title: A pictorial essay on fetal rabbit anatomy using micro-ultrasound and magnetic resonance imaging.
abstract: BACKGROUND
  With this pictorial essay, we aimed to provide gestational age specific reference ranges of relevant fetal structures using micro-ultrasound, as well as its correlation with postmortem MRI and whole body sections.
  
  
  METHODS
  Time-mated pregnant rabbits (n = 24) were assessed once at various gestational ages in the second half of pregnancy (15, 17, 21 to 23, 25 to 28, and 30 to 31 days; term = 31 days). We obtained biometric data, together with Doppler flow patterns in the ductus venosus, umbilical artery and umbilical vein. After euthanasia, micro-ultrasound images were compared with images obtained by 9.4 Tesla MRI and whole body paraffin sections at 15, 23, 26, and 28 days.
  
  
  RESULTS
  We constructed biometric normative curves, which showed a significant correlation with gestational age. The pulsatility index (PI) in the umbilical artery decreased with gestation (PI = 5.746-0.2969(GA) + 0.004931(GA)(2) ; R(2)  = 0.30), whereas pulsatility index for veins (PIV) in the ductus venosus remained constant (median PIV = 0.82 (0.60-1.12)). In this report, we provide an anatomical atlas of fetal thoracic development using both micro-ultrasound and MRI.
  
  
  CONCLUSIONS
  We describe anatomical fetal leporine development as can be visualized by micro-ultrasound and MR imaging. The reported reference ranges may be useful for researchers using the fetal rabbit model.
authors.affiliation: Organ systems cluster, Department of Development and Regeneration, KU Leuven, Leuven, Belgium; Center for Surgical Technologies, KU Leuven, Leuven, Belgium.
authors.forename: Philip
authors.initials: P
authors.lastname: DeKoninck
authors.forename: Masayuki
authors.initials: M
authors.lastname: Endo
authors.forename: Inga
authors.initials: I
authors.lastname: Sandaite
authors.forename: Jute
authors.initials: J
authors.lastname: Richter
authors.forename: Luc
authors.initials: L
authors.lastname: De Catte
authors.forename: Ben
authors.initials: B
authors.lastname: Van Calster
authors.forename: Jaan
authors.initials: J
authors.lastname: Toelen
authors.forename: Uwe
authors.initials: U
authors.lastname: Himmelreich
authors.forename: Filip
authors.initials: F
authors.lastname: Claus
authors.forename: Jan
authors.initials: J
authors.lastname: Deprest
mesh_terms: D000818:Animals; D001699:Biometry / Q000379:methods; D005260:Female; D047109:Fetal Development; D005333:Fetus / Q000098:blood supply; D005865:Gestational Age; D008279:Magnetic Resonance Imaging / Q000662:veterinary*; D023421:Models, Animal; D011247:Pregnancy; D011817:Rabbits / Q000196:embryology*; D012016:Reference Values; D016216:Ultrasonography, Prenatal / Q000662:veterinary*; D014469:Umbilical Arteries / Q000000981:diagnostic imaging; D014471:Umbilical Veins / Q000000981:diagnostic imaging