Three-dimensional analysis of hemodynamic wall parameters in the carotid bifurcation using computer-augmented 4D flow MRI

• Applicant: Professor Dr. Andreas Harloff
• Subject Area: Clinical Neurology; Neurosurgery and Neuroradiology
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 450764008

Internal carotid artery (ICA) stenoses are a major source of stroke. Cardiovascular risk factors, plaque composition, carotid bifurcation geometry, wall shear stress (WSS), and plaque surface pressure (PSP) are considered as risk factors for the progression and rupture of ICA atheroma. MRI is ideally suited to characterize plaque morphology, and 4D flow MRI allows to measure 3D blood flow in vivo, and to calculate WSS and PSP by employing dedicated software. However, the drawback of 4D flow MRI is its limited spatial and temporal resolution that hampers detailed and accurate calculation of wall parameters. This is a particular problem in ICA stenoses with advanced lumen narrowing and blood flow acceleration. In addition, post-processing software has not yet been able to fully use the acquired 3D flow information wherefore visualization and quantification has been restricted to a 2D level. Finally, the precise calculation of WSS and PSP acting on the plaque surface are highly promising to allow prediction of plaque progression, rupture and stroke. However, these calculations are challenging and thus have not yet been correlated with plaque composition in ICA stenosis in vivo. To overcome these limitations, we plan to use a data assimilation approach to combine 4D flow MRI with computational fluid dynamics in order to enhance the quality of the measured flow field (computer-augmented 4D flow MRI). At first, available 4D flow data from a previous study in patients will be used to customize an existing data assimilation framework with a high-order Navier-Stokes solver for flow fields in the carotid bifurcation and the WSS and pressure prediction on the plaque surface and optimal 3D presentation of data. Afterwards, we will recruit at least 100 patients with ≥50% ICA stenosis with a high risk of plaque progression and study them over 24 months. Some patients will show asymptomatic progression of stenosis and/or become symptomatic and undergo surgery. This prospective patient data will be enhanced with the data assimilation framework. The resulting computer-augmented MRI data will be used to identify independent predictors of plaque stability or progression using baseline examinations in comparison with follow-up at the end of the study or prior to surgery. We hypothesize that low absolute or high oscillating shear stress or high PSP are independent predictors of plaque progression, rupture, and cerebrovascular events.In conclusion, we aim to optimally measure and interpret 3D carotid hemodynamics, obtained by 4D flow MRI and enhanced through a data assimilation process with high-order computational fluid dynamics in ≥50% ICA stenosis. It is our goal to develop an improved diagnostic tool for patients with carotid artery plaque. This may help to optimize individual treatment and ultimately prevent cerebrovascular events by determining new risk factors such as WSS and PSP, which destabilize the atheroma.

• DFG Programme: Research Grants
• International Connection: Switzerland
• Cooperation Partner: Professor Dr.-Ing. Dominik Obrist