Thayer School of Engineering, Dartmouth College, Hanover, NH, 03755, USA.
University of Delaware, Newark, DE, 19716, USA.
J Mech Behav Biomed Mater. 2023 May;141:105744. doi: 10.1016/j.jmbbm.2023.105744. Epub 2023 Mar 1.
Measuring tissue parameters from increasingly sophisticated mechanical property models may uncover new contrast mechanisms with clinical utility. Building on previous work on in vivo brain MR elastography (MRE) with a transversely-isotropic with isotropic damping (TI-ID) model, we explore a new transversely-isotropic with anisotropic damping (TI-AD) model that involves six independent parameters describing direction-dependent behavior for both stiffness and damping. The direction of mechanical anisotropy is determined by diffusion tensor imaging and we fit three complex-valued moduli distributions across the full brain volume to minimize differences between measured and modeled displacements. We demonstrate spatially accurate property reconstruction in an idealized shell phantom simulation, as well as an ensemble of 20 realistic, randomly-generated simulated brains. We characterize the simulated precisions of all six parameters across major white matter tracts to be high, suggesting that they can be measured independently with acceptable accuracy from MRE data. Finally, we present in vivo anisotropic damping MRE reconstruction data. We perform t-tests on eight repeated MRE brain exams on a single-subject, and find that the three damping parameters are statistically distinct for most tracts, lobes and the whole brain. We also show that population variations in a 17-subject cohort exceed single-subject measurement repeatability for most tracts, lobes and whole brain, for all six parameters. These results suggest that the TI-AD model offers new information that may support differential diagnosis of brain diseases.
从日益复杂的机械特性模型中测量组织参数，可能会揭示出具有临床应用价值的新对比机制。在基于各向同性阻尼横向各向同性（TI-ID）模型的活体脑部磁共振弹性成像（MRE）的先前工作基础上，我们探索了一种新的横向各向同性各向异性阻尼（TI-AD）模型，该模型涉及六个独立的参数，用于描述刚度和阻尼的各向异性行为。机械各向异性的方向由扩散张量成像确定，我们拟合三个全脑容积的复值模量分布，以最小化测量值和模型值之间的差异。我们在理想化的壳模型模拟中展示了空间准确的特性重建，以及 20 个真实的、随机生成的模拟大脑的集合。我们对所有六个参数在主要白质束中的模拟精度进行了表征，发现它们可以通过 MRE 数据以可接受的精度独立测量。最后，我们提出了活体各向异性阻尼 MRE 重建数据。我们对单个受试者的八次重复 MRE 脑部检查进行了 t 检验，发现大多数束、脑叶和整个大脑的三个阻尼参数在统计学上是不同的。我们还表明，在 17 名受试者队列中，大多数束、脑叶和整个大脑的群体变化超过了单次受试者测量的重复性，所有六个参数均如此。这些结果表明，TI-AD 模型提供了新的信息，可能有助于脑部疾病的鉴别诊断。
