Improved noninvasive assessment of coronary artery disease by quantitative analysis of regional stress myocardial distribution and washout of thallium-201.

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Abstract
Visual interpretation of stress-redistribution 201Tl scintigrams is subject to observer variability and is suboptimal for evaluation of extent of coronary artery disease (CAD). An objective, computerized technique was developed that quantitatively expresses the relative space-time myocardial distribution of 201Tl. Multiple-view, maximum-count circumferential profiles for stress myocardial distribution of 201Tl and segmental percent washout were analyzed in a pilot group of 31 normal subjects and 20 patients with CAD to develop quantitative criteria for abnormality. Subsequently, quantitative analysis was applied prospectively to a group of 22 normal subjects and 45 CAD patients and compared with visual interpretation of scintigrams for detection and evaluation of CAD. The sensitivity and specificity of the quantitative technique (93 and 91%, respectively) were not significantly different from those of the visual method (91 and 86%). The quantitative analysis significantly (P < 0.05) increased the sensitivity of 201Tl imaging over the visual method in the left anterior descending artery (from 56 to 80%), left circumflex artery (from 34 to 63%) and right coronary artery (from 65 to 94%) without significant loss of specificity. Using quantitative analysis, sensitivity for detection of diseased vessels did not diminish as the number of vessels involved increased, as it did with visual interpretation. In patients with 1-vessel disease, 86% of the lesions were detected by both techniques; in patients with 3-vessel disease, quantitative analysis detected 83% of the lesions while the sensitivity was only 53% for the visual method. Coronary arteries with moderate (50-75%) stenosis 70% were detected quantitatively compared with 35% by the visual method. This quantitative technique for analysis of stress-redistribution 201Tl scintigrams is objective and more sensitive than the visual method, especially in patients with multiple-vessel disease and those with moderate coronary artery stenosis.