Interventional loopless antenna at 7 T

Mehmet Arcan Ertürk, Abdel Monem M. El-Sharkawy, Paul A. Bottomley

Research output: Contribution to journalArticlepeer-review

18 Scopus citations


The loopless antenna magnetic resonance imaging detector is comprised of a tuned coaxial cable with an extended central conductor that can be fabricated at submillimeter diameters for interventional use in guidewires, catheters, or needles. Prior work up to 4.7 T suggests a near-quadratic gain in signal-to-noise ratio with field strength and safe operation at 3 T. Here, for the first time, the signal-to-noise ratio performance and radiofrequency safety of the loopless antenna are investigated both theoretically, using the electromagnetic method-of-moments, and experimentally in a standard 7 T human scanner. The results are compared with equivalent 3 T devices. An absolute signal-to-noise ratio gain of 5.7 ± 1.5-fold was realized at 7 T vs. 3 T: more than 20-fold higher than at 1.5 T. The effective field-of-view area also increased approximately 10-fold compared with 3 T. Testing in a saline gel phantom suggested that safe operation is possible with maximum local 1-g average specific absorption rates of <12 W kg-1 and temperature increases of <1.9°C, normalized to a 4 W kg-1 radiofrequency field exposure at 7 T. The antenna did not affect the power applied to the scanner's transmit coil. The signal-to-noise ratio gain enabled magnetic resonance imaging microscopy at 40-50 μm resolution in diseased human arterial specimens, offering the potential of high-resolution large-field-of-view or endoscopic magnetic resonance imaging for targeted intervention in focal disease.

Original languageEnglish (US)
Pages (from-to)980-988
Number of pages9
JournalMagnetic resonance in medicine
Issue number3
StatePublished - Sep 2012
Externally publishedYes


  • 7 T
  • MRI detectors
  • high resolution
  • interventional MRI
  • signal-to-noise ratio


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