Assessing pulmonary exacerbations (PEx) in people with cystic fibrosis (pwCF) with dynamic functional lung MRI

There are two types of functional methodology to assess ventilation with lung MRI:(i)observing ventilatory mechanics during the respiratory cycle as an indirect measure (α-mapping/Fourier decomposition);(ii)observing contrast gas distribution after inhalation; our group uses dynamic oxygen enhanced (OE-)MRI as a feasible alternative to hyperpolarised gas MRI. We hypothesized that OE-MRI would be more sensitive to detect PEx in pwCF than α-mapping. PwCF (n=14) performed spirometry, α-mapping & OE-MRI on the same day. PEx were pragmatically defined as a new course of anti-biotics/fungals to treat worsening symptoms of lung disease and/or unexpected drop in ppFEV1. α-mapping parameters: ventilation defect percentage (α-VDP). OE-MRI parameters: OE-VDP and ∆R₂* (ventilation signal). Data are median(range) and compared with Wilcoxon signed matched pairs. Baseline values: OE-VDP 22.6%(6.9-52.0%), ∆R₂* 0.062(0.03-0.10), α-VDP 9.7% (1.0-39.3%) and ppFEV1 88%(71-105%). PEx values were significantly worse for OE-VDP 32.3%(5.4-57.0%, P<0.001), ∆R₂* 0.05 (0.02-0.09, P<0.001) ppFEV1 85% (65-102%, P<0.05) but not for α-VDP 13.9%(1.1-36.4%, P>0.05). α-VDP was significantly lower than OE-VDP at both visits (P<0.05 and P<0.001 respectively). This sub-study suggests that OE-MRI and α-mapping measure different aspects of respiratory physiology. Assessing longitudinal disease status and detecting accute changes may require a combined approach. This ongoing project will assess repeatability, disease progression, responsiveness, and assess spatial heterogeneity. We aim ultimately to establish the utility of OE-MRI as a clinical and research outcome for the future. Funded by the CF Foundation.