New Technetium-Labeled Myocardial Perfusion Agents

Radionuclide myocardial perfusion imaging in conjunction with exercise or pharmacologic stress testing is an established technique for diagnosing and assessing the severity of coronary artery disease (1 ). Currently TI is the most widely used radiopharmaceutical for myocardial perfusion imaging. Thallium-201, however, has disadvantages such as low photopeak energy (69-83 keV), which can cause decreased image resolution and attenuation by soft tissue. The relatively long half life (73 hr) of 201 Tl limits the dose which can be given to the patient, thus reducing the count statistics. Technetium-99m-labeled radiopharmaceuticals have advantages over 201 TI. Technetium-99m has a higher photopeak energy (140 keV) which will increase image resolution and decrease attenuation. It also has a shorter half-life (6 hr) and a lower radiation dose to the patient which permits a larger amount of radioactivity to be administered, thus increasing the count statistics. Technetium-99m-labeled radiopharmaceuticals can be made in the nuclear medicine laboratory by adding mTc to a prepared kit. Currently there are two FDA approved mTc-labeled myocardial perfusion agents, sestamibi and teboroxime. Three new mTc-labeled myocardial perfusion agents are undergoing various clinical and experimental trials: tetrofosmin (P-53, PPN1011, Myoview® Amersham Medi-Physics International, Arlington Heights, IL), furifosmin (Q-12, Technicard® Mallinckrodt Medical, St. Louis, MO) and NOET (TcNNOET CIS Biointernational, Cedex, France). This review will cover current information on all of the three new mTclabeled myocardial perfusion agents.