All HRCTs were performed in the prone position, acquiring 1.0- or 1.5-mm-thick sections at 1 cm throughout the entire thorax and then in the supine position. Full-volume CT scans reconstructed every 3 mm were acquired at suspended inspiration. HRCTs were reconstructed with a sharp kernel (B50; Siemens; Malvern, PA) and field of view of the widest outer rib to outer rib dimension. All studies were scored by an expert thoracic radiologist (J.G.) blinded to clinical and hemodynamic information, using a Likert scale (where 0 = absent, 1 = 1 to 25%, 2 = 26 to 50%, 3 = 51 to 75% and 4 = 76 to 100%) for extent of parenchymal abnormality in three categories: ground-glass opacity, lung fibrosis, and honeycombing. These scores were also summed into a total CT profusion score. This scoring system is based on that reported by Kazerooni et al.18 The following radiographic definitions were employed: ground-glass opacity, hazy parenchymal opacity in the absence of reticular opacity, or architectural distortion; lung fibrosis, reticular opacification, traction bronchiectasis, and bronchiolectasis; and honeycombing, clustered air-filled cysts with dense walls. Each lung lobe was scored separately (upper, lung apex to aortic arch; middle, aortic arch to inferior pulmonary veins; and lower, inferior pulmonary veins to diaphragm), and the mean score over all five lobes was computed for each category of parenchymal abnormality: fibrosis (CT-determined fibrosis score [CT-fib]), ground-glass opacity (CT-determined ground-glass score [CT-alv]), honeycombing (CT-determined honeycomb score [CT-hc]), and total profusion (CT-determined total profusion score [CT-tot] = CT-fib + CT-alv + CT-hc). Lobe scores were also weighted by typical relative size (right upper lobe, 0.0935; right middle lobe, 0.0935; right lower lobe, 0.363; left upper lobe, 0.155; and left lower lobe, 0.297) and summed to create weighted scores for fibrosis (weighted CT-fib [wCT-fib]), ground-glass (weighted CT-alv [wCT-alv]), honeycombing (weighted CT-hc [wCT-hc]), and total profusion (weighted CT-tot [wCT-tot]). We also created a maximum fibrosis score (mCT-fib) based on the most affected lobe.