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

Abstract

Purpose To assess the feasibility of hyperpolarized 129Xe 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 T1 and (2) variable T1 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 129Xe MRI was performed during consecutive breaths of air following a single 129Xe 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 T1 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 T1 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 T1 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 129Xe multiple‐breath washout imaging is feasible in pediatric participants with CF, and inclusion of variable T1 modeling reduces bias in the fractional ventilation measurements.

Enabling Clinical Technologies for Hyperpolarized 129Xenon Magnetic Resonance Imaging and Spectroscopy

“…possible to measure fractional ventilation in this population. [127] In amore recent study,the size and extent of regional ventilation defects in pediatric CF were quantified by HP 129 Xe MRI and associated with the presence of specific structural abnormalities identified by ultrashort echo time (UTE) 1 HM RI:b ronchiectasis (a lung condition where the bronchial tubes are permanently damaged, widened, and thickened), bronchial wall thickening,m ucus plugs,a nd ground glass opacities. [128]…”

Enabling Clinical Technologies for Hyperpolarized 129Xenon Magnetic Resonance Imaging and Spectroscopy

“…O 2 saturation (SpO 2 ) changes in these young patients are consistent with the expected physiological effects of a short anoxic breath‐hold and known anesthetic properties of xenon. In addition to single‐breath HP 129 Xe MRI scans, multibreath washout protocols have been reported to be feasible in pediatric CF patients, making it possible to measure fractional ventilation in this population [127] . In a more recent study, the size and extent of regional ventilation defects in pediatric CF were quantified by HP 129 Xe MRI and associated with the presence of specific structural abnormalities identified by ultrashort echo time (UTE) 1 H MRI: bronchiectasis (a lung condition where the bronchial tubes are permanently damaged, widened, and thickened), bronchial wall thickening, mucus plugs, and ground glass opacities [128] …”

“…Angewandte Chemie possible to measure fractional ventilation in this population. [127] In amore recent study,the size and extent of regional ventilation defects in pediatric CF were quantified by HP 129 Xe MRI and associated with the presence of specific structural abnormalities identified by ultrashort echo time (UTE) 1 HM RI:b ronchiectasis (a lung condition where the bronchial tubes are permanently damaged, widened, and thickened), bronchial wall thickening,m ucus plugs,a nd ground glass opacities. [128]…”

Novel imaging techniques for cystic fibrosis lung disease

“…Analogous to the multi‐breath washout pulmonary function test used to derive LCI, washout of 3 He or 129 Xe gas over multiple breaths is imaged using MRI, to provide a quantitative estimate of the “fractional ventilation,” the volume of gas‐turnover per breath. The MBW imaging approach is feasible in pediatric patients with CF, though the relationship between imaging‐derived gas‐turnover and LCI is not yet clear 104,105 …”