Figure 1

Measurement of vascular diameter, angles and aneurysm deviation at the middle cerebral artery (MCA) bifurcation. (A) The arterial diameter was measured 5 mm away from the MCA bifurcation apex four times for calculation of the average value. The maximal aneurysm size indicated the maximal length of the aneurysm dome. (B) The smaller and larger lateral angle and bifurcation angle were measured at the MCA bifurcation. (C) Aneurysm deviation was measured by dividing the aneurysm neck length into two sections by the M1 central axis: L1 and L2. If L1 was > L2, the aneurysm deviated towards the L1 side. Otherwise, it deviated towards the L2 side. In this case, the aneurysm deviated towards the L2 and smaller lateral angle side.