Use of [11C]acetate and [15O]O2 PET for the assessment of myocardial oxygen utilization in patients with chronic myocardial infarction
Carbon-11 acetate positron emission tomography (PET) has been widely used to assess regional oxidative metabolism of the heart. However, the accuracy of [11C]acetate PET in assessing oxidative metabolism in infarcted myocardium remains controversial. Thirteen patients with stable coronary artery disease and old myocardial infarction were studied. The 15O-based PET studies yielded regional blood flow (rMBF, ml/min/g) and oxygen consumption (rMMRO2, ml/min/g), which was compared with the myocardial clearance rate constant (k mono) of [11C]acetate in segments with rMBF≥75% (group A), 50%–74% (group B) or <50% (group C) of the normal reference segment. Mean MBF was 0.96±0.08 ml/g/min in group A, 0.67±0.06 ml/g/min in group B and 0.42±0.07 ml/g/min in group C segments. The segmental rMMRO2 correlated linearly with k mono (r=0.89, P<0.001, y=0.61x+0.026). The k mono/rMMRO2 ratio was comparable in the group A and B segments (0.99±0.19 vs 1.07±0.21, P=NS). However, the ratio was significantly higher in the group C segments (1.28±0.35, P=0.037). It is concluded that k mono of [11C]acetate correlates linearly with rMMRO2 determined by [15O]O2 inhalation. However, k mono appears to yield higher rMMRO2 estimates than the [15O]O2 method in low-flow areas.