title: Imaging scattering orientation with spatial frequency domain imaging.
abstract: Optical imaging techniques based on multiple light scattering generally have poor sensitivity to the orientation and direction of microscopic light scattering structures. In order to address this limitation, we introduce a spatial frequency domain method for imaging contrast from oriented scattering structures by measuring the angular-dependence of structured light reflectance. The measurement is made by projecting sinusoidal patterns of light intensity on a sample, and measuring the degree to which the patterns are blurred as a function of the projection angle. We derive a spatial Fourier domain solution to an anisotropic diffusion model. This solution predicts the effects of bulk scattering orientation on the amplitude and phase of the projected patterns. We introduce a new contrast function based on a scattering orientation index (SOI) which is sensitive to the degree to which light scattering is directionally dependent. We validate the technique using tissue simulating phantoms, and ex vivo samples of muscle and brain. Our results show that SOI is independent of the overall amount of bulk light scattering and absorption, and that isotropic versus oriented scattering structures can be clearly distinguished. We determine the orientation of subsurface microscopic scattering structures located up to 600 μm beneath highly scattering (μ(') (s) = 1.5 mm(-1)) material.
authors.affiliation: University of California, Irvine, Beckman Laser Institute and Medical Clinic, Laser Microbeam and Medical Program (LAMMP), 1002 Health Sciences Road, Irvine, California 92612, USA.
authors.forename: Soren D
authors.initials: SD
authors.lastname: Konecky
authors.forename: Tyler
authors.initials: T
authors.lastname: Rice
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Durkin
authors.forename: Bruce J
authors.initials: BJ
authors.lastname: Tromberg
mesh_terms: D000042:Absorption; D000818:Animals; D001923:Brain Chemistry; D002645:Chickens; D003952:Diagnostic Imaging / Q000379:methods*; D008027:Light; D008297:Male; D018482:Muscle, Skeletal / Q000737:chemistry; D019047:Phantoms, Imaging; D051381:Rats; D017207:Rats, Sprague-Dawley; D015203:Reproducibility of Results; D012542:Scattering, Radiation