Novel Pulmonary Function Measures for Diagnosis of Bronchiolitis Obliterans Syndrome Following Hematopoietic Stem-Cell Transplantation in Children

This study is looking for better ways to detect bronchiolitis obliterans syndrome (BOS) — a serious lung complication — in children who have received a haematopoietic stem cell transplant (HSCT, also called a bone marrow transplant). BOS causes scarring in the small airways and can progressively limit breathing. The study is testing whether newer lung imaging techniques (like MRI) can detect BOS earlier and more accurately than standard breathing tests alone. You may be eligible if... - You are a child aged 6–17.9 years - You received a stem cell transplant at least 6 months before enrolling - Your lung function test (FEV1) is above 40% of predicted - You are able to hold your breath for 16 seconds - You meet standard MRI safety criteria You may NOT be eligible if... - You have had a cold or respiratory infection in the last 4 weeks - You need supplemental oxygen or your resting oxygen saturation is 95% or below - You are unable to perform spirometry or plethysmography breathing tests - You are pregnant or breastfeeding Talk to your transplant team about your current lung function, oxygen levels, and any recent respiratory illness before participating in this study.