Design of a radiative surface coil array element at 7 T: the single-side adapted dipole antenna

A.J.E. Raaijmakers, O. Ipek, D.W.J. Klomp, C. Possanzini, P.R. Harvey, J.J.W. Lagendijk, C.A.T. Van Den Berg

Research output: Contribution to journalArticleAcademicpeer-review

167 Citations (Scopus)

Abstract

Ultra high field MR imaging (≥7 T) of deeply located targets in the body is facing some radiofrequency-field related challenges: interference patterns, reduced penetration depth, and higher Specific Absorbtion Ratio (SAR) levels. These can be alleviated by redesigning the elements of the transmit or transceive array. This is because at these high excitation field (B 1) frequencies, conventional array element designs may have become suboptimal. In this work, an alternative design approach is presented, regarding coil array elements as antennas. Following this approach, the Poynting vector of the element should be oriented towards the imaging target region. The single-side adapted dipole antenna is a novel design that fulfills this requirement. The performance of this design as a transmit coil array element has been characterized by comparison with three other, more conventional designs using finite difference time domain (FDTD) simulations and B +1 measurements on a phantom. Results show that the B +1 level at the deeper regions is higher while maintaining relatively low SAR levels. Also, the B +1 field distribution is more symmetrical and more uniform, promising better image homogeneity. Eight radiative antennas have been combined into a belt-like surface array for prostate imaging. T 1-weighted (T1W) and T 2-weighted (T2W) volunteer images are presented along with B +1 measurements to demonstrate the improved efficiency.

Original languageEnglish
Pages (from-to)1488-1497
Number of pages10
JournalMagnetic Resonance in Medicine
Volume66
Issue number5
DOIs
Publication statusPublished - Nov 2011
Externally publishedYes

Keywords

  • body imaging
  • multitransmit
  • surface coil array
  • ultra high field MRI

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