All images were viewed at window settings optimised for assessment of the lung parenchyma (width, 1200 1500 HU; level, -700 to -600 HU) and mediastinum (width, 300 400 HU; level 30 60 HU).
The CT parameters were as follows: section thickness, 1 mm on Sensation 64 and 2 mm on Brilliance 40; tube voltage, 120 kVp; tube current, 150 200 mA; lung window width, 1,500 Hounsfield units [HU] and level, −700 HU; and mediastinal window width, 400 HU and level, 20 HU.
Both CT units were operated under the following common parameters: voltage 120 kVp; tube current 200 mAs (with tube current modulation active on the 16-slice CT unit); 1.0-mm reconstruction slice thickness; 1.0-mm space; 5.0-mm axial MIP thickness; 6.0-mm oblique MIP thickness; and lung visualisation window (width 1000 Hounsfield units (HU), level − 700 HU).
When tumors were located at pulmonary parenchyma away from soft tissues of mediastinum or chest wall, GTV contours were drawn using lung window (window width 1000/window location −650).
The CT images were displayed with conventional window settings specific for lung tissue (window width, 1500 Hounsfield units (HU); and window level - 600 HU).
The images were obtained without injection of contrast material and viewed in a lung window (window width, 1500 HU; window level, âˆ'600 HU), using a high spatial frequency algorithm for image reconstruction.
The thin-section CT images were displayed with lung (level, −600 HU; width, 1700 HU) and mediastinal (level, 30 HU; width, 400 HU) window settings in a multiplanar format and were reviewed separately by two experienced chest radiologists.
However, computed tomography (CT) is highly sensitive in the detection of abnormal air/gas, especially in "lung window" settings (window width, 1,500 HU; window centre, −800 HU).
These images were reconstructed using bone algorithm and viewed using routine lung window settings (window width of 1300 HU and window level of -600 HU).
The standard algorithm generated transverse images: width of the lung window, 1000 Hounsfield units (HU); window level, − 700 HU.
