Development of cerebral aneurysm clips to minimize susceptibility artifact by magnetic resonance imaging

Abstract

OBJECTIVE: Surgical clipping is a major treatment modality in treating cerebral aneurysms. However, in magnetic resonance (MR) imaging, susceptibility artifact due to metal clips impedes postoperative assessments of clipped aneurysms, parent arteries, and adjacent parenchyma. Our goal was to develop an MR-compatible aneurysm clip.

METHODS: To reconcile mechanical/biologic properties with MR demands, we fabricated a prototypic clip (ZC: straight, 9-mm long), made of zirconia (body) and polyurethane (spring). Mechanical properties, closing forces, open-blade width, and artifact volumes (in vitro and in vivo) by 3T MR imaging of ZC and currently available metal clips (Yasargil [YC: curved, 8.3-mm long] and Sugita [SC: straight, 10-mm long]) were compared, using a canine venous pouch aneurysm model for in vivo study.

RESULTS: Respective closing force (N) values, measured at 1-mm and 8-mm distances from blade tip, were 2.09 and 3.77 in YC, 1.85 and 3.04 in SC, and 2.05 and 4.60 in ZC. Maximum open-blade widths (mm) were 6.8, 9.0, and 3.0 in YC, SC, and ZC, respectively. In vitro artifact volumes of YC and ZC were 26.0- and 1.9-fold greater than corresponding actual volumes. In vivo artifact volumes of YC, SC, and ZC were 21.4-, 29.4-, and 2.6-fold greater than actual volumes.

CONCLUSION: Compared with two clips in current use, our prototypic clip showed the least susceptibility artifact, with satisfactory closing forces. However, its narrow open-blade width was a weak point. Further experimentation is needed for design refinements and durability testing before human application is feasible.