Magnetic resonance imaging features of aortic diseases.

The usefulness of magnetic resonance imaging (MRI) for aortic diseases is discussed, with special attention given to the MRI features of aortic dissection and Takayasu arteritis. Computed tomography (CT) and MRI provide excellent visualization of vessels and their relationship to surrounding structures; however, CT depicts the vessel lumen optimally only when contrast enhancement is used. MRI, with its inherent multiplanar imaging capability, is well suited for evaluation of the thoracic and abdominal aorta and can be used with or without contrast enhancement. Basic technical considerations in cardiac imaging, which include conventional spin-echo, fast spin-echo, cine gradient, and echo-planar imaging, with time-of-flight and phase-contrast methods, are discussed and applied to aortic aneurysm, aortic dissection, and Takayasu arteritis. The diagnostic capacity of spin-echo MRI in patients with suspected aortic dissection is enhanced when it is combined with cine MRI. Despite the ability of CT and MRI to demonstrate luminal and mural changes of aortic abnormalities, conventional angiography still may be necessary at first admission for selected patients in the late occlusive phase to provide additional information on the degree and extent of the arteritis. CT angiography and MR angiography are promising imaging techniques that will overcome difficulties in visualizing distal branch vessel lesions and obviate the need for conventional angiography in the near future.