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

Objectives: To quantify lung parenchymal changes in functionally stable lung transplant recipients using combined inspiratory and expiratory CT. Methods/Materials: Twenty patients after double lung trans- plantation, all of which were stable with regards to clinical pre- sentation 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 soft- ware. 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 decreases (p = 0.012 and p 0.05). Conclusions: On quantitative CT, functionally stable lung trans- plant recipients show a consistent pattern of longitudinal tissue loss, combined to increasing gas trapping. None of these changes are detected by the lung function test currently used as reference standard for following these patients.