Eckstein Kevin N, Yoon Daniel, Ruding Margrethe, Balouchzadeh Ramin, Thompson-Mazzeo Aaliyah, Okamoto Ruth J, Johnson Curtis L, McGarry Matthew D J, Bayly Philip V
Mechanical Engineering and Materials Science, Washington University, St. Louis, Missouri, USA.
Biomedical Engineering, University of Delaware, Newark, Delaware, USA.
Magn Reson Med. 2025 May;93(5):2123-2139. doi: 10.1002/mrm.30394. Epub 2024 Dec 3.
Imaging phantoms with known anisotropic mechanical properties are needed to evaluate magnetic resonance elastography (MRE) methods to estimate anisotropic parameters. The aims of this study were to fabricate mechanically anisotropic MRE phantoms, characterize their mechanical behavior by direct testing, then assess the accuracy of MRE estimates of anisotropic properties using a transversely isotropic nonlinear inversion (TI-NLI) algorithm.
Directionally scaled and unscaled lattices were designed to exhibit anisotropic or isotropic mechanical properties. Lattices were three-dimensionally printed in poly(ethelyne glycol) diacrylate using a commercial digital light processing printer, then infilled with gelatin to form a composite material. Benchtop testing determined two shear stiffnesses, and , governing loading parallel and perpendicular to the symmetry axis, and two analogous Young's moduli and . From these measures, shear anisotropy = and tensile anisotropy = were calculated. Three phantoms were driven by a central actuator and imaged with MRE at frequencies from 300 to 500 Hz. From MRE data, the TI-NLI algorithm estimated maps of , , and .
In benchtop tests, geometrically scaled lattice composites exhibited the following anisotropic properties: = 6.1 ± 0.7 kPa, = 0.83 ± 0.13, = 0.78 ± 0.09} (mean ± standard deviation). MRE of scaled lattice composites revealed elliptical wavefields; TI-NLI analysis identified the following median property ranges: = 11-19 kPa, = 0.6-1.0, = 0.8-1.6}.
Anisotropic MRE phantoms are created by embedding anisotropic three-dimensionally printed lattices into a softer matrix. The TI-NLI algorithm accurately estimates spatial contrast in anisotropic properties.
需要具有已知各向异性力学性能的成像体模来评估磁共振弹性成像（MRE）方法以估计各向异性参数。本研究的目的是制造具有机械各向异性的MRE体模，通过直接测试表征其力学行为，然后使用横向各向同性非线性反演（TI-NLI）算法评估MRE对各向异性特性估计的准确性。
设计定向缩放和未缩放的晶格以表现出各向异性或各向同性的力学性能。使用商用数字光处理打印机在聚（乙二醇）二丙烯酸酯中对晶格进行三维打印，然后用明胶填充以形成复合材料。台式测试确定了两个剪切刚度， 和 ，分别控制平行和垂直于对称轴的加载，以及两个类似的杨氏模量 和 。根据这些测量值，计算出剪切各向异性 = 和拉伸各向异性 = 。三个体模由中央致动器驱动，并在300至500Hz的频率下用MRE成像。根据MRE数据，TI-NLI算法估计了 、 和 的图谱。
在台式测试中，几何缩放的晶格复合材料表现出以下各向异性特性： = 6.1±0.7 kPa， = 0.83±0.13， = 0.78±0.09}（平均值±标准差）。缩放晶格复合材料的MRE显示出椭圆形波场；TI-NLI分析确定了以下中位数特性范围： = 11 - 19 kPa， = 0.6 - 1.0， = 0.8 - 1.6}。
通过将各向异性的三维打印晶格嵌入较软的基质中创建各向异性MRE体模。TI-NLI算法准确估计了各向异性特性的空间对比度。
