Zirconia-Polyurethane Aneurysm Clip

Development and Evaluation of an MRI Artifact-Free Aneurysm Clip

BACKGROUND AND OBJECTIVES

The digital subtraction angiography is still the gold standard in the follow-up after aneurysm surgery, although it remains a repeating invasive technique with accumulating X-ray exposure. An alternative magnetic resonance angiography has the disadvantage of metal-related artifacts. A metal-free aneurysm clip could overcome this problem. Recent advances in manufacturing technologies of fiber-reinforced plastics might allow developing a prototype of a metal-free clip.

METHODS

The prototype was formed out of carbon fiber-reinforced polyetheretherketone (CF-PEEK) in accordance with the standard clip design. In vivo and in vitro studies were performed to analyze the central nervous system biocompatibility. The prototype was tested in a phantom in a 3 T MRI scanner and microtomography scanner. For in vivo assessment, the left renal artery of rats was either ligated with a suture, clipped with a regular titanium clip or with the CF-PEEK prototype clip. The animals underwent standard MRI sequences and magnetic resonance angiography and assessment by a blinded neuroradiologist.

RESULTS

Phantom studies showed no signs of artifacts. The prototype showed a reliable clamping and reopening after clip application, although the clamping force was reduced. In vivo studies showed a successful occlusion of the renal artery in all cases in the magnetic resonance angiography. Clip artifacts were statistically significant reduced in the prototype group (P < .01). CF-PEEK showed no signs of impaired biocompatibility compared with the titanium samples in vitro and in vivo.

CONCLUSION

Former attempts of metal-free aneurysm clips did not meet the criteria of the standard clip design. In this study, the practicability of this new CF-PEEK artifact-free aneurysm clip has been proven. The further fabrication developments should overcome the problem of a reduced clamping force in the future. After clinical approval, it will improve the magnetic resonance image quality and might help to reduce the amount of digital subtraction angiography in the follow-up.

Dual-phase Au-Pt alloys free from magnetic susceptibility artifacts in magnetic resonance imaging

PURPOSE

Magnetic resonance imaging (MRI) devices are frequently used in image-based diagnosis. In the case of large artifacts, which are generated in magnetic resonance (MR) images when magnetic materials, such as metals, are present in the body, these devices are less useful. This study aimed to develop a dual-phase Au-Pt alloy that does not generate artifacts in MR images and has high workability to prepare medical devices.

MATERIALS AND METHODS

A processing method to produce a dual-phase Au-Pt alloy was established, and the magnetic susceptibility and artifacts of different alloy compositions were determined using a SQUID (superconducting quantum interference device) flux meter and a 1.5 T-MRI system. The crystallographic phases of the prepared alloy samples were identified using X-ray diffraction. Sample cross-sections were observed using a metallurgical microscope. Furthermore, a thinning test was conducted to examine alloy workability.

RESULTS

Dual-phase Au-Pt alloys Au70Pt30 and Au67Pt33-the former heat-treated at 800 and 850 °C and the latter heat-treated at 900 °C-generated minimal artifacts when imaged in a 1.5 T-MRI system. Their volume magnetic susceptibility increased as the heat-treatment temperature decreased. The alloy surfaces were observed to be uniform. Moreover, the workability of the dual-phase alloy was considerably better than that of the single-phase alloy.

CONCLUSION

Volume magnetic susceptibility could be controlled by changing the composition and processing temperature of the Au-Pt alloys. Dual-phase Au-Pt alloys those do not generate magnetic susceptibility artifacts in MRI images and have good workability could be prepared. The alloys are expected to be used in the preparation of various implantable medical devices.