Characterization of atherosclerotic plaque components and identification of vulnerablity by shear wave elastography:in vivo study on a rabbit model / 中华超声影像学杂志

ABSTRACT

Objective To investigate the value of shear wave elastography (SWE)on characterizing components and identifying the vulnerability of atherosclerotic plaques in vivo on a rabbit model.Methods The accuracy,as well as the inter-and intra-observer variance of quantifying the Young's modulus by SWE technique was first evaluated with the CIRS? phantoms as the golden standard.Animal model was developed by abdominal aorta endothelium denudation and high-cholesterol diet for 24 weeks on 20 purebred New Zealand rabbits.SWE images of atherosclerotic plaques found in the abdominal aortas were acquired in situ to acquire the Young's modulus.Then the plaques were harvested and matched with the distance between the right renal artery and the plaques recorded during SWE imaging.Histological slices were stained for fat,collagen,smooth muscle cells (SMC)and macrophages by Oil O red,picric Sirius red and anti-α-SMC,anti-RAM-1 1 immunohistology.Vulnerability index was also calculated as the percentage of (macrophage+fat)/(smooth muscle cell+collagen ).The correlation between the Young's modulus and plaque components and vulnerability index was analyzed.The value of SWE on differentiating plaque types was evaluated by ROC analysis.Results High agreement was found between the estimated Young's modulus by SWE and the gold standard.The coefficient of variant of inter-and intra-observer was very low at the range of 1.0%-3.8%.Ten fatty and twenty fibro-fatty plaques were obtained,totally.The maximal and mean Young's moduli of the fatty plaque were (49.90±22.95)kPa and (40.15±22.60)kPa,which were lower than those of the fibro-fatty plaques [(88.49±37.27)kPa and (72.93±29.21)kPa,respectively].The maximal Young's modulus obtained by SWE correlated positively with collagen and SMC (r =0.567 and 0.561,respectively with P <0.001),and negatively with fat and macrophage infiltration (r =-0.542 and-00.482,respectively with P <0.005).The mean Young's modulus also correlated positively with collagen and SMC (r=0.532 and 0.550,respectively with P <0.05),and negatively with fat and macrophage (r=-0.527 and -0.421,respectively with P <0.05).The same inclination could be observed between the minimal Young's modulus and the above components without statistical significance.Both the maximal and the mean Young's modulus correlated negatively with the vulnerable index (r =-0.620 and -0.619, respectively with P <0.001 ).ROC analysis revealed high sensitivity (85%)and specificity (80%)for differentiating fatty plaques from fibro-fatty plaques by Young's modulus.Conclusions SWE can be used for estimation of the Young's modulus of atherosclerotic plaques with high accuracy and reproducibility. Good correlation is evidenced between the Young's modulus and plaque components and vulnerability.Fatty and fibro-fatty plaques can be differentiated by Young's modulus with high sensitivity and specificity.Thus, SWE technique is promising for identifying vulnerable plaques.