Speaker
Description
Cylindrical arrays of permanent magnets are being increasingly used to generate the main magnetic field in low-field Magnetic Resonance Imaging (MRI). A class of Halbach arrays, these arrangements of permanent magnets result in increased magnetic flux density within the cylinder, and reduced flux density outside. Sparse Halbach arrays can produce a field strength suitable for low-field MRI, but suffer from field inhomogeneities introduced by approximating the continuous Halbach solution with a finite length bore of discrete magnets. At the dimensions required for practical medical imaging truncation-induced inhomogeneity is a dominant factor affecting image quality.
Correcting for truncation-induced inhomogeneity has typically been restricted to in-plane magnet orientation adjustments. Allowing magnets to be orientated with components down the bore of the cylinder is under-explored.
Here we present the results of computationally optimising magnet orientations to improve field homogeneity in comparison to the conventional Halbach design. Allowing magnets free parameterised orientation enables a computed improvement to field homogeneity of up to 90% at the expense of a loss in field strength of 17%.
A physical demonstration device consisting of 187 cubic N42 magnets was constructed using the optimised design, showing improvements to homogeneity of 73%, providing a benchmark for realistic expectations of field homogeneity when physical limitations such as precision magnet placement and magnet variability are taken into account.
The results show that substantial improvements to field homogeneity can be expected in sparse Halbach arrays when optimised magnet orientations are used, providing a physical realisation of methods to construct such arrays.
| Apply for student award at which level: | MSc |
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| Consent on use of personal information: Abstract Submission | Yes, I ACCEPT |