Utility of hyperpolarised xenon-129 magnetic resonance imaging in primary ciliary dyskinesia

Managing patients with primary ciliary dyskinesia (PCD) is challenging due to limited therapeutic options and lack of sensitive, disease-specific outcome measures. Hyperpolarised 129-xenon magnetic resonance imaging (Xe MRI) is an emerging imaging modality that quantifies ventilation heterogeneity using the ventilation defect per cent (VDP). In other obstructive lung diseases, VDP has demonstrated increased sensitivity compared to conventional lung function measures; however, its utility in PCD has not been established. In PCD, we aimed to: 1) determine the feasibility of Xe MRI; 2) evaluate the same-day repeatability of VDP; and 3) explore the relationship between VDP with lung clearance index 2.5% (LCI_2.5) and forced expiratory volume in 1 s z-score (FEV₁z).

In this cross-sectional observational study, participants >6 years old with confirmed PCD were recruited from two Canadian PCD centres. Participants underwent lung function testing to measure FEV₁z and LCI_2.5. Xe MRI was performed twice within 30-60 min to measure VDP. Intraclass correlation coefficient (ICC) and Bland-Altman plots (B&A) were used to assess same-day repeatability of VDP. Linear correlation between VDP with FEV₁z and LCI_2.5 evaluated their relationships.

16 participants completed the study. In all participants, the VDP was elevated (VDP>2.3) with a median VDP of 11.05% (IQR: 4.83-13.67%). Same-day repeat Xe MRI VDP had an ICC>0.95 and B&A showed good agreement. VDP positively correlated with LCI_2.5 (r=0.89, p<0.05) and negatively correlated with FEV₁z (r=0.6, p<0.05).

Xe MRI is a feasible imaging modality to capture lung disease in PCD. VDP has excellent same-day repeatability and correlated strongly with LCI_2.5. Moreover, VDP was more sensitive at detecting lung function impairments than LCI_2.5 and FEV₁z, demonstrating its potential as a sensitive outcome measure in PCD.