Methodological advances in electrical properties tomography

Iyyakkunnel, Santhosh. Methodological advances in electrical properties tomography. 2023, Doctoral Thesis, University of Basel, Faculty of Science.

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Electrical properties tomography (EPT) aims to non-invasively measure the electrical properties (EPs) of biological tissues using conventional magnetic resonance imaging (MRI). EPT has gained increased interest over the last decade thanks to its potential in various applications, ranging from the optimization of radio frequency (RF) irradiation for increased safety, to the diagnosis and staging of pathologies, such as cancer, as demonstrated in several studies.
In MRI, the electrical properties of the tissue, in addition to the coil and body geometries, affect the RF magnetic field used for spin excitation. EPT reconstructs the EPs from
local changes in the spatial distribution of this field, commonly known as B1+. Typically, a measurement of B1+ is used to correct for effects resulting from inhomogeneous excitation. Measurements used for this purpose are often performed with fast sequences and thus, at low resolution. EPT, however, needs high-resolution measurements to be sensitive to the local variations, often translating into long acquisition times when relying on existing B1+ mapping methods. In addition, both the amplitude and phase of B1+ are required for
accurate EP estimation. These components are generally measured separately, adding to the overall needed scan time. Such long scan times are a large factor in hindering the translation of EPT into the clinics.
This thesis investigated strategies to reduce the scan time for B1+ mapping methods that are suitable for EPT. In particular, a high signal-to-noise ratio and high precision requirements must be met. For this reason, three methods are proposed to improve the time efficiency of the B1+ acquisitions. Two of the implemented methods reduce the scan time by combining B1+ amplitude and phase measurement, virtually halving the acquisition time. The third method increases efficiency by measuring one B1+ component in conjunction with other relevant quantitative parameters. The proposed methods showed promising results in healthy volunteers indicating a potential translation into clinics.
In conclusion, this thesis successfully addressed the challenge of reducing the measurement time for EPT by proposing three methods with increased time efficiency. Combined with more accurate reconstruction algorithms, these methods could serve as a promising starting point for integrating EPT into clinical practice.
Advisors:Bieri, Oliver
Committee Members:Bruder, Christoph and Stuber, Matthias
Faculties and Departments:03 Faculty of Medicine > Bereich Querschnittsfächer (Klinik) > Radiologie USB > Radiologische Physik (Bieri)
03 Faculty of Medicine > Departement Klinische Forschung > Bereich Querschnittsfächer (Klinik) > Radiologie USB > Radiologische Physik (Bieri)
05 Faculty of Science > Departement Physik > Physik > Theoretische Physik (Bruder)
UniBasel Contributors:Iyyakkunnel, Santhosh and Bieri, Oliver and Bruder, Christoph
Item Type:Thesis
Thesis Subtype:Doctoral Thesis
Thesis no:15306
Thesis status:Complete
Number of Pages:xiii, 102
Identification Number:
  • urn: urn:nbn:ch:bel-bau-diss153069
edoc DOI:
Last Modified:03 Apr 2024 04:30
Deposited On:02 Apr 2024 08:29

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