Intra‐ and Inter‐visit Repeatability of ¹²⁹Xenon Multiple‐Breath Washout MRI in Children With Stable Cystic Fibrosis Lung Disease

Abstract

Background Multiple‐breath washout (MBW) 129Xe MRI (MBW Xe‐MRI) is a promising technique for following pediatric cystic fibrosis (CF) lung disease progression. However, its repeatability in stable CF needs to be established to use it as an outcome measure for novel therapies. Purpose To assess intravisit and intervisit repeatability of MBW Xe‐MRI in healthy and CF children. Study Type Prospective, longitudinal cohort study. Subjects A total of 18 pediatric subjects (7 healthy, 11 CF). Field Strength/Sequence A 3 T/2D coronal hyperpolarized (HP) 129Xe images using GRE sequence. Assessment All subjects completed MBW Xe‐MRI, pulmonary function tests (PFTs) (spirometry, nitrogen [N2] MBW for lung clearance index [LCI]) and ventilation defect percent (VDP) at baseline (visit 1) and 1‐month after. Fractional ventilation (FV), coefficient of variation (CoVFV) maps were calculated from MBW Xe‐MRI data acquired between intervening air washout breaths performed after an initial xenon breath‐hold. Skewness of FV and CoVFV map distributions was also assessed. Statistical Tests Repeatability: intraclass correlation coefficients (ICC), within‐subject coefficient of variation (CV%), repeatability coefficient (CR). Agreement: Bland–Altman. For correlations between MBW Xe‐MRI, VDP and PFTs: Spearman's correlation. Significance threshold: P < 0.05. Results For FV, intravisit median [IQR] ICC was high in both healthy (0.94 [0.48, 0.99]) and CF (0.83 [0.04, 0.97]) subjects. CoVFV also had good intravisit ICC in healthy (0.92 [0.42, 0.99]) and CF (0.79 [0.02, 0.96]) subjects. Similarly, for FV, intervisit ICC was high in health (0.94 [0.68, 0.99]) and CF (0.89 [0.61, 0.97]). CoVFV also had good intervisit ICC in health (0.92 [0.42, 0.99]) and CF (0.78 [0.26, 0.94]). FV had better intervisit repeatability than VDP. CoVFV correlated significantly with LCI (R = 0.56). Skewness of FV distributions significantly distinguished between cohorts at baseline. Data Conclusion MBW Xe‐MRI had high intravisit and intervisit repeatability in healthy and stable CF subjects. CoVFV correlated with LCI, suggesting the importance of ventilation heterogeneity to early CF. Evidence Level 1. Technical Efficacy Stage 2.

Assessment of Pulmonary Ventilation Using 3D Ventilation Flow Capacity‐Weighted and Ventilation‐Weighted Maps From 3D Ultrashort Echo Time (UTE) MRI

“…Pulmonary MRI has been used to obtain structural and functional information about the lungs without the risks related to ionizing radiation as compared to CT or SPECT 10–27 . Several MRI methods have been proposed for pulmonary ventilation mapping using exogenous contrast agents, such as hyperpolarized gases ( 3 He and 129 Xe) 10–14 and oxygen, 15,16 or using endogenous contrasts based on changes in proton density or T 1 relaxation times.…”

“…[10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] Several MRI methods have been proposed for pulmonary ventilation mapping using exogenous contrast agents, such as hyperpolarized gases ( 3 He and 129 Xe) [10][11][12][13][14] and oxygen, 15,16 or using endogenous contrasts based on changes in proton density or T 1 relaxation times. Hyperpolarized gas MRI [10][11][12][13][14] provides direct ventilation mapping with high signal-to-noise ratio (SNR) and has high correlation with SPECT, but requires demanding and expensive equipment such as polarizers and dedicated RF coils. Oxygen-enhanced MRI is a cheaper alternative but has a relatively low SNR and requires longer scan times, while still also requiring an oxygen supply device.…”

“…9 Pulmonary MRI has been used to obtain structural and functional information about the lungs without the risks related to ionizing radiation as compared to CT or SPECT. [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] Several MRI methods have been proposed for pulmonary ventilation mapping using exogenous contrast agents, such as hyperpolarized gases ( 3 He and 129 Xe) [10][11][12][13][14] and oxygen, 15,16 or using endogenous contrasts based on changes in proton density or T 1 relaxation times. Hyperpolarized gas MRI [10][11][12][13][14] provides direct ventilation mapping with high signal-to-noise ratio (SNR) and has high correlation with SPECT, but requires demanding and expensive equipment such as polarizers and dedicated RF coils.…”

“…With regard to regional ventilation information, all of these methods provide 2D and/or 3D ventilation-weighted (VW) maps, but they do not provide ventilation flow-weighted (VFW) maps except that some of them additionally provide flow-volume loops for the region of interest [19][20][21] or fractional ventilation defined as the ratio of entering gas to end-expiratory [19][20][21] or end-inspiratory volume. 13 In this study, we proposed ventilation flow capacity, a ventilation flow-related metric defined as the difference between maximum and minimum ventilation flow, and aimed to use 3D ventilation flow capacity-weighted (VFCW) maps, and 3D ventilation-weighted (VW) maps obtained from 3D UTE images, for pulmonary ventilation evaluation. We further aimed to validate the 3D VFW maps by comparing two different breathing conditions [Correction added on 17 April 2024, after first online publication: the preceding sentence has been revised.…”

Editorial for “Intra‐ and Inter‐visit Repeatability of 129Xenon Multiple‐Breath Washout MRI in Children With Stable Cystic Fibrosis Lung Disease”

“…7 In this issue of JMRI, Alam investigated the still open but with respect to interpretation of longitudinal changes important question of intravisit and intervisit repeatability of the parameters FV and coefficient of variation of FV (CoV FV ) as a heterogeneity metric derived from multiple-breath washout hyperpolarized 129 Xe MRI in a well-performed study including pediatric CF and age-matched healthy subjects. 8 Care was taken to obtain accurate estimates of FV by accounting for time-varying polarization decay as a detrimental effect in hyperpolarized gas MRI using previously developed methods. Good repeatability of FV and CoV FV in terms of high intraclass correlation coefficients (ICC) above 0.75 was found for intravisit assessment in both healthy and diseased subjects.…”