Bibliographies thématiques / Vector flow imaging (VFI)

Littérature scientifique sur le sujet « Vector flow imaging (VFI) »

Auteur : Grafiati
Publié le 10 mars 2023

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Articles de revues sur le sujet "Vector flow imaging (VFI)"

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Hansen, Kristoffer, Klaus Juul, Hasse Møller-Sørensen, Jens Nilsson, Jørgen Jensen et Michael Nielsen. « Pediatric Transthoracic Cardiac Vector Flow Imaging – A Preliminary Pictorial Study ». Ultrasound International Open 05, no 01 (21 décembre 2018) : E20—E26. http://dx.doi.org/10.1055/a-0656-5430.

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Abstract Purpose Conventional pediatric echocardiography is crucial for diagnosing congenital heart disease (CHD), but the technique is impaired by angle dependency. Vector flow imaging (VFI) is an angle-independent noninvasive ultrasound alternative for blood flow assessment and can assess complex flow patterns not visible on conventional Doppler ultrasound. Materials and Methods 12 healthy newborns and 3 infants with CHD were examined with transthoracic cardiac VFI using a conventional ultrasound scanner and a linear array. Results VFI examinations revealed common cardiac flow patterns among the healthy newborns, and flow changes among the infants with CHD not previously reported with conventional echocardiography. Conclusion For assessment of cardiac flow in the normal and diseased pediatric heart, VFI may provide additional information compared to conventional echocardiography and become a useful diagnostic tool.
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Brandt, Andreas Hjelm, Jacob Bjerring Olesen, Ramin Moshavegh, Jørgen Arendt Jensen, Michael Bachmann Nielsen et Kristoffer Lindskov Hansen. « Common Carotid Artery Volume Flow : A Comparison Study between Ultrasound Vector Flow Imaging and Phase Contrast Magnetic Resonance Imaging ». Neurology International 13, no 3 (23 juin 2021) : 269–78. http://dx.doi.org/10.3390/neurolint13030028.

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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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Fiorina, Ilaria, Maria Vittoria Raciti, Alfredo Goddi, Vito Cantisani, Chandra Bortolotto, Shane Chu et Fabrizio Calliada. « Ultrasound Vector Flow Imaging – could be a new tool in evaluation of arteriovenous fistulas for hemodialysis ? » Journal of Vascular Access 18, no 4 (24 mai 2017) : 284–89. http://dx.doi.org/10.5301/jva.5000721.

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Introduction We report the use of a new ultrasound technique to evaluate the axial and lateral components of a complex flow in the arteriovenous fistula (AVF). Vector Flow Imaging (VFI) allows to identify different components of the flow in every direction, even orthogonal to the flow streamline, represented by many single vectors. VFI could help to identify flow alterations in AVF, probably responsible for its malfunction. Methods From February to June 2016, 14 consecutive patients with upper-limb AVF were examined with a Resona 7 (Mindray, Shenzhen, China) ultrasound scanner equipped with VFI. An analysis of mean velocity, angular direction and mean number of vectors impacting the vessel wall was carried out. We also identified main flow patterns present in the arterial side, into the venous aneurysm and in correspondence of significant stenosis. Results A disturbed flow with the presence of vectors directed against the vessel walls was found in 9/14 patients (64.28%): in correspondence of the iuxta-anastomotic venous side (4/9; 44.4%), into the venous aneurysmal tracts (3/9; 33.3%) and in concomitance of stenosis (2/9; 22.2%). The mean velocity of the vectors was around 20-25 cm/s, except in presence of stenosis, where the velocities were much higher (45-50 cm/s). The vectors directed against the vessel walls presented high angle attack (from 45° to 90°, with a median angular deviation 65°). Conclusions VFI was confirmed to be an innovative and intuitive imaging technology to study the flow complexity in the arteriovenous fistulas.
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Bechsgaard, Thor, Kristoffer Hansen, Andreas Brandt, Ramin Moshavegh, Julie Forman, Pia Føgh, Lotte Klitfod et al. « Evaluation of Peak Reflux Velocities with Vector Flow Imaging and Spectral Doppler Ultrasound in Varicose Veins ». Ultrasound International Open 04, no 03 (septembre 2018) : E91—E98. http://dx.doi.org/10.1055/a-0643-4430.

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Abstract 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<0.001). No difference in absolute precision (p=0.18) nor relative precision (p=0.79) was found. No correlation to disease severity, according to assessment tools, was found for peak reflux velocities obtained with either method. In vitro, VFI was more accurate but equally precise when compared to SDUS. 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.
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Nguyen, Tin-Quoc, Thor Bechsgaard, Michael Rahbek Schmidt, Klaus Juul, Ramin Moshavegh, Lars Lönn, Michael Bachmann Nielsen, Jørgen Arendt Jensen et Kristoffer Lindskov Hansen. « Transthoracic Vector Flow Imaging in Pediatric Patients with Valvular Stenosis – A Proof of Concept Study ». Ultrasound International Open 07, no 02 (août 2021) : E48—E54. http://dx.doi.org/10.1055/a-1652-1261.

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Abstract Purpose Continuous wave Doppler ultrasound is routinely used to detect cardiac valve stenoses. Vector flow imaging (VFI) is an angle-independent real-time ultrasound method that can quantify flow complexity. We aimed to evaluate if quantification of flow complexity could reliably assess valvular stenosis in pediatric patients. Materials and Methods Nine pediatric patients with echocardiographically confirmed valvular stenosis were included in the study. VFI and Doppler measurements were compared with transvalvular peak-to-peak pressure differences derived from invasive endovascular catheterization. Results Vector concentration correlated with the catheter measurements before intervention after exclusion of one outlier (r=−0.83, p=0.01), whereas the Doppler method did not (r=0.49, p=0.22). The change in vector concentration after intervention correlated strongly with the change in the measured catheter pressure difference (r=−0.86, p=0.003), while Doppler showed a tendency for a moderate correlation (r=0.63, p=0.07). Conclusion Transthoracic flow complexity quantification calculated from VFI data is feasible and may be useful for assessing valvular stenosis severity in pediatric patients.
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Hansen, Peter, Kristoffer Hansen, Mads Pedersen, Theis Lange, Lars Lönn, Jørgen Jensen et Michael Nielsen. « Atherosclerotic Lesions in the Superficial Femoral Artery (SFA) Characterized with Velocity Ratios using Vector Velocity Ultrasound ». Ultrasound International Open 04, no 03 (septembre 2018) : E79—E84. http://dx.doi.org/10.1055/a-0637-2437.

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Abstract Purpose Atherosclerotic arteries are challenging to evaluate quantitatively using spectral Doppler ultrasound because of the turbulent flow conditions that occur in relation to the atherosclerotic stenoses. Vector velocity ultrasound is angle independent and provides flow information, which could potentially improve the diagnosis of arterial stenoses. The purpose of the study is to distinguish significant stenoses in the superficial femoral artery (> 50% diameter reduction) from non-significant stenoses based on velocity ratios derived from the commercially available vector velocity ultrasound technique Vector Flow Imaging (VFI). Materials and Methods Velocity ratios (intrastenotic blood flow velocity divided by pre- or poststenotic velocity) from a total of 16 atherosclerotic stenoses and plaques in the superficial femoral artery of 11 patients were obtained using VFI. The stenosis degree, expressed as percentage diameter reduction of the artery, was determined from digital subtraction angiography and compared to the velocity ratios. Results A velocity ratio of 2.5 was found to distinguish clinically relevant stenoses with>50% diameter reduction from clinically non-relevant stenoses with<50% diameter reduction and the difference was statistically significant. Conclusion The study indicates that VFI is a potential future tool for the evaluation of arterial stenoses.
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Brandt, Andreas Hjelm, Tin-Quoc Nguyen, Henrik Gutte, Jonathan Frederik Carlsen, Ramin Moshavegh, Jørgen Arendt Jensen, Michael Bachmann Nielsen et Kristoffer Lindskov Hansen. « Carotid Stenosis Assessment with Vector Concentration before and after Stenting ». Diagnostics 10, no 6 (20 juin 2020) : 420. http://dx.doi.org/10.3390/diagnostics10060420.

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Digital subtraction angiography (DSA) is considered the reference method for the assessment of carotid artery stenosis; however, the procedure is invasive and accompanied by ionizing radiation. Velocity estimation with duplex ultrasound (DUS) is widely used for carotid artery stenosis assessment since no radiation or intravenous contrast is required; however, the method is angle-dependent. Vector concentration (VC) is a parameter for flow complexity assessment derived from the angle independent ultrasound method vector flow imaging (VFI), and VC has shown to correlate strongly with stenosis degree. The aim of this study was to compare VC estimates and DUS estimated peak-systolic (PSV) and end-diastolic velocities (EDV) for carotid artery stenosis patients, with the stenosis degree obtained with DSA. Eleven patients with symptomatic carotid artery stenosis were examined with DUS, VFI, and DSA before and after stent treatment. Compared to DSA, VC showed a strong correlation (r = −0.79, p < 0.001), while PSV (r = 0.68, p = 0.002) and EDV (r = 0.51, p = 0.048) obtained with DUS showed a moderate correlation. VFI using VC calculations may be a useful ultrasound method for carotid artery stenosis and stent patency assessment.
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Forcada, Pedro J. « Study of Arterial Function and Remodelling by Using Radiofrequency and a New Multidirectional Doppler Technology ». Angiology and Vascular Surgery 6, no 1 (7 mai 2021) : 1–8. http://dx.doi.org/10.24966/avs-7397/100056.

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Introduction: Atherosclerosis is the underlying cause of a cardiovascular disease epidemic worldwide. The understanding of normal artery structure and function and the initial disarrangements conducting to atherosclerosis is of key relevance to develop preventive interventions based on a rational study of arterial structural and functional parameters, their pathologic behaviour and response to therapeutic interventions. New US approaches enable a precise evaluation of the forces and stimuli acting on the arterial wall and measure its responses precisely in different clinical stages of the arterial atherosclerotic disease and a better assessment of the efficacy or not of different therapeutic interventions. The ability to analyse WSS hemodynamically and to measure it accurately is an essential basis for the assessment of the atherosclerotic risk in the general population. A new angle-independent technique, measuring and visualizing blood flow velocities in all directions, called Vector Flow Imaging (VFI), has been proposed. Systems are equipped with VFI based on a multi-angle transmission plane waves method, which allows a very high frame rate and a detailed visualization of complex flow.
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Gould, Sara, Chase Cawyer, Louis Dell’Italia, Lorie Harper, Gerald McGwin et Marcas Bamman. « Resistance Training Does Not Decrease Placental Blood Flow During Valsalva Maneuver : A Novel Use of 3D Doppler Power Flow Ultrasonography ». Sports Health : A Multidisciplinary Approach 13, no 5 (12 mars 2021) : 476–81. http://dx.doi.org/10.1177/19417381211000717.

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Background: The Valsalva maneuver may increase maternal blood pressure and intra-abdominal pressure, resulting in decreased blood flow to the fetus during resistance training. Hypothesis: There is no significant reduction in placental blood flow in pregnancy during resistance training in recreational athletes, as documented by a 3-dimensional power flow Doppler ultrasonography. Study Design: Cohort. Level of Evidence: Level 3. Methods: A cohort of healthy women who participated in recreational athletics was enrolled in a prospective study to assess placental blood flow during a resistance exercise. A 1 repetition maximum (1RM, up to 50 lb) was determined through a modified chest press as a marker of heavy resistance training. Three-dimensional volume measurements and power Doppler flow were determined at the rest phase and during the 1RM lift phase. The vascular flow index (VFI) was calculated to determine placental perfusion during each phase. Results: A total of 22 women participated. The mean age of participants was 31 years. Gestational age ranged from 13 to 28 weeks. Average 1RM weight lifted was 30 lb. Four women (18%) were able to lift 50 lb, the maximum weight that the study allowed. The remaining 18 women (82%) lifted their true 1RM. Mean VFI during lift phase was 2.185 compared with 2.071 at rest ( P = 0.03). There was a slight mean increase in VFI during lift phase, 0.114 (95% CI 0.009-0.182) from 2.071 to 2.185 with lifting ( P = 0.03). The 15 women who participated in structured exercise had a mean VFI at rest and during the lift phase of 2.031 and 2.203, respectively ( P = 0.01). Conclusion: Three-dimensional power flow Doppler imaging can guide resistance training during pregnancy to prevent fetal injury due to hypoperfusion. Resistance training up to an RM1 of 50 lb did not result in a significant reduction of placental blood flow from resting state in the study population. Clinical Relevance: This technique may be used to guide training parameters among pregnant athletes.
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Choudhary, Sumesh, Vineet Mishra, Rohina Aggarwal et Kavita Mistry. « Evaluation and correlation of placental vasculature by three-dimensional power Doppler ultrasonography with umbilical Doppler in normal and IUGR pregnancies ». International Journal of Reproduction, Contraception, Obstetrics and Gynecology 7, no 9 (27 août 2018) : 3818. http://dx.doi.org/10.18203/2320-1770.ijrcog20183801.

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Background: In recent years there have been significant developments in the use of 3D Power Doppler (3DPD) imaging and quantitative 3DPD histogram analysis to estimate both placental volume and intraplacental vasculature. This study is to evaluate the distribution and variation of placental vascular indices according to gestational age and placental volume and position. Co relate the umbilical Doppler indices with placental vascular indices.Methods: From September 2016 to October 2017, three-dimensional (3D)-power Doppler ultrasound was performed in 200 singalton pregnancies from 20 to 40 weeks of gestation. Using the same pre-established settings for all patients, power Doppler was applied to the placenta and placental volume was obtained by the rotational technique (VOCAL). The 3D-power histogram was used to determine the placental vascular indices: vascularization index (VI), flow index (FI) and vascularization-flow index (VFI). Umbilical Doppler was measured on the free loop of umbilical cord. The placental vascular indices were then plotted against gestational age placental volume, position and umbilical Doppler SD ratio, PI and RI. These values were evaluated in IUGR fetus.Results: Analysis of the results showed that the placental vascular indices estimated by 3D-power Doppler ultrasonography presented constant distribution throughout gestation despite the significant increase in placental volume. Placental position at fundal region shows higher value of VI, FI, and VFI. Placental position with relation to VI, FI, and VFI shows statistically significant with p value <0.01. Placental vascular indices VI, FI and VFI when corelated with systolic/ diastolic ratio, pulsatility index and resistive resistance index of umbilical artery shows poor negative correlation, only VI and FI shows statistically significant with SD ratio as p value is <0.01and <0.04. VFI did not show statistically significant as p value is 0.10(NS). With pulsatility index p value is statistically significant is less than<0.01 with vascular indices. Resistive index p value is statistically significant is less than <0.01 for VI and VFI but not significant with FI as p value is 0.06.Conclusions: Doppler ultrasound assists in the evaluation of placental vascularization in normal and IUGR pregnancies, may play an important role in future research on fetoplacental insufficiency.
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Thèses sur le sujet "Vector flow imaging (VFI)"

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Chan, Lok-sang, et 陳樂生. « Adaptive flow detector and estimator for ultrasound high frame rate vector flow imaging ». Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2011. http://hub.hku.hk/bib/B47753043.

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Cardiovascular diseases is a leading cause of death worldwide and improvement of the corresponding screening tool is the best way to deal with this clinical problem. In this thesis we attempted to develop a framework of ultrasound high frame rate vector flow imaging (VFI) by emphasizing on the design of corresponding flow detector and flow estimator. We believe that the high temporal resolution and the complex blood flow visualization ability of high frame rate VFI enables it to be further developed as a reliable flow imaging modality for cardiological examination. In order to achieve high temporal resolution, fast data acquisition algorithm was applied in the framework. Doppler signals acquired using this acquisition algorithm have two unique characteristics comparing with conventional data acquisition algorithm: (1) widen spectral bandwidth and (2) greater clutter to blood signal ratio. These signal characteristics give rise to unique signal processing. In addition, complex blood flow pattern, which is common in cardiological examination, induces extra challenges in implementing high frame rate VFI. In this thesis, flow detector which is adaptive to different flow scenarios and high dynamic range 2D flow estimator were presented. The proposed flow detector employes K-means++ clustering algorithm to classify clutter components from acquired Doppler signals. As a performance analysis, Field II simulation studies were performed by a parabolic flow phantom (flow velocity: 10mm/s to 200mm/s; tissue motion: 10mm/s; beam-flow angle: 60?). The post-filtered Doppler power map and BCR were used as qualitative and quantitativemeasures of detectors performance. Analyzed result has indicated that, as compared with clutter downmixing detector and eigen-based detector, the proposed flow detector could classify and suppress clutter component more effectively. Results also suggested that the proposed flow detector is more adaptive to slow flow scenarios where existing flow detectors failed to distinguish between blood and clutter components. For the proposed flow estimator, it was characterized by the interpolation of speckle tracking results in Lagrangian reference frame. The estimation bias and RMS error were calculated for different flow scenarios (flow velocity: 100mm/s to 500mm/s; beam-flow angle: 15? to 60?). It was found that the proposed flow estimator provides higher dynamic range than conventional speckle tracking-based flow estimator. Nonetheless, it is also observed that the estimation variances and errors increases in slow flow scenarios. In order to demonstrate the medical potential of the proposed high frame rate VFI framework. A carotid bifurcation simulation model with realistic blood flow pattern calculated using computational fluid dynamic software was applied in the performance evaluation study. In the VFI image obtained, complex blood flow pattern was readily visualized. In contrast, conventional ultrasound flow imaging was only able to estimate axial velocity map and thus lead to many ambiguities in analyzing the complex blood flow pattern. It proved that ultrasound high frame rate VFI has the potential to be further developed into a new cardiological examination technique.
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Electrical and Electronic Engineering
Master
Master of Philosophy
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Farrugia, N. « Vector-scalar imaging in combustion using PIV and LIF ». Thesis, Cranfield University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.309583.

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Lenge, Matteo. « Development and validation of innovative ultrasound flow imaging methods ». Thesis, Lyon 1, 2015. http://www.theses.fr/2015LYO10036/document.

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L'échographie est largement utilisée pour l'imagerie du flux sanguin pour ses nombreux avantages tels que son inocuité, son cout réduit, sa facilité d'utilisation et ses performances. Cette thèse a pour objectif de proposer de nouvelles méthodes ultrasonores d'imagerie du flux sanguin. Après une étude bibliographique, plusieurs approches ont été étudiées en détail jusqu'à leur implémentation sur l'échographe de recherche ULA-OP développé au sein du laboratoire et ont été validées en laboratoire et en clinique. La transmission d'ondes planes a été proposée pour améliorer la technique d'imagerie utilisant les oscillations transverses. Des champs de pression ultrasonores présentant des oscillations transverses sont générés dans de larges régions et exploités pour l'estimation vectorielle du flux sanguin à une haute cadence d'imagerie. Des cartes du flux sanguin sont obtenues grâce à une technique s'appuyant sur la transmission d'ondes planes couplées à un nouvel algorithme d'estimation de la vitesse dans le domaine fréquentiel. Les méthodes vectorielles implémentées en temps réel dans le ULA-OP ont été comparées à la méthode Doppler classique lors d'une étude clinique. Les résultats ont montré le bénéfice des méthodes vectorielles en termes de précision et de répétabilité. La nouvelle méthode proposée a démontré sa grande précision ainsi que son gain en termes de temps de calcul aussi bien en simulations qu'en acquisitions en laboratoire ou lors d'essais in vivo. Une solution logicielle temps réel implémentée sur une carte GPU a été proposée et testée afin de réduire encore le temps de calcul et permettre l'emploi de la méthode en clinique
Ultrasound is widely used for blood flow imaging because of the considerable advantages for the clinician, in terms of performance, costs, portability, and ease of use, and for the patient, in terms of safety and rapid checkup. The undesired limitations of conventional methods (1-D estimations and low frame-rate) are widely overtaken by new vector approaches that offer detailed descriptions of the flow for a more accurate diagnosis of cardiovascular system diseases. This PhD project concerns the development of novel methods for blood flow imaging. After studying the state-of-the-art in the field, a few approaches have been examined in depth up to their experimental validation, both in technical and clinical environments, on a powerful ultrasound research platform (ULA-OP). Real-time novel vector methods implemented on ULA-OP were compared to standard Doppler methods in a clinical study. The results attest the benefits of the vector methods in terms of accuracy and repeatability. Plane-wave transmissions were exploited to improve the transverse oscillation imaging method. Double oscillating fields were produced in large regions and exploited for the vectorial description of blood flow at high frame rates. Blood flow maps were obtained by plane waves coupled to a novel velocity estimation algorithm operating in the frequency domain. The new method was demonstrated capable of high accuracy and reduced computational load by simulations and experiments (also in vivo). The investigation of blood flow inside the common carotid artery has revealed the hemodynamic details with unprecedented quality. A software solution implemented on a graphic processing unit (GPU) board was suggested and tested to reduce the computational time and support the clinical employment of the method
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Tsang, Kwok-hon, et 曾國瀚. « Design of an aperture-domain imaging method and signal acquisition hardware for ultrasound-based vector flow estimation ». Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2009. http://hub.hku.hk/bib/B43572315.

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Tsang, Kwok-hon. « Design of an aperture-domain imaging method and signal acquisition hardware for ultrasound-based vector flow estimation ». Click to view the E-thesis via HKUTO, 2009. http://sunzi.lib.hku.hk/hkuto/record/B43572315.

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Correia, Mafalda Filipa Rodrigues. « From 2D to 3D cardiovascular ultrafast ultrasound imaging : new insights in shear wave elastography and blood flow imaging ». Thesis, Sorbonne Paris Cité, 2016. http://www.theses.fr/2016USPCC158.

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Ces travaux de thèse portent sur le développement de nouvelles modalités d’imagerie cardiovasculaire basé sur l’utilisation de l'imagerie ultrarapide 2D et 3D. Les modalités d’imagerie développées dans cette thèse appartiennent au domaine de de l’élastographie par onde de cisaillement et de l'imagerie Doppler des flux sanguins.Dans un premier temps, la technique de l’élastographie par onde de cisaillement du myocarde a été développée pour les applications cliniques. Une approche d'imagerie non-linéaire a été utilisée pour améliorer l’estimation de vitesse des ondes de cisaillement (ou la rigidité des tissus cardiaques) de manière non invasive et localisée. La validation de cette nouvelle approche de « l’imagerie par sommation cohérente harmonique ultrarapide » a été réalisée in vitro et la faisabilité in vivo a été testée chez l’humain. Dans un second temps, nous avons utilisé cette technique sur des patients lors de deux essais cliniques, chacun ciblant une population différente (adultes et enfants). Nous avons étudié la possibilité d’évaluer quantitativement la rigidité des tissus cardiaques par élastographie chez des volontaires sains, ainsi que chez des malades souffrant de cardiomyopathie hypertrophique. Les résultats ont montré que l’élastographie pourrait devenir un outil d'imagerie pertinent et robuste pour évaluer la rigidité du muscle cardiaque en pratique clinique. Par ailleurs, nous avons également développé une nouvelle approche appelée « imagerie de tenseur élastique 3-D » pour mesurer quantitativement les propriétés élastiques des tissus anisotropes comme le myocarde. Ces techniques ont été testées in vitro sur des modèles de de gels isotropes transverses. La faisabilité in vivo de l’élastographie par onde cisaillement à trois-dimensions a été également évaluée sur un muscle squelettique humain.D'autre part, nous avons développé une toute nouvelle modalité d’imagerie ultrasonore des flux coronariens basée sur l’imagerie Doppler ultrarapide. Cette technique nous a permis d'imager la circulation coronarienne avec une sensibilité élevée, grâce notamment au développement d’un nouveau filtre adaptatif permettant de supprimer le signal du myocarde en mouvement, basé sur la décomposition en valeurs singulières (SVD). Des expériences à thorax ouvert chez le porc ont permis d'évaluer et de valider notre technique et les résultats ont montré que la circulation coronaire intramurale, peut être évaluée sur des vaisseaux de diamètres allant jusqu’à 100 µm. La faisabilité sur l’homme a été démontrée chez l’enfant en imagerie clinique transthoracique.Enfin, nous avons développé une nouvelle approche d’imagerie des flux sanguins, « l’imagerie ultrarapide 3-D des flux», une nouvelle technique d'imagerie quantitative des flux. Nous avons démontré que cette technique permet d’évaluer le débit volumétrique artériel directement en un seul battement cardiaque, indépendamment de l'utilisateur. Cette technique a été mise en place à l'aide d'une sonde matricielle 2-D et d’un prototype d’échographe ultrarapide 3-D développé au sein du laboratoire. Nous avons évalué et validé notre technique in vitro sur des fantômes artériels, et la faisabilité in vivo a été démontrée sur des artères carotides humaines
This thesis was focused on the development of novel cardiovascular imaging applications based on 2-D and 3-D ultrafast ultrasound imaging. More specifically, new technical and clinical developments of myocardial shear wave elastography and ultrafast blood flow imaging are presented in this manuscript.At first, myocardial shear wave elastography was developed for transthoracic imaging and improved by a non-linear imaging approach to non-invasively and locally assess shear wave velocity measurements, and consequently tissue stiffness in the context of cardiac imaging. This novel imaging approach (Ultrafast Harmonic Coherent Compounding) was tested and validated in-vitro and the in vivo feasibility was performed in humans for biomechanical evaluation of the cardiac muscle wall, the myocardium. Then, we have translated shear wave elastography to the clinical practice within two clinical trials, each one with a different population (adults and children). In both clinical trials, we have studied the capability of shear wave elastography to assess quantitatively myocardial stiffness in healthy volunteers and in patients suffering from hypertrophic cardiomyopathy. The results in the adult population indicated that shear wave elastography may become an effective imaging tool to assess cardiac muscle stiffness in clinical practice and help the characterization of hypertrophic cardiomyopathy. Likewise, we have also translated Shear Wave Elastography into four-dimensions and we have developed a new approach to map tissue elastic anisotropy in 3-D. 3-D Elastic Tensor Imaging allowed us to estimate quantitatively in a single acquisition the elastic properties of fibrous tissues. This technique was tested and validated in vitro in transverse isotropic models. The in-vivo feasibility of 3D elastic tensor imaging was also assessed in a human skeletal muscle.In parallel, we have developed a novel imaging technique for the non-invasive and non-radiative imaging of coronary circulation using ultrafast Doppler. This approach allowed us to image blood flow of the coronary circulation with high sensitivity. A new adaptive filter based on the singular value decomposition was used to remove the clutter signal of moving tissues. Open-chest swine experiments allowed to evaluate and validate this technique and results have shown that intramural coronary circulation, with diameters up to 100 µm, could be assessed. The in-vivo transthoracic feasibility was also demonstrated in humans in pediatric cardiology.Finally, we have developed a novel imaging modality to map quantitatively the blood flow in 3-D: 3-D ultrafast ultrasound flow imaging. We demonstrated that 3-D ultrafast ultrasound flow imaging can assess non-invasively, user-independently and directly volumetric flow rates in large arteries within a single heartbeat. We have evaluated and validated our technique in vitro in arterial phantoms using a 2-D matrix-array probe and a customized, programmable research 3-D ultrafast ultrasound system, and the in-vivo feasibility was demonstrated in human carotid arteries
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Ramadoss, Balaji. « Vector Flow Model in Video Estimation and Effects of Network Congestion in Low Bit-Rate Compression Standards ». [Tampa, Fla.] : University of South Florida, 2003. http://purl.fcla.edu/fcla/etd/SFE0000139.

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Bayat, Sharareh. « Direct Structured Finite Element Mesh Generation from Three-dimensional Medical Images of the Aorta ». Thèse, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/31023.

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Three-dimensional (3-D) medical imaging creates notable opportunities as input toward engineering analyses, whether for basic understanding of the normal function or patho-physiology of an organ, or for the simulation of virtual surgical procedures. These analyses most often require finite element (FE) models to be constructed from patient-specific 3-D medical images. However, creation of such models can be extremely labor-intensive; in addition, image processing and mesh generation are often operator-dependent, lack robustness and may be of suboptimal quality. Focusing on the human aorta, the goal of the present work is to create a fast and robust methodology for quadrilateral surface and hexahedral volume meshing from 3-D medical images with minimal user input. By making use of the segmentation capabilities of the 3-D gradient vector flow field combined with original ray-tracing and orientation control algorithms, we will demonstrate that it is possible to incrementally grow a structured quadrilateral surface mesh of the inner wall of the aorta. The process does not only require minimal input from the user, it is also robust and very fast compared to existing methods; it effectively combines segmentation and meshing into one single effort. After successfully testing the methodology and measuring the quality of the meshes produced by it from synthetic as well as real medical image datasets, we will make use of the surface mesh of the inner aortic wall to derive hexahedral meshes of the aortic wall thickness and of the fluid domain inside the aorta. We will finally outline a tentative approach to merge several structured meshes to process the main branches of the aorta.
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Rodríguez, Eduardo Rafael Llapa. « Segmentação de fronteiras em imagens médicas via contornos deformáveis através do fluxo recursivo do vetor gradiente ». Universidade de São Paulo, 2005. http://www.teses.usp.br/teses/disponiveis/18/18133/tde-03022016-161317/.

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Devido à variação na qualidade e ao ruído nas imagens médicas, a aplicação de técnicas tradicionais de segmentação é geralmente ineficiente. Nesse sentido, apresenta-se um novo algoritmo a partir de duas técnicas: o modelo de contornos deformáveis por fluxo do vetor gradiente (GVF deformable contours) e a técnica de espaço de escalas utilizando o processo de difusão. Assim, foi realizada uma revisão bibliográfica dos modelos que trabalham com os contornos deformáveis, os quais foram classificados em modelos paramétricos e geométricos. Entre os modelos paramétricos foi escolhido o modelo de contornos deformáveis por fluxo do vetor gradiente (GVF). Esta aproximação oferece precisão na representação de estruturas biológicas não observada em outros modelos. Desta forma, o algoritmo apresentado mapeia as bordas (edge map) e aperfeiçoa a condução da deformação utilizando uma técnica baseada em operações recursivas. Com este cálculo apoiado no comportamento de espaço de escalas, obtem-se a localização e correção de sub-regiões do edge map que perturbam a deformação. Por outro lado, é incorporada uma nova característica que permite ao algoritmo realizar atividades de classificação. O algoritmo consegue determinar a presença ou ausência de um objeto de interesse utilizando um valor mínimo de deformação. O algoritmo é validado através do tratamento de imagens sintéticas e médicas comparando os resultados com os obtidos no modelo tradicional de contornos deformáveis GVF.
Due to the variation of the quality and noise in medical images, the classic image segmentation techniques are usually ineffective. In this work, we present a new algorithm that is composed of two techniques: the gradient vector flow deformable contours (GVF) and the scale-space technique using a diffusion process. A bibliographical revision of the models that work with deformable contours was accomplished, they were classified in parametric and geometric models. Among the parametric models the gradient vector flow deformable contours (GVF) was chosen. This approach offers precision in the representation of biological structures where other models does not. Thus, the algorithm improves the edge map to guide the deformation using recursive operations. With this estimation based on the behavior of the scale-space techniques it is realized, the localization and correction of sub-areas of the edge map that disturb the deformation. On the other hand, it was incorporated a new characteristic that allows the algorithm to accomplish classification activities. That is, the algorithm determines the presence or absence of a target object using a minimal deformation area. Our method was validated on both, simulated images and medical images making a comparison with the traditional GVF deformable contours.
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Goudot, Guillaume. « Applications innovantes des ultrasons en pathologie vasculaire : utilisation de l'imagerie ultrarapide dans l'analyse de la rigidité artérielle et des ultrasons pulsés en thérapie Arterial stiffening assessed by ultrafast ultrasound imaging gives new insight into arterial phenotype of vascular Ehlers–Danlos mouse models Aortic wall elastic properties in case of bicuspid aortic valve Segmental aortic stiffness in bicuspid aortic valve patients compared to first-degree relatives Wall shear stress measurement by ultrafast vector flow imaging for atherosclerotic carotid stenosis Pulsed cavitational therapy using high-frequency ultrasound for the treatment of deep vein thrombosis in an in vitro model of human blood clot ». Thesis, Sorbonne Paris Cité, 2018. https://wo.app.u-paris.fr/cgi-bin/WebObjects/TheseWeb.woa/wa/show?t=2215&f=13951.

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Livres sur le sujet "Vector flow imaging (VFI)"

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Maniatis, Theofanis. Flow velocity vector imaging using color doppler ultrasound. Ottawa : National Library of Canada, 1993.

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Chapitres de livres sur le sujet "Vector flow imaging (VFI)"

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Ohtsuki, Shigeo, Motonao Tanaka et Motoyoshi Okujima. « A Method of Flow Vector Mapping Deduced Doppler Data on Sector Scanned Plane ». Dans Acoustical Imaging, 467–72. Boston, MA : Springer US, 1989. http://dx.doi.org/10.1007/978-1-4613-0791-4_49.

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Yamamoto, A., M. Tanaka, N. Endoh, K. Takahashi, S. Ohtsuki et M. Okujima. « Two-Dimensional Mapping of the Velocity Vector Distribution of the Intraventricular Blood Flow ». Dans Acoustical Imaging, 473–80. Boston, MA : Springer US, 1989. http://dx.doi.org/10.1007/978-1-4613-0791-4_50.

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Vixège, Florian, Alain Berod, Franck Nicoud, Pierre-Yves Courand, Didier Vray et Damien Garcia. « 3-D Intraventricular Vector Flow Mapping Using Triplane Doppler Echo ». Dans Functional Imaging and Modeling of the Heart, 587–94. Cham : Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-78710-3_56.

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Endoh, N., M. Tanaka, A. Yamamoto, K. Takahashi, S. Ohtsuki et M. Okujima. « Analysis of the Behavior of Intraventricular Blood Flow in Myocardial Infarction by Two-Dimensional Velocity Vector Distribution ». Dans Acoustical Imaging, 543–50. Boston, MA : Springer US, 1989. http://dx.doi.org/10.1007/978-1-4613-0791-4_57.

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Xu, Liu-Jun, et Ji-Ping Huang. « Theory for Thermal Wave Refraction : Advection Regulation ». Dans Transformation Thermotics and Extended Theories, 219–32. Singapore : Springer Nature Singapore, 2022. http://dx.doi.org/10.1007/978-981-19-5908-0_16.

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AbstractIn this chapter, we study thermal waves of conduction and advection and further design advection-assisted metamaterials to realize the positive, vertical, and negative refraction of thermal waves. These results have a phenomenological analog of electromagnetic wave refraction despite different mechanisms. The negative refraction of thermal waves means that the incident and refractive thermal waves are on the same side of the normal, but the wave vector and energy flow are still in the same direction. As a model application, we apply the refractive behavior to design a thermal wave concentrator that can increase wave numbers and energy flows. This work provides insights into thermal wave manipulation, which may have potential thermal imaging applications.
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Xu, Chenyang, et Jerry L. Prince. « Gradient Vector Flow Deformable Models ». Dans Handbook of Medical Imaging, 159–69. Elsevier, 2000. http://dx.doi.org/10.1016/b978-012077790-7/50014-x.

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Mazrooei Rad, Elias. « EEG and MRI Processing for Alzheimer’s Diseases ». Dans Vision Sensors - Recent Advances [Working Title]. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.107162.

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A new method for the diagnosis of Alzheimer’s disease in the mild stage is presented according to combining the characteristics of electroencephalogram (EEG) signal and magnetic resonance imaging (MRI) images. Then, proper features of brain signals are extracted according to the nonlinear and chaotic nature of the brain such as Lyapunov exponent, correlation dimension, and entropy. These features combined with brain MRI images properties include medial temporal lobe atrophy (MTA), cerebrospinal fluid flow (CSF), gray matter (GM), index asymmetry (IA), and white matter (WM) to diagnose the disease. Then two classifiers, the support vector machine and Elman neural network, are used with the optimal combined features extracted by analysis of variance. Results showed that between the three brain signals, and between the four modes of evaluation, the accuracy of the Pz channel and excitation mode was more than the others The accuracy of the results in Elman neural network with the combination of brain signal features and medical images is 94.4% and in the case without combining the signal and image features, the accuracy of the results is 92.2%.
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Actes de conférences sur le sujet "Vector flow imaging (VFI)"

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Jensen, Jorgen Arendt, Herve Liebgott, Frederic Cervenansky et Carlos Armando Villagomez Hoyos. « SA-VFI : the IEEE IUS Challenge on Synthetic Aperture Vector Flow Imaging ». Dans 2018 IEEE International Ultrasonics Symposium (IUS). IEEE, 2018. http://dx.doi.org/10.1109/ultsym.2018.8580208.

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Pihl, Michael J., Matthias B. Stuart, Borislav G. Tomov, Jens M. Hansen, Morten F. Rasmussen et Jørgen A. Jensen. « Preliminary examples of 3D vector flow imaging ». Dans SPIE Medical Imaging, sous la direction de Johan G. Bosch et Marvin M. Doyley. SPIE, 2013. http://dx.doi.org/10.1117/12.2006845.

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Anderson, Martin E. « Vector flow estimator isomorphism and wall filter requirements ». Dans Medical Imaging 2001, sous la direction de Michael F. Insana et K. Kirk Shung. SPIE, 2001. http://dx.doi.org/10.1117/12.428198.

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Bradway, David P., Kristoffer L. Hansen, Michael B. Nielsen et Jørgen A. Jensen. « Transverse oscillation vector flow imaging for transthoracic echocardiography ». Dans SPIE Medical Imaging, sous la direction de Johan G. Bosch et Neb Duric. SPIE, 2015. http://dx.doi.org/10.1117/12.2081145.

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Oddershede, Niels, Kristoffer Lindskov Hansen, Michael Bachmann Nielsen et Jørgen Arendt Jensen. « In vivo examples of synthetic aperture vector flow imaging ». Dans Medical Imaging, sous la direction de Stanislav Y. Emelianov et Stephen A. McAleavey. SPIE, 2007. http://dx.doi.org/10.1117/12.706467.

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Jensen, Jorgen Arendt. « Quantitative measurements using ultrasound Vector Flow Imaging ». Dans 2016 IEEE International Ultrasonics Symposium (IUS). IEEE, 2016. http://dx.doi.org/10.1109/ultsym.2016.7728672.

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Hansen, Kristoffer Lindskov, Hasse Moller-Sorensen, Mads Moller Pedersen, Jesper Kjaergaard, Jens Christian Nilsson, Jens Teglgaard Lund, Michael Bachmann Nielsen et Jorgen Arendt Jensen. « Intraoperative vector flow imaging of the heart ». Dans 2013 IEEE International Ultrasonics Symposium (IUS). IEEE, 2013. http://dx.doi.org/10.1109/ultsym.2013.0445.

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Jensen, Jorgen Arendt, Andreas Hjelm Brandt et Michael Bachmann Nielsen. « In-vivo convex array vector flow imaging ». Dans 2014 IEEE International Ultrasonics Symposium (IUS). IEEE, 2014. http://dx.doi.org/10.1109/ultsym.2014.0082.

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Hansen, Kristoffer Lindskov, Hasse Moller-Sorensen, Jesper Kjaergaard, Maiken Brit Jensen, Jens Teglgaard Lund, Michael Bachmann Nielsen et Jorgen Arendt Jensen. « Vector flow imaging of the ascending aorta ». Dans 2015 IEEE International Ultrasonics Symposium (IUS). IEEE, 2015. http://dx.doi.org/10.1109/ultsym.2015.0069.

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Besson, Adrien, Frederic Wintzenrieth et Claude Cohen-Bacrie. « Vector-flow Imaging in Convex-array Configurations ». Dans 2020 IEEE International Ultrasonics Symposium (IUS). IEEE, 2020. http://dx.doi.org/10.1109/ius46767.2020.9251541.

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Rapports d'organisations sur le sujet "Vector flow imaging (VFI)"

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Huang, Qiu, Qiyu Peng, Bin Huang, Arvi Cheryauka et Grant T. Gullberg. Attenuated Vector Tomography -- An Approach to Image Flow Vector Fields with Doppler Ultrasonic Imaging. Office of Scientific and Technical Information (OSTI), mai 2008. http://dx.doi.org/10.2172/943972.

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