Technetium-99m-tetrofosmin in dipyridamole-stress myocardial SPECT imaging: intraindividual comparison with technetium-99m-sestamibi.

UNLABELLED Tetrofosmin is a new 99mTc-labeled myocardial perfusion imaging agent. Biodistribution studies suggest more favorable heart-to-adjacent organ biokinetics than for 99mTc-sestamibi after injection during exercise. The aim of this work was to determine intraindividually whether tetrofosmin is more suitable than sestamibi for pharmacological stress testing in a 1-day protocol. METHODS Thirty subjects underwent two similar 1-day, rest and dipyridamole stress imaging protocols: one using tetrofosmin, the other using sestamibi. SPECT was performed 60 min after tracer administration. Myocardial images were analyzed both visually and quantitatively. RESULTS Heart-to-liver activity ratios measured on the anterior SPECT projections were significantly higher for tetrofosmin than for sestamibi in the rest and stress studies. Heart-to-lung ratios were similar for both tracers. Significant linear correlations between tetrofosmin and sestamibi perfusion indices were found in normals and in patients with proven or suspected coronary artery disease. In segments showing abnormal uptake during stress, the perfusion indices were similar for tetrofosmin and sestamibi at rest and during stress. The degree of reversibility in these segments was also similar for both tracers. Finally, the extent, intensity and severity of perfusion defects were similar for both tracer studies. CONCLUSION Tetrofosmin has a more optimal biodistribution than sestamibi when used in a 1-day, rest and dipyridamole stress myocardial SPECT imaging protocol. No significant difference in either the quality or diagnostic interpretation of the images could be demonstrated.