Potential of [C-11]acetate for measuring myocardial blood flow: Studies in normal subjects and patients with hypertrophic cardiomyopathy

Measuring the rate of clearance of carbon-11 labelled acetate from myocardium using positron emission tomography (PET) is an accepted technique for noninvasively assessing myocardial oxygen consumption. Initial myocardial uptake of [C-11]acetate, however, is related to myocardial blood flow (MBF) and several tracer kinetic models for quantifying MBF using [C-11]acetate have been proposed. The objective of this study was to assess these models. Eighteen healthy subjects and 18 patients with hypertrophic cardiomyopathy (HCM) were studied under baseline conditions with [C-11]acetate and [O-15]water. Four previously reported methods, including single- and multi-tissue compartment models, were used to calculate MBF from the measured [C-11]acetate rate of influx K (1) and the (previously) reported relationship between K (1) and MBF. These MBF values were then compared with those derived from corresponding [O-15]water studies. For all models, correlations between [C-11]acetate and [O-15]water-derived MBF ranged from .67 to .86 (all P < .005) in the control group and from .73 to .85 (all P < .001) in the HCM group. Two out of four models systematically underestimated perfusion with [C-11]acetate, whilst the third model resulted in an overestimation. The fourth model, based on a simple single tissue compartment model with spillover, partial volume and recirculating metabolite corrections, resulted in a regression equation with a slope of near unity and an Y-intercept of almost zero (controls, K (1) = .74[MBF] + .09, r = .86, SEE = .13, P < .001 and HCM, K (1) = .89[MBF] + .03, r = .85, SEE = .12, P < .001). [C-11]acetate enables quantification of MBF in fairly good agreement with actual MBF in both healthy individuals and patients with HCM. A single tissue compartment model with standardized correction for recirculating metabolites and with corrections for partial volume and spillover provided the best results