Planar stress thallium-201 scintigraphy. First experiences with a new circumferential programme.

A new computer programme was used in 22 patients referred for suspected ischaemic heart disease (IHD) or for assessment of the size of a suspected ischaemic or infarcted area. An interpolative method was used to construct the net myocardial images. Initial imaging in three projections was started at five minutes after thallium-201 injection and delayed imaging three hours after the injection. The data were presented as analog images, circumferential profile curves, and washout curves. The calculated delayed/initial count ratio is an important measure of redistribution. In the 12 patients referred to detect clinically or electrocardiographically suspected IHD, the diagnosis IHD was made by the cardiologists on the basis of current routine criteria and the thallium test. The technique was found useful in localising and assessing the size of a suspected ischaemic or infarcted area in nine of 10 patients. Our experience with the new programme confirms the experience of others that a combination of analog images and computer processed data gives much more precise information than the visual inspection of the analog pictures alone.