Comparison of Functional Free-Breathing Pulmonary H and Hyperpolarized Xe Magnetic Resonance Imaging in Pediatric Cystic Fibrosis.

Rationale And Objectives: Phase resolved functional lung (PREFUL) magnetic resonance imaging (MRI) is a free-breathing H-based technique that produces maps of fractional ventilation (FV). This study compared ventilation defect percent (VDP) calculated using PREFUL to hyperpolarized (HP) Xe MRI and pulmonary function tests in pediatric cystic fibrosis (CF).

Materials And Methods: 27 pediatric participants were recruited (mean age 13.0 ± 2.7), including 6 with clinically stable CF, 11 CF patients undergoing a pulmonary exacerbation (PEx), and 10 healthy controls. Spirometry was performed to measure forced expiratory volume in 1 second (FEV), along with nitrogen multiple breath washout to measure lung clearance index (LCI). VDP was calculated from single central coronal slice PREFUL FV maps and the corresponding HP Xe slice.

Results: The stable CF group had a normal FEV (p = 0.41) and elevated LCI (p = 0.007). The CF PEx group had a decreased FEV (p < 0.0001) and elevated LCI (p < 0.0001). PREFUL and HP Xe VDP were significantly different between the CF PEx and healthy groups (p < 0.05). In the stable CF group, PREFUL and HP Xe VDP were not significantly different from the healthy group (p = 0.18 and 0.08, respectively). There was a correlation between PREFUL and HP Xe VDP (R = 0.31, p = 0.004), and both parameters were significantly correlated with FEV and LCI.

Conclusion: PREFUL MRI is feasible in pediatric CF, distinguishes patients undergoing pulmonary exacerbations compared to healthy subjects, and correlates with HP Xe MRI as well as functional measures of disease severity. PREFUL MRI does not require breath-holds and is straight forward to implement on any MRI scanner.