Evaluation of Aortic Geometries created by MRI Data in Man

The development of atherosclerotic plaques has been associated with the patterns of wall shear stress (WSS). However, much is still uncertain with the methods used to calculate WSS. Correct vessel geometries are mandatory to get reliable estimations and the purpose of this study was to evaluate an in vivo method for creating aortic 3D geometry in man based on data from magnetic resonance imaging (MRI) with ultrasound as reference. Methods: The aortas of ten healthy males, 23.4 ± 1.6 years of age, were examined with a 1.5T MRI system using a 3D gadolinium-enhanced gradient-echo sequence. 3D geometries were created using manual segmentation of images. Lumen diameters (LD) were measured in the abdominal aorta (AA) and the thoracic aorta (TA) with non-invasive B-mode ultrasound as a reference. Results: The anteroposterior diameter of the AA was 13.6 ± 1.1 mm for the MRI and 13.8 ± 1.3 mm for the ultrasound (NS). Intraobserver variability (CV) for MRI and ultrasound was <0.92% and <0.40% respectively . Interobserver variability MRI and ultrasound was 0.96% and 0.56% respectively. The diameter of the TA was 19.2 ± 1.4 mm for the MRI, and the intraobserver variability (CV) were <0.78% and interobserver variability (CV) were 0.92%. Conclusion: Specific arterial geometries can be constructed with a high degree of accuracy using MRI. This indicates that the MRI geometries may be used to create realistic and correct geometries in the calculation of WSS in the aorta of man.