title: Three-dimensional ultrasound imaging and measurement of nasal bone length, prenasal thickness and frontomaxillary facial angle in normal second- and third-trimester fetuses.
abstract: OBJECTIVE
  To assess the feasibility of nasal bone length (NBL), prenasal thickness (PT) and frontomaxillary facial (FMF) angle measurements performed on the same three-dimensional (3D) multiplanar-corrected profile view in healthy second- and third-trimester fetuses, to create reference ranges and to review published measurement techniques.
  
  
  METHODS
  3D volumes of 219 healthy second- and third-trimester fetuses were retrospectively analyzed. The quality of images and measurability of the markers were assessed with 5-point and 3-point scoring systems, respectively. Measurements of NBL (with care to exclude the frontal bone), PT and FMF were obtained in the exact mid-sagittal plane. Reference ranges were constructed based on measurements from images with high-quality (4 or 5 points) and high measurability (2 or 3 points) scores and compared with those in the most relevant published literature.
  
  
  RESULTS
  A high-quality score was assigned to 111 images. Among these, a high measurability score was significantly more often achieved for NBL (98.2%) and PT (97.3%) than for the FMF angle (26.1%) (P < 0.001). Both NBL (NBL = - 6.927 + (0.83 × GA) - (0.01 × GA(2))) and PT (PT = (0.212 × GA) - 0.873) (where GA = gestational age) showed growth with gestation, with less pronounced growth for NBL after 28 weeks. Our reference range for the NBL showed a systematically smaller length than those in other two-dimensional (2D) ultrasound-based publications. The FMF angle measurements that we obtained did not show a significant change with GA.
  
  
  CONCLUSIONS
  NBL and PT are easily measured using 3D ultrasound whereas FMF angle measurement is more challenging. When it is measured in the exact mid-sagittal plane and care is taken to exclude the frontal bone, measurements of the NBL are systematically smaller than those in previous 2D ultrasound-based publications.
authors.affiliation: Fetal Medicine Unit, Academic Medical Centre, Amsterdam, The Netherlands. fedja8@yahoo.com
authors.forename: F I
authors.initials: FI
authors.lastname: Vos
authors.forename: E A P
authors.initials: EA
authors.lastname: De Jong-Pleij
authors.forename: L S M
authors.initials: LS
authors.lastname: Ribbert
authors.forename: E
authors.initials: E
authors.lastname: Tromp
authors.forename: C M
authors.initials: CM
authors.lastname: Bilardo
mesh_terms: D003430:Cross-Sectional Studies; D004314:Down Syndrome / Q000000981:diagnostic imaging* / Q000196:embryology; D005145:Face / Q000000981:diagnostic imaging* / Q000196:embryology / Q000502:physiology; D005240:Feasibility Studies; D005260:Female; D005865:Gestational Age; D006801:Humans; D021621:Imaging, Three-Dimensional; D009295:Nasal Bone / Q000000981:diagnostic imaging* / Q000196:embryology / Q000502:physiology; D015588:Observer Variation; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D011263:Pregnancy Trimester, Third; D012016:Reference Values; D016216:Ultrasonography, Prenatal / Q000379:methods