Abstract
We have developed a new computer method designed to quantitate regional myocardial thallium-201 (Tl-201) initial distribution, redistribution, and clearance rate. In addition, this computer method permits the generation of functional images to compare two thallium images in the same projection to one another. These functional images can be used to demonstrate the extent of redistribution and the extent of change in regional perfusion before and after an intervention. To validate and apply this new computer technique, exercise Tl-201 myocardial images obtained before and 1 week after percutaneous transluminal coronary angioplasty (PTCA) were analyzed in 20 patients with isolated left anterior descending coronary artery disease. Significant improvement in initial Tl-201 activity, expressed as a percentage of maximal myocardial activity, was present in the anterior (71.9 ± 12.0 to 84.1 ± 11.5%, p < 0.001) and septal (66.7 ± 15.4 to 75.2 ± 11.0%, p < 0.05) regions of the left ventricle 1 week after PTCA. This increase in relative anterior wall Tl-201 uptake was associated with a significant reduction in the amount of TI-201 redistribution between initial and delayed postexercise images (14.7 ± 14.6 to 3.0 ± 13.2%, p < 0.05) as well as an increase in Tl-201 clearance rate (t 1 2 from 8.8 ± 4.4 to 4.3 ± 2.5 hours, p < 0.001). Quantitative analysis of Tl-201 scans demonstrated improvement in 14 of 20 patients following PTCA. Computer-derived functional difference images depicted diminution in the extent of ischemia as manifested by redistribution of Tl-201. Abnormal lung uptake of Tl-201 immediately after exercise was present in 17 patients before and in only four patients after PTCA. We conclude that this new computer method for quantitative analysis of Tl-201 images objectively and graphically documents improvement in the severity and extent of regional myocardial perfusion defect following interventions such as PTCA.
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