Quantitative CT in the follow up of functionally stable lung transplant recipients

Purpose: To quantify lung parenchymal changes in functionally stable lung transplant recipients using combined inspiratory and expiratory CT. Methods and Materials: Twenty patients after double lung transplantation, all of which were stable with regards to clinical presentation and lung function (i.e., no evidence of graft rejection), underwent yearly combined inspiratory and expiratory CT examinations over 5 years. Lung parenchymal densitometric and quantitative airway metrics were calculated with dedicated software. The longitudinal evolution of the metrics was compared within individual patients, and relative changes were compared between individuals. Comparisons were performed using analyses of variance for repeated measurements, and linear regression analyses were used for data modeling. Results: Over the 5-year study period, CT measured lung weight and histogram peaks showed statistically significant (p = 0.012 and p < 0. 001, respectively) decreases. Moreover, mean lung density (MLD) significantly decreased (p = 0.029), with regression lines showing similar slopes between patients (F = 2.69; p = 0.036). Simultaneously, MLD on expiratory CT examinations also significantly decreased (p = 0.001), while quantitative airway metrics such as wall thickness, wall area percentage and Pi10 did not significantly change over time. Conclusion: On quantitative CT, functionally stable lung transplant recipients show a consistent pattern of longitudinal tissue loss, combined to increasin