Hyperpolarized 129Xe MRI in Pediatric Hematopoietic Stem Cell Transplant Recipients With and Without Bronchiolitis Obliterans Syndrome.

BACKGROUND: Bronchiolitis obliterans syndrome (BOS) is the most common non-infectious complication of allogenic hematopoietic stem cell transplantation (HSCT) and is associated with poor outcomes. Hyperpolarized 129Xe MRI (Xe-MRI) holds promise for sensitive and non-ionizing imaging of lung ventilation in children and has been explored in the post-HSCT population. However, previous work was weighted towards children without BOS. In this pilot cross-sectional study, we hypothesize that ventilation abnormalities measured with Xe-MRI are increased in pediatric post-HSCT participants with BOS compared to those without. METHODS: Two groups of pediatric post-HSCT participants were recruited: those with a diagnosis or clinical findings consistent with BOS and those without. Xe-MRI was performed to calculate the ventilation defect percentage (VDP) and ventilation heterogeneity index (VHI) in all subjects. Group-wise differences were tested with Mann-Whitney U-test. Xe-MRI was compared to same-day spirometry and nitrogen multiple breath washout (MBW). RESULTS: Twelve (6 non-BOS and 6 BOS) participants aged 9-17 years (median 12.5 years) were recruited. VDP (median [range]) was elevated (p < 0.05) in participants with BOS (11.8 [4.3, 20.8]%) compared to those without BOS (4.0 [3.1, 4.9]%). A similar elevation (p < 0.01) in VHI was observed in those with BOS (12.1 [8.3, 16.3])%) compared to those without (7.4 [7.4, 8.1]%). Both VDP and VHI were correlated with forced expiratory volume in 1-second (FEV1) and the lung clearance index (LCI), while VDP also correlated with FEV1 over forced vital capacity ratio (FEV1/FVC). CONCLUSION: Xe-MRI ventilation measures were elevated in pediatric post-HSCT participants within the BOS group compared to those without BOS and correlated with same-day spirometry and MBW.