Physiologic properties of myocardial perfusion tracers.

Accurate noninvasive assessment of coronary blood flow is dependent on the physiologic properties of the perfusion agent as well as the physical imaging properties of its radiolabel. Perfusion agents can accurately assess variable levels of flow by having a high myocardial extraction and retention. Based on extraction values, teboroxime can best determine hyperemic flow, but only if imaged very early after injection. In contrast, sestamibi has the lowest peak extraction and has diminished linear uptake at hyperemic flows. However, sestamibi has stable tissue distribution and good linear uptake over physiologic levels of flow, which make for good clinical utility. 201Tl has extraction properties that are slightly less than those for teboroxime, but its clinical myocardial retention is much higher. Therefore, all three perfusion agents can adequately evaluate variable levels of coronary flow. Uptake of the cationic perfusion agents 201Tl and sestamibi can be used for the assessment of myocardial viability, whereas uptake of the neutral compound teboroxime appears to be related to the level of coronary flow regardless of myocyte function.