title: MR imaging of the temporomandibular joint: comparison between acquisitions at 7.0 T using dielectric pads and 3.0 T.
abstract: OBJECTIVE
  To qualitatively and quantitatively compare MRI of the temporomandibular joint (TMJ) at 7.0 T using high-permittivity dielectric pads and 3.0 T using a clinical high-resolution protocol.
  
  
  METHODS
  Institutional review board-approved study with written informed consent. 12 asymptomatic volunteers were imaged at 7.0 and 3.0 T using 32-channel head coils. High-permittivity dielectric pads consisting of barium titanate in deuterated suspension were used for imaging at 7.0 T. Imaging protocol consisted of oblique sagittal proton density weighted turbo spin echo sequences. For quantitative analysis, pixelwise signal-to-noise ratio maps of the TMJ were calculated. For qualitative analysis, images were evaluated by two independent readers using 5-point Likert scales. Quantitative and qualitative results were compared using t-tests and Wilcoxon signed-rank tests, respectively.
  
  
  RESULTS
  TMJ imaging at 7.0 T using high-permittivity dielectric pads was feasible in all volunteers. Quantitative analysis showed similar signal-to-noise ratio for both field strengths (mean ± SD; 7.0 T, 13.02 ± 3.92; 3.0 T, 14.02 ± 3.41; two-sample t-tests, p = 0.188). At 7.0 T, qualitative analysis yielded better visibility of all anatomical subregions of the temporomandibular disc (anterior band, intermediate zone and posterior band) than 3.0 T (Wilcoxon signed-rank tests, p < 0.05, corrected for multiple comparisons).
  
  
  CONCLUSIONS
  MRI of the TMJ at 7.0 T using high-permittivity dielectric pads yields superior visibility of the temporomandibular disc compared with 3.0 T.
authors.affiliation: 1 Institute for Diagnostic and Interventional Radiology, Department of Radiology, University Hospital Zurich, University of Zurich, Zurich, Switzerland.
authors.forename: Felix P
authors.initials: FP
authors.lastname: Kuhn
authors.affiliation: 2 Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Zurich, Switzerland.
authors.forename: Georg
authors.initials: G
authors.lastname: Spinner
authors.affiliation: 3 Department of Diagnostic and Interventional Radiology, Ospedale Regionale di Lugano, Lugano, Switzerland.
authors.forename: Filippo
authors.initials: F
authors.lastname: Del Grande
authors.affiliation: 2 Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Zurich, Switzerland.
authors.forename: Michael
authors.initials: M
authors.lastname: Wyss
authors.affiliation: 4 Department of Neuroradiology, University Hospital Zurich, University of Zurich, Zurich, Switzerland.
authors.forename: Marco
authors.initials: M
authors.lastname: Piccirelli
authors.affiliation: 5 Center of Dental Medicine, University of Zurich, Zurich, Switzerland.
authors.forename: Stefan
authors.initials: S
authors.lastname: Erni
authors.affiliation: 1 Institute for Diagnostic and Interventional Radiology, Department of Radiology, University Hospital Zurich, University of Zurich, Zurich, Switzerland.
authors.forename: Pascal
authors.initials: P
authors.lastname: Pfister
authors.affiliation: 1 Institute for Diagnostic and Interventional Radiology, Department of Radiology, University Hospital Zurich, University of Zurich, Zurich, Switzerland.
authors.forename: Michael
authors.initials: M
authors.lastname: Ho
authors.affiliation: 1 Institute for Diagnostic and Interventional Radiology, Department of Radiology, University Hospital Zurich, University of Zurich, Zurich, Switzerland.
authors.forename: Bert-Ram
authors.initials: BR
authors.lastname: Sah
authors.affiliation: 1 Institute for Diagnostic and Interventional Radiology, Department of Radiology, University Hospital Zurich, University of Zurich, Zurich, Switzerland.
authors.forename: Lukas
authors.initials: L
authors.lastname: Filli
authors.affiliation: 5 Center of Dental Medicine, University of Zurich, Zurich, Switzerland.
authors.forename: Dominik A
authors.initials: DA
authors.lastname: Ettlin
authors.affiliation: 5 Center of Dental Medicine, University of Zurich, Zurich, Switzerland.
authors.forename: Luigi M
authors.initials: LM
authors.lastname: Gallo
authors.affiliation: 1 Institute for Diagnostic and Interventional Radiology, Department of Radiology, University Hospital Zurich, University of Zurich, Zurich, Switzerland.
authors.forename: Gustav
authors.initials: G
authors.lastname: Andreisek
authors.affiliation: 1 Institute for Diagnostic and Interventional Radiology, Department of Radiology, University Hospital Zurich, University of Zurich, Zurich, Switzerland.|2 Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Zurich, Switzerland.|6 Psychiatric University Hospital, Department of Psychiatry, Psychotherapy and Psychosomatics, University of Zurich, Zurich, Switzerland.
authors.forename: Andrei
authors.identifier: http://orcid.org/0000-0003-1230-5752
authors.initials: A
authors.lastname: Manoliu
mesh_terms: D000328:Adult; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D011446:Prospective Studies; D059629:Signal-To-Noise Ratio; D013704:Temporomandibular Joint / Q000000981:diagnostic imaging*
keywords: magnetic fields; magnetic resonance imaging; signal-to-noise ratio; temporomandibular joint; temporomandibular joint disc