Abstract
Objective: To evaluate deformable slice-to-volume registration (DSVR) to calculate 3D-segmented total lung volume (TLV) in fetuses with congenital diaphragmatic hernia, congenital lung lesions and healthy controls, with comparison to 2D-manual segmentation. To establish normogram of TLV calculated by DSVR in health control fetuses.
Design: Pilot study
Setting: Single regional fetal medicine referral centre
Sample:Fetal MRIs performed for clinical indications (abnormal cases) or as research participants (healthy controls)
Methods: Sixteen MRI datasets of fetuses (22-32 weeks GA). Diagnosis: CDH(n=6, one with coexisting BPS), CPAM(n=2), and healthy controls(n=8). DSVR was used for reconstruction of 3D isotropic (0.85 mm) volumes of the fetal body followed by semi-automated lung segmentation. The resulting 3D TLV were compared to the traditional 2D-based volumetry, and abnormal cases referenced to a normogram produced from 100 normal fetuses whose TLV was calculated by DSVR.
Main Outcome Measures: Concordance with 2D-volumetry assessed with Bland-Altman analysis, results of segmentations presented visually. Observed/Expected values were calculated for abnormal cases based upon the normogram.
Results: DSVR-derived TLV values have high correlation with the 2D-based measurements but with a consistently lower volume; bias -1.44cm3 [95% limits: -2.6 to -0.3] with improved resolution able to exclude hilar structures even in severe motion corruption or in cases of very low lung volumes. lung hypoplasia.
Conclusions: Application of DSVR for fetal MRI is beneficial for the analysis of motion corrupted scans and does not suffer from the interpolation error inherent in currently applied 2D-segmentation as per current clinical practice. It increases information content of acquired data in terms of visualising organs in 3D space and quantification of volumes, which we believe will improve counselling and surgical planning.
Keywords: Fetal MRI; congenital diaphragmatic hernia; congenital lung lesion; congenital pulmonary airway malformation; bronchopulmonary sequestration; lung volume