title: High permittivity dielectric pads improve high spatial resolution magnetic resonance imaging of the inner ear at 7 T.
abstract: OBJECTIVE
  The objective of this study was to evaluate the use of dielectric pads for improving high spatial resolution imaging of the inner ear at 7 T.
  
  
  METHODS
  Two sets of dielectric pads were designed using electromagnetic simulations and implemented using a deuterated suspension of barium titanate. Their effect on transmit efficiency, contrast homogeneity, and diagnostic image quality was evaluated in vivo (N = 10). In addition, their effect on the specific absorption rate was evaluated numerically.
  
  
  RESULTS
  Statistically significant improvements (P < 0.001) in several measures of the image quality were obtained by using dielectric pads. The dielectric pads lead to an increase in the transmit efficiency and uniformity at the location of the inner ear, which is reflected in both an increased contrast homogeneity and an increased diagnostic value. Simulations show that the dielectric pads do not increase the peak local specific absorption rate.
  
  
  CONCLUSIONS
  Using geometrically tailored dielectric pads enables high spatial resolution magnetic resonance imaging of the human inner ear at 7 T. The high spatial resolution improves the depiction of the fine inner ear structures, showing the benefit of magnetic resonance imaging at ultrahigh fields.
authors.affiliation: From the *C.J. Gorter Center for High Field MRI, Department of Radiology, †Department of Otorhinolaryngology-Head and Neck Surgery, Leiden University Medical Center, Leiden, and ‡Department of Radiology, Leiden University Medical Center, Leiden and Radboud University Medical Center, Nijmegen, The Netherlands.
authors.forename: Wyger M
authors.initials: WM
authors.lastname: Brink
authors.forename: Annerie M A
authors.initials: AM
authors.lastname: van der Jagt
authors.forename: Maarten J
authors.initials: MJ
authors.lastname: Versluis
authors.forename: Berit M
authors.initials: BM
authors.lastname: Verbist
authors.forename: Andrew G
authors.initials: AG
authors.lastname: Webb
mesh_terms: D000328:Adult; D007758:Ear, Inner / Q000033:anatomy & histology*; D004867:Equipment Design; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000295:instrumentation* / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000295:instrumentation* / Q000379:methods; D008297:Male; D008954:Models, Biological; D015588:Observer Variation