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Cheishvili K, Kalkman J. Sub-diffusion flow velocimetry with number fluctuation optical coherence tomography. OPTICS EXPRESS 2023; 31:3755-3773. [PMID: 36785361 DOI: 10.1364/oe.474279] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2022] [Accepted: 12/27/2022] [Indexed: 06/18/2023]
Abstract
We have implemented number fluctuation dynamic light scattering optical coherence tomography (OCT) for measuring extremely slow, sub-diffusion flows of dilute particle suspensions using the second-order autocovariance function. Our method has a lower minimum measurable velocity than conventional correlation-based OCT or phase-resolved Doppler OCT, as the velocity estimation is not affected by the particle diffusion. Similar to non-dilute correlation-based OCT, our technique works for any Doppler angle. With our analysis we can quantitatively determine the concentration of particles under flow. Finally, we demonstrate 2D sub-diffusion flow imaging with a scanning OCT system at high rate by performing number fluctuation correlation analysis on subsequent B-scans.
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Cheishvili K, Kalkman J. Scanning dynamic light scattering optical coherence tomography for measurement of high omnidirectional flow velocities. OPTICS EXPRESS 2022; 30:23382-23397. [PMID: 36225019 DOI: 10.1364/oe.456139] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2022] [Accepted: 04/16/2022] [Indexed: 06/16/2023]
Abstract
We show scanning dynamic light scattering optical coherence tomography (OCT) omnidirectional flow measurements. Our method improves the velocity measurement limit over conventional correlation-based or phase-resolved Doppler OCT by more than a factor of 2. Our technique is applicable without a-priori knowledge of the flow geometry as our method works both for non-zero Doppler angle and non-ideal scan alignment. In addition, the method improves the particle diffusion coefficient estimation for particles under flow.
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Nam AS, Braaf B, Vakoc BJ. Using the dynamic forward scattering signal for optical coherence tomography based blood flow quantification. OPTICS LETTERS 2022; 47:3083-3086. [PMID: 35709056 PMCID: PMC9580005 DOI: 10.1364/ol.455475] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2022] [Accepted: 05/24/2022] [Indexed: 06/15/2023]
Abstract
To our knowledge, all existing optical coherence tomography approaches for quantifying blood flow, whether Doppler-based or decorrelation-based, analyze light that is back-scattered by moving red blood cells (RBCs). This work investigates the potential advantages of basing these measurements on light that is forward-scattered by RBCs, i.e., by looking at the signals back-scattered from below the vessel. We show experimentally that flowmetry based on forward-scattering is insensitive to vessel orientation for vessels that are approximately orthogonal to the imaging beam. We further provide proof-of-principle demonstrations of dynamic forward-scattering (DFS) flowmetry in human retinal and choroidal vessels.
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Affiliation(s)
- Ahhyun Stephanie Nam
- Wellman Center for Photomedicine, Massachusetts General Hospital, 40 Blossom St, Boston, MA 02114 USA
- Harvard Medical School, 25 Shattuck St, Boston, MA 02115 USA
| | - Boy Braaf
- Wellman Center for Photomedicine, Massachusetts General Hospital, 40 Blossom St, Boston, MA 02114 USA
- Harvard Medical School, 25 Shattuck St, Boston, MA 02115 USA
| | - Benjamin J. Vakoc
- Wellman Center for Photomedicine, Massachusetts General Hospital, 40 Blossom St, Boston, MA 02114 USA
- Harvard Medical School, 25 Shattuck St, Boston, MA 02115 USA
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Choi H, Zaki FR, Monroy GL, Won J, Boppart SA. Imaging and characterization of transitions in biofilm morphology via anomalous diffusion following environmental perturbation. BIOMEDICAL OPTICS EXPRESS 2022; 13:1654-1670. [PMID: 35414993 PMCID: PMC8973182 DOI: 10.1364/boe.449131] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2021] [Revised: 02/03/2022] [Accepted: 02/03/2022] [Indexed: 06/14/2023]
Abstract
Microorganisms form macroscopic structures for the purpose of environmental adaptation. Sudden environmental perturbations induce dynamics that cause bacterial biofilm morphology to transit to another equilibrium state, thought to be related to anomalous diffusion processes. Here, detecting the super-diffusion characteristics would offer a long-sought goal for a rapid detection method of biofilm phenotypes based on their dynamics, such as growth or dispersal. In this paper, phase-sensitive Doppler optical coherence tomography (OCT) and dynamic light scattering (DLS) are combined to demonstrate wide field-of-view and label-free internal dynamic imaging of biofilms. The probability density functions (PDFs) of phase displacement of the backscattered light and the dynamic characteristics of the PDFs are estimated by a simplified mixed Cauchy and Gaussian model. This model can quantify the super-diffusion state and estimate the dynamic characteristics and macroscopic responses in biofilms that may further describe dispersion and growth in biofilm models.
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Affiliation(s)
- Honggu Choi
- Beckman Institute for Advanced Science and Technology, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
| | - Farzana R. Zaki
- Beckman Institute for Advanced Science and Technology, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
| | - Guillermo L. Monroy
- Beckman Institute for Advanced Science and Technology, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
| | - Jungeun Won
- Beckman Institute for Advanced Science and Technology, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
- Department of Bioengineering, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
| | - Stephen A. Boppart
- Beckman Institute for Advanced Science and Technology, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
- Department of Bioengineering, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
- Department of Electrical and Computer Engineering, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
- Carle Illinois College of Medicine, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
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Tornow RP, Kolar R, Odstrcilik J, Labounkova I, Horn F. Imaging video plethysmography shows reduced signal amplitude in glaucoma patients in the area of the microvascular tissue of the optic nerve head. Graefes Arch Clin Exp Ophthalmol 2021; 259:483-494. [PMID: 32960321 PMCID: PMC7843566 DOI: 10.1007/s00417-020-04934-y] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2020] [Revised: 09/01/2020] [Accepted: 09/10/2020] [Indexed: 01/18/2023] Open
Abstract
PURPOSE To measure parameters of the cardiac cycle-induced pulsatile light absorption signal (plethysmography signal) of the optic nerve head (ONH) and to compare parameters between normal subjects and patients with different stages of glaucoma. PATIENTS AND METHODS A recently developed video ophthalmoscope was used to acquire short video sequences (10 s) of the ONH. After image registration and trend correction, the pulsatile changing light absorption at the ONH tissue (excluding large vessels) was calculated. The changing light absorption depends on the pulsatile changing blood volume. Various parameters, including peak amplitude, steepness, time-to-peak, full width at half maximum (FWHM), and pulse duration, were calculated for averaged individual pulses (heartbeats) of the plethysmography signal. This method was applied to 19 healthy control subjects and 91 subjects with ocular hypertension, as well as different stages of primary open-angle glaucoma (17 subjects with ocular hypertension, 24 with preperimetric glaucoma, and 50 with perimetric glaucoma). RESULTS Compared to the normal subjects, significant reductions (p < 0.001) in peak amplitude and steepness were observed in the group of perimetric glaucoma patients, but no significant difference was found for time-to-peak, FWHM, and pulse duration. Peak amplitude and steepness showed high correlations with RNFL thickness (p < 0.001). CONCLUSIONS The presented low-cost video-ophthalmoscope permits measurement of the plethysmographic signal of the ONH tissue and calculation of different blood flow-related parameters. The reduced values of the amplitude and steepness parameters in perimetric glaucoma patients suggest decreased ONH perfusion and blood volume. This outcome is in agreement with results from other studies using OCT angiography and laser speckle flowgraphy, which confirm reduced capillary density in these patients. Registration site: www.clinicaltrials.gov , Trial registration number: NCT00494923.
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Affiliation(s)
- Ralf-Peter Tornow
- Department of Ophthalmology, Friedrich-Alexander-University of Erlangen-Nuremberg, 91054, Erlangen, Germany.
| | - Radim Kolar
- Department of Biomedical Engineering, Faculty of Electrical Engineering and Communication, Brno University of Technology, 616 00, Brno, Czech Republic
| | - Jan Odstrcilik
- Department of Biomedical Engineering, Faculty of Electrical Engineering and Communication, Brno University of Technology, 616 00, Brno, Czech Republic
| | - Ivana Labounkova
- Department of Biomedical Engineering, Faculty of Electrical Engineering and Communication, Brno University of Technology, 616 00, Brno, Czech Republic
| | - Folkert Horn
- Department of Ophthalmology, Friedrich-Alexander-University of Erlangen-Nuremberg, 91054, Erlangen, Germany
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Chen R, Yao L, Liu K, Cao T, Li H, Li P. Improvement of Decorrelation-Based OCT Angiography by an Adaptive Spatial-Temporal Kernel in Monitoring Stimulus-Evoked Hemodynamic Responses. IEEE TRANSACTIONS ON MEDICAL IMAGING 2020; 39:4286-4296. [PMID: 32790625 DOI: 10.1109/tmi.2020.3016334] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Complex decorrelation-based OCT angiography (OCTA) has the potential for monitoring hemodynamic activities in a label-free, high-resolution, and quantitative manner. To improve the measurement dynamic range and uncertainty of blood flow, an adaptive spatial-temporal (ST) kernel was proposed for decorrelation estimation and it was validated through a theoretical simulation and experimental measurements. The ensemble size in the decorrelation computation was effectively enlarged by collecting samples of the phasor pair in both the spatial and temporal dimensions. The spatial sub-kernel size was adaptively changed to suppress the influence of bulk motion in the temporal dimension by solving a maximum entropy model. Using the flow phantom, it was observed that the decorrelation dynamic range presented an increase of ~49% and the uncertainty exhibited a decrease of ~40% and ~38% in the saturation and background limits, respectively. In monitoring the stimulus-evoked hemodynamic response, the extended dynamic range enabled an improvement of ~180% in the separability between different stimulation modes. Furthermore, the suppressed uncertainty and motion artifacts allowed a reliable temporal analysis of the hemodynamic response. The proposed adaptive ST-kernel will greatly promote the development of decorrelation-based quantitative OCTA in hemodynamic studies.
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Willemse J, Gräfe MGO, Verbraak FD, de Boer JF. In Vivo 3D Determination of Peripapillary Scleral and Retinal Layer Architecture Using Polarization-Sensitive Optical Coherence Tomography. Transl Vis Sci Technol 2020; 9:21. [PMID: 33150047 PMCID: PMC7585391 DOI: 10.1167/tvst.9.11.21] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Accepted: 08/25/2020] [Indexed: 12/24/2022] Open
Abstract
Purpose The purpose of this paper was to determine the architecture of the collagen fibers of the peripapillary sclera, the retinal nerve fiber layer (RNFL), and Henle's fiber layer in vivo in 3D using polarization-sensitive optical coherence tomography (PS-OCT). Methods Seven healthy volunteers were imaged with our in-house built PS-OCT system. PS-OCT imaging included intensity, local phase retardation, relative optic axis, and optic axis uniformity (OAxU). Differential Mueller matrix calculus was used for the first time in ocular tissues to visualize local orientations that varied with depth, incorporating a correction method for the fiber orientation in preceding layers. Results Scleral collagen fiber orientation images clearly showed an inner layer with an orientation parallel to the RNFL orientation, and a deeper layer where the collagen was circularly oriented. RNFL orientation images visualized the nerve fibers leaving the optic nerve head (ONH) in a radial pattern. The phase retardation and orientation of Henle's fiber layer were visualized locally for the first time. Conclusions PS-OCT successfully showed the orientation of the retinal nerve fibers, sclera, and Henle's fiber layer, and is to the extent of our knowledge the only technique able to do so in 3D in vivo. Translational Relevance In vivo 3D imaging of scleral collagen architecture and the retinal neural fibrous structures can improve our understanding of retinal biomechanics and structural alterations in different disease stages of myopia and glaucoma.
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Affiliation(s)
- Joy Willemse
- Department of Physics and Astronomy, LaserLab Amsterdam, Vrije Universiteit de Boelelaan, Amsterdam, The Netherlands
| | - Maximilian G O Gräfe
- Department of Physics and Astronomy, LaserLab Amsterdam, Vrije Universiteit de Boelelaan, Amsterdam, The Netherlands.,Current address: Imedos Systems GmbH, Am Nasstal 4, Jena, Germany
| | - Frank D Verbraak
- Amsterdam University Medical Center, Vrije Universiteit Amsterdam, Ophthalmology Department, de Boelelaan, Amsterdam, The Netherlands
| | - Johannes F de Boer
- Department of Physics and Astronomy, LaserLab Amsterdam, Vrije Universiteit de Boelelaan, Amsterdam, The Netherlands.,Amsterdam University Medical Center, Vrije Universiteit Amsterdam, Ophthalmology Department, de Boelelaan, Amsterdam, The Netherlands
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Tan B, Sim R, Chua J, Wong DWK, Yao X, Garhöfer G, Schmidl D, Werkmeister RM, Schmetterer L. Approaches to quantify optical coherence tomography angiography metrics. ANNALS OF TRANSLATIONAL MEDICINE 2020; 8:1205. [PMID: 33241054 PMCID: PMC7576021 DOI: 10.21037/atm-20-3246] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Optical coherence tomography (OCT) has revolutionized the field of ophthalmology in the last three decades. As an OCT extension, OCT angiography (OCTA) utilizes a fast OCT system to detect motion contrast in ocular tissue and provides a three-dimensional representation of the ocular vasculature in a non-invasive, dye-free manner. The first OCT machine equipped with OCTA function was approved by U.S. Food and Drug Administration in 2016 and now it is widely applied in clinics. To date, numerous methods have been developed to aid OCTA interpretation and quantification. In this review, we focused on the workflow of OCTA-based interpretation, beginning from the generation of the OCTA images using signal decorrelation, which we divided into intensity-based, phase-based and phasor-based methods. We further discussed methods used to address image artifacts that are commonly observed in clinical settings, to the algorithms for image enhancement, binarization, and OCTA metrics extraction. We believe a better grasp of these technical aspects of OCTA will enhance the understanding of the technology and its potential application in disease diagnosis and management. Moreover, future studies will also explore the use of ocular OCTA as a window to link ocular vasculature to the function of other organs such as the kidney and brain.
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Affiliation(s)
- Bingyao Tan
- Institute for Health Technologies, Nanyang Technological University, Singapore, Singapore.,Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Singapore.,SERI-NTU Advanced Ocular Engineering (STANCE) Program, Nanyang Technological University, Singapore, Singapore
| | - Ralene Sim
- Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Singapore
| | - Jacqueline Chua
- Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Singapore.,Academic Clinical Program, Duke-NUS Medical School, Singapore, Singapore
| | - Damon W K Wong
- Institute for Health Technologies, Nanyang Technological University, Singapore, Singapore.,Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Singapore.,SERI-NTU Advanced Ocular Engineering (STANCE) Program, Nanyang Technological University, Singapore, Singapore
| | - Xinwen Yao
- Institute for Health Technologies, Nanyang Technological University, Singapore, Singapore.,Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Singapore.,SERI-NTU Advanced Ocular Engineering (STANCE) Program, Nanyang Technological University, Singapore, Singapore
| | - Gerhard Garhöfer
- Department of Clinical Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Doreen Schmidl
- Department of Clinical Pharmacology, Medical University of Vienna, Vienna, Austria
| | - René M Werkmeister
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria
| | - Leopold Schmetterer
- Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Singapore.,SERI-NTU Advanced Ocular Engineering (STANCE) Program, Nanyang Technological University, Singapore, Singapore.,Academic Clinical Program, Duke-NUS Medical School, Singapore, Singapore.,Department of Clinical Pharmacology, Medical University of Vienna, Vienna, Austria.,Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria.,Yong Loo Lin School of Medicine, National University of Singapore and National University Health System, Singapore, Singapore.,Department of Ophthalmology, Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, Singapore.,Institute of Molecular and Clinical Ophthalmology, Basel, Switzerland
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Gräfe MGO, van de Kreeke JA, Willemse J, Braaf B, de Jong Y, Tan HS, Verbraak FD, de Boer JF. Subretinal Fibrosis Detection Using Polarization Sensitive Optical Coherence Tomography. Transl Vis Sci Technol 2020; 9:13. [PMID: 32818100 PMCID: PMC7396173 DOI: 10.1167/tvst.9.4.13] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2019] [Accepted: 12/16/2019] [Indexed: 12/22/2022] Open
Abstract
Purpose Subretinal fibrosis (SRFib) is an important cause of permanent loss-of-vision diseases with submacular neovascularization, but a reliable diagnostic method is currently missing. This study uses polarization-sensitive optical coherence tomography (PS-OCT) to detect SRFib within retinal lesions by measurement of its birefringent collagen fibers. Methods Twenty-five patients were enrolled with retinal pathology in one or both eyes containing (1) suspected SRFib, (2) lesions suspected not to be fibrotic, or (3) lesions with doubtful presence of SRFib. All eyes were evaluated for SRFIb using conventional diagnostics by three retinal specialists. PS-OCT images were visually evaluated for SRFib based on cumulative phase retardation, local birefringence, and optic axis uniformity. Results Twenty-nine eyes from 22 patients were scanned successfully. In 13 eyes, SRFib was diagnosed by all retinal specialists; of these, 12 were confirmed by PS-OCT and one was inconclusive. In nine eyes, the retinal specialists expected no SRFib, which was confirmed by PS-OCT in all cases. In seven eyes, the retinal specialists’ evaluations were inconsistent with regard to the presence of SRFib. PS-OCT confirmed the presence of SRFib in four of these eyes and the absence of SRFib in two eyes and was inconclusive in one eye. Conclusions In 21 out of 22 eyes, PS-OCT confirmed the evaluation of retinal specialists regarding the presence of SRFib. PS-OCT provided additional information to distinguish SRFib from other tissues within subretinal neovascular lesions in 6 out of 7 eyes. Translational Relevance PS-OCT can identify and quantify SRFib in doubtful cases for which a reliable diagnosis is currently lacking.
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Affiliation(s)
- Maximilian G O Gräfe
- LaserLaB Amsterdam, Department of Physics and Astronomy, Vrije Universiteit, Amsterdam, The Netherlands
| | | | - Joy Willemse
- LaserLaB Amsterdam, Department of Physics and Astronomy, Vrije Universiteit, Amsterdam, The Netherlands
| | - Boy Braaf
- LaserLaB Amsterdam, Department of Physics and Astronomy, Vrije Universiteit, Amsterdam, The Netherlands
| | - Yvonne de Jong
- Department of Ophthalmology, Amsterdam UMC, Amsterdam, The Netherlands
| | - H Stevie Tan
- Department of Ophthalmology, Amsterdam UMC, Amsterdam, The Netherlands
| | - Frank D Verbraak
- Department of Ophthalmology, Amsterdam UMC, Amsterdam, The Netherlands
| | - Johannes F de Boer
- LaserLaB Amsterdam, Department of Physics and Astronomy, Vrije Universiteit, Amsterdam, The Netherlands.,Department of Ophthalmology, Amsterdam UMC, Amsterdam, The Netherlands
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Gräfe MGO, Nadiarnykh O, De Boer JF. Optical coherence tomography velocimetry based on decorrelation estimation of phasor pair ratios (DEPPAIR). BIOMEDICAL OPTICS EXPRESS 2019; 10:5470-5485. [PMID: 31799025 PMCID: PMC6865093 DOI: 10.1364/boe.10.005470] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2019] [Revised: 09/17/2019] [Accepted: 09/20/2019] [Indexed: 05/13/2023]
Abstract
Quantitative velocity estimations in optical coherence tomography requires the estimation of the axial and lateral flow components. Optical coherence tomography measures the depth resolved complex field reflected from a sample. While the axial velocity component can be determined from the Doppler shift or phase shift between a pair of consecutive measurements at the same location, the estimation of the lateral component for in vivo applications is still challenging. One approach to determine lateral velocity is multiple simultaneous measurements at different angles. In another approach the lateral component can be retrieved through repeated measurements at (nearly) the same location by an analysis of the decorrelation over time. In this paper we follow the latter approach. We describe a model for the complex field changes between consecutive measurements and use it to predict the uncertainties for amplitude-based, phase-based and complex algorithms. The uncertainty of the flow estimations follows from a statistical analysis and is determined by the number of available measurements and the applied analysis method. The model is verified in phantom measurements and the dynamic range of velocity estimations is investigated. We demonstrate that phase-based and complex (phasor) based lateral flow estimation methods are superior to amplitude-based algorithms.
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