Hemodynamic analysis of non-stenotic middle cerebral artery in patients with cerebral ischemia based on 4D flow MRI

Abstract

Objectives: Changes in cerebral hemodynamics in symptomatic states among patients with cerebral ischemia remain unclear. This study endeavors to investigate the characteristics of hemodynamics distribution within the non-stenotic middle cerebral artery (MCA) in patients with anterior circulation cerebral ischemia.

Materials and methods: All subjects were prospectively recruited in this study. According to the clinical features of cerebral ischemia symptoms, they were divided into ischemia group and healthy group. MCA was further divided into proximal, curved, and distal segments based on the vascular morphology. Hemodynamic parameters, including flow, peak flow velocity, wall shear stress (WSS), pressure and energy loss (EL) were measured for each segment of the MCA in both groups using 4D flow MRI. The hemodynamic parameters of the proximal, curved, and distal MCA segments were compared within the group, and the influence of MCA morphology on hemodynamics was analyzed. Additionally, the hemodynamic parameters of the proximal, curved, and distal MCA segments were compared between the healthy and the ischemic groups to analyze the hemodynamic changes in the MCA among patients with cerebral ischemia.

Results: A total of 50 MCAs were included in healthy group and 30 MCAs in ischemia group. There were no statistically significant differences in gender, age, heart rate, presence of hypertension and Body mass index (BMI) between the two groups. Results showed that the proximal segment had the highest blood volume (all P < 0.05), the M1 segment of MCA had the highest pressure (Max) and EL (Max and Avg) (all P < 0.01) in both groups. The peak blood flow velocity of the proximal and curved segments, the circumferential WSS of the distal segment, and the EL (Max and Avg) of the M1 segment in the ischemia group were lower than those in the healthy group (all P < 0.05).

Conclusion: The distribution of hemodynamics in MCA is similar between anterior circulation cerebral ischemia patients and healthy group. In the ischemic group, the peak blood flow velocity, circumferential WSS, and EL of MCA were lower compared to the healthy group. The reduced flow velocity and the decrease of circumferential WSS in the curved section may be contributing factors to cerebrovascular events.

Keywords: 4D flow MRI; WSS = wall shear stress; cerebral ischemia; hemodynamics; middle cerebral artery; peak velocity.

FIGURE 1

The acute angle between straight line M1M1’ and straight line M2M2’ is greater than 10°, defined as curved MCA (A), C-type MCA (B), S-type MCA (C). (D) Shows the placement of slices, proximal (red line), curved (green line), distal (yellow line).

FIGURE 2

EL1, EL2 and EL3 represent proximal cross-sections, curved cross-sections, and distal cross-sections, respectively, in MCA. EL_A represents the energy loss between EL1 and EL2; EL_B represents the energy loss between EL2 and EL3; EL_C represents the energy loss between EL1 and EL3. To facilitate representation of statistics, we define EL_A as the EL in the proximal segment, EL_B as the EL in the curved segment, EL_C as the EL in the distal segment. (Pressure is expressed in the same way).

FIGURE 3

Flow chart of patient intake. N represents the number of patients, n represents the number of blood vessels.

FIGURE 4

A 61-year-old male patient was admitted to the hospital because of weakness of the right limb. DWI (A) and ADC (B) images showed that the local diffusion near the posterior horn of the left ventricle was limited, suggesting acute cerebral infarction; FLAIR images (C) showed that there was no old cerebral infarction in the left hemisphere; 3D-TOF-MRA (D) shows that intracranial artery has no stenosis; 4D Flow image generates MCA simulation image, and the selected measurement flow position is as shown in the figure (E):proximal (red), curved (green), distal (yellow) and blood flow parameter values automatically generated in each measurement plane are shown in (F) (the abscissa is the cardiac cycle/ms, the ordinate is the hemodynamic parameter, the same applies to other parameter measurements).

FIGURE 5

Hemodynamic parameters were statistically significantly different within groups. (A–D) Represent the blood volume, Max pressure, Max EL, and Avg EL of the healthy group (blue), respectively. (E–H) Represent the blood volume, Max pressure, Max EL, and Avg EL of the cerebral ischemia group (green), respectively. *<0.05, **<0.01, ***<0.001.

FIGURE 6

Statistically significant differences in hemodynamic parameters were compared between groups. (A–D) Represent the peak velocity, circumferential WSS, Max EL, and Avg energy loss of the healthy group (blue) and cerebral ischemia group (green), respectively. * < 0.05, ** < 0.01, *** < 0.001.