High-Resolution, Anisotropic MR Elastography of the Brain

项目总结/摘要 用磁共振弹性成像（MRE）测量人脑的粘弹性 在神经系统疾病的诊断和分期方面表现出了很大的希望。这项工作的目标是 扩展MRE方法，用于可靠地映射大脑中白色物质（WM）束的机械特性。 由于测量不准确，典型的脑MRE方法在研究WM方面取得的成功微乎其微， MRE模型中的基本假设造成的不确定性。具体而言，MRE假设组织 机械各向同性-即在每个方向上的性质是相同的-这在WM中被违反， 由于其良好有序的轴突纤维结构，其具有机械各向异性。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， 挑战限制了以前的方法。特别是，我们试图使用一个简单但准确的纤维模型- 增强的组织行为;一个强大的反演算法，模拟脑组织的异质性; 以及高分辨率成像技术，以捕获富含不同波传播的位移场。 这些元素代表了大脑MRE的最新技术水平，并已在实验室中开发。 多个PI，以及他们在这个研究项目中的整合将有助于通过一个 新的方法。该项目包括三个目标：（1）通过非线性 结合近不可压缩横向各向同性（NITI）材料模型反演（NLI）算法 采用高分辨率、多激发成像方案;（2）严格验证aMRE测量结果 通过模拟，各向异性幻影，在体内和离体的小型猪脑;和（3）测量人类 在体脑WM力学性能。在项目结束时，我们将开发并验证 一种新的aMRE技术，用于精确和鲁棒地测量人脑的WM机械特性。 我们将定位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状况。

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.