Einfluss der Magnetresonanztomographie auf Oberlidimplantate

Behavior of metal implants used in ENT surgery in 7 Tesla magnetic resonance imaging

Magnetic resonance imaging (MRI) has become increasingly important as an imaging technique in cross-sectional imaging of head and neck diseases. To investigate whether MRI examinations can be performed without risk in patients with metal implants even at higher field strengths, we examined different materials in 7 Tesla MRI. Implants near sensory organs like the middle ear or eye are of particular interest here. Using the 7 Tesla research MRI for small animals, we tested implants made of various metals like titanium, gold, gold/platinum, platinum/iridium, gold-plated silver, PTFE and stainless steel for heating, translocation and rotation according to a standardized protocol. A fiber optic temperature probe measured the heating of the implant before, during and after MRI scanning. None of the implants showed significant heating. The gold-plated stainless steel ventilation tube was the only implant to markedly change its position already in the Petri dish. Of the remaining implants, a trachea support ring, a nose dilatator and the wire from the ventilation tubes moved during vibration of the Petri dish. With exception of two implants, all implants changed positions in the water bath. In the swim test, the gold implants showed the least movement of all the implants. In this study, the properties of the non-ferromagnetic implant materials differed in the 7 Tesla MRI. Stainless steel ventilation tubes, the trachea support ring and the nose dilatator were not suited for the 7 Tesla MRI system, because they changed their position during MRI. In the case of ventilation tubes with a steel wire, the wire should be removed before MRI to prevent injury to the external auditory canal. There was a tendency for the pure gold implants to move less in the 7 Tesla MRI than all other tested materials. General statements cannot be made about the MRI suitability of different implants. Every implant should be individually examined to confirm its definitive MRI compatibility. Particularly, middle ear implants warrant special attention here due to their closeness to the oval window.

[Implantation of lid weights for therapy of lagophthalmos]

BACKGROUND

The aim of this study was to compare the clinical outcome and complication rate of rigid gold implants and flexible platinum chains in 96 patients treated for lagophthalmos.

PATIENTS AND METHODS

We treated 50 patients with peripheral facial palsy and lagophthalmos using rigid gold implants and 46 using a flexible platinum chain. Besides subjective assessment by the patients, reduction of lagophthalmos, improvement of visual acuity, and pre- and postoperative grade of keratopathy were evaluated.

RESULTS

Both groups showed a statistically significant reduction of lagophthalmos and keratopathy and increase of visual acuity. Postoperative complications were observed in both groups. Two extrusions occurred in the group receiving gold implants. The incidence of corneal astigmatism and bulging of the implant was statistically significantly lower in the platinum chain group.

CONCLUSIONS

The use of flexible platinum chains instead of rigid gold implants for therapy of lagophthalmos leads to a reduction of the complication rate, thus improving the clinical outcome.