The Experts below are selected from a list of 124290 Experts worldwide ranked by ideXlab platform
Joseph A. Izatt - One of the best experts on this subject based on the ideXlab platform.
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velocity resolved 3d retinal microvessel Imaging using single pass Flow Imaging spectral domain optical coherence tomography
Optics Express, 2009Co-Authors: Kristen M. Kennedy, Joseph A. IzattAbstract:We demonstrate in vivo velocity-resolved, volumetric bidirectional blood Flow Imaging in human retina using single-pass Flow Imaging spectral domain optical coherence tomography (SPFI-SDOCT). This technique uses previously described methods for separating moving and non-moving scatterers within a depth by using a modified Hilbert transform. Additionally, a moving spatial frequency window is applied, creating a stack of depth-resolved images of moving scatterers, each representing a finite velocity range. The resulting velocity reconstruction is validated with and strongly correlated to velocities measured with conventional Doppler OCT in Flow phantoms. In vivo velocity-resolved Flow mapping is acquired in healthy human retina and demonstrate the measurement of vessel size, peak velocity, and total foveal blood Flow with OCT.
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methods for single pass volumetric bidirectional blood Flow Imaging spectral domain optical coherence tomography using a modified hilbert transform
Optics Express, 2008Co-Authors: Joseph A. Izatt, Anjul M DavisAbstract:The present subject matter relates to in vivo volumetric bidirectional blood Flow Imaging using single-pass Flow Imaging spectral domain optical coherence tomography. This technique uses a modified Hilbert transform algorithm to separate moving and non-moving scatterers within a depth. The resulting reconstructed image maps the components of moving scatterers Flowing into and out of the Imaging axis onto opposite image halfplanes, enabling volumetric bidirectional Flow mapping without manual segmentation.
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doppler Flow Imaging of cytoplasmic streaming using spectral domain phase microscopy
Journal of Biomedical Optics, 2006Co-Authors: Michael A Choma, Audrey K Ellerbee, Siavash Yazdanfar, Joseph A. IzattAbstract:Spectral domain phase microscopy (SDPM) is a function extension of spectral domain optical coherence tomography. SDPM achieves exquisite levels of phase stability by employing common-path interferometry. We discuss the theory and limitations of Doppler Flow Imaging using SDPM, demonstrate monitoring the thermal contraction of a glass sample with nanometer per second velocity sensitivity, and apply this technique to measurement of cytoplasmic streaming in an Amoeba proteus pseudopod. We observe reversal of cytoplasmic Flow induced by extracellular CaCl2, and report results that suggest parabolic Flow of cytoplasm in the A. proteus pseudopod.
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in vivo bidirectional color doppler Flow Imaging of picoliter blood volumes using optical coherence tomography
SPIE milestone series, 2001Co-Authors: Joseph A. Izatt, Siavash Yazdanfar, Manish D Kulkarni, Jennifer K Barton, Ashley J WelchAbstract:We describe a novel optical system for bidirectional color Doppler Imaging of Flow in biological tissues with micrometer-scale resolution and demonstrate its use for in vivo Imaging of blood Flow in an animal model. Our technique, color Doppler optical coherence tomography (CDOCT), performs spatially localized optical Doppler velocimetry by use of scanning low-coherence interferometry. CDOCT is an extension of optical coherence tomography (OCT), employing coherent signal-acquisition electronics and joint time-frequency analysis algorithms to perform Flow Imaging simultaneous with conventional OCT Imaging. Cross-sectional maps of blood Flow velocity with <50-μm spatial resolution and <0.6-mm/s velocity precision were obtained through intact skin in living hamster subdermal tissue. This technology has several potential medical applications.
Ruikang K Wang - One of the best experts on this subject based on the ideXlab platform.
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electrically tunable lens integrated with optical coherence tomography angiography for cerebral blood Flow Imaging in deep cortical layers in mice
Optics Letters, 2019Co-Authors: Peijun Tang, Shaozhen Song, Adiya Rakymzhan, Ruikang K WangAbstract:We report the use of an electrically tunable lens (ETL) in a 1.3 μm spectral-domain optical coherence tomography (SD-OCT) system to overcome the depth of focus (DOF) limitation in conventional OCT systems for OCT angiography (OCTA) in a mouse cerebral cortex. The ETL provides fast and dynamic control of the axial focus of the probe beam along the entire range of the mouse cortex, upon which we performed cerebral blood Flow Imaging of all cortical layers by stitching the OCTA images automatically captured at six focal depths. Capillary vasculature and axial blood Flow velocity were revealed in distinctive cortical layers and, for the first time, to the best of our knowledge, in white matter. The results have shown the system capability to conveniently investigate the hemodynamics in deep cortical layers in the mouse brain. More importantly, the compact integration of an ETL will benefit the future design of handheld or intra-cavity OCT probes for a wide range of applications in research and clinical fields.
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directional blood Flow Imaging in volumetric optical microangiography achieved by digital frequency modulation
Optics Letters, 2008Co-Authors: Ruikang K WangAbstract:An effective digital frequency modulation approach to achieve directional blood Flow Imaging within microcirculations in tissue beds in vivo for optical microangiography is presented. The method only requires the system to capture one three-dimensional data set within which the interferograms are modulated by a constant frequency modulation that gives one directional Flow information. The result is that the Imaging speed is doubled and the computational load is halved. The method is experimentally validated by a Flow phantom and is tested for Imaging of cerebral vascular blood perfusion in a live mouse with the cranium left intact.
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real time Flow Imaging by removing texture pattern artifacts in spectral domain optical doppler tomography
Optics Letters, 2006Co-Authors: Ruikang K WangAbstract:We present a new, simple method to suppress texture pattern artifacts induced by the optical heterogeneity of tissues to improve the performance of Flow Imaging for real-time phase-resolved optical Doppler tomography. The method performs transverse scanning of the probe beam in the forward and then reverse directions, and it takes average of the spatial phase changes between them to obtain the final velocity image. It relies on the fact that the phase changes between successive axial scans due to the optical heterogeneity of the sample are time independent, while those due to the moving particles are time dependent. We experimentally demonstrate this method by real-time Imaging of a Flow phantom.
Jørgen Arendt Jensen - One of the best experts on this subject based on the ideXlab platform.
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Common Carotid Artery Volume Flow: A Comparison Study between Ultrasound Vector Flow Imaging and Phase Contrast Magnetic Resonance Imaging
'MDPI AG', 2021Co-Authors: Andreas Hjelm Brandt, Jørgen Arendt Jensen, Jacob Bjerring Olesen, Ramin Moshavegh, Michael Bachmann Nielsen, Kristoffer Lindskov HansenAbstract:Volume Flow estimation in the common carotid artery (CCA) can assess the absolute hemodynamic effect of a carotid stenosis. The aim of this study was to compare a commercial vector Flow Imaging (VFI) setup against the reference method magnetic resonance phase contrast angiography (MRA) for volume Flow estimation in the CCA. Ten healthy volunteers were scanned with VFI and MRA over the CCA. VFI had an improved precision of 19.2% compared to MRA of 31.9% (p = 0.061). VFI estimated significantly lower volume Flow than MRA (mean difference: 63.2 mL/min, p = 0.017), whilst the correlation between VFI and MRA was strong (R2 = 0.81, p < 0.0001). A Bland–Altman plot indicated a systematic bias. After bias correction, the percentage error was reduced from 41.0% to 25.2%. This study indicated that a VFI setup for volume Flow estimation is precise and strongly correlated to MRA volume Flow estimation, and after correcting for the systematic bias, VFI and MRA become interchangeable
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vector Flow Imaging of the ascending aorta in patients with tricuspid and bicuspid aortic valve stenosis treated with biological and mechanical implants
Ultrasound in Medicine and Biology, 2020Co-Authors: Kristoffer Lindskov Hansen, Jørgen Arendt Jensen, Hasse Mollersorensen, Jesper Kjaergaard, Michael Bachmann NielsenAbstract:Abstract Aortic valve stenosis (AS) is treated with biological prostheses (BPs) and mechanical prostheses (MPs). Vector Flow Imaging (VFI), an angle-independent ultrasound method, can quantify Flow complexity (vector concentration (VC)) and secondary rotation (SR). Ten patients (mean age: 70.7 y) with tricuspid AS scheduled for BPs, 10 patients (mean age: 56.2 y) with bicuspid AS scheduled for MPs and 10 patients (mean age: 63.9 y) with normal aortic valves were scanned intra-operatively on the ascending aorta with VFI and conventional spectral Doppler. Bicuspid AS (peak systolic velocity (PSV): 380.9 cm/s, SR: 16.7 Hz, VC: 0.21) had more complex Flow (p
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pressure difference estimation in carotid bulbs using vector Flow Imaging a phantom study
Internaltional Ultrasonics Symposium, 2019Co-Authors: Tinquoc Nguyen, Jørgen Arendt Jensen, Ramin Moshavegh, Michael Bachmann Nielsen, Lars Lonn, Marie Sand Traberg, J B Olesen, Peter Hasse Mollersorensen, Kristoffer Lindskov HansenAbstract:Hypertension is a common health problem and may be caused by dysfunction of the stretch sensitive baroreceptors in the carotid bulb. Velocity changes and vortices are present in the carotid bulb, and a better evaluation of the local Flow and pressures may be important to further understand hypertension. The intravascular pressure catheter is a common tool in the clinic and is currently considered to be the reference standard for intravascular pressure measurement, but the method is invasive, ionizing, and has been reported to be inaccurate. Vector Flow Imaging (VFI) is an angle independent, noninvasive, and nonionizing ultrasound method that can estimate pressure differences. In this study, pressure differences between the common carotid artery and the carotid bulb obtained with VFI were compared with catheter measurements in three carotid bifurcation phantoms. A fluid-structure interaction (FSI) simulation model was used as reference. Additionally, 10 repeated VFI and catheter measurements were performed in one phantom for a precision assessment. The mean absolute pressure difference between the catheter and FSI method in the three phantoms was 140.5 Pa, and 10 repeated catheter tests measured a mean pressure decrease with a large variation (mean: -133.3 Pa, SD: 786%). VFI estimated pressure increases in all phantoms with a mean standard deviation of 11.6%, and the mean absolute pressure difference compared with FSI was 16.7 Pa. Ten repeated VFI estimations found a mean pressure increase with low variation (mean: 40.1 Pa, SD: 10.9%). VFI precisely estimated small pressure differences in a carotid bifurcation phantom setup, whereas the fluid-filled pressure catheter measurements were imprecise.
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full volumetric 3 d vector Flow Imaging using a 62 62 row column array
Internaltional Ultrasonics Symposium, 2019Co-Authors: Mikkel Schou, Borislav Gueorguiev Tomov, Marie Sand Traberg, Lasse Thurmann Jorgensen, Matthias Bo Stuart, Jørgen Arendt JensenAbstract:Row Column (RC) Arrays can produce high-resolution 3-D volumetric images with only 2N interconnections compared to N2 for matrix probes. A 62+62 RC probe has four times larger surface area and one-eighth of the channel count when compared to the same-pitch fully populated 32x32 matrix probe. This research investigates the performance of such a prototype array for volumetric Synthetic Aperture (SA) B-mode and vector Flow Imaging using defocused waves. An interleaved SA sequence was implemented on the SARUS scanner using a 3 MHz, λ/2-pitch 62+62 RC piezoelectric probe. The sequence contains repeated emissions with rows and columns interleaved with B-mode emissions. The sequence contains 80 emissions in total and can provide a volume rate above 125 Hz yielding continuous data. Velocities were estimated using the Directional Transverse Oscillation Cross-Correlation method. Measurements were made on a circulating Flow rig with a parabolic profile with a peak velocity of 0.25 m/s and beam-to-Flow angle of 90°, and two different rotation angles (0°, 45°). Results showed a maximum bias of -17.5% and a standard deviation of 3.9%. A second setup used a tissue mimicking phantom with pulsating Flow showing full volumetric Flow estimated using the method. The Flow was visualized in the entire rectilinear volume at once, with B-mode planes selectable in the entire region. This was attained using only 62 channels in receive making full volumetric Imaging and velocity estimation implementable on current scanner hardware.
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evaluation of peak reflux velocities with vector Flow Imaging and spectral doppler ultrasound in varicose veins
Ultrasound International Open, 2018Co-Authors: Thor Bechsgaard, Andreas Hjelm Brandt, Ramin Moshavegh, Kristoffer Lindskov Hansen, Julie Lyng Forman, Pia Fogh, Lotte Klitfod, N Baekgaard, Lars Lonn, Jørgen Arendt JensenAbstract:Purpose Spectral Doppler ultrasound (SDUS) is used for quantifying reflux in lower extremity varicose veins. The technique is angle-dependent opposed to the new angle-independent Vector Flow Imaging (VFI) method. The aim of this study was to compare peak reflux velocities obtained with VFI and SDUS in patients with chronic venous disease, i. e., pathological retrograde blood Flow caused by incompetent venous valves. Materials and Methods 64 patients with chronic venous disease were scanned with VFI and SDUS in the great or the small saphenous vein, and reflux velocities were compared to three assessment tools for chronic venous disease. A Flow rig was used to assess the accuracy and precision of the two methods. Results The mean peak reflux velocities differed significantly (VFI: 47.4 cm/s vs. SDUS: 62.0 cm/s, p Conclusion Both VFI and SDUS detected the pathologic retrograde Flow in varicose veins but measured different reflux velocities with equal precision. VFI may play a role in evaluating venous disease in the future.
Fabrizio Calliada - One of the best experts on this subject based on the ideXlab platform.
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high frame rate vector Flow Imaging of the carotid bifurcation in healthy adults comparison with color doppler Imaging
Journal of Ultrasound in Medicine, 2018Co-Authors: Alfredo Goddi, Maria Vittoria Raciti, Ilaria Fiorina, Luca Aiani, Giovanni Magistretti, Carmine Tinelli, Chandra Bortolotto, Ada Sacchi, Fabrizio CalliadaAbstract:OBJECTIVES: To evaluate the carotid bifurcation in healthy adults using a commercial system equipped with high-frame rate vector Flow Imaging (VFI) based on the plane wave and to compare VFI with color Doppler Imaging. METHODS: Carotid bifurcation diameters and Flow characteristics of 60 vessels in 60 healthy volunteers were evaluated quantitatively and qualitatively to assess complex Flow patterns and their extension and duration. RESULTS: Complex Flow in the internal carotid artery (ICA) was associated with a statistically significant difference in the ΔICA sinus-to-common carotid artery (CCA) diameter ratio (the relative change in diameter between the CCA and ICA sinus.) Vector Flow Imaging and color Doppler Imaging were in accordance when detecting complex Flow in 96.7% of cases; in 3.3% of cases, only VFI identified small recirculation areas of short duration. Vector Flow Imaging highlighted a larger extension of the complex Flow (mean ± SD, 47.7 ± 28.5 mm2 ; median, 45.5 mm2 ) compared with color Doppler Imaging (mean, 29.2 ± 19.9 mm2 ; median, 29.5 mm2 ) and better depicted different complex Flow patterns; a strong correlation (r = 0.84) was found between the ΔICA sinus-to-CCA diameter ratio and the complex Flow extension. Vector Flow Imaging showed a longer duration of the Flow disturbances (mean, 380 ± 218 milliseconds; median, 352.5 milliseconds) compared with color Doppler Imaging (mean, 325 ± 206 milliseconds; median, 333 milliseconds), and there was a strong correlation (r = 0.92). CONCLUSIONS: Vector Flow Imaging is as effective as color Doppler Imaging in the detection of Flow disturbances, but it is more powerful in the assessment of complex Flow patterns.
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high frame rate vector Flow Imaging of the carotid bifurcation
Insights Into Imaging, 2017Co-Authors: Alfredo Goddi, Maria Vittoria Raciti, Ilaria Fiorina, Marianna Fanizza, Elena Turpini, Giulia Boffelli, Chandra Bortolotto, Fabrizio CalliadaAbstract:Carotid artery atherosclerotic disease is still a significant cause of cerebrovascular morbidity and mortality. A new angle-independent technique, measuring and visualizing blood Flow velocities in all directions, called vector Flow Imaging (VFI) is becoming available from several vendors. VFI can provide more intuitive and quantitative Imaging of vortex formation, which is not clearly distinguishable in the color Doppler image. VFI, as quantitative method assessing disturbed Flow patterns of the carotid bifurcation, has the potential to allow better understanding of the diagnostic value of complex Flow and to enhance risk stratification. This pictorial review article will show which new information VFI adds for the knowledge of hemodynamics in comparison to the conventional ultrasound techniques. • VFI is an angle-independent technique measuring Flow velocities in all directions. • This kind of VFI is based on a plane wave multidirectional excitation technique. • VFI allows quantitative assessment of carotid streamlines progression and visualizes vorticity. • VFI does not allow a precise comprehension of streamlines’ 3D shape. • VFI allows a better understanding of carotid artery complex Flows.
Michael J Cobb - One of the best experts on this subject based on the ideXlab platform.
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real time in vivo blood Flow Imaging by moving scatterer sensitive spectral domain optical doppler tomography
Optics Letters, 2006Co-Authors: Hongwu Ren, Tao Sun, Daniel J Macdonald, Michael J CobbAbstract:We present a moving-scatterer-sensitive optical Doppler tomography (MSS-ODT) technique for in vivo blood Flow Imaging in real time by using a spectral-domain optical coherence tomography system. In MSS-ODT the influence of stationary scatterers is suppressed by subtracting adjacent complex axial scans before calculating the Doppler frequency shift. We demonstrate that MSS-ODT is a useful technique for accurate determination of blood vessel size by Imaging Flow in a small capillary tube with a 75μm inner diameter. The Flow profile obtained with MSS-ODT yields a substantially more accurate tube diameter than that obtained with the conventional phase-resolved method, which underestimates the diameter by about 23%. We also demonstrate that MSS-ODT provides improved sensitivity over the conventional phase-resolved method for Imaging in vivo blood Flow in small vessels in a mouse ear.