Experimental detection of skull-based ultrasonic Lamb waves as an intracranial pressure monitoring method

Abstract

Pressure within the cranial vault, which consists of cerebrospinal fluid, the central nervous system (CNS), and blood, is referred to as intracranial pressure (ICP). Severely high ICP can damage the CNS so its monitoring is crucial for patients deemed to be at high risk of elevated ICP, such as those with traumatic brain injuries or undergoing neurosurgery. The standard approach requires the insertion of a pressure probe into the ventricles through a burr hole on the skull. A noninvasive alternative to ICP monitoring using guided acoustic waves on the skull was investigated. Different modes of Lamb waves were generated in submerged acrylic skull models and their corresponding leaky components were detected. The behavior of Lamb waves upon asymmetrical pressure loading of the plate was examined to reveal metrics that were sensitive to pressure changes underneath the skull. Dispersion curves, including the anti-symmetrical and symmetrical modes of Lamb waves propagation in thin, isotropic acrylic plate comparable to thickness of cortical skull bone were computed using the Rayleigh–Lamb equation and the bisection method. Physical parameters, such as critical angle, frequency-dependence phase velocity, and time-of-arrival were analyzed.