A modified cylindrical coordinate system for the geometric analysis of abdominal aortic aneurysms

Surgical repair of abdominal aortic aneurysms (AAA) is associated with a considerable mortality rate, thus making less invasive therapies appealing. One of the more popular therapies is the placement of an endovascular prosthesis. Its function is to maintain vessel patency while attenuating the load on the AAA wall. To avoid dislodgment and migration, it is very important that the prosthesis be appropriately sized. The designer must take into account the variety of shapes to which the prosthesis must conform, and the clinician must take care to select an appropriate length. We have developed a finite element based technique which can be used for the geometric analysis of AAA. The technique requires the description of the AAA in a cylindrical coordinate system whose z-axis passes cleanly through the inside of the AAA. For a highly tortuous AAA, such an axis may not exist, rendering the mapping until recently impossible. We present a modified cylindrical coordinate system for the 3D geometric analysis of highly tortuous AAA. The method offers the additional capability for determining AAA length, which is critical to the selection of endovascular prosthesis sizing.