title: Apparent diffusion coefficient measurements of the fetal brain during the third trimester of pregnancy: how reliable are they in clinical practice?
abstract: OBJECTIVE
  The objective of this study was to determine the reproducibility, the inter-hemispheric difference and the reference apparent diffusion coefficient (ADC) values of the fetal brain according to gestational age.
  
  
  METHODS
  One hundred and one normal fetal brain (29.4-38.4 weeks) were analysed with diffusion-weighted MR imaging. ADC was measured in frontal white matter (FWM), occipital white matter (OWM), centrum semi-ovale (CSO), basal ganglia (BG), cerebellar hemisphere (CBM) and pons. ADC ratios (fronto-occipital, fronto-cerebellar and occipito-cerebellar) were calculated. Inter-observer reproducibility was assessed on 27 studies, using intra-class correlation coefficient and Bland-Altman plot. Inter-hemispheric difference was evaluated with Bland-Altman plot. Gestation-specific reference intervals were estimated for each brain region.
  
  
  RESULTS
  Inter-observer bias was near zero. Limits of agreement (LOA) were clinically acceptable (-0.17; 0.20 to -0.38; 0.31 × 10(-3)  mm(2) /s) for all brain regions except for CSO and pons. Inter-hemispheric bias was near zero. Smallest LOA were for FWM (±0.09 mm(2) /s) and BG (±0.019 mm(2) /s). ADC values decreased, whereas ADC ratio increased with gestational age, reflecting normal maturation. Fronto-occipital, fronto-cerebellar and occipito-cerebellar ratios were consistently above 0.8, 1 and 1, respectively.
  
  
  CONCLUSIONS
  The fetal brain regions with the highest reproducibility and smallest inter-hemispheric differences are the frontal, occipital, cerebellar white matter and BG. ADC ratio could be useful to assess differential temporo-spatial maturation.
authors.affiliation: Service de Gynécologie-Obstétrique, Hôpital Robert Debré, AP-HP, Inserm UMR 676, Université Paris Diderot - Sorbonne Paris Cité, Paris, France.
authors.forename: Agnès
authors.initials: A
authors.lastname: Sartor
authors.forename: Owen
authors.initials: O
authors.lastname: Arthurs
authors.forename: Corinne
authors.initials: C
authors.lastname: Alberti
authors.forename: Nadia
authors.initials: N
authors.lastname: Belarbi
authors.forename: Bogdana
authors.initials: B
authors.lastname: Tilea
authors.forename: Priscilla
authors.initials: P
authors.lastname: Boizeau
authors.forename: Jean-Francois
authors.initials: JF
authors.lastname: Oury
authors.forename: Monique
authors.initials: M
authors.lastname: Elmaleh-Berges
authors.forename: Pierre
authors.initials: P
authors.lastname: Gressens
authors.forename: Guy
authors.initials: G
authors.lastname: Sebag
authors.forename: Marianne
authors.initials: M
authors.lastname: Alison
mesh_terms: D000328:Adult; D001479:Basal Ganglia / Q000473:pathology; D001921:Brain / Q000473:pathology*; D002531:Cerebellum / Q000473:pathology; D015331:Cohort Studies; D038524:Diffusion Magnetic Resonance Imaging; D005260:Female; D005333:Fetus / Q000473:pathology*; D005625:Frontal Lobe / Q000473:pathology; D006801:Humans; D008297:Male; D009413:Nerve Fibers, Myelinated / Q000473:pathology*; D009778:Occipital Lobe / Q000473:pathology; D011149:Pons / Q000473:pathology; D011247:Pregnancy; D011263:Pregnancy Trimester, Third; D015203:Reproducibility of Results; D012189:Retrospective Studies