Fig. 4

Comparison of low and high velocity encoded 4D flow CMR of the TIPS stent graft. 4D flow CMR performed at the maximum flow rate of 2.8 l/min resulted in flow acceleration within the TIPS stent graft above 1 m/s. A Velocity encoding at 1 m/s resulted in aliasing within the TIPS stent graft with consecutive erroneous calculation of pathlines as indicated by pathlines perpendicular to the fluid flow (arrow). B Velocity encoding at 2 m/s showed no aliasing within the TIPS stent graft and resulted in correct calculation of velocity-coded pathlines. Note that aliasing with erroneous calculation of pathlines results also in erroneous quantification of flow rates and flow velocities. SMV  superior mesenteric vein, SV  splenic vein, PV  portal vein