The assessment of short- and long-term changes in lung function in cystic fibrosis using 129Xe MRI

Introduction Xenon-129 (129Xe) ventilation magnetic resonance imaging (MRI) is sensitive to detect early cystic fibrosis (CF) lung disease and response to treatment. 129Xe-MRI could play a significant role in clinical trials and patient management. Here we present data on the repeatability of imaging measurements and their sensitivity to longitudinal change. Methods 29 children and adults with CF and a range of disease severity were assessed twice, a median (interquartile range (IQR)) of 16.0 (14.4–19.5) months apart. Patients underwent 129Xe-MRI, lung clearance index (LCI), body plethysmography and spirometry at both visits. 11 patients repeated 129Xe-MRI in the same session to assess the within-visit repeatability. The ventilation defect percentage (VDP) was the primary metric calculated from 129Xe-MRI. Results At baseline, mean±sd age was 23.0±11.1 years and forced expiratory volume in 1 s (FEV1) z-score was −2.2±2.0. Median (IQR) VDP was 9.5 (3.4–31.6)% and LCI was 9.0 (7.7–13.7). Within- and inter-visit repeatability of VDP was high. At 16 months there was no single trend of 129Xe-MRI disease progression. Visible 129Xe-MRI ventilation changes were common, which reflected changes in VDP. Based on the within-visit repeatability, a significant short-term change in VDP is >±1.6%. For longer-term follow-up, changes in VDP of up to ±7.7% can be expected, or ±4.1% for patients with normal FEV1. No patient had a significant change in FEV1; however, 59% had change in VDP >±1.6%. In patients with normal FEV1, there were significant changes in ventilation and in VDP. Conclusions 129Xe-MRI is a highly effective method for assessing longitudinal lung disease in patients with CF. VDP has great potential as a sensitive clinical outcome measure of lung function and end-point for clinical trials.