Comparison of sestamibi, tetrofosmin, and Q12 retention in porcine myocardium

Although there are several Tc-99m perfusion tracers introduced for clinical use, there are no data available directly comparing these tracers with mic rosphere-determined flow. The aim of this study was to compare the myocardi al retention of sestamibi, tetrofosmin, and Q12 in a porcine model. Methods : We used a pig model with (n = 6) or without (n = 3) coronary occlusion. E ach pig received a simultaneous injection of sestamibi and either tetrofosm in (group 1, n = 5) or Q12 (group 2, n = 4) labeled with either Tc-99m or T c-95m (physical half-life, 61 d; photon energy, 204 keV) during pharmacolog ic vasodilation. Absolute myocardial retention of each tracer was calculate d from the myocardial tracer activity and arterial input function. Results: The plot of all three tracers versus flow achieved a plateau at a higher f low range. However, sestamibi showed a higher mean retention than either te trofosmin (group 1, 0.27 +/- 0.11 vs. 0.16 +/- 0.06 mL/g/min, respectively; P < 0.01) or Q12 (group 2, 0.32 +/- 0.13 vs. 0.09 +/- 0.03 mL/g/min, respe ctively; P < 0.01). Furthermore, when a linear regression analysis was perf ormed to assess the relationship between retention and microsphere-determin ed flow, sestamibi showed a greater increment in retention than did tetrofo smin or Q12. Conclusion: Although all of the tracers showed a nonlinear inc rease in retention as flow increased, sestamibi may display more favorable characteristics as a flow tracer in the porcine heart.