Ischemic stroke is a leading cause of death and disability worldwide. It is an emergency condition in which a blood clot obstructs an artery in the brain, leading to progressive brain damage. In recent years, a minimally-invasive endovascular procedure - mechanical thrombectomy - has been developed for the extraction of the thrombus. The procedure has proved to be effective in a large number of cases, however, with variable delays resulting in variable clinical outcomes. The delay comes from multiple factors - difficult clot penetration, unadapted choice of thrombectomy technique, or wrong arterial branch in which the technique is performed. In this thesis, done in collaboration with the team of Prof. Paolo Machi from the University Hospitals of Geneva, we build foundation blocks for the development of an efficient and safe robotic mechanical thrombectomy. We tackle the challenges of clot penetration and identification, and we propose the development of a teleoperated endovascular robotic system, which aims to provide several advantages with respect to the conventional manual procedure - a safer and more ergonomic environment for the interventionalist, potential for strategies with shared control between human and robot, improved precision and improved force sensitivity.
We developed three endovascular robotic devices for guidewire navigation and one haptic leader device. We evaluated the haptic device in combination with one of the guidewire navigating robotic devices in an in vitro experiment with three experts in mechanical thrombectomy. Three robotic control modalities were tested, and even though several improvements are necessary particularly regarding the force feedback implementation, interventionalists recognized the system's potential to enhance not only mechanical thrombectomy but also a range of other neuroendovascular procedures.
We investigated different clot penetration strategies and analyzed the information that can be extracted from the measurement of the interaction forces between the guidewire and the clot. In particular, with a strategy of constant translational velocity, we demonstrated that the interaction forces depend on factors such as the volume of the clot, the stiffness of the clot, and the pressure with which the clot is impacted in the artery. We concluded that additional factors not investigated enough in this thesis, such as the fracture toughness of the clot, may be essential to fully explain the observed force profiles. We also developed an autonomous clot penetration strategy combining translational and rotational movements according to a force-based law. This strategy proved to be efficient in penetrating clots with different consistencies both in a straight arterial model and in a realistic vascular model.
Finally, we developed methods for the identification of the beginning and the end of the clot. We focused on a force-based method with a force measurement at the proximal end of the guidewire, but we al
