Feasibility of free-breathing 0.55-T lung MRI for structural and functional characterization in preterm infants with bronchopulmonary dysplasia

Background Neonatal lung diseases such as bronchopulmonary dysplasia (BPD) are currently characterized by clinical observations alone, owing to the lack of safe, non-invasive diagnostic tools for lung structure and function assessment. Objective This study aims to investigate the feasibility of simultaneous structural and functional lung imaging in preterm infants with BPD using free-breathing 0.55-T MRI. Materials and methods Preterm infants diagnosed with BPD were recruited from the neonatal intensive care unit. A 3D balanced steady-state free precession sequence with half-radial dual-echo readout (bSTAR) was performed at 0.55 T with 1.3-mm isotropic resolution and 8-min scan time. Two pediatric radiologists independently evaluated image quality using Likert scales and scored structural images using the Ochiai system. Fractional ventilation maps were derived from the same acquisition, and two quantitative biomarkers were calculated: ventilation defect percentage (VDP) and ventilation inhomogeneity (VI). Biomarkers were compared across clinical subgroups defined by disease severity, respiratory support, and outcome at discharge. Inter-reader agreement for Ochiai scoring was assessed using weighted Cohen’s κ . Correlations between biomarkers and clinical variables were evaluated using Spearman correlation coefficients. Results Eleven BPD patients were recruited and all successfully underwent 0.55-T lung MRI (gestational age, 23–32 weeks; post-menstrual age at scan, 40–57 weeks; weight, 2.3–6.4 kg). Overall image quality was diagnostic in all cases regardless of respiratory support. bSTAR-based structural assessment using the Ochiai scoring system captured all BPD-associated imaging features and achieved substantial inter-reader agreement ( κ =0.80). The Ochiai score significantly associated with respiratory support at scan ( P =0.03), birth weight ( P =0.02), and duration of mechanical ventilation at discharge ( P =0.002). 3D fractional ventilation maps derived from the same acquisition enabled quantitative characterization of regional ventilation distribution and defect burden. Both VDP and VI were numerically higher in infants with severe BPD and in those remaining on mechanical ventilation at discharge, although these differences did not reach statistical significance. Conclusion Free-breathing 0.55-T MRI is feasible for radiation-free, simultaneous structural and functional lung imaging in preterm infants with BPD, with structural scores associating with respiratory support status and disease severity markers while ventilation maps added complementary regional function information. Larger studies across the full BPD spectrum are needed to determine whether combined structural-functional MRI improves diagnostic confidence over structural imaging alone.