Biometric Data of Adults’ Aortic Knob Diameter in Posteroanterior Chest Radiograph, Correlation to Age and Normative Heart Diameter: A Cross-Sectional Study

Background: The aortic knob (AK) is an essential feature on a chest x-ray. It could be the first sign of a cardiovascular problem if there is any deformation or enlargement of the knob. This study aimed to measure the normal AK diameter (AKD) on a posteroanterior chest radiograph in healthy adult Sudanese. Methods and Results: The study was conducted in the Department of Radiology and Imaging in Ribat Hospital (Sudan) between Jun 2019 and Jan 2020. A total of 113 participants of both sexes (45.1% males and 54.9% females) with a normal chest x-ray and no history of diabetes, blood hypertension, cardiovascular disease, or skeletal abnormality were selected. Participants' age fluctuated from 18 to 75 years. The measurements (AK, heart diameter [HD], cardiothoracic ratio [CTR]) were carried out with the measuring tools available on the software of the computed radiography system. The mean AKD was 2.8±0.8 cm (2.94±0.8 cm in males and 2.51±0.77 cm in females, P=0.005)). The mean HD was 9.22±2.8 cm (9.8±3.3 cm in males and 8.7±0.2.1 cm in females, P=0.005). The mean CTR was estimated as 46.6±7.7% with a significant difference between males and females and significantly correlated with HD and BMI (P<0.05). The AKD increased by 0.019 cm with an increase of one year of age (AKD = 0.0199(age)+1.9469), and there was a strong positive correlation between age and AKD (P<0.001). Conclusion: The study found a significant positive correlation between age and AKD. Increased heart sizes increase AKD. The AKD value is greater in males than in females.