Optical Coherence Tomography Angiography of the Optic Disc; an Overview.

Different diseases of the optic disc may be caused by or lead to abnormal vasculature at the optic nerve head. Optical coherence tomography angiography (OCTA) is a novel technology that provides high resolution mapping of the retinal and optic disc vessels. Recent studies have shown the ability of OCTA to visualize vascular abnormalities in different optic neuropathies. In addition, quantified OCTA measurements were found promising for differentiating optic neuropathies from healthy eyes

Optical coherence tomography in the assessment of acute changes in cutaneous vascular diameter induced by heat stress.

There are limited imaging technologies available that can accurately assess or provide surrogate markers of the in vivo cutaneous microvessel network in humans. In this study, we establish the use of optical coherence tomography (OCT) as a novel imaging technique to assess acute changes in cutaneous microvessel area density and diameter in humans. OCT speckle decorrelation images of the skin on the ventral side of the forearm up to a depth of 500 μm were obtained prior to and following 20-25 mins of lower limb heating in eight healthy males (30.3±7.6 yrs). Skin red blood cell flux was also collected using laser Doppler flowmetry probes immediately adjacent to the OCT skin sites, along with skin temperature. OCT speckle decorrelation images were obtained at both baseline and heating time points. Forearm skin flux increased significantly (0.20±0.15 to 1.75±0.38 CVC, P<0.01), along with forearm skin temperature (32.0±1.2 to 34.3±1.0°C, P<0.01). Quantitative differences in the automated calculation of vascular area densities (26±9 to 49±19%, P<0.01) and individual microvessel diameters (68±17 to 105±25 μm, P<0.01) were evident following the heating session. This is the first in vivo within-subject assessment of acute changes in the cutaneous microvasculature in response to heating in humans and highlights the use of OCT as an exciting new imaging approach for skin physiology and clinical research

In vivo volumetric imaging of human retinal circulation with phase-variance optical coherence tomography

We present in vivo volumetric images of human retinal micro-circulation using Fourier-domain optical coherence tomography (Fd-OCT) with the phase-variance based motion contrast method. Currently fundus fluorescein angiography (FA) is the standard technique in clinical settings for visualizing blood circulation of the retina. High contrast imaging of retinal vasculature is achieved by injection of a fluorescein dye into the systemic circulation. We previously reported phase-variance optical coherence tomography (pvOCT) as an alternative and non-invasive technique to image human retinal capillaries. In contrast to FA, pvOCT allows not only noninvasive visualization of a two-dimensional retinal perfusion map but also volumetric morphology of retinal microvasculature with high sensitivity. In this paper we report high-speed acquisition at 125 kHz A-scans with pvOCT to reduce motion artifacts and increase the scanning area when compared with previous reports. Two scanning schemes with different sampling densities and scanning areas are evaluated to find optimal parameters for high acquisition speed in vivo imaging. In order to evaluate this technique, we compare pvOCT capillary imaging at 3x3 mm^2 and 1.5x1.5 mm^2 with fundus FA for a normal human subject. Additionally, a volumetric view of retinal capillaries and a stitched image acquired with ten 3x3 mm^2 pvOCT sub-volumes are presented. Visualization of retinal vasculature with pvOCT has potential for diagnosis of retinal vascular diseases

A study for optical coherence tomography angiography of finger and phantom

The study demonstrated OCT angiography on a flowing phantom by calculating the intensity (speckle) variance between repeated frames with motion correction on a subpixel level. Other algorithms had also been tested, including phase variance, complex differential variance and Angio-OCT on both flow phantom and finger of human. The result of 3D phantom experiment and finger experiments proved that SV algorithms and Angio-OCT algorithms can be potentially used in our OCT system for finger angiography. Several different settings including scanning range, scan position density in x and y direction, number of repeated scan to use and other parameters have been tried out to improve the quality of angiographic image quality. The result of finger experiment didn’t fulfill the expectation and the maximum intensity projection of angiographic image was not so clear due to the influence of motion and background noise. Some problems still remain unsolved by far. However, the experiences of data processing especially the process of frame registration lays a foundation for future research

Intact in vivo visualization of telencephalic microvasculature in medaka using optical coherence tomography

To date, various human disease models in small fish—such as medaka (Oryzias lapties)--have been developed for medical and pharmacological studies. Although genetic and environmental homogeneities exist, disease progressions can show large individual differences in animal models. In this study, we established an intact in vivo angiographic approach and explored vascular networks in the telencephalon of wild-type adult medaka using the spectral-domain optical coherence tomography. Our approach, which required neither surgical operations nor labeling agents, allowed to visualize blood vessels in medaka telencephala as small as about 8 µm, that is, almost the size of the blood cells of medaka. Besides, we could show the three-dimensional microvascular distribution in the medaka telencephalon. Therefore, the intact in vivo imaging via optical coherence tomography can be used to perform follow-up studies on cerebrovascular alterations in metabolic syndrome and their associations with neurodegenerative disease models in medaka

Flow detection in images from optical coherence tomography

Tato bakalářská práce se zabývá detekcí toku založené na analýze textury šedotónových snímků z Optické koherentní tomografie (OCT). Přesněji se zabývá metodou založenou na detekci změn ve rozložení speklí (Specle variance, SV). Byla nasnímána data na dynamickém fantomu na která se aplikovala právě tato metoda. Poté se vyhodnocoval vliv parametrů na kvalitu této metody.This bachelor thesis deals with the flow detection based on the analysis of texture grayscale images from optical coherence tomography (OCT). More specifically, it deals with a Specle Variance method (SV). We scan the data on the dynamic phantom and then it was applied to this method the data. Then was evaluate the influence of the parameters on the quality of the method.