Cavitation to Study Brain Mechanics and Tissue Interface Strength*

Cavitation is the rapid expansion of an instability within a material. There is a considerable need to study cavitation in biological tissue, as cavitation-related damage has been implicated in explosive blast injuries on military personnel. Post-mortem analysis of human brains exposed to blasts revealed scarring at boundaries between white and gray matter, at the outermost layer, and at blood vessel/tissue interfaces. Our technique introduces a single bubble at the tip of a needle at a specific location and depth to determine localized brain properties and the impact of tissue boundaries on cavitation damage path. Finite element modeling concludes that if a tissue-tissue interface is weaker than the needle injection path, the cavitation damage propagates along the interface. Our data suggests that interfaces synergistically facilitate fracture propagation at critical pressures 5 kPa less than required to cavitate bulk thalamus. When cavitation occurs near the corpus callosum, we observe a fracture propagation along the corpus callosum and cerebral cortex interface. In deeper regions, fracture separates the amygdala from the thalamus region of brain. This approach allows us to study cavitation damage paths to better understand the mechanism for brain injury.