title: Marker-Free Tracking of Facet Capsule Motion Using Polarization-Sensitive Optical Coherence Tomography.
abstract: 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.
authors.affiliation: Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN, 55455, USA. claes027@umn.edu.
authors.forename: Amy A
authors.initials: AA
authors.lastname: Claeson
authors.affiliation: Department of Electrical Engineering, University of Minnesota, Minneapolis, MN, 55455, USA.
authors.forename: Yi-Jou
authors.initials: YJ
authors.lastname: Yeh
authors.affiliation: Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN, 55455, USA.
authors.forename: Adam J
authors.initials: AJ
authors.lastname: Black
authors.affiliation: Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN, 55455, USA.
authors.forename: Taner
authors.initials: T
authors.lastname: Akkin
authors.affiliation: Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN, 55455, USA. baroc001@umn.edu.
authors.forename: Victor H
authors.initials: VH
authors.lastname: Barocas
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008022:Ligaments / Q000502:physiology*; D008159:Lumbar Vertebrae / Q000502:physiology*; D008875:Middle Aged; D009068:Movement / Q000502:physiology*; D041623:Tomography, Optical Coherence
keywords: Biomechanics; Image correlation; Polarized light; Spine