Form-biattenuance in fibrous tissues measured with polarization-sensitive optical coherence tomography (PS-OCT)

Form-biattenuance (Delta chi) in biological tissue arises from anisotropic light scattering by regularly oriented cylindrical fibers and results in a differential attenuation (diattenuation) of light amplitudes polarized parallel and perpendicular to the fiber axis (eigenpolarizations). Form-biattenuance is complimentary to form-birefringence (Delta n) which results in a differential delay ( phase retardation) between eigenpolarizations. We justify the terminology and motivate the theoretical basis for form-biattenuance in depth-resolved polarimetry. A technique to noninvasively and accurately quantify form-biattenuance which employs a polarization-sensitive optical coherence tomography (PS-OCT) instrument in combination with an enhanced sensitivity algorithm is demonstrated on ex vivo rat tail tendon (mean Delta chi=5.3.10(-4), N=111), rat Achilles tendon (Delta chi=1.3.10(-4), N=45), chicken drumstick tendon (Delta chi=2.1.10(-4), N=57), and in vivo primate retinal nerve fiber layer (Delta chi= 0.18.10(-4), N=6). A physical model is formulated to calculate the contributions of Delta chi and Delta n to polarimetric transformations in anisotropic media. (C) 2005 Optical Society of America.