Objective: To study average diameters of normal thoracic aorta in Thai population.
Material and Method: Eight levels of aortic diameters were collected from 100 adult patients who underwent a thoracic
helical CT scan for various non-aortic diseases. Two perpendicular diameters were measured. Mean, minimal, maximal and standard deviation (SD) of all data were analyzed.
Results: There were 51 males, 49 females. Mean age was 57.7 years (range 18 to 92). Average aortic diameter (mean + SD)
was 28.55+5.16 mm at aortic annulus, 34.63+4.74 mm at aortic sinus, 33.62+5.07 mm at ascending aorta, 32.43+4.62 mm at proximal to innominate artery level, 30.68+4.27 mm at left common carotid taking off level, 28.77+3.94 mm at left
subclavian taking off level, 27.59+4.02 mm at descending aorta just distal to left subclavian artery level and 23.28+3.65 mm at diaphragmatic level. Male aortic diameters are larger than female’s. Aortic diameters increased with age in all levels.
Conclusion: Average thoracic aortic diameters in Thai population were proposed. Sex, age and various aortic levels
determine size of the thoracic aorta.

Keywords: Thoracic aorta, Thai population