Data
Each fetus was scanned using T2-weighted ssTSE sequence, producing
between 6 and 10 stacks in different planes, with varying degrees of
motion corruption. In all cases, images were acquired on an Ingenia 1.5
Tesla (Philips) system using T2w ssTSE: TR=15000ms, TE=80ms, voxel size
1.25x1.25mm, slice thickness 2.5mm and spacing 1.25mm. For the initial
16 study cases, 2D slice-wise segmentation of the fetal lungs was
performed in ITK-SNAP (http://www.itksnap.org) in the axial stack with
respect to the fetal trunk and a total fetal lung volume was calculated
using the conventional interpolation approach. These datasets also
underwent DSVR reconstruction to 0.85x0.85x0.85mm resolution using SVRTK
toolbox (https://github.com/SVRTK/SVRTK) and lung volumes were
calculated after automated 3D segmentation followed by manual refinement
in 3D Slicer (https://www.slicer.org). An example of one of the he
original 2D axial stacks affected by minor to moderate motion and the
corresponding 3D DSVR reconstruction are displayed side by side for
descriptive purposes in Figure 1 and Supplementary Video 1. The
processing of the additional 100 cases included reconstruction using the
standard DSVR pipeline 10 followed by semi-automated
lung segmentation.
Lung volumes from the 16 cases derived from 3D DSVR and the conventional
2D-based approach underwent pairwise Bland-Altmann comparison to assess
for bias in measurement. In cases of CLL, lesion volume was calculated
and is provided here in cm3 and as a proportion of
TLV. A normal curve (growth chart) for fetal lung volumes was generated
for 21-32 weeks GA range from 100 DSVR reconstructions , and this curve
was compared descriptively to the previously published MRI-generated
fetal lung volume normograms 11,12.