Nuclear cardiac imaging

Important developments in the field of nuclear cardiac imaging include increasing use of single-photon emission computed tomography; the availability of pharmacologic stress testing; the introduction of newer technetium-labeled perfusion imaging agents; and a number of other newer imaging agents and imaging techniques. Tomographic imaging improves image quality as well as sensitivity. This improvement is probably more noticeable with pharmacologic stress testing and with the newer technetium agents. A number of pharmacologic stress agents are now being used. These include dipyridamole, adenosine, and dobutamine. In our experience, thallium tomographic imaging during adenosine-induced coronary hyperemia has resulted in a high degree of accuracy in the diagnosis of coronary artery disease. Both 99mTc-sestaMIBI (hexakis-2-methoxyisobutyl-isonitrile) and 99mTc-teboroxime may be used for simultaneous assessment of perfusion and function. These agents, although similar to thallium in many aspects, differ in many other aspects as they differ from each other. For example, sestaMIBI has a long retention time, but teboroxime has a very rapid washout time. Therefore, the imaging protocols using these two agents are considerably different. Assessment of myocardial viability has been an area of interest; specifically, the use of the reinjection technique has improved the ability to differentiate between scar tissue and viable myocardium.