[1-C-11]Acetate as a quantitative perfusion tracer in myocardial PET

Our objective was to investigate the properties of [1-C-11]acetate as a qua ntitative perfusion tracer for myocardial PET studies. Methods: We determin ed the flow dependence of the effective acetate extraction by a comparison with [N-13]ammonia in 24 patients at rest (n = 8) and under pharmacologic v asodilation (n = 16). Furthermore, we compared the statistical quality of t he perfusion values derived with both tracers. Quantification was based on an irreversible 2-compartment model for [N-13]ammonia and a reversible 1-co mpartment model for [1-C-11]acetate. Area-conserving polar maps were used t o determine the correlation between the unidirectional uptake parameters of both tracers on a pixel-by-pixel basis for the whole left ventricular myoc ardium. Results: A fit of a generalized Renkin-Crone formula to the data yi elded the unidirectional acetate extraction fraction E(f) = 1 - 0.64e(-1.20 /f). An extraction correction based on this formula led to good quantitativ e agreement of perfusion values derived with [N-13]ammonia and [1-C-11]acet ate over the whole observed flow range (average difference of flow values, 3%; correlation coefficient, 0.96). This agreement proved the applicability of acetate as a quantitative perfusion tracer even under stress conditions . An analysis of the statistical properties of the parameter estimates show ed, moreover, that statistical errors were reduced by a factor of nearly 2 in comparison with ammonia. Conclusion: [1-C-11]acetate allows accurate qua ntification of myocardial perfusion with PET at rest as well as under stres s conditions. The use of acetate leads to distinctly improved statistical a ccuracy for the perfusion estimates in comparison with ammonia. This accura cy facilitates the generation of reliable parametric polar maps, which are especially useful for clinical application of myocardial perfusion quantifi cation.