Comparison of turbulent flow measurement schemes for 4D flow MRI

Recently, time-resolved 3D phase contrast magnetic resonance imaging, which is also called 4D flow MRI or 4D PC-MRI, has been widely utilized to investigate spatial and temporal variations in the hemodynamic characteristics of blood flows. The conventional 4D flow MRI only provides the ensemble-averaged mean flow information but misses flow fluctuation because of turbulence. There have been some new manners for turbulence quantification of the blood flow using 4D flow MRI to acquire the fluctuation intensity of the turbulent flow. Although the previous studies showed that a minimum of six flow encoding is needed to perfectly describe six independent components of the 3 × 3 symmetric Reynolds stress tensor, the optimum flow encoding scheme for turbulence has not been clearly revealed. In this study, we compared and evaluated the uncertainty of mean velocity and Reynolds stress tensor in 4D flow MRI with various flow encoding schemes. The results showed that six- to fifteen-direction measurements could result 29–51% less noise in the velocity field and 34–57% less noise in the TKE field. In addition, higher number of flow encoding had less noise in Reynolds stress estimation.