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

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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.