MRelastografi

MRelastografi, often equated with MR elastography (MRE) in English-language literature, is an MRI-based imaging modality that measures tissue stiffness by imaging the propagation of mechanical shear waves through the body. The technique combines external or internal mechanical excitation with MRI to produce quantitative maps of tissue elasticity, which can aid in characterizing disease processes that alter stiffness, such as fibrosis or tumors.

Principle and workflow: A driver generates low-frequency vibrations applied to the region of interest. The resulting shear waves travel through the tissue and produce tiny displacements that are captured by specially designed MRI sequences with motion encoding gradients. Inversion algorithms then convert the wave field into a stiffness map, or elastogram, with values typically expressed in kilopascals.

Clinical applications: The most established use is noninvasive staging of liver fibrosis, where higher stiffness correlates with advancing fibrosis. MRE also shows promise in evaluating stiffness in the breast, pancreas, kidneys, brain, and heart, and is used in research for tumor characterization and treatment monitoring. Compared with biopsy, MRE provides a global assessment of tissue properties and reduces sampling error; it is often added to a conventional MRI exam for broader tissue characterization.

Limitations and considerations: MRE requires dedicated hardware (a vibration driver) and specific MR sequences. Results can be affected by motion, obesity, iron overload, or severe inflammation. Availability and expertise vary by center. Safety is high, as vibrations are low amplitude and do not involve ionizing radiation.

History: The technique emerged in the 1990s with foundational work leading to widespread clinical adoption in the 2000s, particularly for liver disease. The term MRelastografi reflects a localized or language-specific rendering of MR elastography.