Myocardial extraction of technetium-99m-[2-(1-methoxybutyl) isonitrile] in the isolated rabbit heart: A myocardial perfusion agent with high extraction and stable retention

Abstract

Technetium-99m-[2-(1-methoxybutyl) isonitrile] (MBI) is a potential new compound for the scintigraphic imaging of coronary flow. Evaluation in the blood-perfused isolated rabbit heart model showed this compound to have a myocardial uptake comparable to 201Tl and higher than sestamibi. Although the mean ± s.d. maximum extraction (E(max)) and capillary permeability- surface area product (PS(cap)) of 99mTc-MBI (E(max) = 0.45 ± 0.10, PS(cap) = 1.07 ± 0.47 ml/min · g) were less than 201Tl (E(max) = 0.71 ± 0.07, PS(cap) = 2.21 ± 0.76 ml/min · g, p < 0.0001), the net extraction of 99mTc-MBI (E(net) = 0.52 ± 0.10) was only slightly less than the value for 201Tl (E(net) = 0.56 ± 0.10, p < 0.05). There was no significant difference in the myocardial uptake versus flow between 99mTc-MBI and 201Tl. These data indicate that assessment of relative coronary flow based on the myocardial uptake of 99mTc-MBI should give results comparable to 201Tl. Therefore, 99mTc-MBI may have clinical potential as a radiolabeled myocardial perfusion agent.