Zirconia-Polyurethane Aneurysm Clip

Abstract

Susceptibility artifacts from metal clips in magnetic resonance (MR) imaging present an obstacle to evaluating the status of clipped aneurysms, parent arteries, and adjacent brain parenchyma. We aimed to develop MR-compatible aneurysm clips. Considering the mechanical and biologic properties, as well as MR compatibility of candidate materials, a prototype clip with a zirconia body and a polyurethane head spring (zirconia clip [ZC], straight, 9-mm long) was developed. The closing forces, opening width of blades, and invitro and invivo artifact volumes in 3 tesla MR imaging were compared among the prototype and commercial metal clips such as a Yasargil clip (YC, curved type, 8.3-mm long) and a Sugita clip (SC, straight type, 10-mm long). An invivo animal study was performed with a canine venous pouch aneurysm model. The closing forces (N) at 1 mm and 8 mm from the 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. The maximum opening widths (mm) was 6.8, 9.0, and 3.0 in YC, SC, and ZC, respectively. The invitro artifact volumes of YC, SC, and ZC in time-of-flight MR imaging were 26.9, 29.7, and 1.9 times larger than the respective real volumes. The invivo artifact volumes of YC, SC, and ZC were respectively 21.4, 29.4, and 2.6 times larger than real ones. ZC showed the smallest susceptibility artifacts and satisfactory closing forces. However, the narrow opening width of the blades was a weak point.