[Magnetic resonance diagnosis of aortic dissection: with special reference to the communicating orifice between the true and false lumens].

Magnetic resonance imaging (MRI) was performed in thirty-one patients with aortic dissection to evaluate its usefulness in diagnosing the site of communicating orifice between the true and false lumens and the presence of retrograde dissection. MRI revealed the site of the entry as a defect in the intimal flap in the images of 12 of 15 patients (80%). The site of the communicating orifice between the true and false lumens in the abdominal aorta could be determined in six of eight patients (75%). MRI diagnosis of retrograde dissection was successful in three patients. Cross-sectional analysis of the abdominal aorta based on the location of the true lumen revealed that the celiac and superior mesenteric arteries tended to arise from the true lumen when the latter was situated in the anterior part of the abdominal aorta. The right and left renal arteries arose from the true lumen when it was positioned anterolaterally. In conclusion, MRI was a useful diagnostic method for aortic dissection, especially for determining the site of entry in the thoracic aorta. The changes in signal intensity in the false lumen provided useful information for locating the communicating orifice between the true and false lumens and for diagnosis of retrograde dissection. Cross-sectional analysis of dissection in the abdominal aorta was useful for predicting the branching of the main arteries from the true or false lumen.