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The method of capillary embolization with radioactive macroaggregated albumin particles (MAA), as commonly used in human lung perfusion scanning, was extended to the evaluation of myocardial perfusion in 17 dogs. The intracoronary artery injection of 0.05 mg MAA, labeled either with 131I (50–60 μCi) or 99mTc (200–400 μCi) permitted myocardial scans to be obtained with a gamma scintillation camera. The images were of good quality and allowed the detection of relatively small perfusion defects. The delivery of an average single bolus of 0.13 mg/100 mg left ventricular weight into the left coronary artery did not cause any observable impairment of cardiac performance in 6 dogs undergoing coronary artery catheterization and angiography. In other animals, sequential intracoronary artery injections of these particles up to an accumulated dose 10 times higher than necessary for the scanning procedure did not lead to a significant impairment of left ventricular function. The radioactive particles appeared to be tolerated by the myocardial tissue and to behave in an essentially identical way as similar particles injected into the pulmonary circulation for lung scanning. From these studies, we conclude that the method of microembolization of radioactive particles (MAA) can be applied to the visualization of myocardial perfusion patterns with an acceptable margin of safety when the number of particles is kept to a minimum and the size and consistency of the particles is carefully controlled.
Schelbert et al. (Mon,) studied this question.