| The local hemodynamics, morphology, composition and biological activity of plaque are closely related to the risk of carotid artery plaque rupture. The ulceration on the plaques, which refers to one kind of rupture resulted from the extension of the lipid core of fissures on the plaque, is an indication of prior rupture, which it is considered to be traces of the further rupture of ulceration plaque or sources of emboli. After the rupture of ulceration plaques, the substances which were from the ulceration could go into the blood, and this might lead the artery embolization within circulation and endanger lives. Now the further rupture mechanism of ulceration plaques remains unclear. The area of thrombosis is unable to be located yet. Since hemodynamics play an important role in determining the rupture of the ulceration plaque, the study of vulnerable plaque was little from the perspective of hemodynamic. In order to make the surgical planning for the surgeons, it is necessary to get the understanding and research of the further rupture mechanism of the ulceration plaques, and locate the position of thrombosis after further rupturing.In our study, the 3D models of carotid plaques with ulceration were reconstructed with using blood flow data by noninvasive measurement in vivo and CT angiography images which based on preliminary experimental study. After the steps of image segmentation and smoothing, three-dimensional personalized models of the carotid artery with ulceration plaques were reconstructed(six models were with single ulceration, two models were with two consecutive ulcerations). Followed by a tetrahedral mesh for each model, Finally the boundary conditions were settled, which the condition of inlet was velocity waveform and the outlet was 0 pressure( during the fluid structure interaction, material properties of blood and vessel wall were also needed to set). And then, numerical simulation of hemodynamics was carried out. Hemodynamic numerical simulation results showed that the blood flow in the vicinity of the ulcerations was very complex. In the case of a single ulceration, Wall shear stress(WSS)is respectively from3.29 to 35.41 Pa at the upstream, which was lower than that at the downstream ulceration from 11.90 to 41.85 Pa, and In the case of two consecutive ulcerations, the region between two ulcerations had the highest WSS, which from 18.60 to 30.60 Pa.Wall shear stress gradient(WSSG) in the vicinity of the ulcerations had reached a relatively high level, the distribution of WSSG was as the same as those of WSS.Based on the results in this paper,the following conclusions was obtained:1.The twisting and the curling of the flow at the ulcerations can lead to thrombosis which may break free later and go through the downstream stenosis by the effect of the flow.2. High WSS at the upstream and downstream ulceration and the area between the two consecutive ulcerations make the ulceration plaque to further rupture from these regions, particularly at the downstream ulceration and the area between the two consecutive ulcerations because of higher WSS available. In addition, different degrees of WSS in downstream and upstream ulcerations may tear ulceration by pulling effect.3. Under the wall shear stress constantly changing, the ulceration plaque would fatigue. As a result, this would lead to the further rupture of ulceration plaque.The hemodynamics on the ulceration plaques of the carotid artery stenosis by numerical simulationcan provide a more intuitive understanding of the details of the flow field and stress changes around the ulceration plaques. This can be the reliable theoretical basis of making good individualized treatment plan and intervening carotid plaque ulceration to prevent ischemic stroke in time for clinicians. |
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