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dc.contributor.advisorİder, Y. Ziya
dc.contributor.authorHafalır, Fatih Süleyman
dc.date.accessioned2016-01-08T20:06:29Z
dc.date.available2016-01-08T20:06:29Z
dc.date.issued2013
dc.identifier.urihttp://hdl.handle.net/11693/17094
dc.descriptionAnkara : The Department of Electrical and Electronics Engineering and the Graduate School of Engineering and Science of Bilkent Univ., 2013.en_US
dc.descriptionThesis (Master's) -- Bilkent University, 2013.en_US
dc.descriptionIncludes bibliographical references leaves 54-59.en_US
dc.description.abstractTomographic imaging of electrical conductivity and permittivity of tissues may be used for diagnostic purposes as well as for estimating local specific absorption rate (SAR) distributions. Magnetic Resonance Electrical Properties Tomography (MREPT) aims at noninvasively obtaining conductivity and permittivity images at RF frequencies of MRI systems. MREPT algorithms are based on measuring the B1 field which is perturbed by the electrical properties of the imaged object. In this study, the relation between the electrical properties and the measured B + 1 field is formulated, for the first time as, the well-known convection-reaction equation. The suggested novel algorithm, called “cr-MREPT”, is based on the solution of this equation, and in contrast to previously proposed algorithms, it is applicable in practice not only for regions where electrical properties are relatively constant but also for regions where they vary. The convection-reaction equation is solved using a triangular mesh based finite difference method and also finite element method (FEM). The convective field of the convection-reaction equation depends on the spatial derivatives of the B + 1 field. In the regions where the magnitude of convective field is low, a spot-like artifact is observed in the reconstructed conductivity and dielectric permittivity images. For eliminating this artifact, two different methods are developed, namely “constrained cr-MREPT” and “double-excitation cr-MREPT”. In the constrained cr-MREPT method, in the region where the magnitude of convective field is low, the electrical properties are reconstructed by neglecting the convective term in the equation. The obtained solution is used as a constraint for solving electrical properties in the whole domain. In the double-excitation cr-MREPT method, two B1 excitations, which create two convective field distributions having low magnitude of convective field in different locations, are applied separately. The electrical properties are then reconstructed simultaneously using data from these two applied B + 1 field. These methods are tested with both simulation and experimental data from phantoms. As seen from results, successful electrical property reconstructions are obtained in all regions including electrical property transition region. The performance of cr-MREPT method against noise is also investigated.en_US
dc.description.statementofresponsibilityHafalır, Fatih Süleymanen_US
dc.format.extentxiv, 59 leaves, illustrations, graphsen_US
dc.language.isoEnglishen_US
dc.rightsinfo:eu-repo/semantics/openAccessen_US
dc.subjectB1 mappingen_US
dc.subjectconductivity imagingen_US
dc.subjectconvection-reaction equationen_US
dc.subjectMagnetic Resonance Electrical Properties Tomographyen_US
dc.subjectMREPTen_US
dc.subjectMREITen_US
dc.subjectpermittivity imagingen_US
dc.subjectquantitative MRIen_US
dc.subjecttriangular meshen_US
dc.subjectFEMen_US
dc.subject.lccWN185 .H33 2013en_US
dc.subject.lcshMagnetic resonance imaging--Methods.en_US
dc.titleConvection-reaction equation based magnetic resonance electrical properties tomography (cr-MREPT)en_US
dc.typeThesisen_US
dc.departmentDepartment of Electrical and Electronics Engineeringen_US
dc.publisherBilkent Universityen_US
dc.description.degreeM.S.en_US


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