Main Pulmonary Artery-to-Ascending Aorta Diameter Ratio in Healthy Children on MDCT.

OBJECTIVE. This study was performed to ascertain whether the adult ratio of 1: 1 of the diameter of the main pulmonary artery (MPA) to the diameter of the ascending aorta (AA) (referred to hereafter as the MPA-to-AA ratio) on MDCT is applicable to children. MATERIALS AND METHODS. Our hypothesis, which is based on experiential observation, is that the MPA-to-AA ratio would be higher than 1 in healthy children. A retrospective analysis of vessel calibers in a population of children without pulmonary hypertension who had undergone MDCT was performed. RESULTS. The MPA-to-AA ratio was statistically significantly higher in children of all ages than in adults. We would, therefore, submit that the normal MPA-to-AA ratio in children on MDCT is greater than 1 and closer to 1.09. CONCLUSION. The demonstration of an MPA segment that is slightly larger than the AA in children undergoing MDCT should not suggest a diagnosis of pulmonary arterial hypertension.