Discovery 64 slice ct

CT scans of FAHF cohort were performed on one of the two CT systems (Toshiba: Aquilion CXL 64-slice CT, Aquilion One 320-slice CT). CT scans of SAHX cohort were performed on one of the two CT systems (GE Discovery 64-slice CT, GE Revolution ACTS 16-slice). CT scan parameters were as follows: tube voltage:120 kV; automatic tube current modulation:100–400 mA; rotation time:0.5–1.0 s; Field of view:350 mm × 350 mm; matrix:512 × 512; convolution kernels: B52f.; reconstruction thicknesses and intervals:1.0 mm or 1.25 mm; slice thickness:1.0–5.0 mm (depending on scanners). Interpretation of CT images was done on a lung window (L, –500; W, 1500) by using a workstation on picture archiving and communication system. Delineation of the volume of interest in the targeted tumor was performed with 3D slicer (http://www.slicer.org) by a radiologist with 7 years of experience. The delineation was then reviewed by a radiologist with 15 years of experience in lung cancer diagnosis, who modified the delineation when necessary. All the tumors in the training, internal test, and external test cohorts were segmented manually slice-by-slice. The volume of interest enclosing the CT lung lesion was further refined by excluding areas of fat, air, necrosis, and calcification.