Stiffness Change

Stiffness Change refers to the variation in a material's resistance to deformation, typically quantified via the shear modulus or Young’s modulus. In biological tissues, alterations in extracellular matrix composition, cellular density, or pathological deposits (e.g., fibrosis) lead to measurable shifts in mechanical stiffness. These changes influence the propagation speed and wavelength of shear waves introduced during mechanical excitation.

In Magnetic Resonance Elastography, the spatial distribution of stiffness is inferred by capturing wave-induced phase shifts in the MR signal. Regions with increased stiffness exhibit faster shear wave speeds and shorter wavelengths, while softer regions show slower propagation. The resulting elastogram directly visualizes the stiffness-change across the tissue, enabling detection and quantification of pathological states.

Clinically, mapping stiffness changes aids in the early diagnosis of diseases such as liver cirrhosis, tumors with altered mechanical properties, and neurodegenerative disorders characterized by tissue softening. Quantitative elastography metrics derived from stiffness-change provide objective biomarkers for disease staging and treatment monitoring.