Bauer, Andreas Sebastian (2020):
Validation of Wall Shear Stress Measurements Obtained with Magnetic Resonance Velocimetry.
Darmstadt, Technische Universität,
DOI: 10.25534/tuprints-00009030,
[Ph.D. Thesis]
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Item Type: | Ph.D. Thesis | ||||
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Title: | Validation of Wall Shear Stress Measurements Obtained with Magnetic Resonance Velocimetry | ||||
Language: | English | ||||
Abstract: | Wall shear stress acting on the vessel walls has been identified as an important factor for the initiation and development of cardiovascular diseases. In vivo measurements of the wall shear stress are usually conducted with Magnetic Resonance Velocimetry (MRV). Due to the limited spatial and temporal resolution, measurements in the near-wall region are challenging and the results are associated with high systematic and stochastic errors. Thus, an ongoing effort towards new post-processing methods to overcome this problem is observed. However, the underlying 'true' values of the wall shear stress are seldom known, inhibiting the evaluation of these methods. The present thesis is devoted to investigate this problem by conducting in vitro MRV measurements under well-known flow conditions and by providing reliable reference values of the wall shear stress. Flow situations have been selected in which wall shear stress values from laser Doppler velocimetry (LDV), analytical solutions, and results from numerical simulations are available as a reference. The in vitro experiments are performed in various flows with a step-by-step increase of the complexity, ranging from simple steady laminar pipe flows to unsteady transitional flows through complex geometries, representative for the human aorta. Extensive LDV measurements are presented, and the results of the velocity fields and wall shear stresses are compared to the MRV measurements. This thesis discusses possible systematic and random sources of errors in both measurement techniques. Additionally, it provides helpful advice for the practical measurement of the wall shear stress with LDV. In the course of this work a database has been established, which contains the MRV data as well as the corresponding reference wall shear stress values acquired under the well-known and controlled flow conditions. This database has been used by other research groups in a collaborative interdisciplinary project, which has the final goal of improving the estimation of the wall shear stress from MRV data. |
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Place of Publication: | Darmstadt | ||||
Classification DDC: | 600 Technik, Medizin, angewandte Wissenschaften > 620 Ingenieurwissenschaften | ||||
Divisions: | 16 Department of Mechanical Engineering > Fluid Mechanics and Aerodynamics (SLA) 16 Department of Mechanical Engineering > Fluid Mechanics and Aerodynamics (SLA) > Dynamics of drops and sprays > MRV |
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Date Deposited: | 14 Feb 2020 10:22 | ||||
Last Modified: | 14 Feb 2020 10:22 | ||||
DOI: | 10.25534/tuprints-00009030 | ||||
URN: | urn:nbn:de:tuda-tuprints-90309 | ||||
Referees: | Tropea, Prof. Dr. Cameron ; Grundmann, Prof. Dr. Sven | ||||
Date of oral examination: | 28 January 2020 | ||||
URI: | https://tuprints.ulb.tu-darmstadt.de/id/eprint/9030 | ||||
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