C108-09 Non-invasive Quantification of Ventilation Defects in Bronchopulmonary Dysplasia Using Phase-resolved Functional Lung (PREFUL) MRI: Validation Across 0.55 T and 1.5 T Field Strengths

Abstract Rationale Phase-Resolved Functional Lung (PREFUL) MRI 1 has been extensively investigated for non-invasive quantification of ventilation, including applications in premature infants with bronchopulmonary dysplasia (BPD) 2,3, a population for whom non-invasive lung function testing is unavailable. However, no standard exists for validating in-vivo regional functional measurements in this population. Cross-field-strength validation is a crucial step toward clinical translation yet has not been performed. This study aims to validate ventilation defect quantification using PREFUL MRI at 0.55 T in infants with BPD through direct, paired comparison with PREFUL at 1.5T. Methods Four premature infants with BPD (gestational age: 23-32 weeks; postmenstrual age: 40-44 weeks; weight: 2.5-5.3 kg) were scanned during natural sleep under an Institutional Review Board approved protocol. PREFUL MRI was performed at 1.5 T using a balanced steady-state free precession (bSSFP) sequence (flip angle = 50°, TE/TR = 0.8/1.7 ms, in-plane resolution = 1.5 mm, slice thickness = 10 mm, scan time = 1 min). Subjects were then transferred to an adjacent 0.55 T scanner for repeat PREFUL acquisition at the same slice location using a bSSFP sequence (flip angle = 90°, TE/TR = 1.3/2.6 ms, in-plane resolution = 2 mm, slice thickness = 10 mm, scan time = 1 min). Data from both field strengths were processed identically using a prototype software (MRI LUNG v2.3.0, Siemens Healthcare) to generate ventilation maps. Ventilation defect percentage (VDP) was defined as the ratio of ventilation-defect area to total lung area, with defects identified using a threshold of 0.4 × the 90th percentile of the ventilation distribution. Results Figure 1 shows two representative BPD cases, comparing anatomical images, normalized ventilation, and defect maps between 0.55 T and 1.5 T. In all cases, the location and extent of ventilation defects corresponded well between field strengths. The mean ± SD VDP was 19% ± 7% at 0.55 T and 15% ± 5% at 1.5 T (mean difference = 4%; range = 1%-11%). Conclusion PREFUL MRI at 0.55 T provided quantitative ventilation defect measurements that closely matched those obtained at 1.5 T in premature infants with BPD. The consistency in ventilation defect patterns and VDP values across field strengths demonstrates the robustness of PREFUL MRI for non-invasive functional lung assessment in infants with BPD. References 1 Voskrebenzev et al, MRM(2018) 2 Dyke et al, Pediatr. Radiol.(2023) 3 Zanette et al, JMRI(2022) This abstract is funded by: Keck School of Medicine of USC Dean’s Pilot Grant Program