Traditionally, line scan OCT (LS-OCT) systems use a cylindrical lens to generate a line-shaped beam with Gaussian intensity illumination along the line, which leads to spatially-dependent signal-to-noise ratio (SNR) distribution of the OCT system along the B-scan direction. A novel, Powell lens-based LS-OCT (PL-LS-OCT) system was designed for uniform intensity illumination along the B-scan direction. The PL-LS-OCT can generate images with ~ 2 μm × 1.7 μm (lateral × axial) resolution in free space at image acquisition rate of and 4,500 fps. Images of biological tissues were acquired with the PL-LS-OCT system.
We demonstrate a novel decorrelation-based localized transverse flow measurement using a line-scan OCT system. We take advantage of the phase stability within each B-scan acquired with a line-scan OCT and digitally generate a low-resolution OCT volume. The ratio of the temporal autocorrelations of the original and low-resolution OCT signals only depends on the system resolution and the flow velocity component along the line-illuminating direction. The ratio is free from the diffusion motion of the flow particles, translation motion orthogonal to the line-illumination direction, and noise-induced distortion. The results from a glass capillary phantom experiment are highly correlated with the digital subaperture Doppler OCT ground truth.
A high-speed spectral-domain optical coherence tomography (SD-OCT) system was developed for ophthalmic applications. The system utilizes a supercontinuum laser to achieve ~1 µm axial and ~2µm lateral resolution in biological tissue at a 400 kHz image acquisition rate. This system can be used for in-vivo, non-contact imaging of the cellular structure of the human retina and cornea.
We demonstrate a novel decorrelation-based localized transverse flow measurement using a line-field OCT system. The lateral resolution along the line illumination direction is controlled by digitally altering the aperture size and provides a contrast only depends on the speed and resolution along that direction in the decorrelation function. The results from a capillary phantom experiment are highly correlated with the subaperture-based Doppler OCT ground truth.
Currently, clinical in-vivo imaging of the human limbus cellular structure is only possible with in-vivo confocal microscopy (IVCM). However, IVCM requires physical contact with the imaged object, and may cause incidental tearing or inflammation of the limbal tissue. We present a line-field, spectral-domain OCT system (LF-SD-OCT) that can generate volumetric, cellular resolution images of biological tissue in-vivo and without contact. The system provides 1.7 µm axial and 2.2 × 3.1 µm lateral resolution in tissue and 2.5 kHz frame rate. The quality of healthy human limbus images acquired with LF-SD-OCT is comparable to that of IVCM.
A line-field, spectral-domain optical coherence tomography (LF-SD-OCT) system was build for in-vivo, non-contact, cellular resolution imaging of biological tissue at 2.5 kHz frame rate. Test images acquired from healthy human subjects show that the LF-SD-OCT is able to image the cellular structure of semitransparent tissue such as the human cornea, as well as highly scattering tissue such as skin. This system may serve as a valuable diagnostic tool to ophthalmologists and dermatologists for diagnosis and monitoring the treatment of various corneal and skin diseases.
The corneal sub-basal nerve plexus (SNP) is a network of thin, unmyelinated nerve fibers located between the basal epithelium and the Bowman’s membrane. Both corneal and systemic diseases such as keratoconus and diabetic can alter the nerve fiber density, thickness and tortuosity. Recent developments of cellular resolution OCT technology allowed for in-vivo visualization and mapping of the corneal SNP. We have developed a fully automated algorithm for segmentation of corneal nerves. The performance of the algorithm was tested on a series of enface UHR-OCT images acquired in-vivo from healthy human subjects. The proposed algorithm traces most of the sub-basal corneal nerves correctly. The achieved processing time and tracing quality are the major advantages of the proposed method. Results show the potential application of proposed method for nerve analysis and morphometric quantification of human sub-basal corneal nerves which is an important tool in corneal related diseases.
A line-field, spectral domain optical coherence tomography (LF-SD-OCT) system was developed for in-vivo, noncontact, cellular resolution imaging of biological tissue. The LF-SD-OCT system utilizes a broadband laser with a spectrum centered at ~790 nm and spectral bandwidth of ~140 nm to achieve 1.8 μm axial and ~5 μm isotropic lateral resolution in biological tissue. A high speed 2D camera was used to achieve frame rate of 2.5k B-scans/s. The system’s SNR was measured to be 92 dB at 100 μm away from the zero-delay line for 2.8 mW optical power incident on the imaged object, with 18 dB roll-off over a scanning range of 1 mm. The LF-SD-OCT system was used to image the cellular structure of cucumber and the cucumber seed where the high spatial resolution was sufficient to resolve cellular nuclei. Then the system was used to image in-vivo human skin (fingertip), where the spiral structures of the sweat glands, as well as a large number of capillaries were observed in the epidermal layer. Images of the healthy human cornea were also acquired from locations near the corneal apex and the periphery and showed the tissue cellular structure and vasculature. Currently, the corneal images were acquired ex-vivo, as we are waiting for ethics clearance to conduct in-vivo corneal imaging studies with the novel LF-SD-OCT system.
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