Design and Modeling of a Reloadable Coil-Delivery Instrument for Aneurysm Embolization

Aneurysm, which weakens blood vessels and is possibly lethal, can be treated by coil embolization. The detachable coil is a preferred type of embolic agent for aneurysm treatment because it offers good coil control and ease of use. On the other hand, detachable coils can be more affordable, if the coil-delivery instrument can be reusable. To achieve the reusability of a coil-delivery instrument while keeping the operation simple, this paper presents the development and experimental characterizations of a reloadable coil-delivery instrument for the deployment of detachable coils. The instrument has a distal grasping module that can be remotely controlled by an operation handle. By manipulating the operation handle, surgeons can conveniently reload, deliver, and release detachable coils. The distal grasping module includes a claw-like design with four precurved nitinol rods for clamping the coil securely during a procedure. A mechanics model based on the elliptic integral for the pre-curved beams under large deflections is proposed to model the beam behaviors and facilitate the design of the claws for adequate clamping force. Experiments were conducted to provide a quantitative suggestion on choosing the parameters of the claw and to verify the effectiveness of the elliptic integral modeling method.