The magnetisation geometric effect of a superconducting resonator on the inhomogeneity of magnetic resonance imaging

Résumé fourni par la source

Abstract High-temperature superconducting (HTS) resonators are gaining increasing attention for their application in magnetic resonance imaging (MRI) due to their superior performances. However, their diamagnetic behaviour can lead to artifacts in images when cooled in zero-field cooling, particularly when the HTS resonator is misaligned with a background magnetic field at an angle. To analyse the electromagnetic behaviour of a typical HTS resonator under the imperfect alignment condition, a numerical model has been developed by employing Maxwell’s equations in conjunction with the nonlinear E–J power law of a HTS film. Firstly, the consistency of the numerical results with the previously reported experimental observation was verified. Subsequently, by comparing the magnetisation behaviours under three different magnetic fields, it was elucidated that the image artifacts stem from a magnetisation geometric effect in the HTS resonator with a transverse geometry, characterised by a large width-to-thickness aspect ratio, and the geometric effect is found to be primarily attributed to a stray field which is beyond the predictions of the Bean model. The study also found that adjusting the width-to-thickness aspect ratio significantly impacts the distribution of penetrated magnetic flux density and screening current density of the HTS resonator, distorting the background magnetic field of a MRI scanner. Furthermore, the pronounced effect of creep behaviour on the resonator’s magnetisation behaviours was explored. Additionally, the developed model was used to predict the magnetisation effect and the consequent static field inhomogeneities generated by a superconducting resonator across various temperatures and magnetic fields, providing insights for designing novel resonators for high-field MRI and broadening their scope of application.

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