The radioactive microsphere method for the assessment of regional myocardial blood flow after coronary artery occlusion

In this study, we have tried to determine the magnitude of the inaccuracy of the radioactive microsphere method — due to variations in the diameter distribution of the spheres — for measuring regional myocardial blood flow after coronary artery occlusion. In 5 mongrel dogs, three types of 15 μm microsperes, labelled with125I,141Ce or85Sr, were injected simultaneously after the descending branch of the left coronary artery had been ligated. Myocardial samples were taken from the left ventricle and divided into four groups according to the number of spheres per sample. The radioactivity of the various isotopes per gram tissue was expressed as percentage of their activity per milliliter of the reference sample. The diameter distribution of microspheres, labelled with each of the isotopes, was determined light-microscopically in suspensions belonging to three different batches.