Assessing the feasibility of hyperpolarized Xe multiple-breath washout MRI in pediatric cystic fibrosis.

Purpose: To assess the feasibility of hyperpolarized Xe multiple-breath washout MRI in pediatric cystic fibrosis (CF) participants with preserved lung function. Fractional ventilation (r), defined as the fractional gas replacement per breath, was mapped using 2 signal models: (1) constant T and (2) variable T as a function of the hyperpolarized gas washout.

Methods: A total of 17 pediatric participants were recruited (mean age 11.7 ± 2.8 years), including 7 children with clinically stable CF and 10 aged-matched healthy controls. Pulmonary function tests were performed, including spirometry, to measure the forced expiratory volume in 1 second and nitrogen multiple-breath washout to measure the lung clearance index. Hyperpolarized Xe MRI was performed during consecutive breaths of air following a single Xe inhalation, and fractional ventilation maps were calculated.

Results: The forced expiratory volume in 1 second was similar in both groups (P = .32), but there was a statistically significant difference in lung clearance index between healthy and CF participants (P = .001). With variable T modeling, CF participants had a mean r of 0.44 ± 0.08 and healthy participants had a mean r of 0.37 ± 0.12 (P = .20). With constant T modeling, CF participants had a mean r' of 0.48 ± 0.08, and healthy participants had a mean r' of 0.43 ± 0.12 (P = .32). Therefore, assuming a constant T leads to a relative bias in r of 15.1% ± 6.4% and 20.8% ± 7.4% for CF and healthy participants, respectively (P = .12).

Conclusion: This study demonstrates that hyperpolarized Xe multiple-breath washout imaging is feasible in pediatric participants with CF, and inclusion of variable T modeling reduces bias in the fractional ventilation measurements.