Blood flow visualization and quantification in the carotid vascular tree by phase contrast MRI

Purpose. The objective is to build a phase contrast (PC) MRI protocol, consistent with clinical practice, to provide a 3D blood flow visualization and quantification of hemodynamic parameters in the complete carotid vascular tree. Methods. The protocol composed of 2D and 4D PC-MRI sequences was applied on 6 volunteers and then on one patient diagnosed with facial cancer to prove the feasibility of clinical translation. The vessel geometry was reconstructed from the 4D sequences and the hemodynamic parameters quantified in the common, internal and external carotids and in the facial artery. Wall shear stresses (WSS) were quantified from the 2D PC-MRI sequences to benefit from their higher resolution. Results. Time evolution of the three-dimensional blood flow velocity and vorticity fields was successfully obtained in all the branches of the carotid vascular tree despite the large range of sizes. Consistent maps of blood flow distribution were provided by normalizing the local blood flows by that of the common carotid artery. They indicated that 72.4% (±3.9%) of blood flows into the internal carotid. WSS is higher in the internal (0.95 Pa at peak systole) than in the external carotid (0.53 Pa) and facial artery (0.15 Pa). Conclusion. A PC-MRI protocol, applicable to patients, was designed to quantify hemodynamic parameters in vessels ranging from a few millimeters to the centimeter in diameter. It provided a complete characterization of the hemodynamic condition evolution along the carotid vascular tree, and reference values to be compared to in case of pathology.