Dominik Fleischmann MD, Presenter: Research support, Siemens AG Research support, General Electric Company

1) To present a concept of understanding intramural hematoma (IMH) as an unspecific imaging finding associated with acute hemorrhage itno the aortic wall that can be seen in a variety of acute aortic abnormalities (variant of aortic dissection; associated with penetrating atherosclerotic ulcer; or trauma). IMH is therefore not a 'disease' by itself, but an important indicator of an aortic emergency. 2) Penetrating atherosclerotic ulcer (PAU) is a distinct manifestation of severe atherosclerosis, and the pathologic, clinical and imaging findings will be described to allow the differentiation between acute, life threatening penetrating atherosclerotic ulcers versus commonly seen non-emergent ulcer like lesions of the aortic wall.

INTRAMURAL HEMATOMA (IMH) is defined pathologically as acute hemorrhage into the aortic wall - more specifically - into the aortic media. The typical imaging finding in CT is a hyperdense, crescent shaped or circumferential thickening of the aortic wall on non-contrast enhanced images. While often regarded as a 'cause' of acute aortic syndrome, IMH is not truly a disease entity, but an unspecific manifestation of a variety of acute aortic disorders: IMH can be a manifestation of a diseased aortic media - and in this case represents a variant of aortic dissection (typically seen in younger individuals with severe hypertension). Or IMH can also be seen associated with a penetrating atherosclerotic ulcer, which is often associated with local bleeding into the aortic wall, caused by severe, advanced atherosclerosis (a disease of the intima), typically seen in older individuals. PENETRATING ATHEROSCLEROTIC ULCER (PAU) is defined pathologically as an atherosclerotic ulcer which penetrates through the internal elastic lamina into the media layer of the aorta. Since the layers of the aortic wall cannot be resolved by CT, the imaging finding of an 'ulcer-like' lesion of the aortic wall even with thin-section CTA is unspecific and can be an acute life threatening condition (PAU), or and incidental finding (non-penetrating atherosclerotic ulcer; chronic and healed penetrating atherosclerotic ulcer). Acute and non-acute ulcer like lesions can be differentiated based on the presence of IMH - which is always a sign of an acute aortic process-, and based on clinical symptoms, notably aortic pain. Symptomatic lesions - even without IMH - should be followed closely.  PAUs in the ascending aorta (Type A) are a surgical emergency. PAUs are more commonly seen in the descending thoracic aorta, orften multiple, and stent-grafting is often the best therapeutic option in this population.

Fleischmann, D, Intramural Hematoma and Penetrating Atherosclerotic Ulcer.  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/11000651.html