Identification of intra-individual variation in intracranial arterial flow by MRI and the effect on computed hemodynamic descriptors

Abstract

Objectives: To determine the intra-individual flow variation in serially acquired studies, and the influence of this variation on subsequent hemodynamic simulations using the inlet flow as a boundary condition. Author: Kindly check and confirm whether the corresponding authors are correctly identified.Confirmed.

Materials and methods: This prospective study included 51 patients (37 females and 14 males) with unruptured intracranial aneurysms who have received more than three times follow-up of 2D phase-contrast MR. The flow and velocity parameters were extracted to calculate the reproducibility and variation. Patient-specific computational fluid dynamics simulations were performed using the measured flows.

Results: Intraclass correlation coefficients for mean and maximum velocity and flow parameters ranged from 0.77 to 0.90. A 10% CV of mean flow was identified. Variations of 10% in inlet flow resulted in hemodynamic changes including 41.41% of peak systolic wall shear stress; 39.13% of end-diastolic wall shear stress; 2.79% of low shear area at peak systole; 2.12% of low shear area at end diastole: 47.57% of time-averaged wall shear stress; and 0.17% of oscillatory shear index.

Conclusion: This study identified 10% of intra-individual mean flow variation on phase-contrast MR. Intra-individual flow variation resulted in a non-negligible variation in wall shear stress, but relatively small variation in low shear area in hemodynamic calculations.

Keywords: Flow; Hemodynamics; Intracranial; MR; Reproducibility.

Fig. 1

Placement of 2D PC plane, ROI contouring and flow information extraction for a patient with an aneurysm of the left ICA. A) MIP image of CE-MRA; yellow line on anterior-posterior and lateral view shows the position of perpendicular plane at C2 segment; ROI on B) magnitude and C) phase image after automatic refinement; D) net flow plot through entire cardiac cycle; E) velocity values from 32 phases of one cardiac cycle which is consistent with a generally parabolic velocity distribution.

Fig 2

Bland Altman plots for flow and velocity parameters for paired comparisons from 3 time points. Horizontally, the average of the two measurements is plotted, and vertically, the difference of these two measurements. Middle dash line: mean difference; upper and lower dash line: limit of agreement (mean ± 1.96 standard deviation, the range between the lines represents least detectable difference). Blue: measurement agreement between first and second time point; Green: measurement agreement between first and third time point; Red: measurement agreement between second and third time point.

Fig 3

Example of computed WSS and LSA distribution on diastolic and systolic phase assuming a 10% variation in flow.