Ringleb Stacie I, Chen Qingshan, Lake David S, Manduca Armando, Ehman Richard L, An Kai-Nan
Biomechanics Laboratory, Division of Orthopedic Research, Mayo Clinic College of Medicine, Rochester, MN 55905, USA.
Magn Reson Med. 2005 May;53(5):1197-201. doi: 10.1002/mrm.20449.
Magnetic resonance elastography (MRE), a phase contrast MRI technique, images the propagation of applied mechanical waves in tissue, allowing shear stiffness to be quantified in vivo. This MRE technique has been validated with static mechanical compression tests. Dynamic mechanical analysis (DMA) may be a more appropriate comparison to MRE because it directly measures the shear modulus dynamically, while compression tests convert the measured elastic modulus to shear modulus with an assumed Poisson ratio. This study compared the shear stiffness estimated with various MRE inversion algorithms (i.e., manual calculation, local frequency estimate, phase gradient, direct inversion, and matched filter) to the dynamic mechanical test. The shear stiffness of five agarose gels with concentrations ranging from 1.5 to 3.5% were measured using MRE and DMA. The phase gradient inversion algorithm overestimated the shear modulus at higher concentrations (i.e., 3-3.5% agar), while the results from the other techniques correlated well with the dynamic mechanical test.
磁共振弹性成像(MRE)是一种相位对比MRI技术,它可以对施加的机械波在组织中的传播进行成像,从而能够在体内对剪切刚度进行量化。这种MRE技术已经通过静态机械压缩试验得到了验证。动态力学分析(DMA)可能是与MRE更合适的比较方法,因为它直接动态测量剪切模量,而压缩试验则通过假设的泊松比将测量的弹性模量转换为剪切模量。本研究将使用各种MRE反演算法(即手动计算、局部频率估计、相位梯度、直接反演和匹配滤波器)估计的剪切刚度与动态力学试验进行了比较。使用MRE和DMA测量了五种浓度范围为1.5%至3.5%的琼脂糖凝胶的剪切刚度。相位梯度反演算法在较高浓度(即3 - 3.5%琼脂)下高估了剪切模量,而其他技术的结果与动态力学试验相关性良好。