Quantitative split dose thallium-201 imaging with exercise: a technique for obtaining rest and exercise perfusion images in one setting and markedly reducing the study time

In the current study, a technique for performing serial thallium imaging after two separate tracer injections was applied to exercise thallium imaging, thus allowing the acquisition of rest and exercise images within 1 hour. Twenty-four patients with and 10 patients without significant coronary artery disease were studied. One mCi of thallium-201 was injected intravenously and imaging was performed at rest in three projections. The patient was then stressed and an additional 1 mCi of thallium injected during exercise. Images in the same three projections were collected. After computer realignment, the rest image was subtracted from the exercise image to produce an image representing perfusion during exercise. All 24 patients with coronary artery disease had a positive study, while 9 of 10 without disease had a negative study. The images were then interpreted using a computer method designed to quantitate regional myocardial thallium distribution and redistribution. With quantitative interpretation, 23 of 24 patients with coronary disease had a positive study, while only 1 without disease had a positive study. With qualitative interpretation, 39 (89%) of 44 stenosed coronary arteries demonstrated thallium defects in corresponding myocardial segments, while 54 (93%) of 58 nonstenosed coronary arteries did not. With quantitative interpretation, 38 (86%) of 44 stenosed coronary arteries demonstrated thallium defects in corresponding myocardial segments, while 53 (91%) of 58 nonstenosed coronary arteries did not. A split dose thallium imaging technique that allows imaging before and immediately after exercise, thus markedly reducing the study time, has been validated.