Longitudinal monitoring of lung microstructure with HP gas diffusion-weighted MRI in mild cystic fibrosis children

Abstract

Introduction: Hyperpolarised (HP) gas MRI is sensitive to early lung ventilation heterogeneity in cystic fibrosis (CF) children. However, little is known if changes in lung microstructure accompany the disease progression. HP gas diffusion-weighted (DW) MRI has been shown to be a technique sensitive to changes in lung microstructure at the acinar level. Aims: Compare 3 He DW-MRI metrics of lung microstructure in children with mild CF and healthy controls (HC) at baseline, and to reassess the CF cohort after 2-years. Methods: 19 children with CF and normal spirometry (FEV 1 z-score> -2), and 10 HC were assessed with HP 3 He DW-MRI. 14 of the CF cohort were reassessed after 2-years. Apparent diffusion coefficient (ADC) and estimates of alveolar dimension (Lm D ) were calculated at each visit, and compared to previously reported ventilation defect percentage (VD%) values in the same cohort [Smith, L., et al. (2016). ERJ 48]. Results: No significant difference in mean ADC and Lm­ D ­ was observed between HC and CF children. In contrast, VD% was significantly larger (p D ; despite a significant increase in VD% (p=0.002) (Figure 1b). Conclusion: 3 He DW-MRI suggests that no acinar microstructural changes occur in the ventilated regions of early CF lung disease despite increases in ventilation heterogeneity.