Figure 19b.  Aneurysm of the false lumen in a patient who had type B AAD 10 years earlier. (a) Enhanced CT scan obtained 10 years earlier shows an intimal flap (arrow) in a descending aorta of normal diameter. (b) Helical CT scan shows dilatation and mural thrombosis of the false lumen (arrow). (c) Oblique sagittal MPR image shows irregular mural thrombosis of the false lumen (F), which compresses the true lumen.