Doppler -Optical Coherence Tomography News

Articles in category: Doppler

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1. In vivo lung microvasculature visualized in three dimensions using fiber-optic color Doppler optical coherence tomography
  
  Explore SPIE | Journal Apr 30 2013 Pulmonology , Doppler
  
  For the first time, the use of fiber-optic color Doppler optical coherence tomography (CDOCT) to map in vivo the three-dimensional (3-D) vascular network of airway segments in human lungs is demonstrated. Visualizing the 3-D vascular network in the lungs may provide new opportunities for detecting and monitoring lung diseases such as asthma, chronic obstructive pulmonary disease, and lung cancer. Our CDOCT instrument employs a rotary fiber-optic probe that provides simultaneous two-dimensional (2-D) real-time structural optical coherence tomography (OCT) and CDOCT imaging at frame rates up to 12.5 frames per second. Controlled pullback of the probe allows 3-D vascular mapping ...
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  Mentions: Victor X. D. Yang British Columbia Cancer Agency Stephen Lam
2. Review of speckle and phase variance optical coherence tomography to visualize microvascular networks
  
  Explore SPIE | Journal Apr 28 2013 Doppler
  
  High-resolution mapping of microvasculature has been applied to diverse body systems, including the retinal and choroidal vasculature, cardiac vasculature, the central nervous system, and various tumor models. Many imaging techniques have been developed to address specific research questions, and each has its own merits and drawbacks. Understanding, optimization, and proper implementation of these imaging techniques can significantly improve the data obtained along the spectrum of unique research projects to obtain diagnostic clinical information. We describe the recently developed algorithms and applications of two general classes of microvascular imaging techniques: speckle-variance and phase-variance optical coherence tomography (OCT). We compare and contrast ...
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  Mentions: Ontario Cancer Institute University of Toronto Sunnybrook Health Sciences Centre
3. Measurement of Total Retinal Blood Flow in Patients With Diabetes and Healthy Subjects
  
  Explore ClinicalTrials.gov Apr 26 2013 Ophthalmology , Clinical Trials , Doppler
  
  The prevalence of diabetes and diabetes-associated complications is still increasing. Several major long-term complications of diabetes such as cardiovascular disease, chronic renal failure, diabetic retinopathy and others relate to the damage of blood vessels. Given that the eye provides the unique possibility in the human body to directly visualize blood vessels, much interest has been directed towards studying the ocular circulation. Although data of large epidemiological studies indicate that changes in retinal vessel caliber reflect other diabetes related factors, such as fasting glucose levels, there is still conflicting evidence on blood flow alterations in patients with diabetes. This is also ...
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  Mentions: Medical University of Vienna
4. Coherence-gated Doppler: a fiber sensor for precise localization of blood flow
  
  Explore opticsinfobase.org Apr 24 2013 Doppler
  
  Miniature optical sensors that can detect blood vessels in front of advancing instruments will significantly benefit many interventional procedures. Towards this end, we developed a thin and flexible coherence-gated Doppler (CGD) fiber probe (O.D. = 0.125 mm) that can be integrated with minimally-invasive tools to provide real-time audio feedback of blood flow at precise locations in front of the probe. Coherence-gated Doppler (CGD) is a hybrid technology with features of laser Doppler flowmetry (LDF) and Doppler optical coherence tomography (DOCT). Because of its confocal optical design and coherence-gating capabilities, CGD provides higher spatial resolution than LDF. And compared to ...
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  Mentions: University of Maryland Joseph M. Schmitt Yu Chen
5. High quality optical microangiography of ocular microcirculation and measurement of total retinal blood flow in mouse eye
  
  Explore Conference Proceedings Apr 1 2013 Ophthalmology , Doppler
  
  Visualization and measurement of retinal blood flow (RBF) is important to the diagnosis and management of different eye diseases, including diabetic retinopathy. Optical microangiography (OMAG) is developed for generating 3D dynamic microcirculation image and later refined into ultra-high sensitive OMAG (UHS-OMAG) for true capillary vessels imaging. Here, we present the application of OMAG imaging technique for visualization of depth-resolved vascular network within retina and choroid as well as measurement of total retinal blood flow in mice. A fast speed spectral domain OCT imaging system at 820nm with a line scan rate of 140 kHz was developed to image mouse posterior ...
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  Mentions: University of Washington Ruikang K. Wang Arthur Ho
6. Functional imaging of hemodynamic stimulus response in the rat retina with ultrahigh-speed spectral / Fourier domain OCT
  
  Explore Conference Proceedings Apr 1 2013 Ophthalmology , Doppler
  
  Measuring retinal hemodynamics in response to flicker stimulus is important for investigating pathophysiology in small animal models of diabetic retinopathy, because a reduction in the hyperemic response is thought to be one of the earliest changes in diabetic retinopathy. In this study, we investigated functional imaging of retinal hemodynamics in response to flicker stimulus in the rat retina using an ultrahigh speed spectral / Fourier domain OCT system at 840nm with an axial scan rate of 244kHz. At 244kHz the nominal axial velocity range that could be measured without phase wrapping was +/-37.7mm/s. Pulsatile total retinal arterial blood flow ...
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  Mentions: Massachusetts Institute of Technology James G. Fujimoto Bernhard Baumann
7. Imaging and quantifying Brownian motion of micro- and nanoparticles using phase-resolved Doppler variance optical coherence tomography
  
  Explore SPIE | Journal Apr 1 2013 Doppler
  
  Different types and sizes of micro- and nanoparticles have been synthesized and developed for numerous applications. It is crucial to characterize the particle sizes. Traditional dynamic light scattering, a predominant method used to characterize particle size, is unable to provide depth resolved information or imaging functions. Doppler variance optical coherence tomography (OCT) measures the spectral bandwidth of the Doppler frequency shift due to the Brownian motion of the particles utilizing the phase-resolved approach and can provide quantitative information about particle size. Spectral bandwidths of Doppler frequency shifts for various sized particles were quantified and were demonstrated to be inversely proportional ...
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  Mentions: Zhongping Chen UC Irvine Jun Zhang
8. Imaging and quantifying Brownian motion of micro- and nanoparticles using phase-resolved Doppler variance optical coherence tomography
  
  Explore SPIE | Journal Mar 22 2013 Doppler
  
  Different types and sizes of micro- and nanoparticles have been synthesized and developed for numerous applications. It is crucial to characterize the particle sizes. Traditional dynamic light scattering, a predominant method used to characterize particle size, is unable to provide depth resolved information or imaging functions. Doppler variance optical coherence tomography (OCT) measures the spectral bandwidth of the Doppler frequency shift due to the Brownian motion of the particles utilizing the phase-resolved approach and can provide quantitative information about particle size. Spectral bandwidths of Doppler frequency shifts for various sized particles were quantified and were demonstrated to be inversely proportional ...
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  Mentions: Zhongping Chen UC Irvine Jun Zhang
9. Real-time 3D Fourier-domain optical coherence tomography guided microvascular anastomosis
  
  Explore Conference Proceedings Mar 18 2013 Doppler
  
  Vascular and microvascular anastomosis is considered to be the foundation of plastic and reconstructive surgery, hand surgery, transplant surgery, vascular surgery and cardiac surgery. In the last two decades innovative techniques, such as vascular coupling devices, thermo-reversible poloxamers and suture-less cuff have been introduced. Intra-operative surgical guidance using a surgical imaging modality that provides in-depth view and 3D imaging can improve outcome following both conventional and innovative anastomosis techniques. Optical coherence tomography (OCT) is a noninvasive high-resolution (micron level), high-speed, 3D imaging modality that has been adopted widely in biomedical and clinical applications. In this work we performed a proof-of-concept ...
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  Mentions: Johns Hopkins University Jin U. Kang Yong Huang
10. Blood flow velocity measurement by endovascular Doppler optical coherence tomography
  
  Explore Conference Proceedings Mar 12 2013 Cardiology , Doppler
  
  Blood flow velocity and volumetric flow measurements are important parameters for assessment of the severity of stenosis and the outcome of interventional therapy. However, feasibility of intravascular flow measurement using a rotational catheter based phase resolved Doppler optical coherence tomography (DOCT) is difficult. Motion artefacts induced by the rotating optical imaging catheter, and the radially dependent noise background of measured Doppler signals are the main challenges encountered. In this study, a custom-made data acquisition system and developed algorithms to remove non-uniform rotational distortion (NURD) induced phase shift artefact by tracking the phase shift observed on catheter sheath. The flow velocity ...
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  Mentions: Victor X. D. Yang Brian K. Courtney Beau A. Standish
11. Three-dimensional retinal and choroidal capillary imaging by power Doppler optical coherence angiography with adaptive optics
  
  Explore opticsinfobase.org Mar 7 2013 Ophthalmology , Doppler
  
  Retinal and choroidal vascular imaging is a key to the better understanding and diagnosis of eye diseases. To achieve comprehensive three-dimensional capillary imaging, we used an enhanced vascular imaging technique, so called adaptive optics optical coherence angiography (AO-OCA). AO-OCA enables in vivo high-resolution and high-contrast micro-vascular imaging by detecting Doppler frequency shifts. Using this technique, the retinal and choroidal vasculatures of healthy subjects were imaged. The results show that both intensity and Doppler power images have sufficient contrast to discriminate almost all vasculatures from the static tissue. However, the choriocapillaris, pre-arterioles, and post-venules in the Sattler layer were more contrasted ...
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  Mentions: Shuichi Makita Yoshiaki Yasuno University of Tsukuba
12. Variable-range Doppler optical microangiography using stabilized step scanning and phase variance binarized mask
  
  Explore Conference Proceedings Mar 5 2013 Doppler
  
  Skipping various numbers of A-lines is effective to obtain multi-range velocimetry using Doppler optical coherence tomography (DOCT). High correlation between A-lines is a fundamental prerequisite for DOCT processing. Therefore, high oversampling is normally necessary, especially when skipping A-lines. That requires quite a long time of imaging, which might not be acceptable on some occasions. Step-scanning protocol, which captures repeated A-scans, has been employed for multi-range DOCT previously. We develop it by waiting for the scanner to stabilize, but not capturing continuously. In this way the cross-correlation of step scanning maintains almost constant for all the captured A-lines, and is higher ...
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  Mentions: University of Washington Ruikang K. Wang Suzan Dziennis
13. Quantitative imaging of cerebral blood flow velocity and intracellular motility using dynamic light scattering–optical coherence tomography
  
  Explore Nature Publishing Group Feb 14 2013 Doppler
  
  This paper describes a novel optical method for label-free quantitative imaging of cerebral blood flow (CBF) and intracellular motility (IM) in the rodent cerebral cortex. This method is based on a technique that integrates dynamic light scattering (DLS) and optical coherence tomography (OCT), named DLS–OCT. The technique measures both the axial and transverse velocities of CBF, whereas conventional Doppler OCT measures only the axial one. In addition, the technique produces a three-dimensional map of the diffusion coefficient quantifying nontranslational motions. In the DLS–OCT diffusion map, we observed high-diffusion spots, whose locations highly correspond to neuronal cell bodies and ...
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  Mentions: UC Davis Harsha Radhakrishnan
14. Optimal doppler frequency estimators for ultrasound and optical coherence tomography
  
  Explore IEEE Xplore Jan 29 2013 Doppler
  
  The Kasai autocorrelation estimator is widely used in Doppler optical coherence tomography and ultrasound to determine blood velocities. However, as a non-parametric estimator, it may not be optimal. Assuming an additive white Gaussian noise (AWGN) model, we show that the Kasai estimator variance is far from the Cramer-Rao lower bound. Moreover, paradoxically, the Kasai estimator performance degrades as the acquisition rate is increased. By contrast, the additive white Gaussian noise maximum likelihood estimator (AWGN MLE) variance asymptotically approaches the Cramer-Rao lower bound, making it a better estimator at high acquisition rates. Nevertheless, the Kasai estimator outperforms the AWGN MLE under ...
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  Mentions: Massachusetts Institute of Technology Vivek J. Srinivasan Massachusetts General Hospital
15. Phase-sensitive swept-source optical coherence tomography imaging of the human retina with a vertical cavity surface-emitting laser light source
  
  Explore opticsinfobase.org Jan 25 2013 Ophthalmology , Doppler
  
  Despite the challenges in achieving high phase stability, Doppler swept-source/Fourier-domain optical coherence tomography (OCT) has advantages of less fringe washout and faster imaging speeds compared to spectral/Fourier-domain detection. This Letter demonstrates swept-source OCT with a vertical cavity surface-emitting laser light source at 400 kHz sweep rate for phase-sensitive Doppler imaging, measuring pulsatile total retinal blood flow with high sensitivity and phase stability. A robust, simple, and computationally efficient phase stabilization approach for phase-sensitive swept-source imaging is also presented.
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  Mentions: Massachusetts Institute of Technology James G. Fujimoto Thorlabs
16. Feasibility of capillary velocity assessment by statistical means using dual-beam spectral-domain Optical Coherence Tomography: a preliminary study
  
  Explore Wiley Online Library Jan 12 2013 Doppler
  
  The assessment of vascular dynamics has been shown to yield both qualitative and quantitative metrics and thus play a pivotal role in the diagnosis and prognosis of various diseases, which may manifest as microcirculatory irregularities. Optical Coherence Tomography (OCT) is an established imaging modality which utilises the principle of optical interferometry to distinguish between spatial changes in refractive index and thus formulate a multi-dimensional representation of a specimen in vivo . Nonetheless, difficulties remain in obtaining accurate data (morphological and/or transient) in an environment which is subject to such large biological variability. In an effort to address the issue of ...
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  Mentions: University of Limerick Martin J. Leahy
17. Automatic retinal vessel segmentation based on active contours method in Doppler spectral-domain optical coherence tomography
  
  Explore SPIE | Journal Jan 8 2013 Ophthalmology , Doppler
  
  We achieved fast and automatic retinal vessel segmentation by employing the active contours method in Doppler spectral-domain optical coherence tomography (SD-OCT). In a typical OCT B-scan image, we first extracted the phase variations between adjacent A-lines and removed bulk motion. Then we set the initial contour as the boundary of the whole image and iterated until all of the segmented vessel contours became stabilized. Using a typical office computer, the whole segmentation took no more than 50 s, making real-time retinal vessel segmentation possible. We tested the active contours method segmentation in both controlled phantom and in vivo rodent eye ...
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  Mentions: Northwestern University Ji Yi Hao F. Zhang
18. Retinal Blood Flow Evaluation
  
  Explore Karger Publishers Dec 17 2012 Ophthalmology , Doppler
  
  Much of our basic knowledge of retinal blood flow regulation is based on data obtained from animal experiments through the use of invasive techniques. However, during the last decades, major developments in the field of optics and lasers have led to a variety of noninvasive techniques, which have been applied to the human eye for the investigation of retinal hemodynamics, and more specifically the regulation of retinal blood flow in response to a number of physiological and pharmacological stimuli. The Retinal Vessel Analyzer has markedly simplified the measurement of the diameter of retinal vessels, as well as the change in ...
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19. Real-time eye motion correction in phase-resolved OCT angiography with tracking SLO
  
  Explore opticsinfobase.org Dec 15 2012 Ophthalmology , Doppler
  
  In phase-resolved OCT angiography blood flow is detected from phase changes in between A-scans that are obtained from the same location. In ophthalmology, this technique is vulnerable to eye motion. We address this problem by combining inter-B-scan phase-resolved OCT angiography with real-time eye tracking. A tracking scanning laser ophthalmoscope (TSLO) at 840 nm provided eye tracking functionality and was combined with a phase-stabilized optical frequency domain imaging (OFDI) system at 1040 nm. Real-time eye tracking corrected eye drift and prevented discontinuity artifacts from (micro)saccadic eye motion in OCT angiograms. This improved the OCT spot stability on the retina and ...
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  Mentions: Johannes F. de Boer VU University Amsterdam Koen A. Vermeer
20. Recent advances in optical coherence tomography
  
  Explore Conference Proceedings Dec 15 2012 Doppler
  
  This paper reports recent advances in spectral domain Doppler optical coherence tomography (SD-DOCT) in our group. A high speed SD-DOCT system is developed and applied to animal study and microchip evaluation. Further improvements concerning SD-DOCT are presented, those including higher-order cross-correlation for phase retrieval, transit-time analysis for velocity quantification, and orthogonal dispersive SD-OCT for depth extension.
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  Mentions: Zhihua Ding Zhejiang University
21. Investigation of the human tympanic membrane oscillation ex vivo by Doppler optical coherence tomography
  
  Explore Wiley Online Library Dec 10 2012 Otolaryngology , Doppler
  
  Investigations of the tympanic membrane (TM) can have an important impact on understanding the sound conduction in the ear and can therefore support the diagnosis and treatment of diseases in the middle ear. High-speed Doppler optical coherence tomography (OCT) has the potential to describe the oscillatory behaviour of the TM surface in a phase-sensitive manner and additionally allows acquiring a three-dimensional image of the underlying structure. With repeated sound stimuli from 0.4 kHz to 6.4 kHz, the whole TM can be set in vibration and the spatially resolved frequency response functions (FRFs) of the tympanic membrane can be ...
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  Mentions: Dresden University of Technology Edmund Koch Lars Kirsten
22. Optical Coherence Tomography for Brain Imaging
  
  Explore SpringerLink Home Nov 13 2012 Neurology , Doppler
  
  Recently, there has been growing interest in using OCT for brain imaging. A feasibility study of OCT for guiding deep brain probes has found that OCT can differentiate the white matter and gray matter because the white matter tends to have a higher peak reflectivity and steeper attenuation rate compared to gray matter. In vivo 3D visualization of the layered organization of a rat olfactory bulb with OCT has been demonstrated. OCT has been used for single myelin fiber imaging in living rodents without labeling. The refractive index in the rat somatosensory cortex has also been measured with OCT. In ...
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  Mentions: Zhongping Chen UC Irvine Gangjun Liu
23. Quantitative OCT angiography of optic nerve head blood flow
  
  Explore opticsinfobase.org Nov 12 2012 Ophthalmology , Doppler
  
  Optic nerve head (ONH) blood flow may be associated with glaucoma development. A reliable method to quantify ONH blood flow could provide insight into the vascular component of glaucoma pathophysiology. Using ultrahigh-speed optical coherence tomography (OCT), we developed a new 3D angiography algorithm called split-spectrum amplitude-decorrelation angiography (SSADA) for imaging ONH microcirculation. In this study, a method to quantify SSADA results was developed and used to detect ONH perfusion changes in early glaucoma. En face maximum projection was used to obtain 2D disc angiograms, from which the average decorrelation values (flow index) and the percentage area occupied by vessels (vessel ...
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  Mentions: Massachusetts Institute of Technology James G. Fujimoto David Huang
24. Optical microangiography provides correlation between microstructure and microvasculature of optic nerve head in human subjects
  
  Explore SPIE | Journal Nov 9 2012 Ophthalmology , Doppler
  
  It is demonstrated that optical microangiography (OMAG) is capable of imaging the detailed microstructure and microvasculature of the in vivo human optic nerve head (ONH), including the prelaminar tissue, the lamina cribrosa, the scleral rim and the vessels in the region of the circle of Zin-Haller. For demonstration, an ultrahigh sensitive OMAG system operating in the 850 nm wavelength region and a 500 kHz A-scan rate resulting in a spatial resolution of ∼ 6 μ m were used. It was shown that OMAG provides superior results for three-dimensional imaging of the ONH compared to conventional optical coherence tomography by simultaneously recording both ...
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  Mentions: University of Washington Ruikang K. Wang Lin An
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