Automatic Detection of Stent Graft Markers in 2-D Fluoroscopy Images

An abdominal aortic aneurysm (AAA) is a widening of the aorta which can lead to death if the aneurysm ruptures. To prevent a rupture, the AAA has to be repaired by open surgery or by endovascular aneurysm repair (EVAR). In the recent years, EVAR achieved more popularity. In the procedure, a stent graft is placed at the position of the aneurysm to exclude it from the direct blood flow. The stent graft has to be positioned very precisely to prevent occlusion of the renal arteries. In advanced software tools, a segmentation of the aorta from computed tomography (CT) is available and the position of the two renal arteries is known. Their position is marked as an elliptical marker in the fluoroscopic overlay during the intervention. This paper describes a method to automatically detect stent graft markers to provide a second elliptical marker derived from the current stent position only. This helps the physician to get a comparison between the planned and the current position of the stent graft. The recall of the marker detection is 92% and the sensitivity is 96%. For the center of the fitted object we get a mean error of 1.60±1.69 mm.