Sensitive Optical Coherence Tomography System Research Articles

Optical coherence tomography imaging of evoked neural activity in sciatic nerve of rat

We investigate changes in optical coherence tomography (OCT) images in response to evoked neural activity in the sciatic nerve of rats in vitro. M-scans were obtained on peripheral nerves of rats using a swept source polarisation sensitive OCT system, while a nerve cuff acquired electrical neural recordings. From a total of 10 subjects: three had no stimulation (controls), three had paw stimulation, and four had nerve stimulation. Changes in the OCT signal intensity, phase retardation, phase, and frequency spectra were calculated for each subject and reference samples of a mirror and microspheres in solution. Observed changes in intensity in three paw stimulation and two nerve stimulation subjects and changes in frequency spectra amplitude in two paw stimulation subjects were above the reference noise level and were temporally consistent with osmotic swelling from ion currents during neural activity. Light scattering changes produced by osmotic swelling, which have previously been characterised in squid and crab nerves, are also thought to occur in myelinated fibres on a scale which is detectable using OCT. Imaging neural activity in myelinated tissue using OCT creates new possibilities for functional imaging in the peripheral and central nervous systems.

White light polarization sensitive optical coherence tomography for sub-micron axial resolution and spectroscopic contrast in the murine retina.

A white light polarization sensitive optical coherence tomography system has been developed, using a supercontinuum laser as the light source. By detecting backscattered light from 400 – 700 nm, an axial resolution of 1.0 µm in air was achieved. The system consists of a free-space interferometer and two homemade spectrometers that detect orthogonal polarization states. Following system specifications, images of a healthy murine retina as acquired by this non-contact system are presented, showing high resolution reflectivity images as well as spectroscopic and polarization sensitive contrast. Additional images of the very-low-density-lipoprotein-receptor (VLDLR) knockout mouse model were acquired. The high resolution allows the detection of small lesions in the retina.

Single input state polarization sensitive swept source optical coherence tomography based on an all single mode fiber interferometer.

We present a newly developed single mode fiber based swept source polarization sensitive optical coherence tomography system using a single input state at 1040 nm. Two non-polarizing fiber based beam splitters are combined to form a Mach-Zehnder interferometer, while two polarizing beam splitters are used to obtain a polarization sensitive detection. Both types of beam splitters solely feature conventional single mode fibers. Polarization control paddles are used to set and maintain the polarization states in the fibers of the interferometer and detection unit. By use of a special paddle alignment scheme we are able to eliminate any bulk optic wave plates and polarization maintaining fibers in the interferometer and detection paths while preserving the advantages of a single input state system that illuminates the sample with circularly polarized light. To demonstrate the capabilities of our system, we performed retinal measurements on healthy human volunteers.

Effect of Intraocular Pressure and Anisotropy on the Optical Properties of the Cornea: A Study Using Polarization Sensitive Optical Coherence Tomography.

We hypothesize that because of the anisotropic properties of the cornea, there should be a nonuniform change in birefringence with an increase in intraocular pressure (IOP). In this in vitro study, anisotropic properties, stress distribution within the cornea, and the effect of IOP on changes in stress level were investigated. Button inflation tests for deformation with polarization sensitive optical coherence tomography were used to demonstrate optical and material anisotropy on ex vivo human corneas. Inflation tests were performed on human donor corneoscleral rims. Using a turntable and hydrostatic column, each corneoscleral rim was subjected to a hydrostatic pressure of 0, 10, 15, and 20 mm Hg. At each pressure step, 4 scans at 0, 45, 90, and 135 degrees were taken by a polarization sensitive optical coherence tomography system, and the birefringence images and normal intensity-based images were recorded; images were later compiled for analysis. The retardation changed with the axis of orientation (P [T ≤ t] 1-tailed = 0.025) and IOP (P [T ≤ t] 1-tailed = 0.019). Optical thickness of the cornea decreased with increasing IOP. The optical properties of the cornea are modified with change in IOP. This is not uniform because of distinct anisotropic properties. Anisotropic properties may unpredictably affect the optical quality of cornea during or after the surgeries. Changes in corneal birefringence can be also used as a tool for measuring the IOP of the eye.

High-speed polarization sensitive optical coherence tomography scan engine based on Fourier domain mode locked laser: erratum

We recently reported on a new swept source polarization sensitive optical coherence tomography system and its application to skin imaging [Biomed. Opt. Express 3, 2987 (2012)]. In some of the tomographic images, two skin layers were labeled wrongly (interchanged). We present figures with corrected labeling.

Cross-Sectional Imaging of Materials Structure Using PS-OCT

Optical low-coherence tomography is a measurement technique for non-contact and non-destructive investigation of materials inner structure. Nowadays, this method is highly applied in medical treatment especially in dermatology and ophthalmology. During our research we have developed an optical low-coherence tomography system with polarization state analysis for structure examination of a broad range of technical materials. In this paper we present our recent measurements including polarization sensitive analysis. Those measurements were taken for semitransparent and highly scattering materials like polymer layers and polymer optical retarders, anticorrosion protective coatings or abrasive paper. We proved that with the aid of developed polarization sensitive optical coherence tomography system it is possible to investigate birefringence principles of materials as well as to improve visualization contrast of cross-sectional images.