Asymmetry Is the Norm in “Cloverleaf” Aortic Root Structure

Purpose Except for the aortic root (AoR), the thoracic aorta is a radially symmetric structure. It has recently been described as a three-cloverleaf (sinus) structure, with evidence supporting sinus asymmetry. Due to asymmetry, it is difficult to measure. These measurements are central to clinical evaluation of AoR health. (1) Demonstrate correlation between manually interpreted and machine-assisted (MA) measurements of AoR anatomy. (2) Demonstrate that asymmetry is a consistent characteristic in normal AoRs. Methods Our study employed randomly selected, EKG-gated CT scans which had previously been interpreted to be free of thoracic disease. All AoRs were analyzed independently by a thoracic radiologist (RBM) and through MA interpretation (HZ). In addition to one dimensional (1D, as radius) and 2D (area) manual and MA interpretations, 3D measurements (volume and height) of the AoR were made using MA method. Results 1D and 2D analyses showed high correlations between manual and MA measurements. Asymmetry was apparent in 1D, 2D and 3D measurements between sinuses. 3D measurements demonstrated the strongest pattern of asymmetry, with the average volumes in the noncoronary sinus > right sinus > left sinus as 4660 > 3500 > 2700 mm ³ (p < 0.01). Conclusion Manual and MA interpretations of AoR dimensions are highly correlative. Although asymmetry exist s in all measurements of normal subjects, it is not strong in 1D or 2D measurements. The 3D volume of the noncoronary sinus is larger than the right coronary sinus, which is significantly larger than the left coronary sinus, indicating the importance of 3D measurements.