1. Articles in category: Velocimetry

    1-24 of 330 1 2 3 4 ... 12 13 14 »
    1. Full-range Fourier domain Doppler optical coherence tomography based on sinusoidal phase modulation

      Full-range Fourier domain Doppler optical coherence tomography based on sinusoidal phase modulation

      A novel full-range Fourier domain Doppler optical coherence tomography (full-range FD-DOCT) using sinusoidal phase modulation for B-M scan is proposed. In this sinusoidal B-M scan, zero optical path difference (OPD) position does not move corresponding to lateral scanning points in contrast to linear B-M scan. Since high phase sensitivity arises around the zero OPD position, the proposed full-range FD-DOCT can achieve easily high velocity sensitivity without mirror image around the zero OPD position. Velocity sensitivity dependent on the OPD and the interval of scanning points is examined, and flow velocity detection capability is verified through Doppler imaging of a flow ...

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    2. In vivo OCT microangiography of rodent iris

      In vivo OCT microangiography of rodent iris

      We report on the functional optical coherence tomography (OCT) imaging of iris tissue morphology and microcirculation in living small animals. Anterior segments of healthy mouse and rat eyes are imaged with high-speed spectral domain OCT (SD-OCT) utilizing ultrahigh sensitive optical microangiography (UHS-OMAG) imaging protocol. 3D iris microvasculature is produced by the use of an algorithm that calculates absolute differences between the amplitudes of the OCT interframes. We demonstrate that the UHS-OMAG is capable of delineating iris microvascular beds in the mouse and rat with capillary-level resolution. Furthermore, the fast imaging speed enables dynamic imaging of iris micro-vascular response during drug-induced ...

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    3. Georgetown University Receives NIH Grant for Non-Invasive Evaluation of Transplant Kidney Using OCT

      Georgetown University Receives NIH Grant for Non-Invasive Evaluation of Transplant Kidney Using OCT

      Georgetown University Received at 2014 NIH Grant for $520,754 for Non-Invasive Evaluation of Transplant Kidney Using OCT. The principal investigator is Peter Michael Andrewss. The program began in 2014 and ends in 2018. Below is a summary of the proposed work. There is currently a worldwide shortage of kidneys for transplantation due mainly to the fact that there is no reliable means to determine their viability (i.e., kidneys stored for long periods of time, etc.). Also, following transplantation, kidneys oftn do not function immediately and their status is unclear. Previously, we have shown that the histopathology of living ...

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    4. Doppler Optical Coherence Tomography

      Doppler Optical Coherence Tomography

      Optical Coherence Tomography (OCT) has revolutionized ophthalmology. Since its introduction in the early 1990s it has continuously improved in terms of speed, resolution and sensitivity. The technique has also seen a variety of extensions aiming to assess functional aspects of the tissue in addition to morphology. One of these approaches is Doppler OCT (DOCT), which aims to visualize and quantify blood flow. Such extensions were already implemented in time domain systems, but have gained importance with the introduction of Fourier domain OCT. Nowadays phase-sensitive detection techniques are most widely used to extract blood velocity and blood flow from tissues. A ...

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    5. High speed, wide velocity dynamic range Doppler optical coherence tomography (Part IV): split spectrum processing in rotary catheter probes

      High speed, wide velocity dynamic range Doppler optical coherence tomography (Part IV): split spectrum processing in rotary catheter probes

      We report a technique for blood flow detection using split spectrum Doppler optical coherence tomography (ssDOCT) that shows improved sensitivity over existing Doppler OCT methods. In ssDOCT, the Doppler signal is averaged over multiple sub-bands of the interferogram, increasing the SNR of the Doppler signal. We explore the parameterization of this technique in terms of number of sub-band windows, width and overlap of the windows, and their effect on the Doppler signal to noise in a flow phantom. Compared to conventional DOCT, ssDOCT processing has increased flow sensitivity. We demonstrate the effectiveness of ssDOCT in-vivo for intravascular flow detection within ...

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    6. University of Miami Receives NIH Grant for Advanced Imaging for Diabetic Retinopathy

      University of Miami Receives NIH Grant for Advanced Imaging for Diabetic Retinopathy

      The University of Miami Received a 2014 NIH Grant for $367,808 for Advanced Imaging for Diabetic Retinopathy. The principal investigator is Delia Cabrera Debuc. The program began in 2011 and ends in 2016. Below is a summary of the proposed work. Diabetic retinopathy (DR) is a major cause of visual loss in diabetic individuals that presents a significant diagnostic challenge. Advances in preventing vision loss in these individuals are hindered by limited understanding of mechanisms underlying DR and the altered relationships between the retinal neural tissue and retinal vasculature. Therefore, an objective test for the early diagnosis and evaluation ...

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    7. Quantitative Optical Coherence Tomography Angiography of Choroidal Neovascularization in Age-related Macular Degeneration

      Quantitative Optical Coherence Tomography Angiography of Choroidal Neovascularization in Age-related Macular Degeneration

      Purpose To detect and quantify choroidal neovascularization (CNV) in patients with age-related macular degeneration (AMD) using optical coherence tomography (OCT) angiography. Design Observational, cross-sectional study. Participants A total of 5 normal subjects and 5 subjects with neovascular AMD were included. Methods A total of 5 eyes with neovascular AMD and 5 normal age-matched controls were scanned by a high-speed (100 000 A-scans/seconds) 1050-nm wavelength swept-source OCT. The macular angiography scan covered a 3×3-mm area and comprised 200×200×8 A-scans acquired in 3.5 seconds. Flow was detected using the split-spectrum amplitude-decorrelation angiography (SSADA) algorithm. Motion artifacts were ...

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    8. Feature Of The Week 3/23/14: Tambov State Technical University Investigates One Specific Velocity Color Mapping One Specific Velocity Color Mapping

      Feature Of The Week 3/23/14: Tambov State Technical University Investigates One Specific Velocity Color Mapping One Specific Velocity Color Mapping

      The method of sign-sensitive mapping of the given range of velocities in a flow with complex geometry based on the principles of optical coherence tomography is described. To produce an alternating-sign flow, the 1% aqueous intralipid solution and the tilted capillary entry with the contraction coefficient 4:1 are used. The mapping is controlled using two parameters, the value of one specific velocity (OSV) for mapping and the accuracy of its determination. The structure image and two OSV images (for positive and negative direction of motion) are obtained as a result of selecting and processing the relevant parts of the ...

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    9. Maximum Likelihood Doppler Frequency Estimation under Decorrelation Noise for Quantifying Flow in Optical Coherence Tomography

      Maximum Likelihood Doppler Frequency Estimation under Decorrelation Noise for Quantifying Flow in Optical Coherence Tomography

      Recent hardware advances in optical coherence tomography (OCT) have led to ever higher A-scan rates. However, the estimation of blood flow axial velocities is limited by the presence and type of noise. Higher acquisition rates alone do not necessarily enable precise quantification of Doppler velocities, particularly if the estimator is sub-optimal. In previous work, we have shown that the Kasai autocorrelation estimator is statistically sub-optimal under conditions of additive white Gaussian noise. In addition, for practical OCT measurements of flow, decorrelation noise affects Doppler frequency estimation by broadening the signal spectrum. Here we derive a general maximum likelihood estimator (MLE ...

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    10. Real-time stroboscopic full-field optical coherence tomography based on graphics processing unit

      Real-time stroboscopic full-field optical coherence tomography based on graphics processing unit

      We present the real-time stroboscopic full-field optical coherence tomography (FF-OCT) system that is based on graphics processing unit (GPU). The basic configuration of the proposed FF-OCT system was the Linnik interferometer. While scanning of a reference mirror in the axial direction, a series of the transverse sectional image was captured with a 2-dimensional CCD camera. To get a depth-resolved 3-D image, the light source of OCT was turned on and off like a stroboscope at the Doppler frequency of the OCT system. The CCD camera used in experiment operated at a rate of 200 frames per second, but the Doppler ...

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    11. High-sensitive full-range optical vibrometry based on Fourier-domain optical coherence tomography

      High-sensitive full-range optical vibrometry based on Fourier-domain optical coherence tomography

      Optical vibrometery based on low coherence Fourier-domain optical coherence tomography (FD-OCT) technique are well capable for providing depth resolved vibration information in comparison with conventional laser based vibrometery. Recently, there has been growing interest in developing coherence-domain vibrometry for various clinical and pre-clinical applications. However, a major drawback of the conventional vibrometer based on Fourier-domain low coherence interferometry is the complex-conjugate ambiguity. This is because in FD-OCT, the detected real valued spectral interferogram is Fourier transformed to localize the scatter within the sample. The Fourier transform of a real valued function is Hermitian, so the reconstructed image is symmetric with ...

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    12. Microvascular anastomosis in rodent model evaluated by Fourier domain Doppler optical coherence tomography

      Microvascular anastomosis in rodent model evaluated by Fourier domain Doppler optical coherence tomography

      Vascular and microvascular anastomosis are critical components of reconstructive microsurgery, vascular surgery and transplant surgery. Imaging modality that provides immediate, real-time in-depth view and 3D structure and flow information of the surgical site can be a great valuable tool for the surgeon to evaluate surgical outcome following both conventional and innovative anastomosis techniques, thus potentially increase the surgical success rate. Microvascular anastomosis for vessels with outer diameter smaller than 1.0 mm is extremely challenging and effective evaluation of the outcome is very difficult if not impossible using computed tomography (CT) angiograms, magnetic resonance (MR) angiograms and ultrasound Doppler. Optical ...

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    13. Improved microcirculation imaging of human skin in vivo using optical microangiography with a correlation mapping mask

      Improved microcirculation imaging of human skin in vivo using optical microangiography with a correlation mapping mask

      Optical microangiography based on optical coherence tomography (OCT) is prone to noise that arises from a static tissue region. Here, we propose a method that can significantly reduce this noise. The method is developed based on an approach that uses the magnitude information of OCT signals to produce tissue microangiograms, especially suitable for the case where a swept-source OCT system is deployed. By combined use of two existing OCT microangiography methods—ultrahigh-sensitive optical microangiography (UHS-OMAG) and correlation mapping OCT (cmOCT)—the final tissue microangiogram is generated by masking UHS-OMAG image using the binary representation of cmOCT image. We find that ...

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    14. Gold nanorods as a contrast agent for Doppler optical coherence tomography

      Gold nanorods as a contrast agent for Doppler optical coherence tomography

      PURPOSE: To investigate gold nanorods (GNRs) as a contrast agent to enhance Doppler optical coherence tomography (OCT) imaging of the intrascleral aqueous humor outflow. METHODS: A serial dilution of GNRs was scanned with a spectral-domain OCT device (Bioptigen, Durham, NC) to visualize Doppler signal. Doppler measurements using GNRs were validated using a controlled flow system. To demonstrate an application of GNR enhanced Doppler, porcine eyes were perfused at constant pressure with mock aqueous alone or 1.0×1012 GNR/mL mixed with mock aqueous. Twelve Doppler and volumetric SD-OCT scans were obtained from the limbus in a radial fashion incremented ...

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    15. Five-dimensional analysis of multi-contrast Jones matrix tomography of posterior eye

      Five-dimensional analysis of multi-contrast Jones matrix tomography of posterior eye

      Pixel clustering algorithm tailored to multi-contrast Jones matrix based optical coherence tomography (MC-JMT) is demonstrated. This algorithm clusters multiple pixels of MC-JMT in a five-dimensional (5-D) feature space which comprises dimensions of lateral space, axial space, logarithmic scattering OCT intensity, squared power of Doppler shift and degree of polarization uniformity. This 5-D clustering provides clusters of pixels, so called as superpixels. The superpixels are utilized as local regions for pixels averaging. The averaging decreases the noise in the measurement as preserving structural details of the sample. A simple decision-tree algorithm is applied to classified superpixels into some tissue types. This ...

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    16. System and method for optical coherence tomography

      System and method for optical coherence tomography

      The invention relates to a system and to a corresponding method for optical coherence tomography having an interferometer (10) which has a beam splitter (13), a first reflector (11) and a reflector (12) the optical distance (I) of which from the beam splitter (13) is changeable by a speed (v), and a detector (30) for collecting light which is reflected by a specimen (1) to be examined. In order to reduce the times required for the most reliable possible recording of interference patterns, provision is made such that the intensity of the light (14 or 4) injected into the interferometer ...

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      Mentions: AGFA Healthcare
    17. Noise statistics of phase-resolved optical coherence tomography imaging: single-and dual-beam-scan Doppler optical coherence tomography

      Noise statistics of phase-resolved optical coherence tomography imaging: single-and dual-beam-scan Doppler optical coherence tomography

      Noise statistics of phase-resolved optical coherence tomography (OCT) imaging are complicated and involve noises of OCT, correlation of signals, and speckles. In this paper, the statistical properties of phase shift between two OCT signals that contain additive random noises and speckle noises are presented. Experimental results obtained with a scattering tissue phantom are in good agreement with theoretical predictions. The performances of the dual-beam method and conventional single-beam method are compared. As expected, phase shift noise in the case of the dual-beam-scan method is less than that for the single-beam method when the transversal sampling step is large.

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    18. University of Washington Receives NIH Grant for Studying Non-Invasive Real-Time Label-Free 3D Imaging of Retinal Microcircuation

      University of Washington Receives NIH Grant for Studying Non-Invasive Real-Time Label-Free 3D Imaging of Retinal Microcircuation

      University of Washington Received a 2014 NIH Grant for $465,750 for Studying Non-Invasive Real-Time Label-Free 3D Imaging of Retinal Microcircuation. The principal investigator is Ruikang Wang. The program began in 2014 and ends in 2018. Below is a summary of the proposed work. Non-invasive and label-free imaging techniques for assessing retinal blood perfusion in humans - down to capillary-level resolution, are of paramount importance for improved understanding, diagnosis, treatment and management of diseases that have a vascular component in their pathogenesis, e.g., age related macular degeneration (AMD), diabetic retinopathy (DR), and open angle glaucoma (OAG). Invasive imaging techniques, e ...

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    19. Real-time acquisition and display of flow contrast using speckle variance optical coherence tomography in a graphics processing unit

      Real-time acquisition and display of flow contrast using speckle variance optical coherence tomography in a graphics processing unit

      In this report, we describe a graphics processing unit (GPU)-accelerated processing platform for real-time acquisition and display of flow contrast images with Fourier domain optical coherence tomography (FDOCT) in mouse and human eyes in vivo . Motion contrast from blood flow is processed using the speckle variance OCT (svOCT) technique, which relies on the acquisition of multiple B-scan frames at the same location and tracking the change of the speckle pattern. Real-time mouse and human retinal imaging using two different custom-built OCT systems with processing and display performed on GPU are presented with an in-depth analysis of performance metrics. The ...

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    20. Analysis of cross-sectional image filters for evaluating nonaveraged optical microangiography images

      Analysis of cross-sectional image filters for evaluating nonaveraged optical microangiography images

      Optical microangiography (OMAG) is a method that enables the noninvasive extraction of blood vessels within biological tissues. OMAG B-frames are prone to noise; therefore, techniques such as B-frame averaging have been applied to reduce these effects. A drawback of this method is that the total acquisition time and amount of data collected are increased; hence, the data are susceptible to motion artifacts and decorrelation. In this paper we propose using an image filter on a nonaveraged OMAG B-frame to reduce its noise. Consequently, B-frames comparable to the averaged OMAG B-frame are obtained, while reducing the total acquisition and processing time ...

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    21. Doppler mapping of an alternating-sign flow with complex geometry using optical coherence tomography

      Doppler mapping of an alternating-sign flow with complex geometry using optical coherence tomography

      The method of sign-sensitive mapping of the given range of velocities in a flow with complex geometry based on the principles of optical coherence tomography is described. To produce an alternating-sign flow, the 1% aqueous intralipid solution and the tilted capillary entry with the contraction coefficient 4:1 are used. The mapping is controlled using two parameters, the value of one specific velocity (OSV) for mapping and the accuracy of its determination. The structure image and two OSV images (for positive and negative direction of motion) are obtained as a result of selecting and processing the relevant parts of the ...

      Read Full Article
    22. Measurement of the total retinal blood flow using dual beam Fourier-domain Doppler optical coherence tomography with orthogonal detection planes

      Measurement of the total retinal blood flow using dual beam Fourier-domain Doppler optical coherence tomography with orthogonal detection planes

      We present a system capable of measuring the total retinal blood flow using a combination of dual beam Fourier-domain Doppler optical coherence tomography with orthogonal detection planes and a fundus camera-based retinal vessel analyzer. Our results show a high degree of conformity of venous and arterial flows, which corroborates the validity of the measurements. In accordance with Murray’s law, the log-log regression coefficient between vessel diameter and blood flow was found to be ~3. The blood’s velocity scaled linearly with the vessel diameter at higher diameters (> 60 µm), but showed a clear divergence from the linear dependence at ...

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    23. Noninvasive Imaging of Retinal Morphology and Microvasculature in Obese Mice using Optical Coherence Tomography and Optical Microangiography

      Noninvasive Imaging of Retinal Morphology and Microvasculature in Obese Mice using Optical Coherence Tomography and Optical Microangiography

      Purpose:To evaluate early diabetes-induced changes in retinal thickness and microvasculature in a type II diabetic mouse model using OCT/OMAG. Methods:22 week old obese BTBR mice (OB, n=10) and wild type control mice (WT, n=10) were imaged. Three-dimensional data were captured with OCT using an ultrahigh sensitive OMAG scanning protocol for 3D angiography of the retina and dense A-scan protocol for measurement of the total retinal blood flow (RBF) rate. The thickness of the nerve fiber layer (NFL) and NFL to inner plexiform layer (IPL) were measured and compared between OB and WT mice. The linear ...

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    24. Resolving directional ambiguity in dynamic light scattering-based transverse motion velocimetry in optical coherence tomography

      Resolving directional ambiguity in dynamic light scattering-based transverse motion velocimetry in optical coherence tomography

      Dynamic light scattering-based optical coherence tomography approaches have been successfully implemented to measure total transverse ( x y ) flow speed, but are unable to resolve directionality. We propose a method to extract directional velocity in the transverse plane by introducing a variable scan bias to our system. Our velocity estimation, which yields the directional velocity component along the scan axis, is also independent of any point-spread function calibration. By combining our approach with Doppler velocimetry, we show three-component velocimetry that is appropriately dependent on latitudinal and longitudinal angle ]

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    1-24 of 330 1 2 3 4 ... 12 13 14 »
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