Observation of guided acoustic waves in a human skull

TL;DR

This study reports the first observation of guided acoustic waves in an ex vivo human skull, revealing properties that could improve transcranial ultrasound imaging and therapy by enabling more efficient wave transmission.

Contribution

It is the first to demonstrate guided acoustic waves in the human skull, specifically quasi-Rayleigh waves confined to cortical bone, at frequencies between 0.2 and 1.5 MHz.

Findings

Guided waves observed in human skull are quasi-Rayleigh waves.

These waves are confined to the cortical bone layer.

Findings may enhance transcranial ultrasound techniques.

Abstract

Human skull poses a significant barrier for the propagation of ultrasound waves. Development of methods enabling more efficient ultrasound transmission into and from the brain is therefore critical for the advancement of ultrasound-mediated transcranial imaging or actuation techniques. We report on the first observation of guided acoustic waves in the near-field of an ex vivo human skull specimen in the frequency range between 0.2 and 1.5 MHz. In contrast to what was previously observed for the guided wave propagation in thin rodent skulls, the guided wave observed in a higher frequency regime corresponds to a quasi-Rayleigh wave, mostly confined to the cortical bone layer. The newly discovered near-field properties of the human skull are expected to facilitate the development of more efficient diagnostic and therapeutic techniques based on transcranial ultrasound.