Imaging of atherosclerotic aorta of rabbit model by detection of plaque inflammation with fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>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.</p><p><b>METHODS</b>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.</p><p><b>RESULTS</b>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.</p><p><b>CONCLUSION</b>(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.</p>

In vivo noninvasive detection of vulnerable atherosclerotic plaque by (99)Tc(m)-Annexin V imaging in an atherosclerotic rabbit model / 中华心血管病杂志

<p><b>OBJECTIVE</b>Apoptosis contributes to the instability of the atherosclerotic (AS) lesions. The vulnerable plaque was identified in vivo by detecting the apoptosis with radiolabeled annexin V in an atherosclerotic rabbit model.</p><p><b>METHODS</b>Eight male New Zealand white rabbits on 2% cholesterol diet for 2 weeks had abdominal aortic balloon injury and fed a 2% cholesterol diet for another 15 weeks (AS group), 3 rabbits fed a normal rabbit chow for 17 weeks without balloon injury served as controls. Annexin V labeled with (99)Tc(m) was then intravenously administered and planar whole-body images were captured using a gamma camera in the left lateral position. The entire length of the abdominal aorta was explanted for ex vivo imaging with gamma camera. The aorta then was divided into several segments according to the severity of AS. The segments were separated weighted and counted in an gamma counter for the absorptive dose of annexin per gram of tissue. Histology examinations were made on specimens.</p><p><b>RESULTS</b>At 2 hours post annexin V injection, clear delineation of radiolabel within the abdominal aorta could be evidenced in vivo gamma imaging. After explanation of the aorta, ex vivo imaging showed a robust uptake of radiotracer in the infradiaphragmatic aorta corresponding to the in vivo images and conforming to the macroscopic distribution of atherosclerotic lesions. The uptake of radiolabel was absent in areas without grossly visible atherosclerotic lesions. The in vivo and ex vivo images identified plaque areas were identical and corresponded histological results on the explanted specimen. The aortic specimen was divided into 18 segments on lesions. The magority of the lesions (14/18) manifested as type IV or type V lesions of AHA classification (vulnerable lesions), except segments 1 - 4, which manifested as type I or type II lesions. The thickness of fibrous cap (TFC) and the ratio of cap and lipid nuclear (RCN) were significantly reversely correlated to the unit radioactivity counts, and the correlation between RCN and the unit radioactivity counts was more significant than that between TFC and the unit radioactivity counts (r = -0.904, P < 0.01, and r = -0.8, P < 0.01). Apoptosis detection (TUNEL): annexin V intake in plaques was positively correlated to apoptotic index(r = 0.651, P = 0.012).</p><p><b>CONCLUSION</b>Noninvasive Annexin V imaging could be used to detect vulnerable atherosclerotic plaques in vivo.</p>