Birefringent characterization of nerve tissue and tendon using low coherence interferometry and transmission studies

Diagnostic modalities that determine the extent of damage to peripheral nerve tissues and identify the tendon tissue injury and its differentiation during intra-operative interventions are essential. The present study proposes and demonstrates the polarization-sensitive low-coherence interferometry (PS-LCI) technique combined with polarization-based transmission studies for characterizing chicken sciatic nerve fibers and tendons. A supercontinuum source with optical filters with broadband transmission characteristics around the wavelength region of 1060 and 1300 nm. The spectral information of both polarization states confirmed the birefringence characteristics of the nerve fiber bundle and tendon tissue. The retardance values estimated using the polarization-based transmission measurements show that the refractive index difference, Δn, between the nerve fiber bundle with an overall thickness of ≈1mm and that of the tendon tissue bundle with an overall thickness of ≈1.2mm was ≈0.6×10^-4. The PS-LCI-based birefringence measurements of the sciatic nerve fiber bundle and tendon bundle show Δn≈1.0×10^-4. These observations suggest that a supercontinuum source with different wavelengths has the potential to be used for imaging tissues with birefringence characteristics, such as nerve or tendon, and to identify morphological characteristics.