A Kinetic Model for Cardiac PET with [1-Carbon-11]-Acetate

Carbon-11-labeled acetate is a unique tracer for noninvasive assessment of myocardial oxidative metabolism with PET. Because adequate kinetic 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 duration and blood volume encountered in noninvasive PET investigations. To investigate to what extent the current data evaluation schemes are justified, we developed a comprehensive model of [1-11C]-acetate kinetics in the myocardium which incorporates five tissue compartments: free acetate, activated acetate, CO2 precursors, amino acids and CO2. We derived the analytical solution of the model equations which is used for simulations and data fitting. The five-compartment model can reproduce in detail known experimental data. The resulting values of the eight model parameters compare favorably with existing biochemical facts. We have established the relation between parameters of the detailed model and one- and two-compartment models used for the evaluation of PET investigations. The kinetics of [1-11C]-acetate are adequately described by a five-compartment model. One- and two-compartment models are sufficient for simultaneous quantitative assessment of myocardial oxidative metabolism and perfusion with [1-11C]-acetate and PET.