The main goal was to develop a reproducible method for estimating the diffusion of water in human fetal lung tissue using diffusion-weighted imaging (DWI). A secondary objective was to determine the relationship of the apparent diffusion coefficients (ADCs) in the fetal lung to menstrual age and total lung volume.
Normal pregnant volunteers were scanned on a 1.5-Tesla (T) magnetic resonance imaging (MRI) system. The MRI system was equipped with 40-mT/m gradients (slew rate 200 T/m/s, rise time 0.2 ms). A six-channel body array coil was used for signal reception. Single-shot DWI utilized TE/TR 125/3400 ms, slice thickness 4 mm, field of view 280 mm × 280 mm, interslice gap 0.8 mm and a matrix of 128 × 128. The voxel size was 2.5 mm × 2.5 mm × 4.0 mm. Two b-values (0 and 1000) were chosen along three orthogonal directions. ADC maps were created using assigned b-values. Simple linear regression was performed with Pearson correlation coefficient. Interexaminer and intraexaminer bias, and 95% limits of agreement (LOA) were determined using Bland–Altman plots.
Forty-seven scans were performed at a mean ± SD of 29.2 ± 4.5 weeks. The median coefficient of variation for ADC was 5.6% (interquartile range, 4.0–8.1%). No differences in ADC values were found between right and left lungs. Normally distributed ADC measurements were not significantly correlated with either total lung volume (r2 = 0.0001, P = 0.94) or menstrual age (r2 = 0.003, P = 0.70). The mean ADC value was 1.75 (95% CI, 1.63–1.86). Mean ± SD intraexaminer bias was −0.15 ± 2.3 (95% LOA, −4.7 to + 4.4) and interexaminer bias was 2.2 ± 3.5 (95% LOA, −4.7 to + 9.1).
Our findings suggest that ADC measurements of the fetal lung are reproducible between blinded examiners and are independent of menstrual age, as well as lung volume. Copyright © 2009 ISUOG. Published by John Wiley & Sons, Ltd.