Marker-Free Tracking of Facet Capsule Motion Using Polarization-Sensitive Optical Coherence Tomography

• Published in: Annals of biomedical engineering Vol. 43; no. 12; pp. 2953 - 2966
• Main Authors: Claeson, Amy A., Yeh, Yi-Jou, Black, Adam J., Akkin, Taner, Barocas, Victor H.
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.12.2015; Springer Nature B.V
• Subjects: Adult; Biochemistry; Biological; Biological and Medical Physics; Biomechanical Phenomena; Biomedical and Life Sciences; Biomedical Engineering and Bioengineering; Biomedicine; Biophysics; Classical Mechanics; Humans; Image Processing, Computer-Assisted; Ligaments - physiology; Lumbar Vertebrae - physiology; Markers; Mathematical analysis; Maximum power; Middle Aged; Movement - physiology; Strain; Three dimensional; Tomography, Optical Coherence; Tracking; Two dimensional; Biomechanics; Image correlation; Spine; Polarized light
• ISSN: 0090-6964; 1573-9686
• DOI: 10.1007/s10439-015-1349-9

We proposed and tested a method by which surface strains of biological tissues can be captured without the use of fiducial markers by instead, utilizing the inherent structure of the tissue. We used polarization-sensitive optical coherence tomography (PS OCT) to obtain volumetric data through the thickness and across a partial surface of the lumbar facet capsular ligament during three cases of static bending. Reflectivity and phase retardance were calculated from two polarization channels, and a power spectrum analysis was performed on each a-line to extract the dominant banding frequency (a measure of degree of fiber alignment) through the maximum value of the power spectrum (maximum power). Maximum powers of all a-lines for each case were used to create 2D visualizations, which were subsequently tracked via digital image correlation. In-plane strains were calculated from measured 2D deformations and converted to 3D surface strains by including out-of-plane motion obtained from the PS OCT image. In-plane strains correlated with 3D strains ( R 2  ≥ 0.95). Using PS OCT for marker-free motion tracking of biological tissues is a promising new technique because it relies on the structural characteristics of the tissue to monitor displacement instead of external fiducial markers.