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Design Innovation

A Hybrid Coil/Polymer Device for Occlusion of Cerebral Aneurysms

[+] Author and Article Information
Fangmin Xu, Claire E. Flanagan

Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI 53706

Kevin Hart, John C. Nacker

Department of Engineering Physics, University of Wisconsin-Madison, Madison, WI 53706

Roham Moftakhar

Department of Neurological Surgery, University of Wisconsin-Madison, Madison, WI 53792

Beverly Aagaard-Kienitz

Department of Neurological Surgery, University of Wisconsin-Madison, Madison, WI 53792; Department of Radiology, University of Wisconsin-Madison, Madison, WI 53792

Daniel W. Consigny, Julie R. Grinde

Department of Radiology, University of Wisconsin-Madison, Madison, WI 53792

Wendy C. Crone

Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI 53706; Department of Engineering Physics, University of Wisconsin-Madison, Madison, WI 53706

Kristyn S. Masters1

Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI 53706kmasters@wisc.edu

1

Corresponding author.

J. Med. Devices 3(4), 045001 (Oct 16, 2009) (7 pages) doi:10.1115/1.4000203 History: Received October 28, 2008; Revised July 15, 2009; Published October 16, 2009

The treatment of cerebral aneurysms is frequently accomplished via endovascular delivery of metal coils in order to occlude the aneurysm and prevent rupture. This procedure involves imprecise packing of large lengths of wire into the aneurysm and often results in high rates of aneurysm recanalization. Over time, this incomplete aneurysm occlusion can lead to aneurysm enlargement, which may have fatal consequences. This report describes the fabrication and preliminary testing of a novel aneurysm occlusion device composed of a single metal coil surrounded by a biocompatible polymer shell. These coil-in-shell devices were tested under flow conditions in synthetic in vitro models of saccular aneurysms and deployed in vivo in a short-term porcine aneurysm model to study occlusion efficacy. A single nickel titanium shape memory wire was used to deploy a biocompatible, elastic polymeric shell, leading to aneurysmal sac filling in both in vitro and in vivo aneurysm models. The deployment of this coil-in-shell device in synthetic aneurysm models in vitro resulted in varying degrees of aneurysm occlusion, with less than 2% of trials resulting in significant leakage of fluid into the aneurysm. Meanwhile, in vivo coil-in-shell device implantation in a porcine aneurysm model provided proof-of-concept for successful occlusion, as both aneurysms were completely occluded by the devices. Both in vitro and in vivo studies demonstrated that this coil-in-shell device may be attractive as an alternative to traditional coil embolization methods in some cases, allowing for a more precise and controlled aneurysm occlusion.

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Copyright © 2009 by American Society of Mechanical Engineers
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Figures

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Figure 3

Photographic image of the coil-in-shell aneurysm occlusion device, which consists of a single NiTi wire within a modified polyurethane polymer shell

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Figure 4

Photograph of the coil-in-shell aneurysm occlusion device within the in vitro silicone aneurysm model during flow testing

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Figure 1

Sketch of the coil-in-shell aneurysm occlusion device

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Figure 2

(a) Photograph of the jig used to create NiTi coils for a 10 mm device and a NiTi coil after heat treatment and (b) photograph of coil stretching

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Figure 5

Histogram showing results for all in vitro testing conducted on 10 mm size devices incorporating a 0.0100 in. diameter NiTi wire. Results were classified as: 1=complete occlusion of the aneurysm model; 2=presence of a small air bubble trapped as fluid initially filled the vessel, with no other discernable fluid leakage into the aneurysm; 3=fluid leakage between the aneurysm wall and the device below the midline of the aneurysm; 4=fluid leakage up to the midline of the aneurysm; and 5=fluid leakage up to the apex of the aneurysm.

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Figure 6

Images showing details of the surgical procedure to introduce the coil device within the constructed aneurysm: (top) insertion of the device into the aneurysm pouch surgically attached to the carotid artery; (center) seating of the device at the bottom of the pouch next to the vessel; and (bottom) tying off of the pouch to create a saccular-like lateral sidewall aneurysm

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Figure 7

Angiogram of porcine sidewall aneurysm that was successfully occluded by the coil-in-shell device (arrow indicates occluded aneurysm)

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Figure 8

(Top panels) demonstration of microcatheter-based delivery of a shape memory coil and (bottom panels) demonstration of microcatheter-based delivery of shape memory coils within a polymeric shell

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