18F-choline images murine atherosclerotic plaques ex vivo

Objective - Current imaging modalities of atherosclerosis mainly visualize plaque morphology. Valuable insight into plaque biology was achieved by visualizing enhanced metabolism in plaque-derived macrophages using F-18-fluorodeoxyglucose ( F-18-FDG). Similarly, enhanced uptake of F-18-fluorocholine ( F-18-FCH) was associated with macrophages surrounding an abscess. As macrophages are important determinants of plaque vulnerability, we tested F-18-FCH for plaque imaging. Methods and Results - We injected F-18-FCH ( n = 5) or F-18-FDG ( n = 5) intravenously into atherosclerotic apolipoprotein E-deficient mice. En face measurements of aortae isolated 20 minutes after F-18-FCH injections demonstrated an excellent correlation between fat stainings and autoradiographies ( r = 0.842, P < 0.0001), achieving a sensitivity of 84% to detect plaques by F-18-FCH. In contrast, radiotracer uptake 20 minutes after F-18-FDG injections correlated less with en face fat stainings ( r = 0.261, P < 0.05), reaching a sensitivity of 64%. Histological analyses of cross-sections 20 minutes after coinjections of F-18-FCH and C-14-FDG ( n = 3) showed that F-18-FCH uptake correlated better with fat staining ( r = 0.740, P < 0.0001) and macrophage-positive areas ( r = 0.740, P < 0.0001) than C-14-FDG ( fat: r = 0.236, P = 0.29 and CD68 staining: r = 0.352, P = 0.11), respectively. Conclusions - F-18-FCH identifies murine plaques better than F-18-FDG using ex vivo imaging. Enhanced F-18-FCH uptake into macrophages may render this tracer a promising candidate for imaging plaques in patients.