Automated 3D MRI Aortic Morphometry Demonstrates the Added Value of Volumes as Compared to Diameters

Aim: The diagnosis of thoracic aortic aneurysm is based on local aortic deformation associated to excessive aortic diameter (D). Maximal local aortic diameter was shown to be below the recommended surgical threshold in 30% of patients who ultimately developed aortic dissection. Aortic volumes integrate both dilation and elongation and may be more sensitive to changes in aortic geometry and less dependent on slice orientation and obliquity than diameter measurements. Methods: We studied 278 asymptomatic individuals with 3D aortic MRI: 119 healthy volunteers (hC), 53 hypertensive patients (HT) and 106 patients with dilated ascending aorta of which 62 with tricuspid (APt) and 44 with bicuspid (APb) aortic valve. Automated 3D aortic segmentation was performed and aortic lengths, maximal diameters and volumes were measured from sino-tubular junction to the brachiocephalic trunk for the ascending aorta (AAo) and from the left subclavian artery to the diaphragm for the descending aorta (DAo). Results: While AAo D increased by 40% between APt and HC, AAo volume increased by 170%. Moreover, when comparing HT patients with controls, AAo volume difference was significant (p < 0.05) even after adjustment to BSA while AAo D was not. Conclusion: Aortic volumes measured automatically from 3D MRI were able to characterize subclinical and pathological dilation more accurately than maximal diameters.