title: High isotropic resolution magnetic resonance imaging of the mandibular canal at 1.5 T: a comparison of gradient and spin echo sequences.
abstract: OBJECTIVE
  The precision of localizing the mandibular canal prior to surgical intervention depends on the achievable resolution, whereas identification of the nerve depends on the image contrast. In our study, we developed new protocols based on gradient and spin echo sequences. The results from both sequences were quantitatively compared for their agreement to identify the most suitable approach.
  
  
  METHODS
  By limiting the field of view to one side of the mandible, three-dimensional acquisitions with T1weighted gradient and spin echo sequences were performed with 0.5 × 0.5 × 0.5 mm3resolution within 6.5 min covering the mandibular canal from the mandibular to the mental foramen. Aliasing artefacts were suppressed by different techniques. A manual segmentation of the mandibular canal from seven healthy volunteers was performed on this section by three different observers. The surface distance of the segmented volumes was computed between both sequences as well as between the different observers as a measure of equality.
  
  
  RESULTS
  The quantitative comparison of the segmentation resulted in an average surface distance of 0.26 ± 0.05 mm between both sequences and an interobserver difference of 0.26 ± 0.08 mm for gradient and 0.29 ± 0.07 mm for spin echo data. By repeated evaluation, a difference of 0.15 ± 0.02 mm for gradient and 0.18 ± 0.03 mm for spin echo data was observed, indicating a slightly higher variability for spin echo images.
  
  
  CONCLUSIONS
  Both sequences can be used to achieve high-resolution images with good contrast and can be used for precise localization of the mandibular canal. Despite a slightly increased difference for the spin echo data, the advantage of an easy and robust setup remains.
authors: 1 Research Center for Magnetic Resonance Bavaria, Würzburg, Germany.
authors: Jakob
authors: http://orcid.org/0000-0001-5421-1696
authors: J
authors: Kreutner
authors: 2 Department of Experimental Physics V, University of Würzburg, Würzburg, Germany.
authors: Andreas
authors: A
authors: Hopfgartner
authors: 1 Research Center for Magnetic Resonance Bavaria, Würzburg, Germany.|3 Department of Magnetic Resonance and X-Ray Imaging MRB, Fraunhofer Development Center X-Ray Technology EZRT, Fraunhofer Institute for Integrated Circuits IIS, Würzburg, Germany.
authors: Daniel
authors: D
authors: Weber
authors: 4 Department of Prosthodontics, Dental School, University of Würzburg, Würzburg, Germany.
authors: Julian
authors: J
authors: Boldt
authors: 4 Department of Prosthodontics, Dental School, University of Würzburg, Würzburg, Germany.
authors: Kurt
authors: K
authors: Rottner
authors: 4 Department of Prosthodontics, Dental School, University of Würzburg, Würzburg, Germany.
authors: Ernst
authors: E
authors: Richter
authors: 2 Department of Experimental Physics V, University of Würzburg, Würzburg, Germany.|3 Department of Magnetic Resonance and X-Ray Imaging MRB, Fraunhofer Development Center X-Ray Technology EZRT, Fraunhofer Institute for Integrated Circuits IIS, Würzburg, Germany.
authors: Peter Michael
authors: PM
authors: Jakob
authors: 1 Research Center for Magnetic Resonance Bavaria, Würzburg, Germany.|3 Department of Magnetic Resonance and X-Ray Imaging MRB, Fraunhofer Development Center X-Ray Technology EZRT, Fraunhofer Institute for Integrated Circuits IIS, Würzburg, Germany.
authors: Daniel
authors: D
authors: Haddad
mesh_terms: D015331:Cohort Studies; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods*; D008334:Mandible / Q000000981:diagnostic imaging*; D014070:Tooth / Q000000981:diagnostic imaging
keywords: MRI; mandibular nerve