Title
Transverse 3D Electrical Properties Tomography
Author
An, Xin (TU Delft Electrical Engineering, Mathematics and Computer Science; TU Delft Circuits and Systems)
Contributor
Remis, Rob (mentor)
Degree granting institution
Delft University of Technology
Date
2019-08-27
Abstract
MR-based Electrical Properties Tomography (EPT) is a medical imaging modality to reconstruct the electrical conductivity and permittivity inside the human body based on the magnetic field data obtained from an MRI system. Currently, 2D CSI-EPT implementation is able to generate reliable reconstructions under special assumption of electromagnetic fields, while 3D implementation of CSI-EPT is able to achieve accurate reconstruction. However, much effort is needed to reduce computational cost for practical application in a MRI setting. Several experiments show that the radiofrequency(RF) fields on the midplane of an birdcage RF coil is E-polarized. In this study, we assume that RF field is E-polarised in the midplane of the RF birdcage coil and no other field assumptions are imposed. The electromagnetic fields relations governed by Maxwell’s equations in the birdcage RF coil are simplified by the negligible
transverse electric fields into two equations, referred to as midplane equations. In order to find the parameters that satisfy the midplane equations, an objective function is created by evaluating the difference between the measured and modeled data. A novel alternating-direction iterative method is proposed for minimizing the multivariate objective function where the electrical properties of biological tissues are retrieved in an iterative ’fix-one-optimize-for-the-other’ way. Within each iteration, a two-step procedure is conducted by updating electric field parameter and dielectric parameter in turn. Three different optimization algorithms are implemented for updating the electric field parameter. The magnetic fields data for numerical simulations are generated by placing a male head model or a longitudinal uniform head model inside
a simulated magnetic resonance scanner. The proposed methods are demonstrated by reconstructions from the simulated data, which are in good agreement with true electrical properties values.
Subject
Electrical Property Tomography
Optimization
Alternating Direction Method
To reference this document use:
http://resolver.tudelft.nl/uuid:87d1d976-a0ba-40d2-8fa4-437bd65c5b91
Embargo date
2024-08-27
Part of collection
Student theses
Document type
master thesis
Rights
© 2019 Xin An