Tracer perfusion, regional

A relevant feature of 99mTcN-NOET derives from its in vivo kinetic behavior, which gives rise to the phenomenon called redistribution . This term is commonly referred to as the ability of a tracer to move across viable heart regions filled with a different concentration of activity, a situation that usually occurs when some areas within the heart tissue receive a lower blood supply owing to the partial occlusion of coronary vessels (ischemia). When an ischemic patient is injected with a cardiac tracer under stress conditions, a sharp contrast is observed between normally perfused tissue and ischemic areas (defects). In contrast, when the patient is at rest, the activity becomes more uniformly dis-... 

Since fatty acids are the primary substrate for aerobic metabolism within the heart, they are also of interest as potentially useful tracers of myocardial perfusion (12-18). This class of compounds labeled with the positron emitter is being used with specially designed positron imaging (ECT) systems to quantitatively measure the regional distribution of myocardial blood flow in three dimensions (12,13,14). Carbon-11 labeled palmitic acid is also being evaluated as a tracer for studies of myocardial metabolism. Likewise, the o-iodofatty acids, which are structural analogs of the physiologic substrates, have been shown to be taken up by myocardial tissue in proportion to blood flow (15). Iodine-123 labeled 16-iodo-9-hexadecenoic acid (18,17) and 17-iodo-heptadeca-noic acid (18) have been used in conjunction with conventional scintillation cameras for in vivo studies in humans. In all cases with this class of compounds, turnover of the label within the tissue is related to some aspect of metabolism (17,18). 

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