Right heart border not visible - indicating mediastinal shift to the left
Volume loss of the left hemithorax
'Veil-like' opacification of the left hemithorax obscuring the left heart border - characteristic of left upper lobe collapse
Ovoid density at the left hilum - CT (next image) confirmed a large left hilar mass, which occluded the left upper lobe bronchus
Note the left hemidiaphragm is still visible - indicating sparing of the left lower lobe
The left lower lobe has increased in volume to compensate for the volume loss and can be seen wrapping round the medial side of the collapsed upper lobe (red line) - the 'Luftsichel' (air crescent) sign