Non-rigid 2D-3D image registration for use in Endovascular repair of Abdominal Aortic Aneurysms

Ruptured abdominal aortic aneurysms are a relatively common cause of death in the western world. Endovascular repair can be used to reduce the risk of rupture and is becoming the preferred method of treatment in lieu of open surgery. However, intraoperatively only 2D fluoroscopy imagery is available to the surgeon making complex repair difficult. We have been investigating the use of a rigid 2D-3D registration system which enables information from the CT to be overlaid onto the fluoroscopy images during the procedure. The main limitation of this method is that the rigid interventional instruments deform the aorta. This paper investigates the use of manually picked landmarks and the thin plate spline algorithm to deform the CT surface so it more accurately represents the interventional scene. Experiments are carried out on data from eight patients. Results show that the mean error in visceral ostia positions can be reduced from 4.7mm± 2.9mm (mean±standard deviation) to 2.7±1.2mm and 3.2±1.4mm for intra-observer and interobserver guided deformation respectively.