Application of optical coherence elastography to assess mechanical properties of the anterior cerebral artery
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Abstract
Optical Coherence Elastography (OCE) is a medical imaging technique that is sensitive to mechanical properties of soft biological tissues. In this study Optical Coherence Elastography was used to image steady-state vibration fields and thus assess shear elastic modulus of Anterior Cerebral Arteries (ACAs) and tissue mimicking phantoms.Phantoms and ACA samples were tested under the OCE setup. The elastic waves were excited by a piezoelectric actuator over a broad frequency range, while scanning lens acquired the signal that contain information about the wave propagation. Signal was then processed and displacements data were obtained. Dispersion curves were generated by processing displacements data at each corresponding frequency. In order to replicate the in vivo conditions, ACAs were pre-stretched and pressurized during OCE data acquisition.
Lamb wave theory under the assumption of isotropic, homogeneous and linear elastic material behavior has been applied to interpret the results of the OCE experiments. The dispersion relation was derived for two cases of air-solid-liquid and air-solid-air boundary conditions. Shear modulus was estimated by fitting the theoretical dispersion relation to the experimentally measured dispersion curves.
Both ACAs and phantoms were tested under traditional quasi-static mechanical testing conditions. Biaxial inflation-extension tests were performed on ACA samples and uniaxial tensile tests were performed on the phantoms. Results from the OCE experiment were then compared with mechanical testing, as both demonstrated arterial stiffening with pressurization and aging of the ACA samples.
The Lamb wave approach is based on the assumption that the material properties are homogeneous. To relax this assumption, an initial feasibility study considers an inverse finite element method to extract the spatial distribution of mechanical properties along the sample. A weak form of the inverse problem was derived from the elastic wave equation using a least squares formulation, and assuming the local homogeneity approximation. The research is ongoing to apply inverse method to the phantom’s experimental data and to infer its shear modulus distribution.
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2025