Volumetric segmentation-free method for rapid visualization of vascular wall shear stress using 4D flow MRI

Area of Science:

• Cardiovascular Imaging
• Biomedical Engineering
• Fluid Dynamics

Background:

• Wall shear stress (WSS) is crucial for understanding cardiovascular health and disease.
• Abnormal WSS levels are linked to various cardiovascular pathologies.
• Existing WSS computation methods are hindered by time-consuming manual segmentation.

Purpose of the Study:

• To develop a rapid, segmentation-free method for visualizing and computing WSS in the aorta.
• To enable automated analysis of WSS from 4D Flow MRI data.
• To overcome the limitations of traditional labor-intensive WSS calculation techniques.

Main Methods:

• A novel volumetric technique was employed to compute WSS.
• Inward normal vectors were approximated using the gradient of fluid speed.
• Shear stress was calculated as partial derivatives of velocity with respect to inward normal vectors.
• Edge-emphasized anatomical data was fused with WSS visualization.

Main Results:

• The method successfully visualized and quantified WSS in four cases with aortic pathologies.
• Pathological WSS regions were rapidly localized through visualization.
• Average WSS in non-pathological aorta regions was 50-60 cPa during peak systole.
• Elevated WSS was observed in stenosis, coarctation, and dissection; reduced WSS in aneurysms.

Conclusions:

• A volumetric, automated method for WSS calculation and visualization from 4D Flow MRI has been developed.
• This segmentation-free approach significantly reduces processing time compared to traditional methods.
• The technique shows potential for facilitating clinical translation of WSS analysis in cardiovascular disease.