A comparison of myocardial thallium-201 image quality after either dipyridamole or exercise stress

Abstract

The left anterior oblique images of 30 patients, who had thallium imaging after intravenous dipyridamole (0.56 mg kg-1 over 4 min.) were compared with those of 30 patients who were imaged after symptom limited. Bruce protocol, treadmill exercise in the same time period. Myocardial and lung-background thallium uptake were compared after stress and on redistribution. The ratio of the best segmental myocardial thallium uptake (M) to that in a fixed lung-background region (B) was taken as an index (M/B) of image quality. Myocardial thallium uptake was significantly higher after dipyridamole than after exercise (P<0.001). Lung-background thallium uptake, however, was also higher (P<0.001) so that the resulting image quality indices (M/B) were similar (P=NS). The redistribution images gave the same results. In both techniques myocardial and lung-background thallium uptake counts dropped significantly from stress to redistribution images, but because they declined at similar rates, the resulting image quality index (M/B) remained unchanged.