Abstract
Object: In endovascular coil embolization for a cerebral aneurysm, coil insertion is usually performed simply by advancing the coil-delivery wire steadily, without any torque handling. However, the relation between coil insertion force and coil/microcatheter behavior is complex and has not been sufficiently investigated. In this experiment, the authors measured the coil insertion force and observed the coil and catheter-tip movement during aneurysm embolization. Thus, the generation pattern of coil insertion force was investigated and the most suitable insertion method and speed were discussed.
Methods: A new sensor device which consists of a Y-connector was developed. The sensor principle is based on an optical system measuring how much the coil-delivery wire slightly bends in response to the insertion force. Using this device, experimental coil embolizations were performed with silicone aneurysm models. The manipulations were done by hand or by machine at a constant speed. The sensor continuously monitored the mechanical force during the insertions. The coil movement was observed on a microscopic image. The pattern of coil insertion force and the time distribution ratio of the force were analyzed.
Result: With manual insertion, the coil insertion force was mainly induced by the stop and advance movement of the wire generated in synchrony with the push-pull-push movement of the surgeon's hand. With mechanical insertion, the insertion speed caused a difference in the force pattern. With the coil movement, the friction between the coil and aneurysm wall was determined by insertion method and insertion speed. Thus, the friction state (static friction or kinetic friction) affected the mechanical force.
Conclusion: It was demonstrated that the friction state influenced the generation pattern of coil insertion force. Applying the proper insertion method and insertion speed to maintain the kinetic friction state between the coil and the aneurysm wall might provide less stressful coil insertion force and safer embolization.
