Fig 1. A, Volume-rendering 3D image of left MCA aneurysm, posteroanterior view, before growth. Arrow indicates outpouching (bleb) on the aneurysm dome. B, Volume-rendering 3D image of the same left MCA aneurysm, posteroanterior view, after growth of the aneurysm bleb (arrow). C, A silicon aneurysm model of the left MCA aneurysm before growth. D, A silicon aneurysm model of the left MCA aneurysm after growth.