Department of Radiology, Children's Hospital of Philadelphia, University of Pennsylvania, Philadelphia, PA, USA.
Department of Radiology, Mayo Clinic, Rochester, MN, USA.
Methods Mol Biol. 2021;2216:301-323. doi: 10.1007/978-1-0716-0978-1_18.
Magnetic resonance elastography (MRE) is an emerging imaging modality that maps the elastic properties of tissue such as the shear modulus. It allows for noninvasive assessment of stiffness, which is a surrogate for fibrosis. MRE has been shown to accurately distinguish absent or low stage fibrosis from high stage fibrosis, primarily in the liver. Like other elasticity imaging modalities, it follows the general steps of elastography: (1) apply a known cyclic mechanical vibration to the tissue; (2) measure the internal tissue displacements caused by the mechanical wave using magnetic resonance phase encoding method; and (3) infer the mechanical properties from the measured mechanical response (displacement), by generating a simplified displacement map. The generated map is called an elastogram.While the key interest of MRE has traditionally been in its application to liver, where in humans it is FDA approved and commercially available for clinical use to noninvasively assess degree of fibrosis, this is an area of active research and there are novel upcoming applications in brain, kidney, pancreas, spleen, heart, lungs, and so on. A detailed review of all the efforts is beyond the scope of this chapter, but a few specific examples are provided. Recent application of MRE for noninvasive evaluation of renal fibrosis has great potential for noninvasive assessment in patients with chronic kidney diseases. Development and applications of MRE in preclinical models is necessary primarily to validate the measurement against "gold-standard" invasive methods, to better understand physiology and pathophysiology, and to evaluate novel interventions. Application of MRE acquisitions in preclinical settings involves challenges in terms of available hardware, logistics, and data acquisition. This chapter will introduce the concepts of MRE and provide some illustrative applications.This publication is based upon work from the COST Action PARENCHIMA, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers. This introduction chapter is complemented by another separate chapter describing the experimental protocol and data analysis.
磁共振弹性成像（MRE）是一种新兴的成像方式，可绘制组织的弹性特性，如剪切弹性模量。它可以进行非侵入性的硬度评估，这是纤维化的替代指标。MRE 已被证明能够准确地区分无或低阶段纤维化与高阶段纤维化，主要是在肝脏中。与其他弹性成像方式一样，它遵循弹性成像的一般步骤：（1）向组织施加已知的周期性机械振动；（2）使用磁共振相位编码方法测量机械波引起的内部组织位移；（3）通过生成简化的位移图，从测量的机械响应（位移）推断机械特性。生成的图称为弹性图。虽然 MRE 的主要关注点一直是其在肝脏中的应用，在人类中，它已获得 FDA 批准，并可用于临床，以非侵入性方式评估纤维化程度，但这是一个活跃的研究领域，在大脑、肾脏、胰腺、脾脏、心脏、肺部等方面有新的应用。详细回顾所有的努力超出了本章的范围，但提供了一些具体的例子。MRE 最近在评估肾脏纤维化方面的非侵入性评估中的应用具有很大的潜力，可以用于慢性肾病患者的非侵入性评估。在临床前模型中开发和应用 MRE 主要是为了将测量值与“金标准”侵入性方法进行验证，更好地了解生理学和病理生理学，并评估新的干预措施。在临床前环境中应用 MRE 采集涉及硬件、物流和数据采集方面的挑战。本章将介绍 MRE 的概念，并提供一些说明性的应用。本出版物基于 COST 行动 PARENCHIMA 的工作，这是一个由社区驱动的网络，由欧洲合作科学技术（COST）计划资助，旨在提高肾脏 MRI 生物标志物的可重复性和标准化。本章由另一章单独介绍实验方案和数据分析。
