COMPARISON OF TL-201 AND TC-99M METHOXYISOBUTYL ISONITRILE

Thallium-201 (Tl-201) is a well-established radionuclide used in myocardial perfusion imaging for assessing the presence and prognostic significance of coronary artery disease. Recently, technetium-99m hexakis-2-methoxyisobutyl isonitrile (Tc-99m-sestamibi) has become available for the same diagnostic and prognostic procedures. This discussion compares the imaging characteristics and clinical applications of Tl-201 with those of Tc-99m-sestamibi. There is a strong diagnostic concordance between the 2 agents in symptomatic patients. Various comparative clinical trials have shown in numerous patients that both agents have a similar diagnostic yield in both planar and single-photon emission computed tomography (SPECT) imaging. Because of better image quality of the Tc-99m agent, ther is a trend toward better specificity and normalcy rate, in comparison to Tl-201. However, when using reinjection imaging protocols, Tl-201 retains a unique place as in imaging agent to identify viable myocardium.