The coax monopole antenna: A flexible end-fed antenna for ultrahigh field transmit/receive arrays

Lyanne M.I. Budé, Bart R. Steensma, Irena Zivkovic, Alexander J.E. Raaijmakers (Corresponding author)

Research output: Contribution to journalArticleAcademicpeer-review

1 Citation (Scopus)
49 Downloads (Pure)

Abstract

PURPOSE: The coax monopole antenna is presented for body imaging at 7 T. The antenna is fed at one end, eliminating the possibility of cable-coil coupling and simplifying cable routing. Additionally, its flexibility improves loading to the subject.

METHODS: Like the coax dipole antenna, an interruption in the shield of the coaxial cable allows the current to extend to the outside of the shield, generating a B1 + field. Matching is achieved using a single inductor at the distal side, and a cable trap enforces the desired antenna length. Finite difference time domain simulations are employed to optimize the design parameters. Phantom measurements are conducted to determine the antenna's B1 + efficiency and to find the S-parameters in straight and bent positions. Eight-channel simulations and measurements are performed for prostate imaging.

RESULTS: The optimal configuration is a length of 360 mm with a gap position of 40 mm. Simulation data show higher B1 + levels for the coax monopole (20% in the prostate), albeit with a 5% lower specific absorbance rate efficiency, compared to the fractionated dipole antenna. The S11 of the coax monopole exhibits remarkable robustness to loading changes. In vivo prostate imaging demonstrates B1 + levels of 10-14 μT with an input power of 8 × 800 W, which is comparable to the fractionated dipole antenna. High-quality images and acceptable coupling levels were achieved.

CONCLUSION: The coax monopole is a novel, flexible antenna for body imaging at 7 T. Its simple design incorporates a single inductor at the distal side to achieve matching, and one-sided feeding greatly simplifies cable routing.

Original languageEnglish
Pages (from-to)361-373
Number of pages13
JournalMagnetic Resonance in Medicine
Volume92
Issue number1
Early online date20 Feb 2024
DOIs
Publication statusPublished - Jul 2024

Keywords

  • Engineering
  • RF coil arrays
  • ultrahigh field MRI
  • Prostate/diagnostic imaging
  • Computer Simulation
  • Humans
  • Image Processing, Computer-Assisted/methods
  • Magnetic Resonance Imaging/instrumentation
  • Male
  • Phantoms, Imaging
  • Equipment Design

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