Moore Christopher J, Caughey Melissa C, Meyer Diane O, Emmett Regina, Jacobs Catherine, Chopra Manisha, Howard James F, Gallippi Caterina M
Department of Electrical and Computer Engineering, North Carolina State University, Raleigh, North Carolina, USA.
Department of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA.
Ultrasound Med Biol. 2018 Dec;44(12):2519-2530. doi: 10.1016/j.ultrasmedbio.2018.07.004. Epub 2018 Aug 31.
Our group has previously found that in silico, mechanical anisotropy may be interrogated by exciting transversely isotropic materials with geometrically asymmetric acoustic radiation force excitations and then monitoring the associated induced displacements in the region of excitation. We now translate acoustic radiation force-based anisotropy assessment to human muscle in vivo and investigate its clinical relevance to monitoring muscle degeneration in Duchenne muscular dystrophy (DMD). Clinical anisotropy assessments were performed using Viscoelastic Response ultrasound, with a degree of anisotropy reflected by the ratios of Viscoelastic Response relative elasticity (RE) or relative viscosity (RV) measured with the asymmetric radiation force oriented parallel versus perpendicular to muscle fiber alignment. In vivo results from rectus femoris and gastrocnemius muscles of boys aged ∼7.9-10.4 y indicate that RE and RV anisotropy ratios in rectus femoris muscles of boys with DMD were significantly higher than those of healthy control boys (RE: DMD = 1.51 ± 0.87, control = 0.99 ± 0.69, p = 0.04, Wilcoxon rank sum test; RV: DMD = 1.04 ± 0.71, control = 0.74 ± 0.22, p = 0.02). In the gastrocnemius muscle, only the RV anisotropy ratio was significantly higher in dystrophic than control patients (DMD = 1.23 ± 0.35, control = 0.88 ± 0.31, p = 0.04). In the dystrophic rectus femoris muscle, the RE anisotropy ratio was inversely correlated (slope = -0.03/lbf, r = -0.43, p = 0.07, Pearson correlation) with quantitative muscle testing functional output measures but was not correlated with quantitative muscle testing in the dystrophic gastrocnemius. These results suggest that Viscoelastic Response RE and RV measures reflect differences in mechanical anisotropy associated with functional impairment with dystrophic degeneration that are relevant to monitoring DMD clinically.
我们的团队之前发现，在计算机模拟中，可以通过用几何不对称的声辐射力激发横向各向同性材料，然后监测激发区域内的相关诱导位移来研究机械各向异性。我们现在将基于声辐射力的各向异性评估转化到人体肌肉的体内研究中，并研究其在监测杜氏肌营养不良症（DMD）肌肉退化方面的临床相关性。使用粘弹性响应超声进行临床各向异性评估，各向异性程度由粘弹性响应相对弹性（RE）或相对粘度（RV）的比值反映，这些比值是在不对称辐射力与肌肉纤维排列平行和垂直时测量得到的。对年龄在7.9 - 10.4岁男孩的股直肌和腓肠肌进行的体内研究结果表明，DMD男孩股直肌的RE和RV各向异性比值显著高于健康对照男孩（RE：DMD = 1.51 ± 0.87，对照 = 0.99 ± 0.69，p = 0.04，Wilcoxon秩和检验；RV：DMD = 1.04 ± 0.71，对照 = 0.74 ± 0.22，p = 0.02）。在腓肠肌中，只有营养不良患者的RV各向异性比值显著高于对照患者（DMD = 1.23 ± 0.35，对照 = 0.88 ± 0.31，p = 0.04）。在营养不良的股直肌中，RE各向异性比值与定量肌肉测试功能输出指标呈负相关（斜率 = -0.03/lbf，r = -0.43，p = 0.07，Pearson相关性），但与营养不良的腓肠肌中的定量肌肉测试无关。这些结果表明，粘弹性响应RE和RV测量反映了与营养不良性退化相关的功能损害所导致的机械各向异性差异，这对于临床上监测DMD具有重要意义。
