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

Thomas Dietenbeck1, Sophia Houriez--Gombaud-Saintonge1, Umit Gencer2, Alain Giron1, Gilles Soulat2, Elie Mousseaux2, Philippe Cluzel3, Alban Redheuil3, Nadjia Kachenoura4
1Laboratoire d'Imagerie Biomédicale (LIB), 2Hopital Européen Georges Pompidou, 3Département d’imagerie cardiovasculaire DICVRIT, Institut de Cardiologie, Groupe Hospitalier Pitié Salpêtrière APHP, 4INSERM


Currently, the aortic dilation characterized through local maximal diameter measurement is used for guiding the indication of prophylactic thoracic aorta surgery. However, 20 to 40% of patients with aortic dissection following aneurysm have maximal aortic diameters below the recommended threshold for surgery. Aortic volumes integrate both aortic dilation and elongation and may be more sensitive to changes in aortic geometry and less hampered by slice orientation and obliquity. We studied 278 individuals (171 men, age: 53±15y): 119 healthy volunteers, 53 hypertensive patients and 106 patients with dilated ascending aorta (AAo) (44 with bicuspid valve) who underwent 3D MRI of the aorta. Automated 3D aortic segmentation was performed and length, maximal diameters and volumes were measured from sino-tubular junction to brachiocephalic artery for the AAo. Aortic measures were compared across groups using ANOVA and pairwise comparisons. Compared to healthy controls, AAo volume increased by 17% (p<0.05) in hypertensives, as a result of a significant elongation (+8%, p < 0.01) and a modest dilation (+4%, p=0.58). In patients with AAo aneurysm, the substantial augmentation in AAo volume as compared to healthy controls (tricuspid aneurysmal patients (TA): +170%, p<0.001; bicuspid aneurysmal patients (BA): +180%, p<0.001) contrasted with a smaller increase in AAo diameter of 43% in TA (p<0.001) and of 44% in BA (p<0.001). Such increase in volume resulted from AAo dilation but also from significant AAo elongation (TA: +38%, p<0.001; BA: +39%, p<0.001). In multivariate analysis, AAo length, diameters and volumes were significantly associated with age, sex and group (p<0.001) but not with BMI and central systolic blood pressure. Although diameters were measured automatically along and perpendicular to the aortic centerline, aortic volume changes in hypertension and in aortic aneurysmal diseases were more pronounced than maximal diameters changes, as they integrate both radial dilation and longitudinal elongation.