An adjustable-length dipole using forced-current excitation for 7T MR

Jiaming Cui, Ivan E. Dimitrov, Sergey Cheshkov, Minyu Gu, Craig R. Malloy, Steven M. Wright

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


Ultrahigh field imaging of the body and the spine is challenging due to the large field-of-view (FOV) required. It is especially difficult for RF transmission due to its requirement on both the length and the depth of the B1 + field. One solution is to use a long dipole to provide continuous current distribution. The drawback is the natural falloff of the B1 field toward the ends of the dipole, therefore the B1 + per unit square root of maximum specific absorption rate B1 +/√SARmax) performance is particularly poor toward the end of the dipole. In this study, a segmented element design using forced-current excitation and a switching circuit is presented. The design provides long FOV when desired and allows flexible FOV switching and power distribution without additional power amplifiers. Different element types and arrangements were explored and a segmented dipole design was chosen as the best design. The segmented dipole was implemented and tested on the bench and with a phantom on a 7T whole body scanner. The switchable mode dipole enabled a large FOV in the long mode and improved B1 +/√SARmax efficiency in a smaller FOV in the short mode.

Original languageEnglish (US)
Article number8244292
Pages (from-to)2259-2266
Number of pages8
JournalIEEE Transactions on Biomedical Engineering
Issue number10
StatePublished - Oct 2018


  • 7T
  • High field MRI
  • SAR
  • body coil
  • dipole
  • forced-current excitation

ASJC Scopus subject areas

  • Biomedical Engineering


Dive into the research topics of 'An adjustable-length dipole using forced-current excitation for 7T MR'. Together they form a unique fingerprint.

Cite this