Quantitative analysis of seven-pinhole tomographic thallium-201 scintigrams: Improved sensitivity and estimation of the extent of coronary involvement by evaluation of radiotracer uptake and clearance

Recent studies have shown that the sensitivity of conventional thallium-201 scintigraphy can be increased by the quantitative assessment of myocardial radiotracer clearance rates in conjunction with the evaluation of radionuclide uptake. In this study, a similar analysis of tomographic scintigrams was performed to determine the feasibility and value of this approach, particularly in estimating the extent of disease and detecting three vessel coronary involvement.Seventy patients undergoing cardiac catheterization for chest pain were studied by exercise and 3 hour delayed thallium-201 scintigrams using the seven-pinhole tomographic technique. Each study was evaluated by visual inspection of the tomographic sections and quantitative analysis. The latter approach consisted of comparing circumferential profiles of the initial post-exercise radionuclide uptake and the 3 hour clearance rates generated from each of three left ventricular slices with similar profiles representing the lower 95% confidence limits derived from 15 middle-aged volunteers. An abnormality was considered present when a patient's profile fell below these limits for a 30° arc, and was ascribed to disease in a particular artery when it involved that vessel's usual distribution.Among the 61 patients without apparent primary myocardial or valvular disease, the diagnostic sensitivity of thallium scintigraphy was increased from 86% (43 of 50) to 96% (48 of 50) without a change in specificity (both 9 of 11 or 82%). More importantly, the quantitative approach permitted detection of 85% (107 of 126) of significantly obstructed coronary vessels compared with 47% (59 of 126) by visual analysis (p < 0.001), again without sacrificing specificity (85 versus 87%). Quantitative analysis correctly indicated the number of diseased vessels in 69% of these patients, compared with 26% by visual analysis. All involved vessels were identified in 25 of 32 patients with three vessel disease by quantitative analysis, but in only one patient by visual analysis. Both methods of analysis were inaccurate in patients with aortic valve disease and cardiomyopathy.It is concluded that quantitative analysis of the distribution of thallium-201 within the left ventricle and its subsequent clearance increases the sensitivity of tomographic scintigraphy and, in particular, enhances the ability of this technique to determine the extent of coronary artery involvement and identify three vessel disease