A flexible nested sodium and proton coil array with wideband matching for knee cartilage MRI at 3T

Ryan Brown, Karthik Lakshmanan, Guillaume Madelin, Leeor Alon, Gregory Chang, Daniel K. Sodickson, Ravinder R. Regatte, Graham C. Wiggins

Research output: Contribution to journalArticlepeer-review


Purpose: We describe a 2 × 6 channel sodium/proton array for knee MRI at 3T. Multielement coil arrays are desirable because of well-known signal-to-noise ratio advantages over volume and single-element coils. However, low tissue–coil coupling that is characteristic of coils operating at low frequency can make the potential gains from a phased array difficult to realize. Methods: The issue of low tissue–coil coupling in the developed six-channel sodium receive array was addressed by implementing 1) a mechanically flexible former to minimize the coil-to-tissue distance and reduce the overall diameter of the array and 2) a wideband matching scheme that counteracts preamplifier noise degradation caused by coil coupling and a high-quality factor. The sodium array was complemented with a nested proton array to enable standard MRI. Results: The wideband matching scheme and tight-fitting mechanical design contributed to >30% central signal-to-noise ratio gain on the sodium module over a mononuclear sodium birdcage coil, and the performance of the proton module was sufficient for clinical imaging. Conclusion: We expect the strategies presented in this study to be generally relevant in high-density receive arrays, particularly in x-nuclei or small animal applications. Magn Reson Med 76:1325–1334, 2016.

Original languageEnglish (US)
Pages (from-to)1325-1334
Number of pages10
JournalMagnetic resonance in medicine
Issue number4
StatePublished - Oct 1 2016


  • coupling
  • dual-tuned
  • phased-array
  • preamplifier noise

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging


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