Abstract
Optical coherence elastography (OCE) provides deformation or material properties, mapping of soft tissue. We aim to develop a robust speckle tracking OCE technique with improved resolution and accuracy. A digital image correlation (DIC)-based OCE technique was developed by combining an advanced DIC algorithm with optical coherence tomography (OCT). System calibration and measurement error evaluation demonstrated that this DIC-based OCE technique had a resolution of ~0.6 μm displacement and <0.5% strain measurement in the axial scan direction. The measured displacement ranged from 0.6 to 150 μm, obtained via phantom imaging. The capability of the DIC-based OCE technique, for differentiation of stiffness, was evaluated by imaging a candle gel phantom with an irregularly shaped stiff inclusion. OCE imaging of a chicken breast sample differentiated the fat, membrane, and muscle layers. Strain elastograms of an aneurysm sample showed heterogeneity of the tissue and clear contrast between the adventitia and media. These promising results demonstrated the capability of the DIC-based OCE for the characterization of the various components of the tissue sample. Further improvement of the system will be conducted to make this OCE technique a practical tool for measuring and differentiating material properties of soft tissue.
Highlights
Optical coherence elastography (OCE) provides deformation or the material property mapping of soft tissue.[1,2] The addition of elastographic contrast may improve the inherent ability of optical coherence tomography (OCT) to differentiate the composition and structure of soft tissue.[3]
Speckle-tracking based OCE can measure greater deformation than phase-based OCE methods as phase-based OCE is limited by the phase stability of OCT system[10] and the phase wrapping induced by large physical deformations or high detected particle velocities within the imaging volume
A candle gel and TiO2 phantom including a small stiff part made of silicon and TiO2 were tested by the digital image correlation (DIC)-based OCE technique
Summary
Optical coherence elastography (OCE) provides deformation or the material property mapping of soft tissue.[1,2] The addition of elastographic contrast may improve the inherent ability of optical coherence tomography (OCT) to differentiate the composition and structure of soft tissue.[3]. OCE may provide high-resolution characterization of strains in arterial walls, which would be important complementary information for determining the stability of atherosclerotic lesions.[4] There are two main categories of OCE techniques, phase-based methods[5,6] and speckle tracking techniques,[7,8,9] which rely on the structure of the speckle pattern when it is fixed. Speckle-tracking based OCE can measure greater deformation than phase-based OCE methods as phase-based OCE is limited by the phase stability of OCT system[10] and the phase wrapping induced by large physical deformations or high detected particle velocities within the imaging volume. Phase unwrapping could extend the measurement range of the phase-based method, it is difficult to apply due to noise corruption or discontinuity of the wrapped phase maps in OCT imaging.[6,11] The principle of speckle tracking
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