title: Effect of reperfusion and hyperemia on the myocardial distribution of technetium-99m t-butylisonitrile.
abstract: Technetium-99m t-butylisonitrile ([99mTc]TBI) is a promising new radiotracer for myocardial imaging. Its myocardial uptake is sufficiently high in humans to permit planar, tomographic, and gated images of excellent technical quality. We studied the behavior of [99mTc]TBI in the dog at rest and under conditions of hyperemia and reperfusion in order to determine the relationship between [99mTc]TBI myocardial concentration and blood flow. After permanent occlusion of the left anterior descending artery, the correlation between the relative myocardial concentration of [99mTc]TBI and regional myocardial blood flow (RMBF) measured with radiolabeled microspheres was excellent. In a dog model of transient hyperemia, the concentration of [99mTc]TBI was directly related to blood flow but underestimated the degree of hyperemia. Technetium-99m TBI redistributed into transiently ischemic myocardium. The myocardial concentrations of [99mTc]TBI and thallium-201(201TI) in transiently ischemic myocardium were similar at 10 and 30 min following reperfusion and were significantly higher than blood flow prior to reperfusion. When [99mTc]TBI was injected into the left anterior descending artery, the washout was slow, falling to 78% of initial activity at 120 min after injection. In conclusion, [99mTc]TBI reflects regional myocardial blood flow accurately in ischemic and normal resting myocardium and underestimates blood flow at high flows. The rate of myocardial redistribution after reperfusion is similar for [99mTc]TBI and 201TI.
mesh_terms: D000818:Animals; D003327:Coronary Disease / Q000000981:diagnostic imaging* / Q000378:metabolism; D004285:Dogs; D005260:Female; D006940:Hyperemia / Q000000981:diagnostic imaging* / Q000378:metabolism; D008297:Male; D009206:Myocardium / Q000378:metabolism*; D009570:Nitriles / Q000378:metabolism*; D009942:Organometallic Compounds / Q000378:metabolism*; D015609:Organotechnetium Compounds; D011877:Radionuclide Imaging; D013667:Technetium / Q000378:metabolism*; D013997:Time Factors
chemical_list: D009570:Nitriles; D009942:Organometallic Compounds; D015609:Organotechnetium Compounds; C043714:technetium Tc 99m hexakis(tert-butylisonitrile); D013667:Technetium