[Analytical evaluation of compression and displacement of the esophagus and trachea due to right aortic arch with MR imaging].

We studied 12 cases of right aortic arch (RAA) with MRI, and the anatomical relationship between right aortic arch and the esophagus and trachea were analysed. Three of 12 cases showed RAA with mirror-image branching. Nine cases were RAA with aberrant left subclavian artery. The proximal portion of the aberrant left subclavian artery in the retrotracheoesophageal space was expanded just like a pouch. The pouch was the 8th segment dorsal aortic root and the so-called aortic diverticulum. This was one of the causes of symptoms such as wheezing and dysphagia. We divided the configuration of aortic diverticulum into two types, bulging type and saccular type, on the basis of coronal images. Two cases were bulging type, seven saccular type. The axial images in two cases showed compressed esophagus, and in three cases showed displacement of the trachea, narrowing of the space like a triangle surrounded by the aortic arch, aortic diverticulum and aberrant left subclavian artery. We drew lines and measured the angle of the aortic arch with the aberrant left subclavian artery on the axial images of these cases. We found that cases with an angle of less than 60 degrees showed a high correlation with the causes of compression of the esophagus or displacement of the trachea. It was necessary to follow such patients with MRI.