Adaption of 3D Models to 2D X-Ray Images during Endovascular Abdominal Aneurysm Repair
Endovascular aneurysm repair (EVAR) has been gaining popularity over open repair of abdominal aortic aneurysms (AAAs) in the recent years. This paper describes a distortion correction approach to be applied during the EVAR cases. In a novel workflow, mode
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1 Siemens Healthcare GmbH, Forchheim, Germany Pattern Recognition Lab., Friedrich-Alexander-University Erlangen-Nuremberg, Erlangen, Germany
Abstract. Endovascular aneurysm repair (EVAR) has been gaining popularity over open repair of abdominal aortic aneurysms (AAAs) in the recent years. This paper describes a distortion correction approach to be applied during the EVAR cases. In a novel workflow, models (meshes) of the aorta and its branching arteries generated from preoperatively acquired computed tomography (CT) scans are overlayed with interventionally acquired fluoroscopic images. The overlay provides an arterial roadmap for the operator, with landmarks (LMs) marking the ostia, which are critical for stent placement. As several endovascular devices, such as angiographic catheters, are inserted, the anatomy may be distorted. The distortion reduces the accuracy of the overlay. To overcome the mismatch, the aortic and the iliac meshes are adapted to a device seen in uncontrasted intraoperative fluoroscopic images using the skeletonbased as-rigid-as-possible (ARAP) method. The deformation was evaluated by comparing the distance between an ostium and the corresponding LM prior to and after the deformation. The central positions of the ostia were marked in digital subtraction angiography (DSA) images as ground truth. The mean Euclidean distance in the image plane was reduced from 19.81±17.14 mm to 4.56±2.81 mm. Keywords: computational geometry, as-rigid-as-possible, mesh deformation, abdominal aortic aneurysm, EVAR.
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Introduction
The abdominal aortic aneurysm (AAA) is one of the most frequent aortic diseases. It is a dilatation of the abdominal aorta. AAAs, such as cardiac diseases, are becoming increasingly more common due to the continuous aging of the population. In the case of aneurysm rupture, 60% of the patients reach the hospital alive and 65% of these patients die during elective repair [1]. Detection of AAAs prior to rupture is challenging. They are mostly asymptomatic, thus often found accidentally. If the aneurysm diameter exceeds 5.5 cm or its expansion is rapid, it is decided for elective repair [9]. Endovascular aneurysm repair (EVAR) represents a more novel approach than open surgery. During an EVAR intervention, c Springer International Publishing Switzerland 2015 N. Navab et al. (Eds.): MICCAI 2015, Part I, LNCS 9349, pp. 339–346, 2015. DOI: 10.1007/978-3-319-24553-9_42
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the operating physician inserts endovascular instruments through minor incisions at the groins and places a stent graft into the body of the aneurysm to exclude the weakened wall of the aorta from the blood flow. EVAR causes less trauma to the patient and the recovery times are significantly shorter compared to open repair. There is no difference in long-term mortality rates, but the short-term death rate of EVAR is significantly lower [10]. EVAR procedures are navigated by X-ray fluoroscopic images. To visualize vascular structures during the intervention, iodinated contrast agent is injected. However, as the pa
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