Contrast enhanced MRA of the thoracic aorta has long been established as the imaging modality of choice in clinical routine for a variety of pathologic conditions as well as for congenital malformations. In newborns, children and young adults as well as in patients with congenital heart disease the thoracic aorta in most cases is imaged because of a suspected congenital malformation.
Imaging can be performed either to establish the diagnosis or to follow up patients with congenital heart disease. One of the big advantages of contrast enhanced MRA is the possibility to combine non-invasive luminal imaging of the aorta with flow measurements and imaging of extraaor-tic structures without recourse to ionising radiation or potentially nephrotoxic iodinated contrast media. Further details concerning imaging of pediatric patients are given in chapter VIII.
Concerning elderly patients the thoracic aorta is a frequent focus of arteriosclerotic disease, which can present as either a chronic condition or a life threatening acute condition. For patients with life threatening acute conditions such as aortic trauma or acute aortic dissection, the need for speed, scanner availability and ease of patient management make CT and CTA more favorable diagnostic options for disease evaluation. However, for all other pathologies MRA should at least be considered a viable alternative method if not the imaging modality of choice.
One of the big advantages of contrast enhanced MRA compared with catheter angiography is the possibility to depict the vessel wall and the soft tissue adjacent to a vessel [ 1 ]. This can be very useful in patients with acute aortic syndromes in whom intramural hematoma can only be diagnosed by means of cross sectional imaging if the lesion does not have such a large extent (see Fig. 22) . The same holds true for valve pathologies such as con genital bicuspid aortic valve or degenerative-like stenosis or insufficiency of the aortic valve. For this latter condition also the valvular function of the aorta can be imaged with very high accuracy on MRI .
Combination of MRA with flow measurements permits quantification of the regurgitation fraction in valve insufficiency as well as estimation of the pressure gradient over a stenosis in conditions affecting the pulmonary and aortic valve and stenotic areas in general.
If evaluation of the thoracic aorta is necessary, cross sectional imaging should be performed in addition to MRA in order to gain as much information as possible about a lesion. In certain cases it may also be important to look at the anatomy of the left ventricle to determine whether aortic insufficiency or stenosis has resulted in dilatation of the left ventricle since this may increase the need for surgery.
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