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

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.

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.

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.

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.