Imaging and CFD in the analysis of vascular disease progression

Conventional evaluation of the significance of vascular disease has focused on estimates of geometric factors. There is now substantial interest in investigating whether the onset and progression of vascular pathology can be related to hemodynamic factors. Current imaging modalities have excellent capabilities in delineating the geometric boundaries of the vascular lumen. Advanced non-invasive imaging modalities such as Multi Detector CT and MRI are also able to define the extent of disease within the vessel wall and to provide information on the composition of thrombotic and atherosclerotic components. Finally, it is also possible to use imaging techniques to measure flow velocities across the lumen of vessels of interest, and to determine the pulsatile variation of these velocities through the cardiac cycle. Despite these advanced capabilities, imaging alone is unable to determine important features of the vascular hemodynamics such as wall shear stress or pressure distributions. However, the information on lumenal geometry and the inlet and outlet flow conditions can be used as input into numerical simulation models that are able to predict those quantities. These Computational Fluid Dynamics models can be used to predict hemodynamic parameters on a patient-specific basis. It is therefore possible to use non-invasive imaging methods to follow the progression of vascular disease over time, and to relate changes in lumenal and wall structure to calculated hemodynamic descriptors. This approach can be used not only to understand the natural progression of vascular disease, but as a tool to predict the likely outcome of a surgical intervention.