Wall shear stress calculations using phase contrast MRI

Phase contrast MRI (PC MRI) measurements, also called 4D flow MRI or velocity-encoded MRI, and computational fluid dynamics (CFD) simulations continue to be the only techniques for non-invasive quantification of the direction and magnitude of blood velocities within a large field of view. The techniques can be applied to any vessel of substantial size, and over the last years more and more research groups are using these blood velocities to calculate wall shear stress (WSS). WSS based on 4D flow MRI or CFD have become a readout tool in cardiovascular research, especially in the greater vessels. The aims of this thesis, entitled ‘Wall Shear Stress Calculations Using Phase Contrast MRI’, are to quantify volumetric WSS in any complex vessel geometry, using the velocity vector field data acquired by 4D flow MR measurements, and to validate this method with CFD simulations.
This thesis contributed to the 4D flow MRI field by introducing a new, open-source, algorithm to calculate WSS from 4D flow MRI data. The algorithm was validated with gold standard CFD simulations, the effect of scan parameters was assessed, and a method to compare WSS between patient groups was introduced. This information will help to improve future research on the role of WSS in vascular diseases, and to bring 4D flow MRI with its quantitative parameters a step closer to daily clinical practice.