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Magnetic Resonance Rheology on Phantoms and Human Brains

dc.contributor.advisorUrbach, Carsten
dc.contributor.authorKofahl, Anna-Lisa
dc.description.abstractIn this thesis first systematic measurements on phantoms and human brains using Magnetic Resonance Rheology (MRR) are presented and means to evaluate the acquired data are investigated.
MRR is a novel technique designed to image the mechanical properties of human brain tissue by performing a creep relaxation experiment inside a Magnetic Resonance Imaging (MRI) scanner. Using a lifting device inside the head coil the head is basically dropped a distance of approximately 1 mm. The response of the brain tissue to this shock excitation is then measured using motion sensitive phase imaging techniques.
Hydrogels with varying stiffness inside PMMA containers with different sizes were used as phantoms emulating the soft brain tissue inside the hard skull to investigate the response to the excitation. Homogeneous phantoms were measured to investigate the response to the shock excitation and to determine the influence of size, stiffness and boundary conditions of the probe. An oscillation in the phase could be observed in response to the excitation and its frequency allowed distinguishing between different phantom configurations.
Additionally, different kinds of inhomogeneous phantoms were investigated to evaluate the feasibility to spatially resolve substructures in the mechanical properties of the phantom material. For local structures depicting the phase strain proved to be a useful tool to identify the inclusions.
The results from the phantom measurements were transferred to the in vivo measurement of ten healthy volunteers to evaluate the experimental set-up under real conditions. These measurements showed that the brain responses to excitation as expected with a distinct oscillation in each hemisphere. The frequencies extracted showed mostly comparable values over the ten volunteers. In both the phase and the phase strain images similar localized features were visible, some corresponding to anatomical structures like sulci.
These result show that in vivo MRR measurements of the human brain are feasible and comparable and though there is room for improvement concerning the reproducibility of the excitation between different measurement sets, MRR appears to be an interesting tool to investigate human brain tissue.
dc.rightsIn Copyright
dc.subject.ddc530 Physik
dc.titleMagnetic Resonance Rheology on Phantoms and Human Brains
dc.typeDissertation oder Habilitation
dc.publisher.nameUniversitäts- und Landesbibliothek Bonn
ulbbnediss.affiliation.nameRheinische Friedrich-Wilhelms-Universität Bonn
ulbbnediss.instituteMathematisch-Naturwissenschaftliche Fakultät : Fachgruppe Physik/Astronomie / Helmholtz-Institut für Strahlen- und Kernphysik (HISKP)
ulbbnediss.fakultaetMathematisch-Naturwissenschaftliche Fakultät
dc.contributor.coRefereeMaier, Karl

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