Novel input polarisation independent endoscopic cross-polarised optical coherence tomography probe

Polarization-insensitive optical coherence tomography based on partly depolarized light

Polarization-related image artifacts are frequently observed in optical coherence tomography (OCT) data. As most modern OCT layouts rely on polarized light sources, only the co-polarized component of the light scattered from within a sample can be detected after interference with the reference beam. Cross-polarized sample light does not interfere with the reference beam and thus produces artifacts ranging from a reduction to the full absence of OCT signals. Here we present a simple yet effective technique to prevent polarization artifacts. By partly depolarizing the light source at the interferometer entrance, we achieve OCT signals regardless of the sample polarization state. We demonstrate the performance of our approach in a defined retarder as well as in birefringent dura mater tissue. This simple and cost-effective technique can be applied to obviate cross-polarization artifacts in virtually any OCT layout.

A Proposal to Perform High Contrast Imaging of Human Palatine Tonsil with Cross Polarized Optical Coherence Tomography

The palatine tonsils provide the first line of immune defense against foreign pathogens inhaled or ingested. However, a disruption in the epithelial layer within the tonsil crypts can lead to recurrent acute tonsillitis (RAT). Current imaging techniques suffer from poor resolution and contrast and do not allow a classification of the severity of RAT. We have developed a cross-polarized optical coherence tomography system. The system can detect a change in the polarization of the light after the light-tissue interaction. We demonstrate improved resolution and contrast in tonsil imaging with the developed method. Intensity, as well as retardance images of the excised tonsil tissue, were acquired. Features such as crypt epithelium, lymphoid follicles, and dense connective tissue were observed with improved contrast. Cross polarized optical coherence tomography can be a valuable tool in the clinic to evaluate palatine tonsils as it would allow visualizing common tonsil features without the need for any external contrast agent.

Orthogonal-polarization-gating optical coherence tomography for human sweat ducts in vivo

We propose an orthogonal-polarization-gating optical coherence tomography (OPG-OCT) for human sweat ducts in vivo. OPG-OCT is composed of the orthogonal linearly polarized light of a sample arm individually interfering with orthogonal linearly polarized lights of the reference arms, where OPG-OCT induces two images, one reflecting the projection intensity and the other the horizontal linear diattenuation (HLD). The results demonstrate that OPG-OCT projection intensity could improve the image quality of sweat ducts. HLD also clearly illustrates the spiral shape of the sweat ducts. Finally, sweat ducts in intensity image are segmented by employing convolutional neural networks (CNN). The proportions of left-handed and right-handed ducts are extracted to characterize the sweat ducts based on HLD. Therefore, the OPG-OCT technique employing CNN for the human sweat glands has the potential to automatically identify the human sweat ducts in vivo.