gms | German Medical Science

Objective: The digital subtraction angiography is still the gold standard in the follow-up for patients, who have undergone a clipping of an intracranial aneurysm. This is still a recurrent invasive method with accumulating x-ray exposure. MRI angiography could be an alternative. However, it has the drawback, that the metal clip causes artifacts around the intracranial vessels and impairs the clinical assessment. A metal-free aneurysm clip could overcome this problem. Recent advances in manufacturing technologies of fiber-reinforced plastics made it possible to produce a prototype of a metal-free clip.

Methods: The prototype was formed out of carbon-fiber-reinforced PEEK (CF-PEEK) in accordance with the standard clip design. The prototype was tested in a phantom in a 3-Tesla MRI scanner and in a microtomography scanner. In vivo experiments followed. The left renal artery of Sprague Dawley rats was either ligated with a suture, clipped with a regular titanium clip or with the CF-PEEK prototype. Sham operated animals served as control. The animals underwent standard MRI sequences and MRI angiography. The size of the artifacts as well as the quality of the vessel imaging was analyzed. In vivo and in vitro studies were performed to analyze the CNS biocompatibility of CF-PEEK compared to titanium and PEEK.

Results: The results of the phantom studies with the prototype showed no signs of artifacts. The in vivo studies showed a clear reduction of the artifacts size of the prototype compared to the titanium clip (0.07±0.0 x0.06±0.06 cm vs. 2.8±0.16x1.09±0.1 cm). In the MRI angiography, the vessels adjacent to the clipped vessel could be identified clearly in the suture group and the CF-PEEK clip group. The renal artery was successfully occluded in all treatment groups. Samples of CF-PEEK showed no signs of impaired biocompatibility compared to the titanium samples in vitro and in vivo. The clamping force of the prototype was markedly reduced compared to the standard titanium clip.

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 artifact-free aneurysm clip based on CF-PEEK has been proven. The further development in the fabrication techniques should overcome the problem of a reduced clamping force in the future. This might help to reduce the amount of DSA in the follow up of patients suffering from aneurysm.