Structure-sensitive quantitative MR imaging of renal mechanical properties: Combined anisotropic MR elastography and diffusion tensor imaging for the assessment of renal function

磁共振弹性成像（MRE）可以无创地表征体内组织的粘弹性，它是一种成熟的方法，已应用于肝纤维化分期，肿瘤分级等领域。在拟议的项目中，将开发多频MRE（MMRE）和扩散张量成像（DTI）的组合，用于肾功能的机械评估。该项目旨在首次研究体内天然肾脏的机械性能，充分考虑各向异性，这是肾脏的一个关键特征，因为沿着Henle袢，集合小管和血管束的径向取向结构。该技术将首先在离体组织样本中进行验证，然后在健康志愿者中进行测试，最后应用于慢性肾脏病（CKD）患者。拟议项目分为以下工作包：（1）在Charité CCM放射科的临床MRI扫描仪上实施MMRE/DTI组合以及患者激活的呼吸门控系统和自动气动执行器。(2)在琼脂糖凝胶包埋的离体猪肾上验证组合MMRE/DTI。(3)数据后处理和各向异性反演方法的发展。(4)将MMRE/DTI联合技术应用于健康志愿者的肾脏，并建立肾皮质、髓质和肾门等区域各向异性粘弹性参数的参考值。(5)CKD患者的初步研究以及各向异性粘弹性参数与临床数据的相关性。我们结合MMRE/DTI将提供恢复的全弹性张量，提供了一个全面的各向异性材料的力学描述。这项技术可能会带来纤维化和灌注相关的肾硬度变化的见解。MMRE/DTI联合检测的肾脏力学特性可作为新的定量成像指标用于CKD患者肾功能损害的检测。

Magnetic Resonance Elastography (MRE) allows non-invasive characterization of the viscoelastic properties of tissue in vivo, it is a well established method which has been applied in areas such as liver fibrosis staging, tumor grading, etc. In the proposed project, combined multifrequency MRE (MMRE) and diffusion tensor imaging (DTI) will be developed for the mechanical assessment of renal function. The project aims to investigate, for the first time, the mechanical properties of native kidneys in vivo taking full consideration of anisotropy which is a key feature in kidney due to the radially oriented architecture along the Henle loops, collecting tubules and vascular bundles. This proposed MRE/DTI technique will be firstly validated in ex vivo tissue sample, then tested in healthy volunteers and finally applied to patients with chronic kidney disease (CKD). The proposed project is divided into the following work packages: (1) Implementation of combined MMRE/DTI together with the patient-activated respiratory gating system and automated pneumatic actuator on a clinical MRI scanner of the Department of Radiology, Charité CCM. (2) Validation of combined MMRE/DTI on ex vivo porcine kidney embedded in agarose gel. (3) Method development in data post-processing and anisotropic inversion. (4) Application of the combined MMRE/DTI techniques to the kidneys in healthy volunteers and establish reference values for anisotropic viscoelastic parameters for regions such as renal cortex, medulla and hilus. (5) Pilot study in patients with CKD and correlation of anisotropic viscoelastic parameters to clinical data. Our combined MMRE/DTI will provide the recovery of the full elasticity tensor which offers a comprehensive mechanical description of anisotropic materials. This technique may bring insights into fibrosis and perfusion related renal stiffness changes. The renal mechanical properties obtained from combined MMRE/DTI could be used in the future as new quantitative imaging maker for detecting renal dysfunction in patients CKD.