Abstract
OBJECTIVES: The mechanisms behind the onset of acute aortic dissection have not been fully elucidated. We developed dynamic synchrotron-based X-ray phase-contrast tomography to quantitatively study the dynamics of biological samples and applied it to the fresh aortic wall in acute type-A aortic dissection (ATAAD). METHODS: Fresh, ring-shaped aortas undergoing aortic repair in ATAAD were measured in a container filled with normal cold saline within 24 h of surgery. As a control, we obtained 5 formalin-fixed normal ascending aortas from autopsies (female: 2, 59.7 years) [standard deviation (SD): 5.5 years]. To evaluate the quantitative morphological change, we estimated the density at each step stretched by 2 mm per step. The fresh specimens were analysed pathologically using the area ratio of the elastic fibres. RESULTS: Samples were obtained from 5 patients [1 man and 4 women, 59.4 (SD: 8.7) years]. The overall density of the tunica media (TM) in the fresh aorta was 1.062 (SD: 0.006) g/cm3 and differed significantly between the dissected and non-dissected portions [1.05 (SD: 0.004) vs 1.066 (SD: 0.004) g/cm3, respectively; P = 0.0122]. When the fresh aortic wall was stretched and became thinner, the density of the TM remained unchanged. Compared with the pathological findings, the area ratios of the elastic fibres of the TM were lower in the non-dissected portion than normal [48.6 (SD: 7.1)% vs 60.5 (SD: 5.7 %, P < 0.001]. CONCLUSIONS: Dynamic synchrotron-based X-ray phase-contrast tomography can trace the deformation process that occurs in situ in fresh aorta in ATAAD. We confirmed that the densitometric property of the aortic wall in ATAAD was unchanged during the stretching process.