(14)(15)(16). Schelbert et al have previously demonstrated that uptake ofN-13 ammonia is linearly related to perfusion determined by radioactive microspheres from 0.5 to 3.0 times normal resting flow (13).…”

Flow-Based Functional Assessment of Coronary Artery Disease by Myocardial Perfusion Positron Emission Tomography in the Era of Fractional Flow Reserve

“…PET-measured MBF has shown excellent agreement with that measured by microsphere injection and invasive activity measurement (18)(19)(20)(21)(22). MBF can be measured by compartment modeling and estimation of rate constant values among tissue compartments ( Fig.…”

Changes in Myocardial Perfusion Reserve after PTCA: Noninvasive Assessment with Positron Tomography

“…The criteria for successful PTCA according to the NIH registry for coronary angioplasty has been a >20% increase in luminal diameter following the pro cedure (72). However, visual determination of percent narrowing is highly variable and coronary lesions are often eccentric (7,2). Recent studies have suggested that percent diameter narrowing may not accurately reflect coronary flow reserve since flow is affected by other dimensions such as length and absolute radius (1-3).…”

“…Positron emission tracers have decay characteristics that permit measurement of the uptake of tracers such as rubidium-82 (82Rb)and nitrogen-13 (I3N) ammonia to quantitatively assess regional perfusion (4)(5)(6)(7). Accordingly, the purpose of the current study is to determine the relation between changes in relative myo cardial perfusion reserve by positron emission tomog raphy, and coronary anatomy after percutaneous trans luminal coronary angioplasty.…”