Pediatric <scp>¹²⁹Xe Gas‐Transfer MRI</scp>—Feasibility and Applicability

Abstract

Background 129 Xe gas‐transfer MRI provides regional measures of pulmonary gas exchange in adults and separates xenon in interstitial lung tissue/plasma (barrier) from xenon in red blood cells (RBCs). The technique has yet to be demonstrated in pediatric populations or conditions. Purpose/Hypothesis To perform an exploratory analysis of 129 Xe gas‐transfer MRI in children. Study Type Prospective. Population Seventy‐seven human volunteers (38 males, age = 17.7 ± 15.1 years, range 5–68 years, 16 healthy). Four pediatric disease cohorts. Field Strength/Sequence 3‐T, three‐dimensional‐radial one‐point Dixon Fast Field Echo (FFE) Ultrashort Echo Time (UTE). Assessment Breath hold compliance was assessed by quantitative signal‐to‐noise and dynamic metrics. Whole‐lung means and standard deviations were extracted from gas‐transfer maps. Gas‐transfer metrics were investigated with respect to age and lung disease. Clinical pulmonary function tests were retrospectively acquired for reference lung disease severity. Statistical Tests Wilcoxon rank‐sum tests to compare age and disease cohorts, Wilcoxon signed‐rank tests to compare pre‐ and post‐breath hold vitals, Pearson correlations between age and gas‐transfer metrics, and limits of normal with a binomial exact test to compare fraction of subjects with abnormal gas‐transfer. P ≤ 0.05 was considered significant. Results Eighty percentage of pediatric subjects successfully completed 129 Xe gas‐transfer MRI. Gas‐transfer parameters differed between healthy children and adults, including ventilation (0.75 and 0.67) and RBC:barrier ratio (0.31 and 0.46) which also correlated with age ( ρ = −0.76, 0.57, respectively). Bone marrow transplant subjects had impaired ventilation (90% of reference) and increased dissolved 129 Xe standard deviation (242%). Bronchopulmonary dysplasia subjects had decreased barrier‐uptake (69%). Cystic fibrosis subjects had impaired ventilation (91%) and increased RBC‐transfer (146%). Lastly, childhood interstitial lung disease subjects had increased ventilation heterogeneity (113%). Limits of normal provided detection of abnormalities in additional gas‐transfer parameters. Data Conclusion Pediatric 129 Xe gas‐transfer MRI was adequately successful and gas‐transfer metrics correlated with age. Exploratory analysis revealed abnormalities in a variety of pediatric obstructive and restrictive lung diseases. Level of Evidence 2 Technical Efficacy Stage 2

Topics & Concepts