Magnetic Resonance Electrical Impedance Tomography For Human Head Conductivity Distribution Measurement

Accurate electrical impedance image is important in medical applications. Magnetic Resonance Electrical Impedance Tomography (MREIT) is a new, noninvasive conductivity imaging modality that integrates current density imaging (CDI) and traditional electrical impedance tomography (EIT). Both the accuracy and spatial resolution of MREIT are better than traditional EIT, and more and more scientists pay attention to the research of it. The two problems that limit the development of MREIT are: 1) Current MREIT algorithms reconstruct only two-dimensional (2D) subject conductivity distribution. 2) The rotation problem exists in magnetic resonance imaging (MRI) system. Aiming at these two problems, this thesis makes systematical research of MREIT. A 3D MREIT algorithm is firstly proposed. Then two original MREIT algorithms that reconstruct subject conductivity image without rotation are proposed and satisfactory simulation results are obtained. This thesis is organized as follows:In chapter 1, the research meaning is briefly introduced. Firstly, the medical application of electrical impedance image and the difficulty of traditional EIT were introduced briefly. Then the development and the research potential of MREIT were stated in detail. Finaly, the strcture of the thesis and the main purpose of the research were presented.In Charpter 2, the imaging theory of magnetic resonance imaging (MRI) system and current density imaging (CDI) technique were introduced, and then the development history of the forward problem, inverse problem and the difficulty of MREIT were stated.In charpt 3, a 3D MREIT algorithm was proposed and the forward problem, inverse problem and the uniqueness of the solution were discussed in detail. Computer simulations were conducted on a four-sphere head model to detect the availability of the proposed 3D MREIT algorithm and encouraging simulation results were obrained.In charpt 4, a novel MREIT algorithm, RBF-MREIT algorithm, was proposed. This new algorithm reconstrucs 3D subject conductivity using only one component magnetic flux density measurement, and therefore solves the rotation problem in MREIT effectively. A series of computer simulations were conducted on a three-sphere head model and a realistic-geometry head model, and the simulation results are encouraging.In charpt 5, another MREIT algorithm, RSM-MREIT algorithm was proposed to reconstruct 3D subject conductivity image without roation. Computer simulations were conducted on a three-sphere head model and a realistic-geometry head model. The promising simulation results demonstrated the feasibility of the proposed RSM-MREIT algorithm.Charpt 6 is the conclusion and suggestions for fouture research. The research content and original point of the present research was concluded. Accorting to the defects of the presented research, future research directions were stated.