Longitudinal wall shear stress evaluation using centerline projection approach in the numerical simulations of the patient-based carotid artery
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Published on: January 15, 2022
Kevin Richter1, Tristan Probst1, Anna Hundertmark1
1Institute of Mathematics, Faculty of Natural and Environmental Sciences, University of Kaiserslautern-Landau, Germany.
Insights
This study improves ischemic stroke risk assessment by developing a new method to analyze blood flow stress (wall shear stress) in carotid arteries. The improved technique reliably detects reversed blood flow, a key indicator of stroke risk.
Area of Science:
- Biomedical Engineering
- Computational Fluid Dynamics
- Cardiovascular Science
Background:
- Assessing ischemic stroke risk involves analyzing blood flow dynamics and vessel wall stress.
- Wall shear stress (WSS) and its oscillatory index are common indicators, but traditional methods struggle with complex geometries and flow patterns.
- Existing methods using amplitude-based WSS are limited in detecting negative shear stresses indicative of reversed flow.
Purpose of the Study:
- To develop and validate an improved method for evaluating longitudinal wall shear stress (WSS) for more accurate ischemic stroke risk assessment.
- To overcome limitations in current orientation-based shear evaluation caused by non-smooth vessel geometry and discontinuous tangential vector fields.
- To enhance the detection of negative WSS, signifying reversed or transverse flow, which is crucial for cardiovascular risk assessment.
Main Methods:
- Numerical simulation of blood flow in patient-specific carotid bifurcations and stenotic internal carotid arteries.
- Development of a novel approach using vessel centerline projection to create a smooth, longitudinally aligned tangential vector field.
- Validation of the improved longitudinal WSS and oscillatory index against automatically generated tangents and amplitude-based indicators in rigid and elastic models.
Main Results:
- The proposed method successfully generates a smooth, reliable tangential vector field for orientation-based shear evaluation.
- Longitudinal WSS evaluation accurately detects negative shear stresses, indicating persistent reversed or transverse flow.
- This directional analysis provides risk insights unattainable with amplitude-based WSS methods.
Conclusions:
- The improved longitudinal WSS evaluation method enhances the reliability of cardiovascular risk assessment for ischemic stroke.
- Detecting negative WSS through directional analysis is a significant advancement over amplitude-based methods.
- This technique offers a more precise tool for identifying patients at high risk of stroke due to abnormal blood flow patterns.
Abstract:
In this numerical study, areas of the carotid bifurcation and of a distal stenosis in the internal carotid artery are closely observed to evaluate the patient's current risks of ischemic stroke. An indicator for the vessel wall defects is the stress exerted by blood on the vessel tissue, typically expressed by the amplitude of the wall shear stress vector (WSS) and its oscillatory shear index. To detect negative shear stresses corresponding with reversal flow, we perform orientation-based shear evaluation. We investigate the longitudinal component of the wall shear vector, where tangential vectors aligned longitudinally with the vessel are necessary. However, resulting from imaging segmentation resolution of patients' computed tomography angiography scans and stenotic regions, the geometry model's mesh is non-smooth on its surface areas and the automatically generated tangential vector field is discontinuous and multi-directional, making an interpretation of our orientation-based risk indicators unreliable. We improve the evaluation of longitudinal shear stress by applying the projection of the vessel's centerline to the surface to construct smooth tangential field aligned longitudinally with the vessel. We validate our approach for the longitudinal WSS component and the corresponding oscillatory index by comparing them to results obtained using automatically generated tangents in both rigid and elastic vessel modeling and to amplitude-based indicators. We present the major benefit of our longitudinal WSS evaluation based on its directionality for the cardiovascular risk assessment, which is the detection of negative WSS indicating persistent reversal or transverse flow. This is impossible in the case of the amplitude-based WSS.
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