Ultra-wideband optical coherence elastography from acoustic to ultrasonic frequencies

TL;DR

This paper introduces an optical coherence elastography method that extends the frequency range from acoustic to ultrasonic, enabling detailed mechanical property analysis of various materials and tissues with high resolution.

Contribution

The authors developed a novel optical coherence elastography technique that significantly broadens the measurable frequency range to MHz, allowing in situ 3D characterization of materials.

Findings

Measured stiffness of hard materials including bones with mm-scale resolution.

Characterized soft viscoelastic materials from 100 Hz to 1 MHz.

Profiled depth-dependent shear modulus in ex vivo cartilages and in vivo human skin.

Abstract

Visualizing elastic waves by noninvasive imaging has been useful for analyzing the mechanical properties of materials and tissues. However, the maximum wave frequency of elastography has been limited to ~10 kHz due to the finite sensitivity to small vibration and finite imaging speed. Here, we present an optical coherence elastography technique that extends the frequency range to MHz by noise reduction, anti-aliasing demodulation, and advanced wave analysis. Our system can measure the stiffness of hard (GPa) materials including bones with mm-scale resolution and characterize soft, viscoelastic materials from 100 Hz to 1 MHz. The dispersion of Rayleigh surface waves over the wide frequency range allowed us to profile depth-dependent shear modulus (10 kPa to 100 MPa) in cartilages ex vivo and the human skin in vivo. This technique opened a new window for the characterization of materials in situ with 3-dimensional resolution.