Two-dimensional versus three-dimensional registration for image fusion in endovascular aortic surgery

ObjectiveImage fusion allows for reduced operative time and radiation exposure during endovascular aortic operations. There are two approaches to register a preoperative CT scan to the patient; two X-ray images (2D) or a cone beam CT (CBCT, 3D). The goal of this study was to compare accuracy of initial image fusion alignment and time for image fusion setup using 2D versus 3D registration.MethodsWe performed an analysis of patients who underwent endovascular aortic aneurysm repair at our institution. Offline, we re-registered the patient's preoperative CT scan to the images stored from the procedure. We used an anterior-posterior image and a lateral image to register for the 2D approach and used a CBCT for the 3D registration. We then used the patient's initial aortogram to assess accuracy between the actual aortogram and the created virtual mask for both 2D and 3D registration. We chose the inferior angle between renal artery and aorta as the fiducial marker. We measured the time to complete two registration processes. We employed the Wilcoxon matched-pairs signed-rank test to compare the two populations.ResultsA total of 27 patients were evaluated; 11 patients underwent EVAR, 3 FEVAR, 13 PMEG. The median (Q1,Q3) distance between the aortogram and the virtual mask for 3D registration was 8 mm (4,11) and for 2D was 14 mm (9,18.75), (p < .001). 22 patients (81%) had a more accurate registration with 3D image fusion. 2D fusion on average was faster by 93 seconds (p < .001) where time to register was 105 seconds for 2D and 197 seconds for 3D registration.ConclusionsIn the current study, 3D registration showed improved alignment of the fusion image over the 2D registration, at the expense of a longer registration time. This should be further evaluated in larger studies. Despite this added effort, we believe that 3D registration should be considered the preferred initial approach given the importance of an accurate mask for complex procedures.