Category: Doppler

Embodiments of the present invention include but are not limited to methods and systems for optical coherence imaging. A method for optical coherence imaging may comprise scanning a sample with an incident beam from a light source; detecting one or more spectral interference signals from the sample; modulating the one or more spectral interference signals by a linear translation of a reference mirror while scanning the sample in a cross-sectional direction; and obtaining at least one image of the sample from the modulated one or more spectral interference signals, the at least one image including a selected one of a ...

Visualizing retinal photocoagulation by real-time OCT measurements may considerably improve the understanding of thermally induced tissue changes and might enable a better reproducibility of the ocular laser treatment. High speed Doppler OCT with 860 frames per second imaged tissue changes in the fundus of enucleated porcine eyes during laser irradiation. Tissue motion, measured by Doppler OCT with nanometer resolution, was correlated with the temperature increase, which was measured non-invasively by optoacoustics. In enucleated eyes, the increase of the OCT signal near the retinal pigment epithelium (RPE) corresponded well to the macroscopically visible whitening of the tissue. At low irradiance, Doppler ...

We present an approach to measure pulsatile total retinal arterial blood flow in humans and rats using ultrahigh speed Doppler OCT. The axial blood velocity is measured in an en face plane by raster scanning and the flow is calculated by integrating over the vessel area, without the need to measure the Doppler angle. By measuring flow at the central retinal artery, the scan area can be very small. Combined with ultrahigh speed, this approach enables high volume acquisition rates necessary for pulsatile total flow measurement without modification in the OCT system optics. A spectral domain OCT system at 840nm ...

Speckle contrast based optical coherence angiography (OCA) and optical coherence Doppler tomography (ODT) have been applied to image cerebral blood flow previously. However, the contrast mechanisms of these two methods are not fully studied. Here, we present both flow phantom and in vivo animal experiments using ultrahigh-resolution OCA (μOCA) and ODT (μODT) to investigate the flow sensitivity differences between these two methods. Our results show that the high sensitivity of μOCA for visualizing minute vasculature (e.g., slow capillary beds) is due to the enhancement by random Brownian motion of scatterers (e.g., red and white blood cells) within the ...

A spectral domain optical coherence tomography (SD-OCT) system and an oral imaging probe have been developed to visualize the microstructural morphology and microvasculature in the human oral cavity. Structural OCT images of ex vivo pig oral tissues with the histology of the same sites were acquired and compared for correlations. Structural in vivo OCT images of healthy human tissue as well as a pathologic site (ulcer) were obtained and analyzed based on the results of the ex vivo pig study, drawing on the similarity between human and swine oral tissues. In vivo Doppler and speckle variance OCT images of the ...

Purpose:To determine the relationship among visual field, neural structural, and blood flow measurements in glaucoma. Methods:Case-control study. Forty-seven eyes of 42 patients with perimetric glaucoma were age-matched with 27 normal eyes of 27 patients. All patients underwent Doppler Fourier-domain optical coherence tomography to measure retinal blood flow and standard glaucoma evaluation with visual field testing and quantitative structural imaging. Linear regression analysis was performed to analyze the relationship among visual field, blood flow, and structure, after all variables were converted to logarithmic decibel scale. Results:Retinal blood flow was reduced in glaucoma eyes compared to normal eyes (p

In this paper, the features of the intensity-based Doppler variance (IBDV) method were analyzed systemically with a flow phantom. The effects of beam scanning density, flow rate and the time interval between neighboring A-lines on the performance of this method were investigated. The IBDV method can be used to quantify the flow rate and its sensitivity can be improved by increasing the time interval between the neighboring A-lines. A higher sensitivity IBDV method that applies the algorithm along the slower scan direction was proposed. In comparison to laser speckle imaging maps of blood flow, we demonstrated the ability of the ...

We investigate the effect of multiple scattering on the optical coherence tomography (OCT) signal and the Doppler OCT signal of flowing blood. Doppler OCT measurements at 1300 nm are performed on flowing diluted porcine blood with hematocrit ranging between 0% and 15%. Measured blood hematocrit and mean red blood cell volume are used to calculate, using the discrete dipole approximation model, the (single) scattering coefficient and scattering anisotropy of blood. Monte Carlo simulations, based on the calculated scattering coefficients and scattering anisotropies, are compared to Doppler OCT measurements for hematocrit smaller than 10%. Good quantitative agreement between Doppler OCT measurements ...

Blood flow in murine epicardial and intra-myocardial coronary arteries was measured in vivo with spectral domain optical Doppler tomography (SD-ODT). Videos at frame rates up to 180 fps were collected and processed to extract phase shifts associated with moving erythrocytes in the coronary arteries. Radial averaging centered on the vessel lumen provided spatial smoothing of phase noise in a single cross-sectional frame for instantaneous peak velocity measurement without distortion of the flow profile. Temporal averaging synchronized to the cardiac cycle (i.e., gating) was also performed to reduce phase noise, although resulting in lower flow profiles. The vessel angle with ...

An office based Doppler and polarization sensitive swept-source optical coherence tomography (Doppler-PS-SS-OCT) was developed for diagnosis and evaluation of abnormalities of anterior eye segment in clinic. A healthy eye was measured in vivo by the Doppler PS-OCT. The results showed that the Doppler PS-OCT may have potential to identify blood vessels and discriminate fibrous tissues in abnormalities, such as scarring in bleb, and scleral inflammation.

Capillary-driven flow (CD-flow) in microchannels plays an important role in many microfluidic devices. These devices, the most popular being those based in lateral flow, are becoming increasingly used in health care and diagnostic applications. CD-flow can passively pump biological fluids as blood, serum or plasma, in microchannels and it can enhance the wall mass transfer by exploiting the convective effects of the flow behind the meniscus. The flow behind the meniscus has not been experimentally identified up to now because of the lack of high-resolution, non-invasive, cross-sectional imaging means. In this study, spectral-domain Doppler optical coherence tomography is used to ...

To date, two main categories of OCT techniques have been described for imaging hemodynamics: Doppler OCT and OCT angiography. Doppler OCT can measure axial velocity profiles and flow in arteries and veins, while OCT angiography can determine vascular morphology, tone, and presence or absence of red blood cell (RBC) perfusion. However, neither method can quantify RBC velocity in capillaries, where RBC flow is typically transverse to the probe beam and single-file. Here, we describe new methods that potentially address these limitations. Firstly, we describe a complex-valued OCT signal in terms of a static scattering component, dynamic scattering component, and noise ...

Doppler Fourier domain optical coherence tomography is able to be used for in vivo blood flow measurement. In conventional methods, the highest velocity that can be measured is limited to the range the phase shift between two successively recorded depth profiles at the same probe-beam location, which cannot exceed (-π, π), otherwise phase wrapping will occur. This phase-wrapping limit is determined by the time interval between two consecutive A-scans. We present a novel approach to shorten the time interval between two consecutive A-scans and thus increase the phase-wrapping limit by using an area scan camera to record the interference spectrum ...

This Letter reports the use of an ultrahigh resolution optical microangiography (OMAG) system for simultaneous 3D imaging of microstructure and lymphatic and blood vessels without the use of an exogenous contrast agent. An automatic algorithm is developed to segment the lymphatic vessels from the microstructural images based on the fact that the lymph fluid is optically transparent. An OMAG system is developed that utilizes a broadband supercontinuum light source, providing an axial resolution of 2.3 μm and lateral resolution of 5.8 μm, capable of resolving the capillary vasculature and lymphatic vessels innervating microcirculatory tissue beds. Experimental demonstration is ...

Needles provide an effective way to reach lesions in soft tissue and are frequently used for diagnosis and treatment. Examples include biopsies, tumor ablation, and brachytherapy. Yet, precise localization of the needle with respect to the target is complicated by motion and deformation of the tissue during insertion. We have developed a prototypical needle with an embedded optical fiber allowing to obtain optical coherence tomography images of the tissue in front of the needle tip. Using the data and particularly the Doppler information it is possible to estimate the motion of the needle tip with respect to the surrounding soft ...