MRElastographie

Magnetic resonance elastography (MRE) is an MRI-based imaging technique that non-invasively measures tissue stiffness by visualizing the propagation of mechanical shear waves through body tissues. A driver placed on the surface delivers low-frequency vibrations, typically 40–60 Hz. A phase-contrast MRI sequence with motion-encoding gradients captures the resulting displacements, and data from several slices and directions are used to generate an elastogram, a quantitative map of tissue stiffness usually expressed in kilopascals (kPa). Higher stiffness indicates that tissue is less compliant, which can reflect fibrosis, tumor involvement, edema, or other pathology.

The workflow involves applying external vibration, acquiring MR images that encode tissue motion, and applying an inversion algorithm to convert the measured displacement field into a stiffness map. The resulting elastogram is often color-coded and superimposed on conventional MRI images. MRE is widely used because it provides a quantitative, operator-independent measure of tissue elasticity and can be integrated into routine liver MRI protocols.

Clinical use and limitations: MRE is most established for staging liver fibrosis, where stiffness correlates with fibrosis stage and helps guide management. It is also explored in other organs such as the brain, breast, pancreas, and joints. Compared with ultrasound elastography, MRE can offer higher accuracy in certain patient groups, including those with obesity or ascites. Limitations include reduced signal in cases of iron overload, severe breath-holding difficulty, or excessive body habitus, and susceptibility to motion or artifact. Availability requires MRI-compatible hardware and appropriate post-processing.