# An Assisted Numerical Simulation Diagnosis Method for Atherosclerosis Based on Hemodynamics
## 5 Conclusions  
The numerical simulation of blood flow in blood vessels is a combination of biomedical engineering, fluid mechanics, and computer science. This research can help visualize the physical mechanisms of blood flow, predict and evaluate the occurrence and development of cardiovascular diseases, and guide clinical treatment and surgical procedures. A region with high flow velocity in the middle of the lumen and a region with low flow velocity in the secondary flow near the medial wall of the lumen could be found at the distal end of the stenosis in a single lesioned vessel; the flow rate was between 0.09 m/s and 0.15 m/s. Lower blood flow rates and overall shear stress levels in the region induce changes in fluid properties that were more suitable for lesion development. The shear stress here was all less than 20 Pa, which was 35-45% lower than the shear stress in normal blood vessels. Greater stenosis resulted in a lower flow velocity in the region of secondary flow caused by the vessel and a greater difference in flow velocity at the peak and trough of the cardiac cycle; the difference between the maximum and minimum values was greater than 1.5 m/s. The bifurcation structure of the vessel posed a remarkable effect on the rheological properties of blood flow. The shear stress at the proximal and distal ends of normal blood vessels was about 20 Pa, while that at the proximal and distal ends of diseased blood vessels was about 80 Pa and 30 Pa, respectively. The shear stress in the downstream area of the fork was less than 10 Pa. Very low shear stress was produced at the bifurcation site, creating a focal area of atherosclerosis. When a lesion occurred at the bifurcation site, a more pronounced mechanical environment with very low and oscillating tangential stresses was produced at the distal end. At this time, the shear stress at the distal end was between 1.3 Pa and 1.6 Pa. In comparison, at the lesion structure, blood pressure at the proximal end of the bifurcation site was considerably greater than that at the distal end, creating conditions for the detachment of the atheromatous lesion tissue, because of the greater shear stress experienced by the atheromatous tissue. The proximal blood flow rate was higher than 1.0 m/s, which was more than 30% higher than the normal blood vessel flow rate. Low shear stress and high pressure difference were the main factors for atherosclerosis. The pressure difference between the two sides of the stenosis was greater than 900 Pa, compared with 150 Pa at the same distance in the healthy blood vessels. In the lesioned vessels, dramatic oscillatory changes could be produced by wall shear stress, and a remarkable increase in local blood pressure differential within the vessel was observed. Such phenomena were clearly different from the flow characteristics of healthy vessels. The difference in pressure between healthy and diseased blood vessels was very significant. Therefore, through the feedback mechanism of lesions on blood flow characteristics, numerical simulation of blood flow characteristics could be used to achieve the prediction and follow-up of atherosclerosis. Blood flow parameters such as blood pressure and shear stress were obtained by numerical simulation. The simulation results were compared with a large sample of patient data to establish associations between these parameters and lesions. This approach was not limited to the prediction and diagnosis of atherosclerosis. It could also be used for prediction and diagnosis of other vascular diseases. Mathematical models could be built to accurately predict various vascular diseases by obtaining enough cases as samples to train mathematical models and boundary conditions. This would help doctors make accurate diagnoses and treatment plans quickly. There were only few artery samples performed in this study. The sample size may not be enough to cover all cases.