2-18F-fluoracetate (F-FACE) metabolites inhibit one of the key enzymes in the mitochondrial tricarboxylic acid cycle, leading to accumulation of metabolized substances in aerobic conditions. F-FACE uptake is therefore posited to reflect glial acetate metabolism, and consequently correlate with areas of ischemia. In this study, the authors use this compound to evaluate areas of the brain at-risk for ischemia in patients with atherosclerotic large vessel disease.
In 9 patients with unilateral symptomatic atherosclerotic occlusion or stenosis of the internal carotid artery (ICA) or middle cerebral artery (MCA), F-FACE uptake on PET increased ipsilateral to the occluded/stenosed artery. F-FACE uptake increased in areas where cerebral blood flow (CBF) and cerebral metabolic rate of oxygen (CRMO2) were decreased, and decreased in areas with increased oxygen extraction fraction (OEF). The strongest associations were seen with decreased CBF and increased OEF.
This study is limited in size, but does give evidence that F-FACE uptake is increased in tissue at-risk for ischemia. The authors suggest that F-FACE uptake could potentially help identify tissue at most risk for ischemic damage, and may select patients who need immediate treatments. The use of this modality for patient selection for acute intervention would likely be very limited given time constraints for intervention and availability of the imaging modality, but may have a role in patient selection for carotid stents, endarterectomies, or surgical bypass, which is more congruent with the study population. For example, patients being considered for bypass may undergo perfusion studies with an acetazolamide challenge; it would be of interest to see whether F-FACE might better identify which patients would benefit from intervention compared to conventional imaging.