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

Abstract

This study was designed to compare the tracer kinetics between 99mTc-sestamibi and 99mTc-tetrofosmin in a heterogeneous group of 24 patients admitted for routine perfusion imaging. Twelve patients were studied with 99mTc-tetrofosmin and 12 with 99mTc-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. Myocardial uptake of 99mTc-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 99mTc-sestamibi. Biological half-life for 99mTc-tetrofosmin (278 +/- 32 min) in normal myocardium was significantly shorter (p = 0.008) than for 99mTc-sestamibi (680 +/- 45 min). Biological liver half-life for 99mTc-tetrofosmin (67 +/- 16 min) was also significantly shorter (p = 0.02) than for 99mTc-sestamibi (136 +/- 18 min). Heart-to-lung ratios for 99mTc-tetrofosmin (2.49 +/- 0.43 at 5 min to 2.66 +/- 0.55 at 60 min) and 99mTc-sestamibi (2.52 +/- 0.37 at 5 min to 2.95 +/- 0.50 at 60 min) were similar. Whereas heart-to-liver ratios for 99mTc-tetrofosmin (1.04 +/- 0.24 at 5 min, increasing to 1.51 +/- 0.44 at 60 min) were significantly higher from 30-60 min postinjection (p = 0.05 at 30 min to p = 0.02 at 60 min) compared to the 99mTc-sestamibi (0.83 + 0.16 at 5 min to 1.08 +/- 0.27 at 60 min). Technetium-99m-tetrofosmin displays a shorter myocardial half-life compared to 99mTc-sestamibi. The rapid liver clearance of 99mTc-tetrofosmin, combined with comparable myocardial retention, resulted in higher heart-to-liver ratios but similar heart-to-lung contrasts compared to 99mTc-sestamibi from 30-60 min.