Potential of [11C]acetate for measuring myocardial blood flow: Studies in normal subjects and patients with hypertrophic cardiomyopathy
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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 [11C]acetate, however, is related to myocardial blood flow (MBF) and several tracer kinetic models for quantifying MBF using [11C]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 [11C]acetate and [15O]water. Four previously reported methods, including single- and multi-tissue compartment models, were used to calculate MBF from the measured [11C]acetate rate of influx K1 and the (previously) reported relationship between K1 and MBF. These MBF values were then compared with those derived from corresponding [15O]water studies.
For all models, correlations between [11C]acetate and [15O]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 [11C]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, K1 = .74[MBF] + .09, r = .86, SEE = .13, P < .001 and HCM, K1 = .89[MBF] + .03, r = .85, SEE = .12, P < .001).
[11C]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.