Advanced Magnetic Resonance Elastography

描述（由申请人提供）：磁共振弹性成像（MRE）是一种新兴的成像方式，旨在恢复组织机械性能的高分辨率图。虽然这项技术在过去几年中取得了长足的进步，目前正在研究许多有前景的临床应用，但迄今为止产生的几乎所有结果都是基于组织是线性弹性的假设。然而，人们普遍认为，许多组织并不像各向同性线弹性介质那样响应，而是表现出更复杂的力学行为。具体来说，它们可以用粘弹性、各向异性和非线性力学性能来更准确地表示。因此，如果该技术要实现其作为诊断决策辅助的全部潜力，扩展MRE方法以解释这些更完整和准确的机械性能特征似乎至关重要。拟议项目的总体目标是开发、验证和评估MRE方法，用于成像与组织的常规模型描述相关的机械性能参数，这些模型描述是粘弹性、各向异性或非线性介质，就MRE过程中施加的刺激的机械响应而言。该项目的具体目标是：(1)开发MR数据采集技术，以观察具有目标行为的幻影中这些复杂的机械效应；(2)开发将MR位移数据转换为表征所使用的幻影材料的机械性能估计的算法；(3)通过一系列模拟和幻影实验验证这些发展：(a)确定准确性；力学性能估计过程的稳定性和唯一性，(b)优化模型复杂性(准确表征运动（和力学性能）和模型效率/稳定性（当算法应用于体内数据时提供鲁棒性）之间的权衡，以及(c)确定当介质表现出更复杂的力学性能时，由线性弹性假设引起的剪切模量估计的不准确性程度。

DESCRIPTION (provided by applicant): Magnetic Resonance Elastography (MRE) is an emerging imaging modality which seeks to recover high resolution maps of tissue mechanical properties. While the technique has been advanced considerably over the last several years and a number of promising clinical applications are now being investigated, almost all of the results produced to date have been based on the assumption that tissue is linearly elastic. However, it is generally accepted that many tissues do not respond as an isotropic linearly-elastic medium but rather exhibit more complex mechanical behaviors. Specifically, they can be more accurately represented by viscoelastic, anisotropic and nonlinear mechanical properties. As a result it seems critical to extend MRE methodology to account for these more complete and accurate mechanical property characterizations if the technique is to realize its full potential as an aid to diagnostic decision-making. The overall goal of the proposed project is to develop, validate and evaluate MRE methods for imaging the mechanical property parameters associated with conventional model descriptions of tissue as either a viscoelastic, an anisotropic or a nonlinear medium in terms of its mechanical response to the stimulus applied during MRE procedures. The specific aims of the project are to (1) Develop the MR data acquisition techniques required to observe these complex mechanical effects in phantoms that possess the targeted behaviors, (2) Develop the algorithms for converting the MR displacement data into mechanical property estimates which characterize the phantom materials used, and (3) Validate these developments through a series of simulation and phantom experiments which (a) determine the accuracy, stability and uniqueness of the mechanical property estimation process, (b) optimize the trade-off between model complexity which accurately characterizes the motion (and mechanical properties) and model efficiency/stability which provides robustness when algorithms are applied to in vivo data, and (c) identify the magnitude of the inaccuracies in shear modulus estimation incurred by assumptions of linear elasticity when the medium exhibits more complex mechanical properties.