Sonja Jäckle

• Currently, two-dimensional (2D) fluoroscopy and conventional digital subtraction angiography are the gold standard for the navigation of medical instruments in many minimal-invasive interventions like the endovascular aneurysm repair (EVAR) procedures. However, this requires X-rays, contrast agent is used, and the depth information is missing. A three-dimensional (3D) guidance based on tracking systems does no have these disadvantages. The key hypothesis of the PhD work is that a tracking-based guidance of medical instruments is possible and that it facilitates the navigation in minimal invasive interventions. The evaluated use case will be the navigation of a stent graft during an EVAR procedure. First, an analysis and optimization of a fiber optical shape sensing (FOSS) model is conducted: The usage of an optical fiber with fiber Bragg gratings (FBGs) allows measuring the shape of a medical tool. Here, methods from literature are analyzed and evaluated in different experiments. The accuracy of the obtained optimized shape sensing model is evaluated with different 3D measurements. Then, novel tracking-based guidance methods are introduced: The combination of FOSS and EM sensors allows determining the located shape of medical instruments. For this purpose, a spatial calibration method for an optical fiber and EM sensors is introduced. Moreover, the methods for obtaining the located shape using three, two or only one EM sensor (together with preoperative data). The guidance methods have been evaluated in different experiments and compared with an image-based 3D shape localization approach. In addition, the developed approaches are applied in order to guide a stent graft in EVAR procedures. A spatial calibration between stent graft and tracking systems and a suitable visualization of the guidance information are described. This stent graft guidance method was evaluated by conducting an EVAR procedure on a torso phantom.