RF head coil design with improved RF magnetic near-fields uniformity for magnetic resonance imaging (MRI) systems

Sung Min Sohn, Lance DelaBarre, Anand Gopinath, John Thomas Vaughan

Research output: Contribution to journalArticlepeer-review

34 Scopus citations


Higher magnetic field strength in magnetic resonance imaging (MRI) systems offers higher signal-to-noise ratio, contrast, and spatial resolution in magnetic resonance (MR) images. However, the wavelength in ultrahigh fields (7 T and beyond) becomes shorter than the human body at the Larmor frequency with increasing static magnetic field (B0) of the MRI system. At short wavelengths, an interference effect appears, resulting in nonuniformity of the RF magnetic near-field (B1) over the subject and MR images may have spatially anomalous contrast. The B1 near-field generated by the transverse electromagnetic RF coil's microstrip line element has a maximum near the center of its length and falls off towards both ends. In this study, a double trapezoidal-shaped microstrip transmission line element is proposed to obtain uniform B1 field distribution by gradual impedance variation. Two multi-channel RF head coils with uniform and trapezoidal shape elements were built and tested with a phantom at 7-T MRI scanner for comparison. The simulation and experimental results show stronger and more uniform B 1+ near-field with the trapezoidal shape.

Original languageEnglish (US)
Article number6846380
Pages (from-to)1784-1789
Number of pages6
JournalIEEE Transactions on Microwave Theory and Techniques
Issue number8
StatePublished - Aug 2014
Externally publishedYes


  • RF coil
  • magnetic resonance imaging (MRI)
  • transverse electromagnetic (TEM) resonator

ASJC Scopus subject areas

  • Radiation
  • Condensed Matter Physics
  • Electrical and Electronic Engineering


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