Figure 14b.  Aortic coarctation and dissection. (a) Oblique sagittal MPR image shows focal narrowing of the thoracic descending aorta (long arrow) and an intimal flap in the ascending aorta (short arrow). (b) SSD image shows a dilated ascending aorta and aortic narrowing immediately distal to the left subclavian artery (arrow). Dissection is not seen because an SSD image shows only the aortic surface.