Slice-to-Volume Registration of the Fetal Thorax to Assess Observed/Expected Total Fetal Lungs Volume in Fetuses with Congenital Diaphragmatic Hernia Who Underwent Fetoscopic Endoluminal Tracheal Occlusion

INTRODUCTION: The objectives of this study were to evaluate the feasibility of slice-to-volume registration (SVR) of the fetal thorax in congenital diaphragmatic hernia (CDH) and to compare observed-to-expected total fetal lung volume (O/E TFLV) obtained from original and SVR MRI volumes for prediction of postnatal survival. METHODS: We retrospectively analyzed 35 fetuses with CDH undergoing MRI before and after fetoscopic endoluminal tracheal occlusion (FETO). High-resolution, motion-corrected SVR volumes were reconstructed using an automated pipeline. O/E TFLV was measured on both original and SVR volumes, and results were compared between survivors and non-survivors at 6 months of age. Agreement, correlation, and predictive accuracy were assessed using Pearson correlation and ROC analysis. RESULTS: Four (11.4%) cases were excluded due to uncorrectable artifacts or technical issues. SVR reconstruction required only three acquisitions versus a median of six for conventional imaging. Post-processing took a median of 14 min, and lung delineation was longer for SVR than for original volumes. O/E TFLV measurements showed good to very good agreement between original and SVR volumes (r = 0.75 before and r = 0.96 after FETO), with comparable predictive accuracy for survival (AUC original = 0.81-0.83 vs. AUCSVR = 0.83, p > 0.7). CONCLUSION: SVR of the fetal thorax is feasible in CDH and provides reliable O/E TFLV measurements with prognostic accuracy comparable to conventional MRI, while reducing the need for repeated acquisitions.