Clinical significance of 201Tl lung uptake in heart disease

In order to evaluate the clinical significance of 201Tl lung uptake, 201Tl myocardial scintigraphy was performed in 675 cases with various cardiac diseases. The lung uptake ratio of 201Tl (L/T) was calculated by ratio of the total radioactivity of the unilateral lung to the injected dose of 201Tl in 69 cases. Using both 201Tl scintigraphy and cardiac pool scintigraphy with 99mTc-human serum albumin, images of 201Tl of the intravascular space and extravascular space were obtained in 14 cases. The image of 201Tl of the extravascular space was almost the same as the original 201Tl image as regards the pattern of 201Tl-distribution, and the lung uptake ratio of the former was 95.7 ± 2.8% of that of the latter. The mean values of L/T of the right and left lungs were 1.5 ± 0.9%, 1.2 ± 0.6% in the healthy lungs, 2.8 ± 1.4% and 1.4 ± 0.7% in heart diseases without left heart failure, and 4.4 ± 1.8% and 2.6 ± 1.2% in those with left heart failure, respectively. Increased lung uptake ratio of 201Tl, which was related to post-capillary pulmonary hypertension, prolonged pulmonary circulation time and findings of left heart failure, was observed more frequently in mitral valvular diseases (72.2%) and dilated cardiomyopathies (60.0%). Increased lung uptake of 201Tl was associated with normal or increased pulmonary perfusion in many cases or areas, but with pulmonary hypoperfusion in some cases with post-capillary pulmonary hypertension, in whom both increased lung uptake of 201Tl and pulmonary hypoperfusion were shown in the lower lung fields. In conclusion, increased lung uptake of 201Tl suggests increased pulmonary extravascular space and calculation of the lung uptake ratio of 201Tl seems to be useful for the evaluation of left ventricular dysfunction. (author)