Polarization-sensitive optical coherence tomography (PSOCT) has established itself as an important non-invasive optical
imaging tool to study the birefringent biological tissues. The complex 3D structure architecture of the collagen fibers in
articular cartilage is investigated using a time domain PSOCT (TD-PSOCT) system and the depth-wise cumulative
retardance profiles obtained are compared with a three layer cartilage model. The PSOCT result obtained from the
variable incidence angle (VIA) experiment of bovine cartilage sample is found to be consistent with the proposed
lamellar cartilage model based on scanning electron microscope studies. This shows potential use of PSOCT -VIA
technique to obtain depth-wise information about the complex 3D architecture of collagen fibers in the cartilage. Further
studies would have to be carried out to map out depth wise retardance information at different sites of the cartilage,
which could establish the general validity of this approach.
In a recent publication, Tomlins and Wang pointed out an SNR improvement that could be gained in optical
coherence tomography (OCT), by altering the averaging scheme used. Specifically they noticed that, given a large
number of noisy OCT A-scans, it is preferable if possible to perform the ensemble-averaging over the A-scans and then
extract the OCT envelope rather than extract the envelope from each noisy A-scan and then average. In this paper we
demonstrate that a similar argument can be applied to the calculation of the degree of polarization (DOP) using
polarization-sensitive OCT. However, the difference now is that direct A-scan averaging can reduce the systematic error
in DOP calculation that occurs in the presence of noise due to noise-bias terms.
Optical coherence tomography (OCT) has been used to image equine bone samples. OCT and polarization sensitive OCT
(PS-OCT) images of equine bone samples, before and after demineralization, are presented. Using a novel approach,
taking a series of images at different angles of illumination, the polar angle and true birefringence of collagen within the
tissue is determined, at one site in the sample. The images were taken before and after the bones were passed through a
demineralization process. The images show an improvement in depth penetration after demineralization allowing better
visualization of the internal structure of the bone and the optical orientation of the collagen. A quantitative measurement
of true birefringence has been made of the bone; true birefringence was shown to be 1.9x10-3 before demineralization
increasing to 2.7x10-3 after demineralization. However, determined collagen fiber orientation remains the same before
and after demineralization. The study of bone is extensive within the field of tissue engineering where an understanding
of the internal structures is essential. OCT in bone, and improved depth penetration through demineralization, offers a
useful approach to bone analysis.
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