Vascular diseases, such as stenosis and aneurysms, are often associated with changes in blood flow patterns and the distribution of wall shear stress (WSS). Modelling and analysis of the hemodynamics in the human vascular system improve our understanding of vascular disease, and provide valuable insights, which can help in the development of efficient treatment methods. In recent years, computational methods have been widely used for patient-specific modelling of blood flow in vascular structures. However, there has been limited applications of computational hemodynamics in clinical practice.
In this work, a robust and semi-automatic modelling pipeline for blood flow through subject-specific arterial geometries is presented. The framework consists of image segmentation, domain discretization (mesh generation) and computational fluid dynamics. All the three subtopics of the pipeline are explained using an example of flow through a severely stenosed human carotid artery.
Proposed Pipeline
Flowchart of the proposed pipeline. |
Blood Vessel Geometry Extraction
Segmentation of a carotid artery using GPF-based deformable model: (a) initial surface, (b) after 11, (c) after 81, (d) after 187, and (e) after 241 time-steps. |
Surface Meshing
Voxel thinning process. Initial object voxels (top left) and final skeleton (bottom right). |
Axis smoothing: (a) Initial voxel skeleton, (b) the initial centroidal lines (circles indicate voxel centres), and (c) the centroidal lines after the smoothing. |
Surface mesh generated by marching cube methods: (a) standard method and (b) advanced method. |
Cropping the surface mesh: (a) automatic determination of inlet/outlet position with different cropping planes and (b) cropped mesh. |
Surface mesh cropping: (a) unclosed mesh after trimming and (b) closed mesh after the triangulation of the inlet and outlet surfaces. |
Surface meshes: (a) mid-cut mesh after before mesh cosmetics; (b) after 10 steps of the Taubin smoothing; and (c) after edge splitting/contraction. |
Volume Meshing
Volume mesh generated for a carotid artery. |
Example results - final mesh
Final mesh used for the computation, which consists of 4 126 777 linear tetrahedral elements and 708 191 nodes with 10 structured boundary layers. |
Example results - 3D velocity distribution
3D velocity distribution within 13 slices (cm/s): (a) mid accl, (b) peak, (c) mid decel, and (d) dicrotic notch. |
Example results - wall parameter distributions
Haemodynamic wall parameter distributions. (a) and (b) Time-averaged WSS (dyne/cm2), (c) and (d) OSI. (a and c) Anterior and (b and d) posterior. |
Fundings
This project was supported by the EPSRC under grants D070554 and H024271. It was also partially supported by the Leverhulme Trust under grant F/00391/R.
Publications