Transient perturbation to permanent magnetic field by gradient pulses in MRI magnets

K. Sivasubramaniam, M. Xu, X. Huang, W. Barber, K. Amm, E. T. Laskaris, T. Havens, B. Xu, P. Jarvis

Research output: Contribution to journalArticlepeer-review


Open MRI magnets are generally designed with ferromagnetic poles to contain and shape the magnetic flux and to reduce conductor cost. Permanent magnet MR magnets have blocks of PM and bulk ferromagnetic materials on or close to the pole face. These electrically conducting regions are sources of eddy currents that affect the image quality because of their relatively long time constants and close proximity to the imaging volume. The impact on image quality can be minimized by appropriate segmentation and/or lamination of these components. Detailed eddy current diffusion models are necessary to quantify the field distortion and time constants of the resulting field to perform design studies. The three dimensional frequency or time domain models required to accurately predict effects of eddy currents due to gradient fields are not computationally economical. This paper describes modeling of a PM imaging system using simplified 2D models with appropriate assumptions to evaluate the impact of these eddy currents. Experimental validation of some of the results with a prototype magnet is provided.

Original languageEnglish (US)
Article number1643151
Pages (from-to)1550-1553
Number of pages4
JournalIEEE Transactions on Applied Superconductivity
Issue number2
StatePublished - Jun 2006
Externally publishedYes


  • Eddy current
  • Image quality
  • Mri magnet
  • Pm material

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Electrical and Electronic Engineering


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