Feasibility of Nondestructive Measurement of 3D Vascular Intramural Strains by Optical Coherence Elastography Based on Distortion Correction and Digital Volume Correlation

Background The displacements and strains in the cylindrical coordinate system provide information easier to correlate to the pathologic feature of the tubular blood vessel than those in the Cartesian coordinate system. However, distortions and speckle decorrelation have obstructed accurate vascular strain measurement. Objective This study is to introduce an improved optical coherence elastography (OCE) method based on digital volume correlation (DVC) and correction of distortions to measure the full-field vascular deformation. Methods Refractive index normalization together with refractive distortion correction based on the Fermat’s principle was proposed to recover the actual shape of the vascular wall imaged by optical coherence tomography (OCT). Meanwhile, the displacement fields calculated by DVC were also corrected. The cylindrical coordinate system was created with the origin at the central line of the vascular phantom or sample. Then the full-field 3D displacements in cylindrical coordinates were obtained through coordinate transformation and strains were calculated. Results A vascular phantom and a porcine artery inflated from 80 mmHg to 85 mmHg were measured. 3D intramural displacements and strains were obtained. The absolute difference between the measured and theoretically calculated strains of the phantom is less than 0.2%. The standard deviation is less than 0.2% as well. A stripe is shown on the radial strain image, which is consistent with the feature of the layered structure. Conclusions To the best of our knowledge, this is the first experimental study of the 3D intramural vascular deformation under inflation. The proposed DVC-OCE method based on distortion correction and coordinate transformation has the potential to be further developed as an effective full-field nondestructive measurement method of vascular mechanics.