Universität zu Lübeck
Dauerhafte URI für den Bereichhttps://epub.uni-luebeck.de/handle/zhb_hl/1
Listen
Auflistung Universität zu Lübeck nach Titel
Gerade angezeigt 1 - 20 von 3359
- Treffer pro Seite
- Sortieroptionen
Item 4D Fluss MRT zur Analyse der aortalen Wandschubspannung auf Basis verschiedener Software-Lösungen(2019) Beldoch, Michael PeterItem 4D Fluss MRT zur Analyse der thorakalen aortalen Flusscharakteristika bei Patienten mit Sinusprothese(2017) Oechtering, Thekla H.Item A Fourier-analytical approach for field-free-point magnetic particle imaging(2025) Maaß, MarcoMagnetic particle imaging is a tracer-based medical imaging technique that measures the spatial distribution of superparamagnetic nanoparticles. Alternating magnetic fields with different excitation sequences are used to measure the nanoparticle distribution in a scanner. Usually, the simplified Langevin model of paramagnetism is used as a first approximation for the complicated nonlinear magnetization behavior of nanoparticles. Although the modified Langevin model of paramagnetism can provide suitable image reconstructions for one-dimensional excitation, the situation is more complicated for higher-dimensional excitation, as several aspects cannot be fully explained by the Langevin model. A well-known example is the spatial similarity of the frequency components of the system function with tensor products of Chebyshev polynomials. This was observed for a higher-dimensional excitation of the Lissajous trajectory type and was unproven for almost ten years. With the aim of explaining such observations mathematically, this thesis makes an important contribution to the mathematical foundations of magnetic particle imaging. To this end, the spatio-temporal system function based on the Langevin model is transformed into the frequency domain using various concepts of Fourier analysis. The scientific contribution of the newly developed mathematical framework is manifold. Firstly, the developed model is able to separate the scanner-dependent excitation from the particle magnetization model, allowing better utilization of the imaging operator so that faster reconstruction methods could be developed. Secondly, it is now easier to investigate both the effect of the magnetization model and that of the excitation sequence in the imaging model separately. Thus, an extended equilibrium magnetization model is introduced in this thesis and a series representation is developed for it. Furthermore, the exact relationship between the frequency components of the system function and the tensor products of Chebyshev polynomials is shown for excitations of the Lissajous trajectory type. Finally, using the developed mathematical framework, the frequency representations of various excitation sequences known from the literature are calculated, which further increases the applicability of the model for magnetic particle imaging.Item A metabolomics and lipidomics profile of ischemic stroke(2022) Folberth, JuliaItem Abhängigkeit des Bereitschaftspotentials vom zeitlichen Rahmen und der Aufmerksamkeit(2021) Baur, Alexandra ElisabethItem ABS-Interventionen bei intensivmedizinisch versorgten septischen Patienten(2022) Gansewig, Bente AnekeItem Abscheiden von Schichten aus Poly-Parylen für medizinische Zwecke am Beispiel der künstlichen Blase(2014) Schamberger, FlorianItem Active contours with spatially-variant definitions of energy terms based on local region descriptors(2008) Darolti, CristinaItem Adaptation of Mycobacterium tuberculosis complex strains to antibiotics(2023) Sonnenkalb, Lindsay Ruth