Doppler -Optical Coherence Tomography News

Articles in category: Doppler

121-144 of 279 « 1 2 ... 3 4 5 6 7 8 9 ... 10 11 12 »
1. Two-Beam Optical Coherence Tomography Apparatus
  
  Explore wipo.int Dec 16 2010 Patents , Doppler
  
  The sample scan speed of a Doppler OCT or the like is increased, and measurement of a blood flow speed and a blood flow rate can be quickly performed. A wide-band light beam from a light source (2) is converted into a linearly polarized light beam by means of a polarization control device (3). The linearly polarized light beam is split in a sample arm into a vertically polarized light beam and a horizontally polarized light beam by means of a Wollaston prism (14). The light beams are simultaneously applied to two locations of the sample different in scan direction ...
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  Mentions: Shuichi Makita Yoshiaki Yasuno University of Tsukuba
2. Measuring hemodynamics in the developing heart tube with four-dimensional gated Doppler optical coherence tomography
  
  Explore SPIE Digital Library Dec 13 2010 Cardiology , Developmental Biology , Doppler
  
  Hemodynamics is thought to play a major role in heart development, yet tools to quantitatively assess hemodynamics in the embryo are sorely lacking. The especially challenging analysis of hemodynamics in the early embryo requires new technology. Small changes in blood flow could indicate when anomalies are initiated even before structural changes can be detected. Furthermore, small changes in the early embryo that affect blood flow could lead to profound abnormalities at later stages. We present a demonstration of 4-D Doppler optical coherence tomography (OCT) imaging of structure and flow, and present several new hemodynamic measurements on embryonic avian hearts at ...
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  Mentions: Andrew M. Rollins Case Western Reserve University Madhusudhana Gargesha
3. Spectral Doppler optical coherence tomography imaging of localized ischemic stroke in a mouse model
  
  Explore SPIE Digital Library Dec 7 2010 Doppler
  
  We report the use of spectral Doppler optical coherence tomography imaging (SDOCTI) for quantitative evaluation of dynamic blood circulation before and after a localized ischemic stroke in a mouse model. Rose Bengal photodynamic therapy (PDT) is used as a noninvasive means for inducing localized ischemia in cortical microvasculature of the mouse. Fast, repeated Doppler optical coherence tomography scans across vessels of interest are performed to record flow dynamic information with high temporal resolution. Doppler-angle-independent flow indices are used to quantify vascular conditions before and after the induced ischemia by the photocoagulation of PDT. The higher (or lower) flow resistive indices ...
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  Mentions: Zhongping Chen Bernard Choi UC Irvine
4. Effects of the optical transfer function on velocity estimation with optical coherence tomography
  
  Explore SPIE Digital Library Nov 8 2010 Doppler
  
  Doppler optical coherence tomography (DOCT) is an extension of optical coherence tomography (OCT) for measuring blood flow dynamics simultaneously with the microscopic structures at high spatial and velocity resolution. In this paper, we analyze the effects of parameters of the DOCT system on the optical transfer function (OTF) which finally affects the accuracy of the velocity estimation. Experimental data are given to show the effects. The methods of overcoming the effects are also pointed out.
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5. Pilot Study of Optical Coherence Tomography Measurement of Retinal Blood Flow in Retinal and Optic Nerve Diseases
  
  Explore iovs.org Nov 6 2010 Ophthalmology , Doppler
  
  Purpose: To investigate blood flow changes in retinal and optic nerve diseases with Doppler Fourier domain optical coherence tomography (OCT). Methods: Sixty-two participants were divided into five groups: normal, glaucoma, nonarteritic ischemic optic neuropathy (NAION), treated proliferative diabetic retinopathy (PDR), and branch retinal vein occlusion (BRVO). Doppler OCT was used to scan concentric circles of 3.4 and 3.75 mm diameters around the optic nerve head. Flow in retinal veins were calculated from the OCT velocity profiles. Arterial and venous diameters were measured from OCT Doppler and reflectance images. Results: Total retinal blood flow in normal subjects averaged 47 ...
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  Mentions: Joseph A. Izatt David Huang Duke University
6. Heart wall velocimetry and exogenous contrast-based cardiac flow imaging in Drosophila melanogaster using Doppler optical coherence tomography
  
  Explore SPIE Digital Library Oct 29 2010 Cardiology , Developmental Biology , Doppler
  
  Drosophila melanogaster (fruit fly) is a central organism in biology and is becoming increasingly important in the cardiovascular sciences. Prior work in optical imaging of the D. melanogaster heart has focused on static and dynamic structural anatomy. In the study, it is demonstrated that Doppler optical coherence tomography can quantify dynamic heart wall velocity and hemolymph flow in adult D. melanogaster. Since hemolymph is optically transparent, a novel exogenous contrast technique is demonstrated to increase the backscatter-based intracardiac Doppler flow signal. The results presented here open up new possibilities for functional cardiovascular phenotyping of normal and mutant D. melanogaster.
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  Mentions: Guillermo J. Tearney Brett E. Bouma Massachusetts General Hospital
7. Autocorrelation optical coherence tomography for mapping transverse particle-flow velocity
  
  Explore opticsinfobase.org Oct 18 2010 Doppler
  
  We present an autocorrelation method to quantitatively map transverse particle-flow velocity with a Fourier-domain optical coherence tomography system. This method is derived from the intensity fluctuation of the backscattered light modulated by flowing particles. When passing through the probe beam, moving particles encode a transit time into the backscattered light. The slope of the normalized autocorrelation function of the backscattered light is proportional to the transverse velocity. The proposed method is experimentally verified using an intralipid scattering flow phantom.
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  Mentions: Oregon Health & Science University University of Washington Ruikang K. Wang
8. Stable absolute flow estimation with Doppler OCT based on virtual circumpapillary scans
  
  Explore opticsinfobase.org Oct 1 2010 Ophthalmology , Doppler
  
  Doppler optical coherence tomography has the capability to measure blood flow quantitatively and in vivo. As only the axial component of the velocity can be assessed, the measurements have to be corrected for the angle of the vessels. We present a novel approach to extract quantitative flow data from circumpapillary scans in vivo on the human retina by registering the circular scan to a reference volume scan and extracting the angle directly from the volume. In addition, we perform phase unwrapping and interpolation of the flow under the assumption of a parabolic flow profile. We demonstrate the repeatability of the ...
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  Mentions: Rainer A. Leitgeb Medical University of Vienna Tilman Schmoll
9. Feature Of The Week 9/19/10: Researchers from University of Central Florida and University of Rochester demonstrate Doppler Imaging with Dual-Detection Full-Range Frequency Domain Optical Coherence Tomography
  
  Explore Optical Coherence Tomography News Sep 19 2010 Doppler
  
  Feature Of The Week 9/19/10: Recent development in Doppler optical coherence tomography (DOCT) is mostly based on phase sensitive detection so-called phase-resolved DOCT. It is commonly known that the performances of phase-resolved Doppler OCT, such as the stability and accuracy of the measured Doppler phase shift, highly rely on the signal-to-noise ratio (SNR). Therefore, the ability to employ a maximum SNR out of a given phase-resolved DOCT system is desirable. Even though, the high speed imaging capability of FD-OCT is attractive for real time in vivo monitoring of flow activity in biological sample as well as for 3D ...
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  Mentions: University of Rochester Kye-Sung Lee Panomsak Meemon
10. Swept-source based, single-shot, multi-detectable velocity range Doppler optical coherence tomography
  
  Explore opticsinfobase.org Sep 16 2010 Doppler
  
  Phase-Resolved Doppler Optical Coherence Tomography (PR-DOCT) allows visualization and characterization of the location, direction, velocity, and profile of flow activity embedded in a static sample structure. The detectable Velocity Dynamic Range (VDR) of each particular PR-DOCT system is governed by a detectable Doppler phase shift, a flow angle, and an acquisition time interval used to determine the Doppler phase shift. In general, the lower boundary of the detectable Doppler phase shift is limited by the phase stability of the system, while the upper boundary is limited by the π phase ambiguity. For a given range of detectable Doppler phase shift ...
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  Mentions: University of Rochester Panomsak Meemon Jannick P. Rolland
11. Doppler imaging with dual-detection full-range frequency domain optical coherence tomography
  
  Explore opticsinfobase.org Aug 10 2010 Doppler
  
  Most of full-range techniques for Frequency Domain Optical Coherence Tomography (FD-OCT) reported to date utilize the phase relation between consecutive axial lines to reconstruct a complex interference signal and hence may exhibit degradation in either mirror image suppression performance or detectable velocity dynamic range or both when monitoring a moving sample such as flow activity. We have previously reported a technique of mirror image removal by simultaneous detection of the quadrature components of a complex spectral interference called a Dual-Detection Frequency Domain OCT (DD-FD-OCT) [Opt. Lett. 35, 1058-1060 (2010)]. The technique enables full range imaging without any loss of acquisition ...
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  Mentions: University of Rochester Kye-Sung Lee Panomsak Meemon
12. Signal power decrease due to fringe washout as an extension of the limited Doppler flow measurement range in spectral domain optical coherence tomography
  
  Explore SPIE Digital Library Jul 23 2010 Doppler
  
  The recently introduced new phase-dependent Doppler model for spectral domain optical coherence tomography (SD OCT) has shown that the simple linear relation between the Doppler phase shift and the axial velocity component of an obliquely moving sample is not valid. Additionally, for nearly transverse sample motion with high velocities the phase shift will approach a constant value. Consequently, for small Doppler angles the velocity measurement range of the phase-resolved Doppler analysis is limited in SD OCT. Since these undesirable small Doppler angles can not be prevented, for example, in the in vivo 3-D measurement, we introduce a novel method extending ...
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  Mentions: Julia Walther Dresden University of Technology Henning Morawietz
13. Doppler optical coherence tomography for imaging of brain hemodynamics
  
  Explore Home: SPIE.org Jul 6 2010 Microscopy , Doppler
  
  Advanced microscopic techniques enable depth-resolved imaging of changes in blood flow during brain activation. ptical imaging has become an important tool in neuroscience research.1 Using methods such as optical intrinsic signal imaging (OISI), laser-Doppler imaging, and laser-speckle imaging, investigators can record changes in blood flow and blood volume in the brain, as well as alterations in blood oxygen concentration, in response to different types of stimulation. By measuring these changes, they can gain deeper insight into the functioning of the brain, which in turn can contribute to better understanding of a range of behaviors and conditions. However, these techniques ...
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  Mentions: Massachusetts Institute of Technology James G. Fujimoto Thorlabs
14. High-velocity-flow imaging with real-time Doppler optical coherence tomography
  
  Explore opticsinfobase.org May 27 2010 Doppler
  
  We present a real-time time-domain Doppler optical coherence tomography (OCT) system based on the zero-crossing method for velocity measurements of fluid flows with attainable velocities up to 10 m/s. In the current implementation, one-dimensional and two-dimensional velocity profiles of fluid flows ranging from 1 cm/s to more than 3 m/s were obtained for both laminar and turbulent flows. The line rate was approximately 500 Hz, and the images were treated in real time. This approach has the advantage of providing reliable velocity maps free from phase aliasing or other artifacts common to several OCT systems. The system ...
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  Mentions: Polytechnique Montreal Romain Maciejko
15. Effect of light scattering superficial layer on the accuracy of flow velocity profiles measurements by Doppler optical coherence tomography
  
  Explore SPIE Digital Library May 18 2010 Doppler
  
  Doppler Optical Coherence Tomography (DOCT) is a modern technique used for accurate measurements of blood flow in the superficial layers of human skin, retina or other tissues and their phantoms. In this work, we considered the effect of both static and dynamic superficial layer of the scattering medium on the measured velocity of a flow located beneath this layer. In the case of static layer a tissue phantom consisting of a plain glass capillary (inner size 0.3 × 3 mm) embedded into a slab of Intralipid solution mimicking human skin was designed. Flow velocity profiles were measured at different embedding ...
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  Mentions: Janne Lauri Risto A. Myllylä University of Oulu
16. Velocity Variation Assessment of Red Blood Cell Aggregation with Spectral Domain Doppler Optical Coherence Tomography
  
  Explore SpringerLink Home May 15 2010 Doppler
  
  We propose spectral domain Doppler optical coherence tomography (SD-D-OCT) to qualitatively measure red blood cell aggregation. Variance/standard deviation (SD) of the Doppler frequency spectrum in Doppler variance imaging of flowing blood under shearing conditions was developed as a new aggregation index. In in vitro microchannel-flow experiments, porcine blood at various hematocrits with aggregation characteristics induced by dextran 500 or at the presence of plasma fibrinogen was measured by a SD-D-OCT system with a spectrum centered at 1310 nm. The effects of shear rate, hematocrit, aggregation level on the SD values were investigated. The results demonstrate that Doppler variance imaging ...
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  Mentions: Zhongping Chen UC Irvine Lingfeng Yu
17. Doppler optical coherence tomography in cardiovascular applications
  
  Explore SpringerLink Home Apr 28 2010 Doppler
  
  Abstract The study of flow dynamics in complex geometry vessels is highly important in various biomedical applications where the knowledge of the mechanic interactions between the moving fluid and the housing media plays a key role for the determination of the parameters of interest, including the effect of blood flow on the possible rupture of atherosclerotic plaques. Doppler Optical Coherence Tomography (DOCT), as a functional extension of Optical Coherence Tomography (OCT), is an optic, non-contact, noninvasive technique able to achieve detailed analysis of the flow/vessel interactions. It allows simultaneous high resolution imaging (∼10 µm typical) of the morphology and ...
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  Mentions: University of Sheffield Steven J. Matcher Medical University of Vienna
18. Optimized speckle variance OCT imaging of microvasculature
  
  Explore opticsinfobase.org Apr 14 2010 Cardiology , Doppler
  
  We optimize speckle variance optical coherence tomography (svOCT) imaging of microvasculature in high and low bulk tissue motion scenarios. To achieve a significant level of image contrast, frame rates must be optimized such that tissue displacement between frames is less than the beam radius. We demonstrate that higher accuracy estimates of speckle variance can enhance the detection of capillaries. These findings are illustrated in vivo by imaging the dorsal window chamber model (low bulk motion). We also show svOCT imaging of the nonstabilized finger (high bulk motion), using optimized imaging parameters, demonstrating better vessel detection than Doppler OCT.
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  Mentions: University of Toronto Brian C. Wilson Victor X. D. Yang
19. Imaging of subcutaneous blood vessels and flow velocity profiles by optical coherence tomography
  
  Explore SpringerLink Home Mar 11 2010 Dermatology , Doppler
  
  We have applied a compact low power rapid scanning Doppler Optical Coherence Tomography system to monitor multi-dimensional velocity profiles within the complex vessels and simultaneous real-time non-invasive imaging of skin tissues morphology in vivo, in the wavelength range of 1.3–1.5 nm. Optical clearing of skin tissues has been utilized to achieve depth of OCT images up to 1.7 mm. Current approach enables applying low-power (0.4–0.5 mW) and low-noise broadband near-infrared light sources and obtaining OCT images with down to 12 μm spatial resolution. Two-dimensional time-domain OCT images of complex flow velocity profiles in ...
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  Mentions: Medical University of Vienna Cranfield University Marco Bonesi
20. High-sensitive blood flow imaging of the retina and choroid by using double-beam optical coherence angiography
  
  Explore SPIE Digital Library Mar 5 2010 Ophthalmology , Doppler
  
  Wide-field and high-sensitive Doppler optical coherence angiography of the posterior human eye has been demonstrated. High-sensitive phase-resolved spectral-domain optical coherence tomography using the superluminescent diode with the central wavelength of 840 nm and bandwidth of 50 nm (FWHM) is developed. Two OCT signals with a time separation are acquired simultaneously with double sampling beams divided by using a Wollaston prism and a polarization-sensitive spectrometer consisting of two line scan cameras. The total power of two beams on the cornea is 700 µW. The line scan rate of cameras is 27 kHz and each OCT channel has the sensitivity of 93 ...
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  Mentions: Shuichi Makita Yoshiaki Yasuno Masahiro Miura
21. True velocity mapping using joint spectral and time domain optical coherence tomography
  
  Explore SPIE Digital Library Mar 2 2010 Ophthalmology , Doppler
  
  We present both axial and transverse components estimation using joint Spectral and Time domain Optical Coherence Tomography (STdOCT) method. Whereas axial component of velocity vector can be determined from the time-dependent Doppler beating frequency, the transverse component can be assessed by the analysis of the broadening of flow velocity profiles (Doppler bandwidth). This enables us to quantitatively determine the absolute value of the velocity vector. The accurate analyses are performed using well-defined flow of Intralipid solution in the glass capillary. This enables performing in vivo imaging and allows to calculate velocity maps of the retinal vasculature
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  Mentions: Maciej Wojtkowski Nicolaus Copernicus University Andrzej A. Kowalczyk
22. Functional Doppler optical coherence tomography for cortical blood flow imaging
  
  Explore SPIE Digital Library Mar 2 2010 Doppler
  
  Optical methods have been widely used in basic neuroscience research to study the cerebral blood flow dynamics in order to overcome the low spatial resolution associated with magnetic resonance imaging and positron emission tomography. Although laser Doppler imaging and laser speckle imaging can map out en face cortical hemodynamics and columns, depth resolution is not available. Two-photon microscopy has been used for mapping cortical activity. However, flow measurement requires fluorescent dye injection, which can be problematic. The noninvasive and high resolution tomographic capabilities of optical coherence tomography make it a promising technique for mapping depth resolved cortical blood flow. Here ...
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  Mentions: Zhongping Chen Bernard Choi UC Irvine
23. The study of effects of pore architecture in chitosan scaffolds on the fluid flow pattern by Doppler OCT
  
  Explore SPIE Digital Library Feb 24 2010 Doppler
  
  Optimizing and fully understanding the dynamic culture conditions in tissue engineering could accelerate exploration of this new technique into a promising therapy in the medical field. Scaffolds used in tissue engineering usually are highly porous with various pore architecture depending on techniques that manufacture them. Perfusing culture fluid through a scaffold in a bioreactor has proven efficient in enhancing the exchange of nutrients and gas within cell-scaffold constructs. Upon perfusion, flowing fluid in pores inevitably produces shear stress on the wall of the pores, which will in turn induce cellular response for the cells possessing mechanotransducers. Thus, establishing a relationship ...
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  Mentions: Oregon Health & Science University Ruikang K. Wang Ying Yang
24. Full-range spectral domain Doppler optical coherence tomography
  
  Explore SPIE Digital Library Feb 23 2010 Doppler
  
  Spectral domain optical coherence tomography (SD-OCT) systems achieve higher sensitivities compared to time domain OCT systems. However, one of the main challenges in SD-OCT is the obscuring object structure called "ghost image" or "mirror image" that arises from the Fourier transform of a real function. We have designed and developed a phaseshifting- based full-range SD-OCT system that we refer to as the dual detection full range SD-OCT. The proposed technique simultaneously obtains the quadrature components of a complex spectral interference. Therefore, the technique enables full range imaging without any loss of speed and is intrinsically less sensitive to movements of ...
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  Mentions: University of Rochester Kye-Sung Lee Panomsak Meemon
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