Myocardial technetium-99m-tetrofosmin and technetium-99m-sestamibi kinetics in normal subjects and patients with coronary artery disease

This study was designed to compare the tracer kinetics between (99m)Tc- sestamibi and (99m)Tc-tetrofosmin in a heterogeneous group of 24 patients admitted for routine perfusion imaging. Methods: Twelve patients were studied with (99m)Tc-tetrofosmin and 12 with (99m)Tc-sestamibi. In each group, six patients had a low likelihood for coronary artery disease, and six patients had angiographically proven coronary artery stenoses of >75% or previous myocardial infarction. Analysis of myocardial and liver uptake and clearance as well as target-to-organ contrasts were performed with planar stress images. Results: Myocardial uptake of (99m)Tc-tetrofosmin was higher from 5 min (0.37 ± 0.12 counts/pixel X MBq^-1, p = 0.008) to 60 min (0.32 ± 0.10 counts/pixel x MBq^-1, p = 0.04) compared to (99m)Tc-sestamibi. Biological half-life for (99m)Tc-tetrofosmin (278 ± 32 min) in normal myocardium was significantly shorter (p = 0.008) than for (99m)Tc-sestamibi (680 ± 45 min). Biological liver half-life for (99m)Tc-tetrofosmin (67 ± 16 min) was also significantly shorter (p = 0.02) than for (99m)Tc-sestamibi (136 ± 18 min). Heart-to-lung ratios for (99m)Tc-tetrofosmin (2.49 ± 0.43 at 5 min to 2.66 ± 0.55 at 60 min) and (99M)Tc-sestamibi (2.52 ± 0.37 at 5 min to 2.95 ± 0.50 at 60 min) were similar. Whereas heart-to-liver ratios for (99m)Tc- tetrofosmin (1.04 ± 0.24 at 5 min, increasing to 1.51 ± 0.44 at 60 min) were significantly higher from 30-80 min postinjection (p = 0.05 at 30 min to p = 0.02 at 60 min) compared to the (99m)Tc-sestamibi (0.83 + 0.16 at 5 min to 1.06 ± 0.27 at 60 min). Conclusion: Technetium-99m-tetrofosmin displays a shorter myocardial half-life compared to (99m)Tc-sestamibi. The rapid liver clearance of (99m)Tc-tetrofosmin, combined with comparable myocardial retention, resulted in higher heart-to-liver ratios but similar heart-to- lung contrasts compared to (99m)Tc-sestamibi from 30-60 min.