Tidal changes on CT and progression of ARDS

Cereda, Maurizio; Xin, Yi; Hamedani, Hooman; Bellani, Giacomo; Kadlecek, Stephen; Clapp, Justin; Guerra, Luca; Meeder, Natalie; Rajaei, Jennia; Tustison, Nicholas J; Gee, James C; Kavanagh, Brian P; Rizi, Rahim R

Concentric propagation of radiological opacities developed from the sites of initial injury; this was apparent from serial CT images and from the PRM ( figure 3A ). In the PRM, the distribution of paired EI and EE density values evolved, with more voxels developing in the severe injury domain. In contrast, where injury progression was limited, the voxel distribution was more stable ( figure 3A) . Identification of high-risk voxels (online supplementary figure 5 ) was through capture at EE of voxels of higher density (0 to −600 HU) that were closer to normal at EI (−300 to −700 HU); this was assumed to represent lung tissue with unstable inflation. Such high-risk voxels comprised 33.6%±21.0% of all lung voxels in experimental animals (averaged across all animals) and 4.7%±1.0% in healthy animals (online supplementary table 2). Voxels were backtracked to the original EI images and colour labelled to visualise their distribution. The high-risk voxels (figure 3B, yellow) were predominantly distributed in areas surrounding foci of severe injury (figure 3B, red), and propagation was characterised by progressive replacement of 'at-risk' tissue with frank injury.