title: A polarization-sensitive light field imager for multi-channel angular spectroscopy of light scattering in biological tissues.
abstract: BACKGROUND
  Angular spectroscopy of light scattering can be used for quantitative analysis of cellular and subcellular properties, and thus promises a noninvasive methodology for in vivo assessment cellular integrity to complement in vitro histological examination. Spatial information is essential for accurate identification of localized abnormalities. However, conventional angular spectroscopy systems only provide single-channel measurement, which suffers from poor spatial resolution or requires time-consuming scanning over extended area. The purpose of this study was to develop a multi-channel angular spectroscopy for light field imaging in biological tissues.
  
  
  METHODS
  A microlens array (MLA) (8×8) based light field imager for 64-channel angular spectroscopy was developed. A pair of crossed polarizers was employed for polarization-sensitive recording to enable quantitative measurement at high signal specificity and sensitivity. The polarization-sensitive light field imager enables rapid measurement of multiple sampling volumes simultaneously at 18 μm spatial-resolution and 3° angular-resolution. Comparative light field imaging and electrophysiological examination of freshly isolated and physiologically deteriorated lobster leg nerves have been conducted.
  
  
  RESULTS
  Two-dimensional (2D) polarization-sensitive scattering patterns of the fresh nerves were highly elliptical, while they gradually lost the ellipticity and became rotationally symmetric (i.e., circular) as the nerves physiologically deteriorated due to repeated electrical stimulations. Characterized parameters, i.e., the ellipticity and the scattering intensity, rendered spatially various characteristics such as different values and deteriorating rates.
  
  
  CONCLUSIONS
  The polarization-sensitive light field imager is able to provide multi-channel angular spectroscopy of light scattering with both spatial and angular resolutions. The light scattering properties of nerves are highly dependent on the orientation of nerves and their physiological status. Further development of polarization-sensitive multi-channel angular spectroscopy may promise a methodology for rapid and reliable identification of localized abnormalities in biological tissues.
authors.affiliation: Department of Biomedical Engineering, University of Alabama at Birmingham, Birmingham, AL 35294, USA.
authors.forename: Rongwen
authors.initials: R
authors.lastname: Lu
authors.affiliation: Department of Biomedical Engineering, University of Alabama at Birmingham, Birmingham, AL 35294, USA.
authors.forename: Qiuxiang
authors.initials: Q
authors.lastname: Zhang
authors.affiliation: Department of Biomedical Engineering, University of Alabama at Birmingham, Birmingham, AL 35294, USA.
authors.forename: Yanan
authors.initials: Y
authors.lastname: Zhi
authors.affiliation: Department of Biomedical Engineering, University of Alabama at Birmingham, Birmingham, AL 35294, USA.
authors.forename: Xincheng
authors.initials: X
authors.lastname: Yao
keywords: Microlens array (MLA); angular spectroscopy; light field; nerve