Low-dose chest computed tomography for quantitative and visual anatomical analysis in patients with acute respiratory distress syndrome

Chest computed tomography (CT) is a fundamental tool for the characterization of acute respiratory distress syndrome (ARDS). Its frequent use is, however, hindered by the associated radiation exposure. The aim of the present study was to evaluate, in patients with ARDS, the accuracy of quantitative and visual anatomical lung analysis performed on low-dose CT. We hypothesized that low-dose CT would provide accurate quantitative and visual anatomical results. Chest CT was performed in 45 ARDS patients in static conditions at set airway pressures of 45 and 15 or 45 and 5 cmH(2)O. During each pause, two consecutive scans were obtained at two different tube current-time products (mAs). In 24 patients 110 mAs was coupled with 60 mAs; in 21 patients 110 was coupled with 30 mAs. All other CT parameters were kept unaltered. Quantitative and visual anatomical results obtained at different mAs were compared via Bland-Altman analysis. Good agreements were observed between 110 and 60 mAs and between 110 and 30 mAs both for quantitative and visual anatomical results (all biases below 1.5 %). Estimated mean effective dose at 110, 60, and 30 mAs corresponded to 5.3 +/- A 1.6, 2.8 +/- A 0.8, and 1.4 +/- A 0.3 mSv, respectively. In patients with ARDS a reduction of mAs up to 30 (70 % effective dose reduction) can be achieved without significant effect on quantitative and visual anatomical results. Low-dose chest CT, with related quantitative and visual anatomical analysis, could be a valuable tool to characterize and potentially monitor lung disease in patients with ARDS.