Experimental study of coil delivery wire insertion force in intracranial aneurysm embolization: force discrepancy generated inside the microcatheter through that coil delivery wire passes.

In endovascular coil embolization for intracranial aneurysms, as coils are filled in the aneurysm and the stage of procedure is advanced, the force to push forward the coil delivery wire (insertion force) increases. However, the coil insertion force that interventionist's felt at his fingertips does not directly reflect the stress of the aneurysm and is affected by the resistance generated inside the microcatheter through that the wire passes. The authors evaluated this force discrepancy by subtracting the loading force at the tip of delivery wire from the insertion force of delivery wire and examined the relationship among them. Experiments were performed with the device that applies a constant loading force to the delivery wire tip with the coil removed. A force gauge was connected to the end-tip of the delivery wire to measure the insertion force. The force was measured by changing delivery wire in different coil brands and the conditions of microcatheter (straight or bent position). The results demonstrated that force discrepancy generated inside the microcatheter increased as the loading force increased in a linear relationship. Different coil delivery wires produced differences in the way that force discrepancy changed, thus reflecting the properties of each wire. Microcatheters with more curvature were associated with a higher force discrepancy. In conclusions, as the loading force increases, the force discrepancy increases, and it means that the coil insertion force that the interventionist feels at his fingertips also increases. This force discrepancy is impacted by the delivery wire properties and microcatheter curvature.

Clinical Application of Insertion Force Sensor System for Coil Embolization of Intracranial Aneurysms.

INTRODUCTION: In endovascular embolization for intracranial aneurysms, it is important to properly control the coil insertion force. However, the force can only be subjectively detected by the subtle feedback experienced by neurointerventionists at their fingertips. The authors envisioned a system that would objectively sense and quantify that force. In this article, coil insertion force was measured in cases of intracranial aneurysm using this sensor, and its actual clinical application was investigated. METHODS: The sensor consists of a hemostatic valve (Y-connector). A little flexure was intentionally added in the device, and it creates a bend in the delivery wire. The sensor measures the change in the position of the bent wire depending on the insertion force and translates it into a force value. Using this, embolization was performed for 10 unruptured intracranial aneurysms. RESULTS: The sensor adequately recorded the force, and it reflected the operators' usual clinical experience. The presence of the sensor did not affect the procedures. The sensor enabled the operators to objectively note and evaluate the insertion force and better cooperative handling was possible. Additionally, other members of the intervention team shared the information. Force records demonstrated the characteristic patterns according to every stage of coiling (framing, filling, and finishing). CONCLUSIONS: The force sensor system adequately measured coil insertion force in intracranial aneurysm coil embolization procedures. The safety of this sensor was demonstrated in clinical application for the limited number of patients. This system is useful adjunct for assisting during coil embolization for an intracranial aneurysm.