title: Fetal lung maturity assessment with MRI fetal lung-to-liver signal-intensity ratio.
abstract: OBJECTIVE
  The purpose of this study was to retrospectively determine whether the ratio of fetal lung-to-liver signal intensities at single-shot fast spin-echo MRI is associated with fetal gestational age.
  
  
  METHODS
  All fetal MRI examinations over a 4-year period were reviewed. All MRI examinations were performed with a 1.5-T magnet for indications other than lung maturity. Only examinations performed with a single-shot fast spin-echo sequence of the fetal chest and abdomen were included in the study. Images from a total of 82 fetal MRI examinations were evaluated. Gestational age ranged from 20 weeks to 39 weeks 3 days. Two board-certified subspecialty-trained radiologists with 11 and 17 years of experience blinded to estimated gestational age (EGA) reviewed the images independently. The regions of interest (ROIs) of the fetal lung and liver were drawn in the same plane and on the same image in each case. Fetal EGA was determined either by first-trimester ultrasound when available or by last menstrual period. Linear regression analysis was used to analyze the relation between the lung-to-liver signal-intensity ratio (LLSIR) in the ROIs and fetal EGA for both readers. The association between the LLSIRs estimated by the two readers was assessed by Bland-Altman plot.
  
  
  RESULTS
  Summary statistics for LLSIR showed a median value of 2.29 for reader 1 and 2.21 for reader 2. The mean value for reader 1 was 2.4 and for reader 2 was 2.5. The Pearson correlation coefficients between the LLSIR and EGA variables were 0.44 for reader 1 and 0.45 for reader 2. Linear regression analysis showed a statistically significant association between LLSIR and EGA for both readers (p < 0.0004). This ratio increased in a linear manner as EGA progressed.
  
  
  CONCLUSIONS
  Fetal LLSIR at single-shot fast spin-echo MRI is associated with fetal gestational age.
authors.affiliation: 1 Department of Radiology, University of Washington Medical Center, 1959 NE Pacific St, Box 357115, Seattle, WA 98195.
authors.forename: Mariam
authors.initials: M
authors.lastname: Moshiri
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Mannelli
authors.forename: Michael L
authors.initials: ML
authors.lastname: Richardson
authors.forename: Puneet
authors.initials: P
authors.lastname: Bhargava
authors.forename: Theodore J
authors.initials: TJ
authors.lastname: Dubinsky
mesh_terms: D000293:Adolescent; D000328:Adult; D005260:Female; D005325:Fetal Organ Maturity; D005865:Gestational Age; D006801:Humans; D008099:Liver / Q000196:embryology*; D008168:Lung / Q000196:embryology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D011247:Pregnancy; D012189:Retrospective Studies