FIGURE 1.

Definitions of lines that determine tumour location. CT: computed tomography. Concentric lines arising from the hilum (yellow lines) are spherical or dumbbell shaped in three dimensions. Concentric lines arising from the midline (red lines) are cylindrical or conical in three dimensions. Sagittal lines arising from the midline (blue lines) are rectangular parallelepipeds in three dimensions. Solid lines and broken lines refer to the inner one-third and two-thirds lines, respectively. a) Coronal CT at the tracheal bifurcation level. b) Axial CT image at the manubrium body level. There is no yellow line because it arises from the hilum. c) Axial CT image at the hilum level. The red and yellow lines are the same. d) Axial CT image at just above the diaphragm. There is no yellow line because it arises from the hilum.