LAUSR

Background: Long term survival after lung transplantation (LTx) is limited by bronchiolitis obliterans syndrome (BOS), defined as a sustained decline in FEV1 not explained by other causes. Early diagnosis may increase the probability of successful treatment with novel therapeutic agents. Functional Respiratory Imaging (FRI) was used to determine the CT image features that correlate with onset of BOS. Methods: Paired inspiratory-expiratory CT scans of 71 LTx patients (41 BOS and 30 non-BOS) were analyzed. The BOS cohort experienced a reduction in FEV1>10% compared to baseline (BOS 0-p). FRI yielded regional parameters of lung and airway volumes. Differences between the two groups were analyzed for lung function and FRI parameters. Results: The FEV1 decline in the BOS cohort was related to an increase in lung volume (p = 0.027) and central airway volume at functional residual capacity (FRC) (p = 0.018). The change in these parameters was not observed for the non-BOS patients with declining FEV1. On the other hand, the non-BOS cohort experienced a decrease in central airway volume at total lung capacity (TLC) with declining FEV1 (p = 0.039). Conclusion: FRI could distinguish the onset of BOS from reversible causes of FEV1 decline, such as pulmonary infection, in patients that underwent LTx and presented with FEV1 decline. The results illustrate the potential of FRI derived quantitative imaging biomarkers to assist in early diagnosis of BOS and in the elucidation of the mechanism accounting for FEV1 decline.