A KINETIC-MODEL FOR CARDIAC PET WITH [1-CARBON-11]-ACETATE

Carbon-11-labeled acetate is a unique tracer for noninvasive assessmen t of myocardial oxidative metabolism with PET. Because adequate kineti c models have been missing, data evaluation in the past was performed mostly with phenomenological approaches such as mono- or biexponential fitting which cannot account for the influence of finite input durati on and blood volume encountered in noninvasive PET investigations. Met hods: to investigate to what extent the current data evaluation scheme s are justified, we developed a comprehensive model of [1-C-11]-acetat e kinetics in the myocardium which incorporates five tissue compartmen ts: free acetate, activated acetate, CO2 precursors, amino acids and C O2. We derived the analytical solution of the model equations which is used for simulations and data fitting. Results: the five-compartment model can reproduce in detail known experimental data. The resulting v alues of the eight model parameters compare favorably with existing bi ochemical facts. We have established the relation between parameters o f the detailed model and one- and two-compartment models used for the evaluation of PET investigations. Conclusion: the kinetics of [1-C-11] -acetate are adequately described by a five-compartment model. One- an d two-compartment models are sufficient for simultaneous quantitative assessment of myocardial oxidative metabolism and perfusion with [1-C- 11]-acetate and PET.