AJP - Heart and Circulatory Physiology, Vol 242, Issue 1 62-H67, Copyright © 1982 by American Physiological Society
Kinetics of positron emitters in vivo characterized with a beta probe
R. A. Lerch, H. D. Ambos, S. R. Bergmann, B. E. Sobel and M. M. Ter-Pogossian
To facilitate characterization of regional myocardial kinetics of
positron-emitting tracers in vivo without distortion by activity outside
the region of interest, a probe was developed and evaluated for monitoring
radioactivity by detection of positrons themselves. These particles (beta
particles) have a maximal range in tissue of only few millimeters rather
than the larger range of gamma photons emitted as a result of positron
annihiliation. Regional myocardial time-activity curves were determined in
open-chest dogs after intracoronary injection of 0.5-1.5 mCi [15O]H2O, a
tracer used for measurement of myocardial blood flow, or 6.0-8.0 mCi
[11C]palmitate, a tracer used for noninvasive assessment of myocardial
metabolism. Time-activity curves after [11C]palmitate injection clearly
delineated specific components of myocardial tracer clearance previously
identified in vitro in isolated perfused hearts. Myocardial washout of
[15O]H2O was monoexponential for more than 2 min without distortion induced
by recirculating tracer in ventricular blood. Reproducibility of measured
tracer clearance rates during monoexponential clearance was high based on
duplicate determinations for both tracers. The beta-detector probe
developed overcomes several intrinsic limitations of gamma-probe systems or
well counting of serial myocardial biopsies for studies of
positron-emitting tracers in vivo and should facilitate assessment of
factors of influencing tracer kinetics in vivo relevant to
positron-emission tomography.
