Jugé Lauriane, Petiet Anne, Lambert Simon A, Nicole Pascal, Chatelin Simon, Vilgrain Valerie, Van Beers Bernard E, Bilston Lynne E, Sinkus Ralph
Neuroscience Research Australia, Randwick, Sidney, NSW, Australia.
School of Medical Sciences, University of New South Wales, Kensington, Sidney, NSW, Australia.
NMR Biomed. 2015 Dec;28(12):1763-71. doi: 10.1002/nbm.3438.
Magnetic Resonance Elastography (MRE) uses macroscopic shear wave propagation to quantify mechanical properties of soft tissues. Micro-obstacles are capable of affecting the macroscopic dispersion properties of shear waves. Since disease or therapy can change the mechanical integrity and organization of vascular structures, MRE should be able to sense these changes if blood vessels represent a source for wave scattering. To verify this, MRE was performed to quantify alteration of the shear wave speed cs due to the presence of vascular outgrowths using an aortic ring model. Eighteen fragments of rat aorta included in a Matrigel matrix (n=6 without outgrowths, n=6 with a radial outgrowth extent of ~600 µm and n=6 with ~850 µm) were imaged using a 7 Tesla MR scanner (Bruker, PharmaScan). High resolution anatomical images were acquired in addition to multi-frequency MRE (ν = 100, 115, 125, 135 and 150 Hz). Average cs was measured within a ring of ~900 µm thickness encompassing the aorta and were normalized to cs0 of the corresponding Matrigel. The frequency dependence was fit to the power law model cs ~ν(y). After scanning, optical microscopy was performed to visualize outgrowths. Results demonstrated that in presence of vascular outgrowths (1) normalized cs significantly increased for the three highest frequencies (Kruskal-Wallis test, P = 0.0002 at 125 Hz and P = 0.002 at 135 Hz and P = 0.003 at 150 Hz) but not for the two lowest (Kruskal-Wallis test, P = 0.63 at 100 Hz and P = 0.87 at 115 Hz), and (2) normalized cs followed a power law behavior not seen in absence of vascular outgrowths (ANOVA test, P < 0.0001). These results showed that vascular outgrowths acted as micro-obstacles altering the dispersion relationships of propagating shear waves and that MRE could provide valuable information about microvascular changes.
磁共振弹性成像（MRE）利用宏观剪切波传播来量化软组织的力学特性。微小障碍物能够影响剪切波的宏观色散特性。由于疾病或治疗会改变血管结构的机械完整性和组织结构，如果血管是波散射的来源，那么MRE应该能够检测到这些变化。为了验证这一点，使用主动脉环模型进行MRE，以量化由于血管增生的存在而导致的剪切波速度cs的改变。将包含在基质胶中的18个大鼠主动脉片段（n = 6无增生，n = 6径向增生范围约为600 µm，n = 6约为850 µm）用7特斯拉磁共振扫描仪（布鲁克，PharmaScan）成像。除了多频MRE（ν = 100、115、125、135和150 Hz）外，还采集了高分辨率解剖图像。在围绕主动脉的约900 µm厚度的环内测量平均cs，并将其归一化为相应基质胶的cs0。频率依赖性拟合幂律模型cs ~ν(y)。扫描后，进行光学显微镜检查以观察增生情况。结果表明，在存在血管增生的情况下，（1）对于三个最高频率，归一化的cs显著增加（Kruskal-Wallis检验，125 Hz时P = 0.0002，135 Hz时P = 0.002，150 Hz时P = 0.003），但对于两个最低频率则不然（Kruskal-Wallis检验，100 Hz时P = 0.63，115 Hz时P = 0.87），并且（2）归一化的cs遵循幂律行为，而在没有血管增生的情况下未观察到这种行为（方差分析检验，P < 0.0001）。这些结果表明，血管增生充当微小障碍物，改变了传播剪切波的色散关系，并且MRE可以提供有关微血管变化的有价值信息。
