Limitations of thallium-201 myocardial perfusion scintigrams.

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Abstract
The reliability of myocardial perfusion scintigrams was 201Tl for detecting areas of hypoperfusion was assessed in 16 closed-chest dogs. Variable areas of ischemia were produced either by occluding or stenosing the left anterior descending coronary artery. Cardiac scintigrams taken in 4 projections were compared with regional myocardial perfusion maps. Segmental concentrations and segmental perfusions were quantitated by counting the emissions from 201Tl and the microspheres in each of 96 segments of the left ventricle. Studies with a phantom were performed. The emissions from 201Tl and from microspheres correlated well in ischemic segments (r = 0.93 .+-. SE 0.02). Seven of 12 ischemic hearts had definitely abnormal scintigrams and in each of these the hypoperfused zone was greater than 4.9 g and perfusion was decreased by more than 45%. In the phantom, abnormal scintigrams could be detected in the presence of lesser deficits than in the dogs. The limitation of the Tl perfusion scintigrams is the inconsistent detection of small perfusion deficits.