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 Tc-99m- sestamibi and Tc-99m-tetrofosmin in a heterogeneous group of 24 patien ts admitted for routine perfusion imaging. Methods: Twelve patients we re studied with Tc-99m-tetrofosmin and 12 with Tc-99m-sestamibi. In ea ch group, six patients had a low likelihood for coronary artery diseas e, and six patients had angiographically proven coronary artery stenos es of >75% or previous myocardial infarction. Analysis of myocardial a nd liver uptake and clearance as well as target-to-organ contrasts wer e performed with planar stress images. Results: Myocardial uptake of T c-99m-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 Tc-99m-sestamibi. Biological half-life for Tc-99m -tetrofosmin (278 +/- 32 min) in normal myocardium was significantly s horter (p = 0.008) than for Tc-99m-sestamibi (680 +/- 45 min). Biologi cal liver half-life for Tc-99m-tetrofosmin (67 +/- 16 min) was also si gnificantly shorter (p = 0.02) than for Tc-99m-sestamibi (136 +/- 18 m in). Heart-to-lung ratios for Tc-99m-tetrofosmin (2.49 +/- 0.43 at 5 m in to 2.66 +/- 0.55 at 60 min) and Tc-99m-sestamibi (2.52 +/- 0.37 at 5 min to 2.95 +/- 0.50 at 60 min) were similar. Whereas heart-to-liver ratios for Tc-99m-tetrofosmin (1.04 +/- 0.24 at 5 min, increasing to 1.51 +/- 0.44 at 60 min) were significantly higher from 30-60 min post injection (p = 0.05 at 30 min to p = 0.02 at 60 min) compared to the T c-99m-sestamibi (0.83 + 0.16 at 5 min to 1.08 +/- 0.27 at 60 min). Con clusion: Technetium-99m-tetrofosmin displays a shorter myocardial half -life compared to 997c-sestamibi. The rapid liver clearance of Tc-99m- tetrofosmin, combined with comparable myocardial retention, resulted i n higher heart-to-liver ratios but similar heart-to-lung contrasts com pared to Tc-99m-sestamibi from 30-60 min.