Assessing the feasibility of hyperpolarized 129Xe multiple-breath washout MRI in pediatric cystic fibrosis

Purpose To assess the feasibility of hyperpolarized Xe-129 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-1 and (2) variable T-1 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-129 MRI was performed during consecutive breaths of air following a single Xe-129 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-1 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-1 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-1 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-129 multiple-breath washout imaging is feasible in pediatric participants with CF, and inclusion of variable T-1 modeling reduces bias in the fractional ventilation measurements.