COMPARTMENTAL ANALYSIS OF TECHNETIUM-99M-TEBOROXIME KINETICS EMPLOYING FAST DYNAMIC SPECT AT REST AND STRESS

We have examined the feasibility of compartmental analysis of Tc-99m-t eboroxime kinetics in measuring physiological changes in response to a denosine-induced coronary vasodilation. To evaluate the effect of trac er recirculation on Tc-99m-teboroxime kinetics in the myocardium, we a lso compared compartmental analysis with washout analysis (monoexponen tial fitting), which does not account for this effect. Methods: Eight healthy male volunteers were imaged using fast dynamic SPECT protocols (5 sec per tomographic image) at rest and during adenosine infusion. A two-compartment model was used and compartmental parameters K1 and k 2 (characterizing the diffusion of Tc-99M-teboroxime from the blood to the myocardium and from the myocardium to the blood, respectively) we re fitted from myocardial time-activity curves and left ventricular in put functions. Results: Both K1 and washout estimates for the whole le ft ventricular myocardium changed significantly in response to coronar y vasodilation. Mean stress-to-rest (S/R) ratios were almost two times higher for K1 (S/R = 2.7 +/- 1.1) than for washout estimates (S/R = 1 .5 +/- 0.3). Estimation of K1 for all local regions, except the septal wall, is feasible because variations in K1 estimates for all local re gions, except the septum during stress, are comparable with those for the global region. Conclusions: We conclude that quantitative compartm ental analysis of Tc-99m-teboroxime kinetics provides a sensitive indi cator for changes in response to adenosine-induced coronary vasodilati on.