title: Reproducibility of Frankfort horizontal plane on 3D multi-planar reconstructed MR images.
abstract: OBJECTIVE
  The purpose of this study was to determine the accuracy and reliability of Frankfort horizontal plane identification using displays of multi-planar reconstructed MRI images, and propose it as a sufficiently stable and standardized reference plane for craniofacial structures.
  
  
  METHODS
  MRI images of 43 subjects were obtained from the longitudinal population based cohort study SHIP-2 using a T1-weighted 3D sequence. Five examiners independently identified the three landmarks that form FH plane. Intra-examiner reproducibility and inter-examiner reliability, correlation coefficients (ICC), coefficient of variability and Bland-Altman plots were obtained for all landmarks coordinates to assess reproducibility. Intra-examiner reproducibility and inter-examiner reliability in terms of location and plane angulation were also assessed.
  
  
  RESULTS
  Intra- and inter-examiner reliabilities for X, Y and Z coordinates of all three landmarks were excellent with ICC values ranging from 0.914 to 0.998. Differences among examiners were more in X and Z than in Y dimensions. The Bland-Altman analysis demonstrated excellent intra- as well as inter-examiner agreement between examiners in all coordinates for all landmarks. Intra-examiner reproducibility and inter-examiner reliability of the three landmarks in terms of distance showed mean differences between 1.3 to 2.9 mm, Mean differences in plane angulation were between 1.0° to 1.5° among examiners.
  
  
  CONCLUSIONS
  This study revealed excellent intra-examiner reproducibility and inter-examiner reliability of Frankfort Horizontal plane through 3D landmark identification in MRI. Sufficiently stable landmark-based reference plane could be used for different treatments and studies.
authors.affiliation: Polyclinic of Prosthodontics and Biomaterials, Greifswald University, Greifswald, Germany. daboulamro@gmail.com
authors.forename: Amro
authors.initials: A
authors.lastname: Daboul
authors.forename: Christian
authors.initials: C
authors.lastname: Schwahn
authors.forename: Grit
authors.initials: G
authors.lastname: Schaffner
authors.forename: Silvia
authors.initials: S
authors.lastname: Soehnel
authors.forename: Stefanie
authors.initials: S
authors.lastname: Samietz
authors.forename: Ahmad
authors.initials: A
authors.lastname: Aljaghsi
authors.forename: Mohamad
authors.initials: M
authors.lastname: Habes
authors.forename: Mohammad
authors.initials: M
authors.lastname: Habes
authors.forename: Katrin
authors.initials: K
authors.lastname: Hegenscheid
authors.forename: Ralf
authors.initials: R
authors.lastname: Puls
authors.forename: Thomas
authors.initials: T
authors.lastname: Klinke
authors.forename: Reiner
authors.initials: R
authors.lastname: Biffar
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods* / Q000592:standards; D008279:Magnetic Resonance Imaging / Q000379:methods* / Q000592:standards; D008297:Male; D008875:Middle Aged; D012015:Reference Standards; D015203:Reproducibility of Results; D012886:Skull