Myocardial scintigraphy using 99m-Tc-methoxyisobutylisonitrile (Tc-MIBI): Is it equivalent to 201-Tl?

The results of selective coronary angiography, myocardial 201-Tl scintigraphy (stress and redistribution) and after 99m-Tc-methoxyisobutylisonitrile stress and rest injections (Tc-MIBI, Cardiolite, DuPont de Nemours, USA) were compared in 19 patients with manifest ischemic heart disease in identical three projections and after same ergometric load. All three investigations were carried out within three consecutive days. 16 patients had significant stenoses of 1-3 main coronary arteries inclusive of left coronary artery main stem, insignificant stenoses (less than 50%) were present in remaining 3 patients. Scintigraphic localizations of accumulation defects in both Tc-MIBI and 201-Tl stress scintigraphy were in accordance in 70.6% of evaluated left ventricular wall segments. A positive 201-Tl redistribution and rest-stress Tc-MIBI scintigraphic difference agreed in 52.6% images of all three projections with verified accumulation defects. The sensitivity of the detection of ischemic area in reference to the coronary angiography was nearly identical in 201-Tl (75%) and Tc-MIBI scintigraphy (81.2%). False positive accumulation defects in the apical area were revealed in three patients with insignificant coronaro-angographic findings equally after both radiopharmaceuticals. Better physical properties of 99m-Tc from the point of view of a gamma camera detection, a possibility to get markedly higher counting rate and sufficient accumulation of the radiopharmaceutical in the perfused myocardium enable to reach scintigraphic pictures with a high contrast after labelled Tc-MIBI injection, even in case of sequential impulse summation during heart cycle (gating). Thus MIBI labelled by 99m-Tc is equivalent to 201-Tl as used for myocardial scintigraphy in patients with ischemic heart disease.