Fig 4. Patient with a fusiform aneurysm of the distal basilar artery. Left, Registration of the lumen of the baseline study (blue) and the most recent study (red). Consistency of threshold across studies is ensured by requiring volume preservation in a reference segment of the carotid artery (black arrow). A detail of this registration by using a mesh display is shown on the right side showing the asymmetrical increase of the lumen volume of the aneurysm.