Comparison of phase III slope analysis from MBW with hyperpolarised gas MRI in children with mild CF

Abstract

Introduction: Ventilation heterogeneity (VH) is an early finding in cystic fibrosis (CF) lung disease. S cond , derived from phase III slope analysis of multiple-breath washout (MBW), is believed to reflect convection-dependent VH. Hyperpolarised gas MRI (HP-MRI) is sensitive to regional VH & may help elucidate the mechanisms underlying S cond . Aim: To assess the relationship between S cond & VH indices from HP-MRI in children with mild CF & healthy controls (HC). Methods: 19 children with CF & 10 HC completed spirometry, supine MBW & HP-MRI. HP-MRI was quantified using coefficient of variance of lung signal intensity (CV) & unventilated defect volume (VD). Results: All subjects had FEV 1 z-score>-1.96. Compared to HC, CF subjects had significantly higher (p cond (0.054 vs 0.025), CV(13.5 vs 12.3%) & VD(2.3 vs 1.5%) though no significant difference in FEV 1 or S acin . There were strong correlations between S cond & both CV (r=0.75, p 1 did not correlate with VH parameters. Conclusion: In mild CF, VH from supine MBW & HP-MRI is raised in comparison to HC. S cond demonstrates a strong relationship with CV & VD and appears to be the MBW metric most closely associated with VH seen on MRI in early CF lung disease. These findings could help shed light on the contribution of regional lung VH to the S cond signal.