Figure 3.

A lesion at the entrance of the middle cerebral artery produces the largest difference in the proximal and distal velocities. Lesions of increasing size from 25% to 75% of the artery diameter were placed at the entrance of MCA, ACA, MCA-1, and MCA-2 (areas affected by low WSS) in order to produce stenotic lesions (a). Dotted lines represent slices where the mean velocity was measured in the proximal (top panel) and distal (middle panel) MCA. Mean velocity in the proximal MCA increased with lesion magnitude when narrowing occurred at the entrance of the MCA (b) and ACA (c). Lesions in M2-A and M2-B had a negligible effect on velocity, despite lesion magnitudes of 75% (d, e). In the distal end of the MCA, the mean velocity decreased with increasing MCA stenosis (f). Increasing the magnitude of the ACA lesion led to an increased velocity in the distal MCA (g), and stenoses in the M2-A and M2-B did not affect velocity (h, i), matching observations seen in the proximal MCA. In the bottom panel, percent change in the maximum mean velocity was calculated in respect to lesion magnitude and location. A lesion in the MCA entrance produced the greatest difference in percent change, increasing and decreasing in the proximal and distal MCA velocity, respectively (j). Lesions in the ACA, MCA-1, and MCA-2 entrances have the same effect on both the proximal and distal velocities (k–m)