title: Magnetic resonance imaging of third molars: developing a protocol suitable for forensic age estimation.
abstract: BACKGROUND
  Established dental age estimation methods in sub-adults study the development of third molar root apices on radiographs. In living individuals, however, avoiding ionising radiation is expedient. Studying dental development with magnetic resonance imaging complies with this requirement, adding the advantage of imaging in three dimensions.
  
  
  OBJECTIVE
  To elaborate the development of an MRI protocol to visualise all third molars for forensic age estimation, with particular attention to the development of the root apex.
  
  
  METHODS
  Ex vivo scans of porcine jaws and in vivo scans of 10 volunteers aged 17-25 years were performed to select adequate sequences. Studied parameters were T1 vs T2 weighting, ultrashort echo time (UTE), fat suppression, in plane resolution, slice thickness, 3D imaging, signal-to-noise ratio, and acquisition time. A bilateral four-channel flexible surface coil was used. Two observers evaluated the suitability of the images.
  
  
  RESULTS
  T2-weighted images were preferred to T1-weighted images. To clearly distinguish root apices in (almost) fully developed third molars an in plane resolution of 0.33 × 0.33 mm2was deemed necessary. Taking acquisition time limits into account, only a T2 FSE sequence with slice thickness of 2 mm generated images with sufficient resolution and contrast. UTE, thinner slice T2 FSE and T2 3D FSE sequences could not generate the desired resolution within 6.5 minutes.
  
  
  CONCLUSIONS
  Three Tesla MRI of the third molars is a feasible technique for forensic age estimation, in which a T2 FSE sequence can provide the desired in plane resolution within a clinically acceptable acquisition time.
authors.affiliation: a Department of Radiology and Nuclear Medicine , Ghent University , Gent , Belgium.
authors.forename: Jannick
authors.initials: J
authors.lastname: De Tobel
authors.affiliation: a Department of Radiology and Nuclear Medicine , Ghent University , Gent , Belgium.
authors.forename: Elke
authors.initials: E
authors.lastname: Hillewig
authors.affiliation: b Ghent Institute for Functional and Metabolic Imaging (GIFMI) , Gent , Belgium.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Bogaert
authors.affiliation: a Department of Radiology and Nuclear Medicine , Ghent University , Gent , Belgium.
authors.forename: Karel
authors.initials: K
authors.lastname: Deblaere
authors.affiliation: a Department of Radiology and Nuclear Medicine , Ghent University , Gent , Belgium.
authors.forename: Koenraad
authors.initials: K
authors.lastname: Verstraete
mesh_terms: D000293:Adolescent; D000328:Adult; D000366:Age Determination by Teeth / Q000379:methods*; D000818:Animals; D005260:Female; D006801:Humans; D007568:Jaw / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D008279:Magnetic Resonance Imaging; D008297:Male; D008964:Molar, Third / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D034421:Sus scrofa / Q000033:anatomy & histology*; D055815:Young Adult
keywords: Surface head coil; apical development; sub-adult