Fig 1. Anteroposterior views of rotational angiogram, magnitude image, and 2D velocity vector field traversing M1 segment and two M2 segments of the right middle cerebral artery (MCA).

A, A surface rendering image obtained from rotational digital subtraction angiogram of the right internal carotid artery reveals that the blood flow moves through the M1 segment of right middle cerebral artery (MCA) (white arrow) and then diverges into the two M2 segments (anterior trunk of MCA [white small arrow] and posterior trunk of MCA [white arrowhead]). There is an aneurysm in this bifurcation of MCA.

B, A magnitude image traversing M1 segment and two M2 segments of the right MCA. White arrow, M1 segment; white small arrow, anterior trunk of MCA; white arrowhead, posterior trunk of MCA.

C, 2D velocity vector field traversing the M1 segment and two M2 segments of right MCA shows counter-clockwise vortex flow in the aneurysm. It demonstrates flow velocities near the vascular wall. 2D velocity vector fields can be displayed as cine images like a movie on a computer display. Numbers and colors correspond with flow rate in the legend at the right side in the figure regarding 2D velocity vector fields. Units in meters per second. Flow rate in the aneurysm is less than 15 cm/s.