In vitro measurement of tool-artery interaction forces during endovascular neuro-surgery using silicone phantoms
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Endovascular neurosurgery has gained acceptance as the better method of treatment of cerebral vascular abnormalities like atherosclerosis and cerebral aneurysm. However, the procedure is associated with difficulties in tool/tissue manipulation. Navigating tools through arterial complexities without appropriate visual or force feedback information often causes tool snagging, plaque dislocations and formation of thrombosis from the damage of the arterial wall by the tools. As stroke is a defined risk at every stage of these procedures, proper visual and force feedbacks and adequate cognitive and technical training are essential for safe performance of cerebral endovascular procedures. Currently, there is no haptic device available for pre-operative planning and training of junior surgeons, which identifies critical areas in the path of stent movement and provides the surgeons with measured force values at particular locations to prevent wall damage, thrombosis, or plaque dislocation. This work is the first step in developing such a simulator, where forces of stenting were measured in vitro and dependency of these forces on the vessel geometry were evaluated. Based on these forces, a data base for a fast synthetic endovascular force simulator can be developed, which will provide the surgeon with information of tool-artery interaction forces, based on the various combinations of tool-artery diameters and vessel complexity. Forces were measured and mapped along the path of stent movement using a color code. It was observed that the forces changed along the length of the vessel, independent of the insertion length but based on the curvature of the vessel and the contact area of the tools in the vessel lumen. The geometrical complexity of the phantom was calculated as tortuosity and the forces were correlated. However, the measured forces did not correlate well with the tortuosity index calculated.