Evaluation of Nonradioactive, Colored Microspheres for Measurement of Regional Myocardial Blood

Measurement of regional myocardial blood flow (RMBF) is crucial in experimental studies of myocardial ischemia and reperfusion in dogs. The standard measurement technique uses radioactive microspheres; however, not all institutions are able to dispose of radioactive waste and therefore cannot make use of this method. We tested a new, nonradioactive microsphere, labeled with colors instead of nuclides. Simultaneous blood flow measurements with two nuclide-labeled and two colored microspheres were performed after coronary occlusion in dogs. Both techniques show a within-method correlation of r>0.98. Duplicate variability for paired RMBF values in 80 samples was 8.7 ± 0.1 % when computed with radioactive microspheres and 13.2±1.8 % when computed with colored microspheres. There was a good correlation in the measurement ofRMBF between the radioactive- and colored-microsphere methods (r = 0.98). The best-fitting linear regression line was expressed by the formula: Colored-microsphere RMBF=1.11(radioactive-microsphere RMBF)-0.02. When measured by colored micro-spheres, RMBF was approximately 8 % higher than when computed with radioactive micro-spheres for blood flow values of 0-2 ml/min/g. When blood flow was increased pharmacologi-cally to levels of 2-7.5 ml/min/g, colored microspheres yielded blood flow values 39 % highe