title: High-resolution quantitative sodium imaging at 9.4 Tesla.
abstract: OBJECTIVE
  Investigation of the feasibility to perform high-resolution quantitative sodium imaging at 9.4 Tesla (T).
  
  
  METHODS
  A proton patch antenna was combined with a sodium birdcage coil to provide a proton signal without compromising the efficiency of the X-nucleus coil. Sodium density weighted images with a nominal resolution of 1 × 1 × 5 mm(3) were acquired within 30 min with an ultrashort echo time sequence. The methods used for signal calibration as well as for B0, B1, and off-resonance correction were verified on a phantom and five healthy volunteers.
  
  
  RESULTS
  An actual voxel volume of roughly 40 μL could be achieved at 9.4T, while maintaining an acceptable signal-to-noise ratio (8 for brain tissue and 35 for cerebrospinal fluid). The measured mean sodium concentrations for gray and white matter were 36 ± 2 and 31 ± 1 mmol/L of wet tissue, which are comparable to values previously reported in the literature.
  
  
  CONCLUSIONS
  The reduction of partial volume effects is essential for accurate measurement of the sodium concentration in the human brain. Ultrahigh field imaging is a viable tool to achieve this goal due to its increased sensitivity.
authors.affiliation: Department for Biomedical Magnetic Resonance, University of Tübingen, Tübingen, Germany.|High-Field MR Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany.
authors.forename: Christian C
authors.initials: CC
authors.lastname: Mirkes
authors.affiliation: High-Field MR Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany.
authors.forename: Jens
authors.initials: J
authors.lastname: Hoffmann
authors.affiliation: High-Field MR Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany.
authors.forename: G
authors.initials: G
authors.lastname: Shajan
authors.affiliation: High-Field MR Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany.
authors.forename: Rolf
authors.initials: R
authors.lastname: Pohmann
authors.affiliation: Department for Biomedical Magnetic Resonance, University of Tübingen, Tübingen, Germany.|High-Field MR Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany.
authors.forename: Klaus
authors.initials: K
authors.lastname: Scheffler
mesh_terms: D000328:Adult; D000465:Algorithms; D001921:Brain / Q000033:anatomy & histology / Q000378:metabolism*; D003198:Computer Simulation; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008959:Models, Neurological; D057054:Molecular Imaging / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012964:Sodium / Q000493:pharmacokinetics*; D014018:Tissue Distribution
chemical_list: D012964:Sodium
keywords: UTE imaging; sodium MRI; sodium quantification; traveling wave