Material characterization of in vivo and in vitro porcine brain using shear wave elasticity

Shear wave elasticity imaging was used to examine changes in porcine brain tissue shear modulus as a function of several experimental and physiological parameters. Animal studies were performed with two different ultrasound transducers. Four in vivo subjects were exposed to inversion and increased ICP, over a relevant physiological range (0-40mmHg), was correlated with shear wave speed estimates. Additional in vitro specimens were used to investigate presence of changes with temperature, confinement, spatial location, and transducer orientation. Statistically significant results include a 28% decrease in stiffness with increased temperature and a 22-50% increase in stiffness with decreasing external confinement.