Normal diameter of the thoracic aorta in adults: a magnetic resonance imaging study

To determine the evolution of the diameter of the thoracic aorta with age in order to detect dilatation more reliably by imaging, we performed a retrospective analysis of the MRI examinations of the normal thoracic aorta of 66 subjects aged 44.1±19.1 years (range 19.1–82.4 years) obtained between 1991 and 2000 on a Magnetom SP 42 1T apparatus (Siemens) using T1-weighted spin echo sequences with electrocardiographic synchronization. Sixteen measurements were made in the axial plane, the oblique sagittal plane in the axis of the aortic arch, and the oblique frontal plane perpendicular to the latter at the level of the ascending aorta, the arch and the descending thoracic aorta. We found an increase in the thoracic aorta diameter and a significant relationship between this diameter and the age of our subjects, wherever the measure was performed. However, there was no systematic correlation between aortic diameter and age. The aortic diameter evolved with age and a marked difference seemed to exist in measurements made in groups younger and older than 40 years. This study, conducted on a small population of 66 patients, thus helps to define a normal aortic diameter, thereby making the diagnosis of pathological dilatation of the aorta more reliable.