Polarization-sensitive optical coherence tomography (PS-OCT) quantifies the polarization state of the light scattered at each depth within the tissue. Similar to polarized light microscopy, this enables analysis of tissue polarization properties, but using OCT’s depth sectioning to isolate individual sample layers. Many tissue components influence the polarization of propagating and/or scattered light. Tissues with a fibrillar architecture, such as collagen fibers, actin and myosin of muscle fibers, or myelin sheaths surrounding axons exhibit tissue birefringence, an optical property that results in a differential delay, or retardation, between light polarized parallel to the fibrillar components versus light having a perpendicular polarization. Propagation through randomly oriented birefringent elements, or scattering on anisotropic particles results in a spatial randomization of the detected polarization states, leading to depolarization1. These polarization features offer a versatile endogenous contrast mechanism that we explored for intravascular imaging of collagen in the vessel wall of coronary arteries2, imaging stromal tissue surrounding breast tumor3, and monitoring wound healing in an excisional scar model in rats4.
PS-OCT employs multiple subsequent or multiplexed polarization states to illuminate the sample. Combined with polarization diverse detection, this enables reconstruction of the corresponding Jones or Mueller matrix, describing the propagation of the input light through the optic components of the imaging system to a given depth in the tissue, and back through the system components to the detector. The Stokes-Mueller formalism provides a convenient toolset to analyze polarization properties of tissue. We are developing refined methods to reconstruct depth-resolved polarization properties of tissues imaged with PS-OCT, such as depth-resolved optic axis orientation or local depolarization properties.
- Martin Villiger
- Norman Lippok
- Lippok, N., Villiger, M., Albanese, A., Meijer, E. F. J., Chung, K., Padera, T. P., Bhatia, S. N. & Bouma, B. E. Depolarization signatures map gold nanorodswithin biological tissue. Nature Photon 1–9 (2017). doi:10.1038/nphoton.2017.128
- van der Sijde, J. N., Karanasos, A., Villiger, M., Bouma, B. E. & Regar, E. First-in-man assessment of plaque rupture by polarization-sensitive optical frequency domain imaging in vivo. European Heart Journal 37, 1932 (2016).
- Villiger, M., Lorenser, D., McLaughlin, R. A., Quirk, B. C., Kirk, R. W., Bouma, B. E. & Sampson, D. D. Deep tissue volume imaging of birefringence through fibre-optic needle probes for the delineation of breast tumour. Rep. 6, 28771 (2016).
- Lo, W. C. Y., Villiger, M., Golberg, A., Broelsch, G. F., Khan, S., Lian, C. G., Austen, W. G., Yarmush, M. & Bouma, B. E. Longitudinal, 3D Imaging of Collagen Remodeling in Murine Hypertrophic Scars In Vivo Using Polarization-Sensitive Optical Frequency Domain Imaging. Invest. Dermatol. 136, 84–92 (2016).