Diagnosis of Carotid Plaque Using FDG-PET

Positron emission tomography (PET) with 18F-2-deoxy-2-fluoro-D-glucose (FDG) provides valuable metabolic information regarding arteriosclerotic lesions and may be applied for the detection of vulnerable plaque. When FDG, as a glucose analog, is phosphorylated in the intracytoplasmic area, its metabolism stops and remains, so-called intracellular metabolic trapping, and images are made utilizing this characteristic. Pathological examination of extirpated plaque confirmed that FDG accumulation was strongly correlated with the distribution and density of inflammatory cells, especially macrophages. Images suggestive of plaque inflammation and therefore its vulnerability were obtained. Even in patients with relatively slight stenosis, FDG accumulation was often observed; it was not always correlated with the percent stenosis, but quantitative values of FDG uptake or its changes may reflect the progression of arteriosclerosis. FDG is also utilized as a surrogate marker of drug efficacy, such as statin. Some studies indicated its association with vascular events, but no long-term, large-scale, prospective study excluding cancer-bearing patients has been conducted. In the future, data must be further accumulated. Concerning carotid artery lesions, there are no data on the onset of asymptomatic lesions or prediction of treatment-related risks, and future studies may provide promising information.