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)可以无创地表征活体组织的粘弹性特性，它是一种成熟的方法，已被应用于肝纤维化分期、肿瘤分级等领域。在拟议的项目中，将开发联合多频MRE(MMRE)和弥散张量成像(DTI)来进行肾功能的机械评估。该项目旨在首次研究活体天然肾脏的力学特性，充分考虑各向异性，这是肾脏的一个关键特征，因为沿Henle环的放射状结构，收集小管和血管束。这项提出的MRE/DTI技术将首先在体外组织样本中得到验证，然后在健康志愿者身上进行测试，最后应用于慢性肾脏疾病(CKD)患者。拟议的项目分为以下工作包：(1)在CharitéCCM放射科临床MRI扫描仪上实施MMRE/DTI与患者激活的呼吸门控系统和自动气动执行器相结合。(2)MMRE/DTI联合应用于琼脂糖凝胶包埋猪肾的验证。(3)数据后处理和各向异性反演方法的发展。(4)将MMRE/DTI技术应用于健康志愿者的肾脏，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患者的先导性研究及各向异性粘弹性参数与临床资料的相关性。我们的MMRE/DTI组合将提供完全弹性张量的恢复，该张量提供各向异性材料的全面力学描述。这项技术可能带来对纤维化和与肾血流灌注相关的肾僵硬变化的洞察。MMRE/DTI联合应用所获得的肾脏力学特性可作为新的定量成像指标用于检测CKD患者的肾功能障碍。

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.