Spectroscopic optical coherence elastography

Abstract

We present an optical technique to image the frequency-dependent complex mechanical response of a viscoelastic sample. Three-dimensional hyperspectral data, comprising two-dimensional B-mode images and a third dimension corresponding to vibration frequency, were acquired from samples undergoing external mechanical excitation in the audio-frequency range. We describe the optical coherence tomography (OCT) signal when vibration is applied to a sample and detail the processing and acquisition techniques used to extract the local complex mechanical response from three-dimensional data that, due to a wide range of vibration frequencies, possess a wide range of sample velocities. We demonstrate frequency-dependent contrast of the displacement amplitude and phase of a silicone phantom containing inclusions of higher stiffness. Measurements of an ex vivo tumor margin demonstrate distinct spectra between adipose and tumor regions, and images of displacement amplitude and phase demonstrated spatially-resolved contrast. Contrast was also observed in displacement amplitude and phase images of a rat muscle sample. These results represent the first demonstration of mechanical spectroscopy based on B-mode OCT imaging. Spectroscopic optical coherence elastography (S-OCE) provides a high-resolution imaging capability for the detection of tissue pathologies that are characterized by a frequency-dependent viscoelastic response.

Analysis of image formation in optical coherence elastography using a multiphysics approach

“…For example, needle OCE [50, 51] could be simulated by restricting the simulation output to a single A-scan. Dynamic loading methods such as shear wave [5,6], surface wave [7,8], or frequency-swept loading [9,10], could be modeled by running the simulation for each time step. Similarly, the simulation framework is extendable to modeling deformation in 3-D.…”

“…In OCE, a mechanical load is applied to a sample, and the resulting deformation is detected using optical coherence tomography (OCT) [1]. There are many forms of OCE, differentiated by the method of mechanical loading, such as compressive [2][3][4], shear wave [5,6], surface wave [7,8], frequency-swept [9,10] and localized loading using magnetic nanoparticles [11]. Similarly, there are several methods for measuring the resulting sample deformation, including phase-sensitive detection [12,13], speckle tracking [2,4,14,15], and Doppler spectrum analysis [16][17][18].…”

Observation of sound-induced corneal vibrational modes by optical coherence tomography

“…Air-puff can be combined with Scheimpflug camera [7] or optical coherence tomography (OCT) [8] for image-based analysis and estimates of corneal viscoelastic parameters [9]. Other emerging techniques for measuring elastic modulus with spatial resolution include supersonic shear imaging [10], optical coherence elastography [11][12][13][14][15][16], and Brillouin microscopy [17].…”

Optical coherence tomography—current technology and applications in clinical and biomedical research

“…Another embodiment of OCE detects the Doppler shift arising from mechanical vibrations that are excited in the material [104][105][106]. A recently developed detection scheme enables the characterization of the sample response over a wide range of vibration frequencies up into the kilohertz-regime [107,108].…”