title: Frontomaxillary facial angle measurement at 11-14 weeks: assessment of interobserver and intraobserver agreement in 2D and 3D imaging.
abstract: BACKGROUND
  The primary aim of this study was to assess the interobserver and intraobserver reproducibility of the first-trimester frontomaxillary facial angle (FMFA) measurement using both 2D and 3D ultrasound. Assessment of the relationship between crown-to-rump length (CRL) and FMFA measurement was also reviewed.
  
  
  METHODS
  Two experienced operators imaged the same 30 patients over a 1-month period collecting both 2D static images and 3D volumes during nuchal translucency assessment at 11-14 weeks' gestation. The operators were blinded to each other's images and results.
  
  
  RESULTS
  The mean 2D FMFA measurement was 88.0° and 88.4° for observer 1 and 2, respectively; while the mean 3D FMFA measurement was 87.8° and 88.0°, respectively. Intraclass correlation suggests good intraobserver and interobserver agreement with no statistically significant difference between operators in either 2D (p = 0.14) or 3D (p = 0.11) measurements. The FMFA was unchanged with increasing CRL.
  
  
  CONCLUSIONS
  Both 2D and 3D FMFA measurements have been demonstrated to be equivalent and reliable. Strict image acquisition criteria must be followed for accurate and reproducible FMFA measurements. There was no change demonstrated in FMFA measurement with increasing CRL.
authors.affiliation: The University of Sydney, Faculty Health Sciences, Lidcombe, NSW, Australia. jalphonse@sufw.com.au
authors.forename: Jennifer
authors.initials: J
authors.lastname: Alphonse
authors.forename: Jenny
authors.initials: J
authors.lastname: Cox
authors.forename: Jillian L
authors.initials: JL
authors.lastname: Clarke
authors.forename: Catherine L
authors.initials: CL
authors.lastname: Robinson
authors.forename: Philip J
authors.initials: PJ
authors.lastname: Schluter
authors.forename: Andrew
authors.initials: A
authors.lastname: McLennan
mesh_terms: D000782:Aneuploidy; D015331:Cohort Studies; D018568:Crown-Rump Length; D004314:Down Syndrome / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods; D048208:Nuchal Translucency Measurement; D015588:Observer Variation; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D011446:Prospective Studies; D015203:Reproducibility of Results; D016216:Ultrasonography, Prenatal / Q000379:methods*