Imaging of atherosclerotic aorta of rabbit model by detection of plaque inflammation with fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography.

BACKGROUND: Atherosclerotic plaque rupture is the primary mechanism of thrombosis which plays a key role in the onset of acute coronary syndromes. Detection of these plaques prone to rupture (vulnerable plaque) could be clinically significant for prevention of cardiac events. It has been shown that high metabolism cells have a high uptake of fluorine-18 fluorodeoxyglucose ((18)F-FDG). The objective of this study was to investigate the correlation of FDG uptake and the immuno-histochemistry parameters of plaques, and the effect of atorvastatin on vulnerable atherosclerotic plaque in a rabbit model.
METHODS: Ten male New Zealand White rabbits were divided into three groups as follows: (1) normal control group (n = 2, C group): the animals were fed a standard diet at 120 g/d and were given water ad labium; (2) atherosclerosis group (n = 4, As group): animals were fed with high fat diet for 5 months after aortic endothelia damage; (3) treatment group (atherosclerosis + atorvastatin, n = 4, Statin group): animals were fed with high fat diet for 5 months and then changed into normal chow plus atorvastatin (2.5 mg·d(-1)·kg(-1)) treatment for another 4 months. Then these four rabbits were imaged with fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography (PET/CT) and sacrificed for pathohistologic studies. FDG uptake by the aorta was expressed as target-to-background ratio (TBR). Maximal standardized uptake value (SUV) was measured over the thoracic and abdominal aortas. The aortic smooth muscle cell (SMC) number, CD-14 antibody positive cell (macrophage) number and the ratio of the thickness of fibrous cap to the thickness of lipid core (cap-to-core ratio) in atherosclerotic plaques were analyzed.
RESULTS: As group showed significantly higher uptake of FDG than C group (SUVs: 0.746 ± 0.172 vs. 0.286 ± 0.073, P < 0.001). After 4 months of atorvastatin treatment and the modification of diet, SUVs decreased significantly (Statin group: 0.550 ± 0.134, compared to As group, P < 0.001). However, no marked difference was found in TBR, the number of macrophages, the number of SMC and the cap-to-core ratio in the aortic segments between Statin group and As group. The correlation of aortic FDG uptake with SMC assessed by histopathology was negatively significant (r = -0.57, P < 0.001). When aortic FDG uptake was expressed as TBR, it correlated significantly (r = 0.69, P < 0.001) with the macrophage number, and also correlated significantly (r = -0.78, P < 0.001) with the cap-to-core ratio.
CONCLUSION: (18)F-FDG PET/CT might serve as a useful non-invasive imaging technique for detection of atherosclerotic plaque and potentially permit monitoring of relative changes in inflammation within the atherosclerotic lesion.