Density of fresh wall of acute aortic dissection with synchrotron-based x-ray phase tomography.

OBJECTIVES The mechanisms behind the onset of acute aortic dissection have not been fully elucidated. We developed dynamic Synchrotron-based X-ray phase tomography to quantitatively study the dynamics of biological samples and applied it to the fresh aortic wall in acute type-A aortic dissection. METHODS Fresh, ring-shaped aortas undergoing aortic repair in acute type-A aortic dissection were measured in a container filled with normal cold saline within 24 hours of surgery. As a control, we obtained five formalin-fixed normal ascending aortas from autopsies (female : 2, 59.7 (SD : 5.5) years). To evaluate the quantitative morphological change, we estimated the density at five each step stretched by 2 mm per step. The fresh specimens were analyzed pathologically about the area ratio of elastic fibre. RESULTS Samples were obtained from five patients (1 man and 4 women, 59.4 (SD: 8.7) years) The overall density of the tunica media in the fresh aorta was 1.062(SD : 0.006) g/cm3 and differed significantly between the dissected and non-dissected portion (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 tunica media remained unchanged. Compared with pathological findings, area ratio of the elastic fibre of the tunica media were lower in non-dissected portion than normal (48.6 (SD : 7.1) % v.s 60.5 (SD : 5.7) %, p < 0.001). CONCLUSIONS Dynamic-XPCT can trace the deformation process that occurs in situ in fresh aorta in acute type-A aortic dissection. We confirmed that densitometric property of the aortic wall in acute type-A aortic dissection was unchanged during the stretching process.