Phase resolved functional lung (PREFUL) MRI detects ventilation and perfusion deficits in paediatric lung transplant recipients

<bold>Background:</bold> Spirometry and radiation-based imaging are commonly used to detect chronic lung allograft dysfunction (CLAD) after lung transplantation (LTx). Magnetic resonance imaging (MRI) has been evaluated as a sensitive and radiation free technique in adults, but paediatric data is lacking. <bold>Aim:</bold> We investigated whether functional MRI is feasible in children after LTx and correlates with FEV1 derived from spirometry and lung clearance index (LCI) from nitrogen multiple breath washout (N2-MBW). <bold>Method:</bold> A prospective, single-centre cross-sectional observational study was performed in paediatric patients after LTx and healthy controls. All underwent PREFUL MRI, spirometry and N2-MBW. PREFUL-MRI derived functional proton ventilation and perfusion parameters were quantified as ventilation-perfusion (V/Q) matching. <bold>Results:</bold> PREFUL MRI was feasible in 22 patients (median age 13.6 years, IQR 10.4-16.0; ten boys [45%]) after LTx (time span from LTx 3.9 years, IQR 1.9-6.2) and 11 healthy controls (median age 10.7 years, IQR 8.0-15.4; five boys [45%]). 3 patients were defined as CLAD 0p without higher grades of CLAD in the cohort (median FEV1 of 100%, IQR 95-101 of baseline post LTx). LCI identified increased ventilation inhomogeneity in 10 patients after LTx. Both pulmonary domains (ventilation-perfusion [V/Q] match) were higher in healthy controls (87%, IQR 85-91) than patients after LTx (83%, IQR 72-88; p=0.04). There was no correlation between V/Q match and FEV1 or LCI. <bold>Conclusion:</bold> PREFUL MRI detects ventilation and perfusion deficits in children after LTx with stable spirometry. Longitudinal studies will elucidate possible early prediction of organ rejection.