Experimental studies of the physiologic properties of technetium-99m agents: myocardial transport of perfusion imaging agents.
The physiologic properties of new technetium-99m-labeled myocardial imaging agents (Tc-99m sestamibi, an isonitrile; and Tc-99m teboroxime, a boronic acid adduct of technetium dioxime) are discussed and compared to thallium-201 (Tl-201). Studies with isolated hearts, subcellular fractions and cell cultures indicate that Tc-99m sestamibi, Tc-99m teboroxime and Tl-201 do not share common transport or sequestration mechanisms. Although peak Tc-99m sestamibi myocardial extraction over time is about half that of Tl-201 at equivalent coronary blood flows, the amount of Tc-99m sestamibi that remains in the heart is similar to that of Tl-201 because of its higher retention efficiency. The high retention efficiency for Tc-99m sestamibi also results in minimal redistribution. In contrast, Tc-99m teboroxime myocardial extraction is higher than that of Tl-201, but its retention is less efficient, resulting in relatively rapid washout characteristics which may quickly result in tracer redistribution. During reperfusion after a no-flow period, Tc-99m sestamibi extraction and retention increase, but for Tc-99m teboroxime and Tl-201 these values tend to decrease. All tracers show adequate transport characteristics for perfusion imaging, and differences in transport and retention should lead to the development of new clinical protocols.
Meerdink
D J
DJ
Department of Nuclear Medicine, University of Massachusetts Medical Center, Worcester.
Leppo
J A
JA
D000818:Animals; D003326:Coronary Circulation; D006321:Heart / Q000000981:diagnostic imaging*; D009206:Myocardium / Q000378:metabolism; D009570:Nitriles; D015609:Organotechnetium Compounds; D010091:Oximes; D011877:Radionuclide Imaging; D017256:Technetium Tc 99m Sestamibi; D013794:Thallium Radioisotopes
D009570:Nitriles; D015609:Organotechnetium Compounds; D010091:Oximes; D013794:Thallium Radioisotopes; D017256:Technetium Tc 99m Sestamibi; C060156:technetium Tc 99m teboroxime