Figure 2 A thrombotic aneurysm on the posterior communicating artery of the right internal carotid artery of a 51-year-old man. (A) Initial reconstructed virtual reality image of 3-dimensional time of flight magnetic resonance angiography (3D-TOF-MRA) showing a right internal carotid artery posterior communicating initiating aneurysm, but not maximal visualization of the aneurysm. (B) On the basis of Figure A, the virtual reality image with a larger window width showing the aneurysm to the greatest extent, and displaying the rough and uneven shape of aneurysm with a size of 2.1 cm and aspect ratio value of 2.9. Line (a) represents the aneurysm neck; line (b) represents the height of the aneurysm; line (c) represents the width of the aneurysm; (d1) and (d2) represent the diameter of the aneurysm parent artery related to the aneurysm; that is, the largest parent within 5 mm from the proximal aneurysm neck. (C) Sagittal T2WI image from the GE 2D HR-MRI scanner showing the uneven hypointense thrombus spreading from the aneurysm body to the neck. (D) Enlarged view of (B) showing the morphology and distribution of the thrombus within the aneurysm neck. All images were analyzed by GE adw 4.5 post-processing workstation.