title: Three-dimensional ultrasound volume calculations of human embryos and young fetuses: a study on the volumetry of compound structures and its reproducibility.
abstract: OBJECTIVE
  To evaluate volumetry with three-dimensional (3D) ultrasonography in the assessment of the size of human embryos and fetuses.
  
  
  METHODS
  Forty-four healthy embryos/fetuses with crown-rump length (CRL) ranging from 9 mm to 58 mm were studied using a 7.5-MHz annular array transvaginal 3D probe. EchoPAC 3D software was used to calculate the volumes of the head, body and limbs in the same data set by two observers working independently of each other. Regression analysis was used to assess the relationship between estimated volumes and CRL.
  
  
  RESULTS
  The embryonic and fetal volume estimates of both observers ranged from a mean of 93 mm3 at 10 mm CRL to a mean of 11 169 mm3 at 55 mm CRL. The volume of the limbs as a proportion of the mean whole-body volume increased from 4.7% at a CRL of 15 mm to 9.3% at a CRL of 55 mm. Limits of agreement between the observers were calculated to be -0.12 +/- 9.2%.
  
  
  CONCLUSIONS
  It is possible to reconstruct complex small anatomic structures and calculate the volumes of human embryos and fetuses in vivo by using dedicated 3D ultrasound equipment. The reproducibility of whole-body volume estimates seems to be high. The limbs represent a significant proportion of the size of the embryonic/fetal body.
authors.affiliation: National Center for Fetal Medicine, St Olav's Hospital, Trondheim University Hospital, Finland. harm-gerd.blaas@ntnu.no
authors.forename: H-G K
authors.initials: HG
authors.lastname: Blaas
authors.forename: P
authors.initials: P
authors.lastname: Taipale
authors.forename: H
authors.initials: H
authors.lastname: Torp
authors.forename: S H
authors.initials: SH
authors.lastname: Eik-Nes
mesh_terms: D000886:Anthropometry / Q000379:methods; D018568:Crown-Rump Length; D004622:Embryo, Mammalian / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D005121:Extremities / Q000000981:diagnostic imaging / Q000196:embryology; D005260:Female; D047109:Fetal Development; D005333:Fetus / Q000033:anatomy & histology*; D006257:Head / Q000000981:diagnostic imaging / Q000196:embryology; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods*; D015588:Observer Variation; D011247:Pregnancy; D012016:Reference Values; D015203:Reproducibility of Results; D016216:Ultrasonography, Prenatal / Q000379:methods*