A Fast and Reliable Eddy Current Measurement Method in Portable Low-Field MRI

Abstract Portable permanent low-field magnetic resonance imaging (MRI) is gaining increasing attention due to its low-cost, safer scanning, and broad range of applications, such as emergency. However, frequent relocation of portable systems may alter their eddy current performances, which can degrade image quality unless timely recalibration is performed. The conventional eddy current measurement method relies on image-phase analysis and typically requires several hours in low-field MRI due to low signal-to-noise ratios (SNRs). In this work, a fast eddy current measurement method using field probes, which consists of an array of six 1H probes, is presented. The acquisition time was reduced by a factor of 100, from 9 h to 5 min while successfully reducing residual eddy currents to within ±0.03% of the applied gradient amplitude over the whole measurement. To overcome the poor SNR, the probe size was increased by leveraging the reduced susceptibility effects in low fields. Measurement sequences were optimized to address challenges such as field inhomogeneity and residual magnetism effects in low fields. Gradient preemphasis parameters were adjusted according to the derived eddy current parameters. To evaluate correction efficiency, phantom and volunteer experiments were conducted by acquiring eddy current maps, fast-spin-echo, and diffusion-weighted echo-planar imaging (DWI-EPI) images. It was found that corrections obtained using the field probe method outperformed those obtained by the image-phase-based method within the same measurement iterations, providing a more stable reduction of eddy current-induced artifacts. These results demonstrate the potential of the proposed method as a reliable, timely solution for eddy current correction in portable permanent low-field MRI.

Recommended citation: Chen, S., Qiu, Y., Zhong, S., Lee, P. K., Chen, H., & Zhang, Z. (2026). "A Fast and Reliable Eddy Current Measurement Method in Portable Low-Field MRI." IEEE Transactions on Instrumentation and Measurement, 75. doi: 10.1109/TIM.2026.3657556
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