The Interaction of electromagnetic waves with dielectric bodies and metals has been extensively studied because of its importance to problems including propagation through rain or snow, scattering by and detection of airborne particles, coupling to missiles with plasma plumes or dielectric-filled apertures, performance of communication antennas in the presence of dielectric and magnetic inhomogeneities, and medical diagnostics and power absortion in biological bodies. Computational electromagnetics methods (CEM) offer and indispensable tool for calculating the electromagnetic scattering from an internal field distribution of arbitrarily shaped, inhomogeneous, dielectric bodies. The aim of this thesis is the study and simulation of a RF coils system design by developing a novel parallel fast Method of Moments (MoM) modeling approach suitable for the simulation of dilectric bodies and metals. The parallel fast MoM implementation uses volume and surface basis functions with special properties appropriate for the representation of flux current densities for perfect electric conductors (PEC) and dielectrics. The results obtained with our modeling method were confirmed by comparisons with analytical solutions and other commercial software results, yielding very good agreement. The RF coil is employed in high field Magnetic Resonance Imaging (MRI) to obtain high quality brain images. Among all the clinical imaging techniques, MRI stands as a noninvasive technique that provides accurate, detailed anatomic images, which has had a major impact in the diagnosis of human deaseases. MRI is a widely use soft-tissue imaging modality that has envolved over the past several years into a powerful and versatile medical diagnostic tool capable of providing in-vivo diagnostic images of human anatomy. Current research areas in MRI system design are driven by the need to obtain detailed high resolution images with improved image signal-to-noise ratio (SNR) at a given magnetic field streght. One of the most critical factor that influences the quality and resolution of the MRI is the homogeneity of the RF field. To this end, this requirement demands the development of high performance MRI radio frequency (RF) coils and a standard procedure for enhancing the unifromity of the field directly at the modeling stage of the RF Coil. Even if our parallel fast MoM for the hybrid volume-surface integral equation solving has indeed several applications. In this dissertation, we use our MoM implementation to model and design a novel 16-channel transmit-only RF coil for human brain imaging in a clinical 7T system. A multi-chanel array concept was utilized for the new coil design, where the 16 conducting strips were arranged in a cilindrical conforming profile with the intention of improving homogeneity and magnetic field penetration for enhancing the sensitivity and SNR. Additionally, we introduces a realistic head brain model to simulate with the RF coil which can give more information about tissue-field interactions.

Massively Parallel Method of Moments for Fast and Reliable Electromagnetic Simulations for Dielectric Bodies and Metals / PEREZ CERQUERA, MANUEL RICARDO. - STAMPA. - (2013).

Massively Parallel Method of Moments for Fast and Reliable Electromagnetic Simulations for Dielectric Bodies and Metals

PEREZ CERQUERA, MANUEL RICARDO
2013

Abstract

The Interaction of electromagnetic waves with dielectric bodies and metals has been extensively studied because of its importance to problems including propagation through rain or snow, scattering by and detection of airborne particles, coupling to missiles with plasma plumes or dielectric-filled apertures, performance of communication antennas in the presence of dielectric and magnetic inhomogeneities, and medical diagnostics and power absortion in biological bodies. Computational electromagnetics methods (CEM) offer and indispensable tool for calculating the electromagnetic scattering from an internal field distribution of arbitrarily shaped, inhomogeneous, dielectric bodies. The aim of this thesis is the study and simulation of a RF coils system design by developing a novel parallel fast Method of Moments (MoM) modeling approach suitable for the simulation of dilectric bodies and metals. The parallel fast MoM implementation uses volume and surface basis functions with special properties appropriate for the representation of flux current densities for perfect electric conductors (PEC) and dielectrics. The results obtained with our modeling method were confirmed by comparisons with analytical solutions and other commercial software results, yielding very good agreement. The RF coil is employed in high field Magnetic Resonance Imaging (MRI) to obtain high quality brain images. Among all the clinical imaging techniques, MRI stands as a noninvasive technique that provides accurate, detailed anatomic images, which has had a major impact in the diagnosis of human deaseases. MRI is a widely use soft-tissue imaging modality that has envolved over the past several years into a powerful and versatile medical diagnostic tool capable of providing in-vivo diagnostic images of human anatomy. Current research areas in MRI system design are driven by the need to obtain detailed high resolution images with improved image signal-to-noise ratio (SNR) at a given magnetic field streght. One of the most critical factor that influences the quality and resolution of the MRI is the homogeneity of the RF field. To this end, this requirement demands the development of high performance MRI radio frequency (RF) coils and a standard procedure for enhancing the unifromity of the field directly at the modeling stage of the RF Coil. Even if our parallel fast MoM for the hybrid volume-surface integral equation solving has indeed several applications. In this dissertation, we use our MoM implementation to model and design a novel 16-channel transmit-only RF coil for human brain imaging in a clinical 7T system. A multi-chanel array concept was utilized for the new coil design, where the 16 conducting strips were arranged in a cilindrical conforming profile with the intention of improving homogeneity and magnetic field penetration for enhancing the sensitivity and SNR. Additionally, we introduces a realistic head brain model to simulate with the RF coil which can give more information about tissue-field interactions.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11583/2507374
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