Design and application of combined 8-channel transmit and 10-channel receive arrays and radiofrequency shimming for 7-T shoulder magnetic resonance imaging

Invest Radiol. 2014 Jan;49(1):35-47. doi: 10.1097/RLI.0b013e3182a5662d.

Abstract

Objective: The objective of the study was to investigate the feasibility of 7-T shoulder magnetic resonance imaging by developing transmit and receive radiofrequency (RF) coil arrays and exploring RF shim methods.

Materials and methods: A mechanically flexible 8-channel transmit array and an anatomically conformable 10-channel receive array were designed and implemented. The transmit performance of various RF shim methods was assessed through local flip angle measurements in the right and left shoulders of 6 subjects. The receive performance was assessed through signal-to-noise ratio measurements using the developed 7-T coil and a baseline commercial 3-T coil.

Results: The 7-T transmit array driven with phase-coherent RF shim weights provided adequate B₁⁺ efficiency and uniformity for turbo spin echo shoulder imaging. B₁⁺ twisting that is characteristic of high-field loop coils necessitates distinct RF shim weights in the right and left shoulders. The 7-T receive array provided a 2-fold signal-to-noise ratio improvement over the 3-T array in the deep articular shoulder cartilage.

Conclusions: Shoulder imaging at 7-T is feasible with a custom transmit/receive array either in a single-channel transmit mode with a fixed RF shim or in a parallel transmit mode with a subject-specific RF shim.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Adult
  • Equipment Design
  • Equipment Failure Analysis
  • Female
  • Humans
  • Image Enhancement / instrumentation*
  • Image Interpretation, Computer-Assisted / instrumentation*
  • Magnetic Resonance Imaging / instrumentation*
  • Magnetics / instrumentation*
  • Male
  • Reproducibility of Results
  • Sensitivity and Specificity
  • Shoulder / anatomy & histology*
  • Signal Processing, Computer-Assisted / instrumentation*