Speaker
Description
Introduction: Magnetic Resonance Imaging (MRI) is a powerful diagnostic tool that provides detailed images of soft tissues, making it essential for a wide range of medical applications. However, conventional MRI systems rely on high-field (1.5 – 3.0 Tesla [1, 2]) superconducting magnets, resulting in high cost [3, 4], significant infrastructure requirements, and limited accessibility in many healthcare settings. Ultra-low-field (ULF) MRI systems operate below 0.1 Tesla [5, 6], and introduce an alternative approach, leveraging permanent magnet arrays and modern image-processing techniques to achieve clinically relevant imaging at a fraction of the cost. This research project focuses on the design, simulation, and evaluation of gradient coils optimized for a Halbach-based ULF MRI system. The magnetic field in a Halbach array is oriented perpendicular to the bore, requiring gradient coils that can operate effectively in this non-traditional geometry.
Methods: By integrating coil design methodologies such as the target field and stream function method [7, 8], and numerical simulations done within COMSOL Multiphysics, this project aims to identify the feasibility of a Halbach-based ultra-low-field system and enhance image quality and system performance by designing and developing physically realizable coil windings and custom geometries for x- and y-gradient coils. Simulation studies were conducted in COMSOL Multiphysics to evaluate magnetic field linearity and generate profiles of the x and y direction gradients.
Results: Gradient linearity was quantitatively assessed by comparing simulated magnetic field profiles using a percentage difference calculation over ideal linear gradients. Results showed gradient linearity values of 2.41% and 0.89% for the x- and y-gradient coil geometries, respectively, indicating strong encoding fidelity and minimal distortion over a 20-centimeter imaging region.
Discussion: We show an effective design for a ULF MRI. Further studies include expanded parameters in the simulations, such as differing wiring materials, time dependence, and thermal performance of the gradient coils.
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