"uuid","repository link","title","author","contributor","publication year","abstract","subject topic","language","publication type","publisher","isbn","issn","patent","patent status","bibliographic note","access restriction","embargo date","faculty","department","research group","programme","project","coordinates" "uuid:2de7c624-6749-4487-be0f-db61fc73c7f5","http://resolver.tudelft.nl/uuid:2de7c624-6749-4487-be0f-db61fc73c7f5","Development of a variable rigidity guide wire","Knippenberg, S.B.","Dankelman, J. (mentor); Loeve, A.J. (mentor)","2016","In some types of endovascular surgery on the aorta, a catheter needs to be placed in a renal artery to enable renal artery stenting. Therefore, a catheter and a medical guide wire are maneuvered through the vascular system and placed inside the renal artery. In one in eight patients, the renal artery is angulated ≤50°, which could cause the catheter and the guide wire to deflect from the renal artery in direction of the heart. In the case that deflection leads to retraction of the catheter and guide wire from the renal artery, new attempts should be made to access the renal artery. The associated risks with the placement of a catheter and a guide wire are: embolization, subintimal dissection (18% of the renal artery stenting attempts) and prolonged intervention time and fluoroscopy. To prevent the foregoing problems, this project was dedicated to the development of a medical guide wire that comprises of a distal segment, from which its rigidity could be controlled and varied. A concept of laced cylinders was designed that consisted of four segments: a Variable Rigidity Segment (VRS); a shaft; a locking system and a handle. The VRS was made from a stack of cylindrical structures with curved contact surfaces between the structures. The curved contact surfaces enabled bending of the VRS because the structures were essentially rotated over one another. The cylindrical structures were stacked upon the shaft of the laced cylinders concept. Compression of the cylinders was realized by a pull wire, which ran on the inside of the laced cylinders concept from the most distal cylinder to the proximal side of the concept—where the pull wire was attached to a handle. By pulling the handle, the cylinders in the VRS were pressed on the shaft and thus the rigidity of the VRS was increased. A demonstrator of the laced cylinders concept was manufactured, which comprised a stack of 50 cylinders with a diameter of 7 mm. The stack of cylinders enabled omni-directional bending, wherein the rigidity in the stack of cylinders could be altered—without inflicting movement. Based on the experiments that were done on the demonstrator, was determined that the rigidity could be altered between 3-22 GPa, as a function of 3-21 N tensile force on the pull wire. To put the rigidity of the demonstrator in perspective; 22 GPa was half the rigidity of a commonly used stiff Radifocus guide wire (Terumo corp., Tokyo, Japan). The feasibility and functionality of the demonstrator, has shown the potential of the laced cylinders concept and has advanced the creation of a variable rigidity guide wire. Concerning rigidity control, the friction force between the cylinders was found to be the primary parameter and essential for estimation. The estimations on rigidity in the demonstrator correlated highly (R=0.98) with the experimental rigidity. Although the results were obtained with few measurements (n=3), the high correlation indicated that the estimator in this project was a good tool for determining the rigidity in the variable rigidity segment. However, more measurements are required for proper validation of the estimator.","medical guide wire; variable rigidity; catheterisation; rigidity control","en","master thesis","","","","","","","","","Mechanical, Maritime and Materials Engineering","Biomedical Engineering","","","",""