Dual isotope myocardial perfusion SPECT in the detection of coronary artery disease: comparison of separate and simultaneous acquisition protocols.

A time-saving dual isotope acquisition protocol was carried out for the simultaneous assessment of stress and rest myocardial perfusion, and the diagnostic value of the technique was evaluated using coronary angiography results as a reference. Fifty-five patients undergoing coronary angiography before surgery were included in the study. Stress tests were applied, either with a treadmill (25 patients) or dobutamine infusion (30 patients in 5-40 micrograms/kg/min doses). All patients received 3 mCi of thallium-201 at rest. Stress tests were applied 30 minutes later, and at peak stress 7 mCi of 99mTc-MIBI was administered. A dual isotope SPECT study was carried out one hour after the administration of 99mTc-MIBI. Tracer doses were optimised with phantom studies, and the down-scatter of each radioisotope on the other data was investigated. In 30 patients, 10 minutes after the 201Tl injection a separate rest 201Tl acquisition was also performed, to compare the data with dual acquisition. 201Tl rest imaging SPECT data was evaluated by segmental analysis according to coronary artery regions. In 55% of the segments stress defects were observed. Similar results were obtained for the detection of defect reversibility; i.e. stress MIBI/rest 201Tl (75%) and stress MIBI/simultaneous 201Tl (78%). The overall sensitivity and specificity of simultaneous dual isotope SPECT with respect to coronary angiography results were 88% and 84%, respectively. A good correlation and no significant difference was observed between the two acquisition methods. However, the simultaneous acquisition protocol has many advantages, i.e. halving the acquisition time, shortening the overall decision-making time, and decreasing unmatched stress-rest artifacts.