Halbach Magnet Design for Low-Field MRI using Higher-Order Halbach Shimming and Layer-independent Segmentation.

Motivation: Existing low-field magnet designs are too heavy. They often have small usable imaging regions and inconvenient bore diameters. Goal(s): To design a compact, lightweight, and portable low-field magnet system with a large usable imaging region and a small length-to-bore aspect ratio. Approach: Our approach includes data-driven higher-order Halbach-based shim design. We also employed Mu-metal to enhance the shimming. We further improved the homogeneity by discretizing the multilayered Halbach into segments. We used COMSOL multiphysics for simulation. Results: In COMSOL-based magnetostatic simulation, we achieved a compact, lightweight magnet design with an imaging region spanning over half the magnet's bore. Impact: The improvement of the low-field MRI design with a lightweight and inexpensive magnet system with a potential benefit in resource-constrained and point-of-care settings.