High-Resolution, Anisotropic MR Elastography of the Brain

项目摘要/摘要 磁共振弹性成像(MRE)活体测量人脑的粘弹性特性 在诊断和分期神经疾病方面显示出巨大的希望。这项工作的目标是 扩展MRE方法，以可靠地绘制大脑中白质(WM)束的机械特性图。 典型的脑MRE方法在研究WM方面取得的成功微乎其微，原因是测量不准确和 由MRE模型中的基本假设引起的不确定性。具体地说，MRE假设组织是 力学各向同性-即每个方向的特性相同-这在WM中被违反，即 由于其有序的轴突纤维结构，其力学各向异性。为了应对这一挑战，我们建议 开发一种各向异性MRE(AMRE)方法，融合三项技术创新以克服 挑战限制以前的方法。特别是，我们试图使用一种简单但准确的纤维模型- 强化的组织行为；一种健壮的反转算法，模拟了脑组织的异质性； 以及高分辨率成像技术，以捕获丰富的不同波传播的位移场。 这些元素代表了脑部磁共振成像的最先进技术，并已在 多个PI，它们在本研究项目中的集成将通过 新的方法。该项目包括三个目标：(1)通过非线性发展AMRE 结合近不可压缩横观各向同性(NITI)材料模型的反演算法 采用高分辨率、多激发成像方案；(2)AMRE测量的严格验证 通过模拟、各向异性体模、小型猪脑的活体和体外实验；(3)人体测量 活体脑白质力学特性的研究。在项目结束时，我们将开发并验证 用于准确和稳健地测量人脑WM力学特性的新AMRE技术。 我们将把AMRE用于未来包括WM在内的神经系统疾病的研究 损伤或变性，如多发性硬化症和创伤性脑损伤，通过敏感的 通过机械性能评估微观结构健康。

Project Summary/Abstract Viscoelastic properties of the human brain measured in vivo with magnetic resonance elastography (MRE) have shown great promise in diagnosing and staging neurological conditions. The objective of this work is to extend MRE methods for reliably mapping the mechanical properties of white matter (WM) tracts in the brain. Typical brain MRE methods have had minimal success in studying WM due to measurement inaccuracies and uncertainty caused by underlying assumptions in the MRE model. Specifically, MRE assumes tissue is mechanically isotropic – i.e. properties are the same in each direction – which is violated in WM that is mechanically anisotropic due to its well-ordered axonal fiber structure. To address this challenge, we propose to develop an anisotropic MRE (aMRE) approach that fuses three technological innovations to overcome the challenges limiting previous methods. In particular, we seek to use a simple but accurate model of fiber- reinforced tissue behavior; a robust inversion algorithm that models the heterogeneous nature of brain tissue; and a high-resolution imaging technique to capture displacement fields rich with diverse wave propagation. These elements represent the state-of-the-art in brain MRE and have been developed in the labs of the multiple PIs, and their integration in this research project will serve to significantly advance the field through a new methodology. This project encompasses three aims: (1) development of aMRE through the nonlinear inversion (NLI) algorithm with nearly-incompressible, transversely-isotropic (NITI) material model combined with a high-resolution, multi-excitation imaging scheme; (2) rigorous validation of the aMRE measurements through simulations, anisotropic phantoms, mini-pig brains in vivo and ex vivo; and (3) measurement of human brain WM mechanical properties in vivo. At the end of the project we will have developed and validated the novel aMRE technique for accurate and robust measures of WM mechanical properties of the human brain. We will have positioned aMRE to be used in the future study of neurological conditions that include WM damage or degeneration, such as multiple sclerosis and traumatic brain injury, through the sensitive assessment of microstructural health via mechanical properties.