Axial Computed Tomography Angiography of a Pre-Procedural Stanford B Aortic DissectionA pre-procedural axial computed tomography angiogram shows the caliber sizes of the respective true (blue arrow) and false (green arrow) dissection lumens. The aortic diameter measures 27.8 millimeters in diameter at this level. The false lumen measures 17.8 millimeters and is noticeably larger than the true lumen, measuring 10 millimeters.