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Analysis of wave behavior in lossy dielectric samples at high field

  1. Qing X. Yang1,*,
  2. Jinghua Wang1,
  3. Xiaoliang Zhang2,
  4. Christopher M. Collins1,
  5. Michael B. Smith1,
  6. Haiying Liu2,
  7. Xiao-Hong Zhu2,
  8. J. Thomas Vaughan1,
  9. Kamil Ugurbil2,
  10. Wei Chen2

Article first published online: 23 APR 2002

DOI: 10.1002/mrm.10137

Issue

Magnetic Resonance in Medicine

Magnetic Resonance in Medicine

Volume 47, Issue 5, pages 982–989, May 2002

Additional Information

How to Cite

Yang, Q. X., Wang, J., Zhang, X., Collins, C. M., Smith, M. B., Liu, H., Zhu, X.-H., Vaughan, J. T., Ugurbil, K. and Chen, W. (2002), Analysis of wave behavior in lossy dielectric samples at high field. Magn. Reson. Med., 47: 982–989. doi: 10.1002/mrm.10137

Author Information

  1. 1

    Center for NMR Research, Department of Radiology, Pennsylvania State University College of Medicine, Hershey, Pennsylvania

  2. 2

    Center for MR Research, Department of Radiology, School of Medicine, University of Minnesota, Minneapolis, Minnesota

*Center for NMR Research, NMR/MRI Building, Department of Radiology H066, Pennsylvania State University College of Medicine, 500 University Drive, Hershey, PA 17033

Publication History

  1. Issue published online: 23 APR 2002
  2. Article first published online: 23 APR 2002
  3. Manuscript Revised: 3 JAN 2002
  4. Manuscript Accepted: 3 JAN 2002
  5. Manuscript Received: 18 APR 2001

Funded by

  • Whitaker Foundation. Grant Number: RG-99-0157
  • NIH. Grant Numbers: NS38070, NS39043, P41 RR08079
  • Keck Foundation
  • National Foundation for Functional Brain Imaging
  • U.S. Department of Energy

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Keywords:

  • calculations;
  • B1;
  • high field;
  • MRI;
  • radiofrequency

Abstract

Radiofrequency (RF) field wave behavior and associated nonuniform image intensity at high magnetic field strengths are examined experimentally and numerically. The RF field produced by a 10-cm-diameter surface coil at 300 MHz is evaluated in a 16-cm-diameter spherical phantom with variable salinity, and in the human head. Temporal progression of the RF field indicates that the standing wave and associated dielectric resonance occurring in a pure water phantom near 300 MHz is greatly dampened in the human head due to the strong decay of the electromagnetic wave. The characteristic image intensity distribution in the human head is the result of spatial phase distribution and amplitude modulation by the interference of the RF traveling waves determined by a given sample-coil configuration. The numerical calculation method is validated with experimental results. The general behavior of the RF field with respect to the average brain electrical properties in a frequency range of 42–350 MHz is also analyzed. Magn Reson Med 47:982–989, 2002. © 2002 Wiley-Liss, Inc.

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