Localized characterization of brain tissue mechanical properties by needle induced cavitation rheology and volume controlled cavity expansion

Changes in the elastic properties of brain tissue have been correlated with injury, cancers, and neurodegenerative diseases. However, discrepancies reported moduli are persistent, spatial inhomogeneities complicate interpretation macroscale measurements such as rheology. Here we introduce needle induced cavitation rheology (NICR) volume-controlled cavity expansion (VCCE) facile methods to measure apparent Young's modulus E minimally manipulated tissue, at specific locations sub-millimeter resolution. For different porcine regions sections analyzed by NICR, found be 3.7 ± 0.7 kPa 4.8 1.0 for gray matter, white respectively. VCCE, was 0.76 0.02 matter 0.92 0.01 matter. Measurements from VCCE were more similar those obtained shear (0.75 0.06 kPa) instrumented microindentation (0.97 0.40 (0.86 0.20 kPa). We attributed higher stiffness NICR that method's assumption a instability due neo-Hookean constitutive response, which does not capture strain-stiffening behavior under large strains, therefore did provide appropriate measurements. demonstrate via both analytical modeling spherical finite element geometry, this strain stiffening may prevent instability. take into account employing an incompressible one-term Ogden model find nonlinear tissue. Overall, afforded rapid measurement mechanical intact, healthy mammalian enabling quantitative comparison among also between species. Finally, accurate estimation requires include models here represented inclusion VCCE.