A two-center analysis of hyperpolarized 129Xe lung MRI in stable pediatric cystic fibrosis: Potential as a biomarker for multi-site trials.

BACKGROUND:The ventilation defect percent (VDP), measured from hyperpolarized (HP) 129Xe magnetic resonance imaging (MRI), is sensitive to functional changes in cystic fibrosis (CF) lung disease. The purpose of this study was to measure and compare VDP from HP 129Xe MRI acquired at two institutions in stable pediatric CF subjects with preserved lung function. METHODS:This retrospective analysis included 26 participants from two institutions (18 CF, 8 healthy, age range 10-17). Pulmonary function tests, N2 multiple breath washout (to measure lung clearance index, LCI), and HP 129Xe MRI were performed. VDP measurements were compared between two trained analysts using mean-anchored linear binning. Correlations were investigated for VDP compared to the forced expiratory volume in one second (FEV1) and LCI. RESULTS:VDP measurements agreed for the two analysts with an intraclass correlation coefficient of 0.99. In the combined dataset, VDP measured by Analyst 1 was 5.96 ± 1.82% and 15.96 ± 6.76% for the healthy and CF groups, respectively (p = .0004). Analyst 2 showed similar differences between healthy and CF (p = .0003). VDP measured by either analyst was shown to correlate with FEV1 (R2 = 0.33, p = .003; and R2 = 0.26, p = .009 for Analysts 1 and 2, respectively) and LCI (R2 = 0.76, p < .0001; and R2 = 0.77, p < .0001 for Analysts 1 and 2, respectively). CONCLUSION:HP 129Xe MRI provides a robust measurement of ventilation heterogeneity in stable pediatric CF subjects at two sites. Since measurements performed at two sites yielded similar VDP values with near-identical values between different analysts, implementation of the technique in multi-center trials in CF appears feasible.