EVALUATION OF THE SHEAR MODULUS FOR THE BLOOD VESSEL WALL USING INTRAVASCULAR OPTICAL COHERENCE TOMOGRAPHY RAW DATA
A comparison of the effectiveness of the two approaches to evaluation of the shear modulus using optical coherence elastography is presented. The first approach is based on reference data on the density of the examined tissue. Intravascular optical coherence tomography (IOCT) structural images are read and segmented. The main layers (media, adventitia, and intima) of the blood vessel under the study are identified. Shear wave propagation in the layers is monitored. The shear wave propagation velocity in each layer is calculated using the tilt angle in relation with the scanning moments. The shear modulus is calculated using the shear wave velocity and the density of the tissue. The second approach is based on quantitative estimation of the deformation magnitude. The initial stages (reading, segmentation, identification) of the second approach are identical to the corresponding stages of the first approach. Then, the surface area of deforming effect is considered to be equal to the scanning area of the used intravascular OCT-probe. The shear stress force is calculated based on the magnitudes of systolic and diastolic pressure and the coefficient of the shear component of the deforming pulse wave. The centroids are calculated for each segment of each A-scan of the structural IOCT-image at maximum deformation and the structural IOCT-image at the moment of diastole (minimal deformation). The displacements of individual sections in the structure of the blood vessel wall are calculated subtracting displacement moduli of the centroids. The thickness of the deformable region is calculated as the mean value of the thicknesses’ sum of all segmented layers of the two structural images. Shear modulus value for a particular section of the blood vessel wall is calculated using the standard formula.
Tambov State Technical University
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