Fig 2. An example of how hemodynamic parameters are computed. A, Wall shear stress distribution. Wall shear stress is in newtons per square meter. Maximum wall shear is determined from the entire aneurysm region and is not limited to the ostium. B, Aneurysm surface is defined, and mean wall shear stress is the average of the wall shear over the entire aneurysm surface. C, The ostium is determined by a plane between the aneurysm and the parent artery, and the ostium area is calculated from the shaded region. D, The mean ostium shear is calculated from the average of wall shear around the circumference of the ostium. A similar procedure is used to determine the average wall shear for the parent artery. A variable wall shear stress is often found at the ostium.