Nav EVAR

This BMBF-funded project (funding code: 13GW0228C) began in October 2017 and will conclude in October 2020. In addition to Fraunhofer MEVIS, the consortium includes the Institute for Robotics and Cognitive Systems at the University of Lübeck, the Medical Laser Center Lübeck GmbH and the Clinics for Surgery and Radiology at the University Hospital Schleswig-Holstein in Lübeck.

In western industrialized nations, cardiovascular diseases, such as abdominal aortic aneurysm, (AAA) are some of the most frequent causes of death. In 80% of cases, AAAs are symptom free and are usually detected only by chance. When AAAs are detected, they are treated using an endovascular aortic repair (EVAR) procedure, in which a stent graft is placed in the aneurysm region. Before the procedure, a preoperative 3D CT scan is made to analyze the position and size of the aneurysm and to prepare the surgeon. Nowadays, endovascular aneurysm repair (EVAR) procedures are conducted with 2D fluoroscopy and conventional digital subtraction angiography for catheter guidance. These image modalities have several drawbacks: They require X-ray exposure and, in addition, potentially kidney damaging contrast agent is used to visualize the vessel volume. Moreover, the depth information is missing. Thus, different technologies are being evaluated to answer the following questions:

• How can the position and shape of a catheter be determined without using X-ray imaging and contrast agent?
• How can images and data be visualized alongside the catheter position during the operation to be suitable for the surgeon?
• What accuracy can be achieved, and can we forgo X-ray imaging by adopting other technologies?

Tracking based catheter guidance

Optical fibers with fiber Bragg gratings (FBGs) are a suitable alternative to reconstruct the shape of medical tools. FBGs are small interference filters carved into the core of an optical fiber. These reflect a specific wavelength, which is changed when the fiber is bent. This makes up the basic principle of shape sensing. Combined with electromagnetic tracking, the 3D shape of the catheter can be located.

2D/3D registration

The fusion of currently acquired 2D fluoroscopy image with the preoperative CT scan can facilitate navigating surgical instruments inside the body. The goal of 2D/3D registration is to transform the 3D image so that its projection best matches the 2D image. The resulting transformation connects the 3D images with the 2D images. This allows to transfer the planning information into the currently acquired fluoroscopy image or to back-project the tracked medical instruments.

Improved visualization

Using the preoperative CT scan, the aorta structure and a generated virtual angioscopy can be shown the physician during the intervention without using additional tools or devices. Moreover, all images and objects are visualized with augmented reality devices. By wearing smart glasses with augmented reality, such as the HoloLens, screens and 3D objects can be placed in the field of view. To show all image information, the generated images are streamed to the HoloLens.