| Zugriffsnummer | 41379 |
| Dokumenttyp | Dissertation |
| Peer Review | unbekannt |
| Sprache | Englisch |
| Titel | Evaluation of imaging parameters in Magnetic Particle Imaging |
| Autor(in); Institution |
Schmidt, Daniel; 8.2, Biosignale, PTB-Berlin
|
| Quelle/Jahr | (2017), XVII, 150 S. |
| Schriftenreihe | Berichte aus dem Institut für Elektrische Messtechnik und Grundlagen der Elektrotechnik: 57 |
| Dissertationsvermerk | Dissertation, Technische Universität Braunschweig, 2018 |
| Herausgeber(in) |
Schilling, Meinhard; Institut für Elektrische Messtechnik und Grundlagen der Elektrotechnik, TU Braunschweig, Braunschweig, GERMANY
|
| ISBN | 978-3-86387-870-2 (print) |
| Persistent Identifier | |
| URL | |
| Verlag | Berlin: Mensch und Buch Verlag |
| Zusammenfassung | Magnetic Particle Imaging (MPI) is a medical imaging modality, that is (in the current state in 2017) in the preclinical stage. It is based on the spatially encoded detection of magnetic nanoparticles that are magnetized by an external magnetic field. Employing gradient fields for spatial encoding and pickup coils to measure the overall magnetization, the particle distribution can be reconstructed from the measurement signal. Body tissue is ignored with this technology. Due to the non-usage of radiopharmaceuticals or ionizing radiation, MPI has an inherent advantage over its potential competitors CT-angiography and the methods of nuclear medicine imaging like SPECT and PET. Based on this advantage and the potential high spatial and temporal resolution, MPI is a worldwide topic of research. Besides MPI, the Magnetic Particle Spectroscopy (MPS) has been established for the characterization of magnetic nanoparticles under MPI conditions. Except for the gradient field and therefore the spatial encoding, the potential tracers are exposed to the typical MPI environment and their response to the excitation field is measured. This response is taken as an indicator of the suitability of the magnetic nanoparticles as a tracer for MPI. Since this method only yields relative information, an MPI scanner is still needed for quantitative estimations regarding the spatial resolution under consideration of the signal-to-noise ratio. This leaves room for optimization. The first part of the thesis describes the influence of the measurement signal on the spatial resolution in MPI. Based on classic theories of signal-processing and imaging, the MPI signal is analyzed regarding the Nyquist-Shannon-Sampling-Theorem and the spatial frequencies and a direct relationship between spatial frequencies and harmonic structure is indicated. Depending on the amount of tracers and their properties, the signal-to-noise ratio varies and the spatial resolution is related to the harmonics above noise level. In the second part, it is presented based on simulation results how the tracer properties may be optimized for MPI to maximize the spatial resolution. It is shown, that due to dynamic effects, tracers need to be attuned specifically for MPI via several parameters and sometimes even slight deviations from this may diminish the corresponding MPI signal. Finally, a parameter is presented that was mostly independent of the applied field strength and frequency. This parameter may therefore be suitable as a general criterion for optimized MPI tracers. In the third and last part of the thesis, an enhancement of the standard MPS characterization is presented. In contrast to the established method, an estimation of the spatial resolution of the tracer is possible with this new method in dependence on the amount of the tracer and its properties. Besides the characterization of several commercially available tracers, the theory from the first part of the thesis is successfully verified. Moreover, a study is presented in which several resolution phantoms were imaged in a commercial MPI-scanner and compared to the previous resolution characterization of the tracer. It turned out, that the results of both phantom study and the method presented here were very similar. It is therefore concluded that the new method is suitable to characterize the spatial resolution in MPI. |
