Intra<scp>‐</scp> and <scp>Inter‐visit</scp> Repeatability of <scp>¹²⁹Xenon Multiple‐Breath</scp> Washout <scp>MRI</scp> in Children With Stable Cystic Fibrosis Lung Disease

Abstract

Background Multiple‐breath washout (MBW) 129 Xe MRI (MBW Xe‐MRI) is a promising technique for following pediatric cystic fibrosis (CF) lung disease progression. However, its repeatability in stable CF needs to be established to use it as an outcome measure for novel therapies. Purpose To assess intravisit and intervisit repeatability of MBW Xe‐MRI in healthy and CF children. Study Type Prospective, longitudinal cohort study. Subjects A total of 18 pediatric subjects (7 healthy, 11 CF). Field Strength/Sequence A 3 T/2D coronal hyperpolarized (HP) 129 Xe images using GRE sequence. Assessment All subjects completed MBW Xe‐MRI, pulmonary function tests (PFTs) (spirometry, nitrogen [N 2 ] MBW for lung clearance index [LCI]) and ventilation defect percent (VDP) at baseline (visit 1) and 1‐month after. Fractional ventilation (FV), coefficient of variation (CoV FV ) maps were calculated from MBW Xe‐MRI data acquired between intervening air washout breaths performed after an initial xenon breath‐hold. Skewness of FV and CoV FV map distributions was also assessed. Statistical Tests Repeatability: intraclass correlation coefficients (ICC), within‐subject coefficient of variation (CV%), repeatability coefficient (CR). Agreement: Bland–Altman. For correlations between MBW Xe‐MRI, VDP and PFTs: Spearman's correlation. Significance threshold: P &lt; 0.05. Results For FV, intravisit median [IQR] ICC was high in both healthy (0.94 [0.48, 0.99]) and CF (0.83 [0.04, 0.97]) subjects. CoV FV also had good intravisit ICC in healthy (0.92 [0.42, 0.99]) and CF (0.79 [0.02, 0.96]) subjects. Similarly, for FV, intervisit ICC was high in health (0.94 [0.68, 0.99]) and CF (0.89 [0.61, 0.97]). CoV FV also had good intervisit ICC in health (0.92 [0.42, 0.99]) and CF (0.78 [0.26, 0.94]). FV had better intervisit repeatability than VDP. CoV FV correlated significantly with LCI ( R = 0.56). Skewness of FV distributions significantly distinguished between cohorts at baseline. Data Conclusion MBW Xe‐MRI had high intravisit and intervisit repeatability in healthy and stable CF subjects. CoV FV correlated with LCI, suggesting the importance of ventilation heterogeneity to early CF. Evidence Level 1. Technical Efficacy Stage 2.

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