The computational model of thrombosis is of great importance that decides the simulation performance. In the present study, a hybrid particle-continuum model with plasma, vascular wall, and thrombus being continuous material and platelets being discrete particles, was developed to simulate the thrombus growth. In the computational model, the thrombus growth was reformulated as a novel continuous surface expansion problem implemented by level set method due to its capability of effectively handling the topological changes comprising splitting and merging, rather than a traditional particle accumulation problem. Additionally, a Gaussian-based function and distance regularization function, serving as speed functions to drive the thrombus growth, were proposed and compared in our study. Experiments demonstrated that the growing thrombus could retain the particle texture of platelets by both level set speed functions, while the distance regularization function performed better in improving computational complexity and surface tracking behaviors. Both simulations demonstrated better visuality in the progress of thrombosis, and the geometry shape of the virtual primary thrombi were similar to the realistic counterpart.
Abstract:Recently, the study of thrombosis simulation based on computational models has been one of the most popular research areas. In this paper, a 3D simulation method based on a hybrid model is proposed for platelet thrombus formation. The flow of platelets is modeled in a macroscale submodel using Navier-Stokes equations and the physiological processes such as adhesion and aggregation of platelets are modeled in a microscale submodel. In the adhesion and aggregation phases, the attraction of platelets due to blood coagulation factors (von Willebrand factor) is modeled using the external force, and the conversion from unstable aggregation to stable aggregation is modeled using the increase in local viscosity. The proposed model is implemented and is applied to the 3D simulation of platelet thrombus formation. The flow of platelets and the transformation from normal platelet to thrombus are well shown by the 3D view of the simulation. The velocity field and viscosity field are also rendered to observe their changes in the process of thrombus formation. In the simulation, as the increase in blood velocity, the primary thrombus grows rapidly before a velocity threshold, and then the growth rate decreases. It concurs with the experimental results in vivo.
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