Wash-in/wash-out phase xenon-enhanced area-detector CT (ADCT): utility for regional ventilation, pulmonary functional loss and clinical stage evaluations of smokers

Background: Xenon (Xe)-enhanced area-detector computed tomography (ADCT) can visualize regional distribution of Xe within the lungs and demonstrate regional ventilation differences in smokers and patients with pulmonary diseases. Purpose: The purpose of this study was to evaluate the capability of wash-in and wash-out (WI/WO) phase Xe-enhanced ADCT for detecting regional ventilation differences based on underlying lung conditions, pulmonary functional loss evaluation, and clinical stage prediction for smokers with and without chronic obstructive pulmonary disease (COPD). Material and Methods: The pulmonary function test as well as inspiratory/expiratory unenhanced and WI/WO phase Xe-enhanced ADCT were prospectively administered to a group of 40 smokers consisting of 25 men (mean age ± standard deviation [SD] = 65.1 ± 9.5 years) and 15 women (65.2 ± 9.4 years), after which WI, WO, WI/WO ratio, and ventilation ratio as well as parametric response maps were generated. All Xe-enhanced ADCT indexes and pulmonary function test results were subjected to step-wise regression analyses. Finally, discrimination analysis was performed to determine the concordance capability for clinical stage classification of smokers. Results: %VC was significantly affected by the WI index (P < 0.0001), while FEV1/FVC% and %FEV1 were significantly affected by the ventilation ratio (P < 0.0001). Accuracy of the WI index combined with the ventilation ratio was significantly higher than that of the WI index (P = 0.008), WI/WO ratio (P = 0.02), and WI index combined with the WI/WO ratio (P = 0.02). Conclusion: WI/WO phase Xe-enhanced ADCT is useful for assessing smoking-related regional ventilation change and pulmonary functional loss, as well as evaluating the severity of smokers’ diseases.