Figure 8b. Stanford type A aortic dissection in a 60-year-old man. (a) Axial T1-weighted black-blood image shows nearly circumferential compression of the true aortic lumen by a false lumen (arrow). High signal intensity in the false lumen makes it difficult to differentiate thrombosis from flowing blood. (b) Axial reformatted image from contrast-enhanced MR angiography shows an intimal flap (black arrow) with flow in the false lumen (white arrow).