Frequency-dependent shear properties of annulus fibrosus and nucleus pulposus by magnetic resonance elastography
Frequency-dependent shear properties of annulus fibrosus and nucleus pulposus by magnetic resonance elastography
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DOI：
10.1002/nbm.3918
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发表时间：
2018-10-01
影响因子：
2.9
通讯作者：
Perie, D.
中科院分区：
文献类型：
--
作者：
Beauchemin, P. F.;Bayly, P. V.;Perie, D.
衰老和退变与椎间盘机械性能的变化有关，这引起了人们对建立机械性能作为退行性级联的早期生物标志物的兴趣。椎间盘的磁共振弹性成像 (MRE) 通常仅限于髓核，因为纤维环较硬且含水量较少。这项工作的目的是使高频针 MRE 能够表征髓核和纤维环的剪切模量。从新鲜牛尾中取出牛椎间盘，并通过针状 MRE 进行表征。将针插入圆盘的中心，并通过放大的压电致动器产生振动。 MRE 采集是在 4.7-T 小动物 MR 扫描仪上使用具有正弦运动编码梯度的自旋回波序列进行的。在 1000-1800Hz 的频率范围内重复采集。使用局部频率估计反演算法来计算剪切模量。硬度图允许可视化被均匀凝胶包围的较硬的纤维环包围的软髓核。观察到髓核和纤维环之间的剪切模量存在显着差异，并且剪切模量随着激励频率的增加而增加，这与文献一致。这项研究表明，使用临床前磁共振成像 (MRI) 扫描仪通过针 MRE 可以对椎间盘的髓核和纤维环进行整体表征。 MRE 是绘制椎间盘复杂特性的强大方法。所开发的方法可以通过保留相邻椎骨并刺穿椎间盘的侧面来适应原位使用，从而可以评估渗透压对椎间盘机械行为的影响。
Aging and degeneration are associated with changes in mechanical properties in the intervertebral disc, generating interest in the establishment of mechanical properties as early biomarkers for the degenerative cascade. Magnetic resonance elastography (MRE) of the intervertebral disc is usually limited to the nucleus pulposus, as the annulus fibrosus is stiffer and less hydrated. The objective of this work was to adapt high-frequency needle MRE to the characterization of the shear modulus of both the nucleus pulposus and annulus fibrosus. Bovine intervertebral discs were removed from fresh oxtails and characterized by needle MRE. The needle was inserted in the center of the disc and vibrations were generated by an amplified piezoelectric actuator. MRE acquisitions were performed on a 4.7-T small-animal MR scanner using a spin echo sequence with sinusoidal motion encoding gradients. Acquisitions were repeated over a frequency range of 1000-1800Hz. The local frequency estimation inversion algorithm was used to compute the shear modulus. Stiffness maps allowed the visualization of the soft nucleus pulposus surrounded by the stiffer annulus fibrosus surrounded by the homogeneous gel. A significant difference in shear modulus between the nucleus pulposus and annulus fibrosus, and an increase in the shear modulus with excitation frequency, were observed, in agreement with the literature. This study demonstrates that global characterization of both the nucleus pulposus and annulus fibrosus of the intervertebral disc is possible with needle MRE using a preclinical magnetic resonance imaging (MRI) scanner. MRE can be a powerful method for the mapping of the complex properties of the intervertebral disc. The developed method could be adapted for in situ use by preserving adjacent vertebrae and puncturing the side of the intervertebral disc, thereby allowing an assessment of the contribution of osmotic pressure to the mechanical behavior of the intervertebral disc.