Visualizing ultrasonically induced shear wave propagation using phase-sensitive optical coherence tomography for dynamic elastography

Abstract

We report on the use of phase-sensitive optical coherence tomography (PhS-OCT) to detect and track temporally and spatially shear wave propagation within tissue induced by ultrasound radiation force. Kilohertz-range shear waves are remotely generated in sample using focused ultrasound emission and their propagation is tracked using PhS-OCT. Cross-sectional maps of the local shear modulus are reconstructed from local estimates of shear wave speed in tissue-mimicking phantoms. We demonstrate the feasibility of combining ultrasound radiation force and PhS-OCT to perform high-resolution mapping of the shear modulus.

Optical coherence elastography – OCT at work in tissue biomechanics [Invited]

“…ARF in OCE makes use of 10s μs-10 ms bursts of ultrasound in the megahertz range to modulate the force applied to the sample. The resulting displacement has been detected as the axial displacement along the ultrasound beam at focus [83][84][85][86][87] or as an axial displacement associated with a shear wave generated by the burst at some lateral offset from the focus [88][89][90]. By scanning the frequency of the amplitude modulation, it has also been demonstrated that acoustic mechanical resonance can be detected along the axial direction [91].…”

Shear wave elastography using amplitude-modulated acoustic radiation force and phase-sensitive optical coherence tomography

“…Water was the coupling medium between the transducer and the sample. The sample was also covered with a thin layer of echographic gel to prevent strong US reflections at the sample top surface, 14 and a thin cover glass to avoid surface ripple artifacts. 14,19 The layer of gel also works as a mechanical coupling medium that reduces the effect of surface acoustic waves at the top interface of the sample.…”

“…In a previous paper, 14 we presented a system for shear wave elastography using phase-sensitive OCT (PhS-OCT) and ARF to map the stiffness of tissue-mimicking phantoms. ARF can potentially generate shear waves in the cornea as well as in the intraocular lens.…”

Longitudinal shear wave imaging for elasticity mapping using optical coherence elastography

“…Benefiting from the micrometer spatial resolution and millimeter penetration of optical coherence tomography (OCT), optical coherence elastography (OCE) based on the shear wave measurement has shown promising results in biomedical studies, including blood coagulation assessment, 8 ocular elasticity assessment, 4,9 and cardiac muscle measurement. 10 In an OCE application, an excitation from a force source, such as an ultrasonic transducer, [11][12][13][14][15] an airpuff device, 9 and a piezo-transducer (PZT), 16 is commonly applied to induce vibration, and OCT is used to detect the displacement and visualize the shear wave. Using shear wave elastography, the shear modulus is quantified by tracking the shear wave propagation.…”

“…Using shear wave elastography, the shear modulus is quantified by tracking the shear wave propagation. In previous measurements, the transverse shear wave propagates perpendicular to the force direction, so the shear modulus in the lateral region of the force can be quantified; [11][12][13] however, the shear modulus in the axial region of the force cannot be measured.…”