title: A double-quadrature radiofrequency coil design for proton-decoupled carbon-13 magnetic resonance spectroscopy in humans at 7T.
abstract: OBJECTIVE
  Carbon-13 magnetic resonance spectroscopy ((13) C-MRS) is challenging because of the inherent low sensitivity of (13) C detection and the need for radiofrequency transmission at the (1) H frequency while receiving the (13) C signal, the latter requiring electrical decoupling of the (13) C and (1) H radiofrequency channels. In this study, we added traps to the (13) C coil to construct a quadrature-(13) C/quadrature-(1) H surface coil, with sufficient isolation between channels to allow simultaneous operation at both frequencies without compromise in coil performance.
  
  
  METHODS
  Isolation between channels was evaluated on the bench by measuring all coupling parameters. The quadrature mode of the quadrature-(13) C coil was assessed using in vitro (23) Na gradient echo images. The signal-to-noise ratio (SNR) was measured on the glycogen and glucose resonances by (13) C-MRS in vitro, compared with that obtained with a linear-(13) C/quadrature-(1) H coil, and validated by (13) C-MRS in vivo in the human calf at 7T.
  
  
  RESULTS
  Isolation between channels was better than -30 dB. The (23) Na gradient echo images indicate a region where the field is strongly circularly polarized. The quadrature coil provided an SNR enhancement over a linear coil of 1.4, in vitro and in vivo.
  
  
  CONCLUSIONS
  It is feasible to construct a double-quadrature (13) C-(1) H surface coil for proton decoupled sensitivity enhanced (13) C-NMR spectroscopy in humans at 7T.
authors.affiliation: Laboratory of Functional and Metabolic Imaging LIFMET/EPFL, Lausanne, Switzerland.
authors.forename: Eulalia
authors.initials: E
authors.lastname: Serés Roig
authors.forename: Arthur W
authors.initials: AW
authors.lastname: Magill
authors.forename: Guillaume
authors.initials: G
authors.lastname: Donati
authors.forename: Martin
authors.initials: M
authors.lastname: Meyerspeer
authors.forename: Lijing
authors.initials: L
authors.lastname: Xin
authors.forename: Ozlem
authors.initials: O
authors.lastname: Ipek
authors.forename: Rolf
authors.initials: R
authors.lastname: Gruetter
mesh_terms: D000328:Adult; D002247:Carbon Isotopes / Q000032:analysis / Q000737:chemistry; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005240:Feasibility Studies; D006003:Glycogen / Q000032:analysis*; D006801:Humans; D008280:Magnetics / Q000295:instrumentation*; D008297:Male; D018482:Muscle, Skeletal / Q000737:chemistry*; D066244:Proton Magnetic Resonance Spectroscopy / Q000295:instrumentation*; D011522:Protons; D011846:Radio Waves; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014018:Tissue Distribution
chemical_list: D002247:Carbon Isotopes; D011522:Protons; D006003:Glycogen
keywords: 13C-MRS; RF coils; double-quadrature; glycogen; human calf; trap