Verhalten von Titan-Mittelohrimplantaten bei 1,5 und 3 Tesla Feldstärke in der Magnetresonanztomographie

Zusammenfassung

Hintergrund: Untersuchungen über die MRT-Tauglichkeit von Mittelohrimplantaten aus Titan bei 1,5 und 3 Tesla Feldstärke (TF) MRT-Systemen.

Methode: Die Erwärmung von 17 verschiedenen Mittelohr-Implantaten (Mittelohr: MO) aus Titan unter dem Einfluss von starken Hochfrequenzimpulsen wurde in vitro untersucht. Die Beurteilung der Anziehungskräfte der Implantate erfolgte schwimmend auf Moosgummi (MG) im Wasserbad.

Ergebnisse: Eine Erwärmung der Implantate wurde bei keiner der verwendeten Sequenzen sowohl bei 3 als auch bei 1,5 TF beobachtet. Alle 17 Implantate schwammen mit geringer Geschwindigkeit (0,0004–0,0014 m/s) auf das Magnetfeld zu. Bei 1,5 TF kam es bei den getesteten MO-Implantaten schwimmend zu einer Geschwindigkeit von max. 0,0002 m/s und 0,0005 m/s bei den Paukenröhrchen.

Schlussfolgerung: Es fand sich keine Erwärmung bei allen untersuchten MO-Implantaten sowohl bei 1,5 und 3 TF. Die durch das statische Magnetfeld wirkenden Anziehungskräfte sind bei 1,5 und 3 TF insgesamt gering, sodass bei sachgerechter intraoperativer Verankerung keine Dislokation zu erwarten ist. Die Indikation zur Untersuchung sollte bei 3 TF aufgrund der anatomisch sensiblen Region streng geprüft werden.

Abstract

Behaviour of Titanium Middle Ear Implants at 1.5 and 3 Tesla Field Strength in Magnetic Resonance Imaging

Background: Investigations into the MRI compatibility of middle ear implants made from titanium alloys with 1.5 and 3.0 tesla MRI systems which are frequently used for imaging diagnostics.

Method: 17 different middle ear (ME) implants (ossicular replacement prosthesis (ORP) and ventilation tubes) made from titanium were tested in vitro. Potential warming was determined via an MRI-compatible fibre optic temperature sensor under the influence of sequences with high-level high frequency impulses. An assessment of the attractive force of the implants was carried out placed on a Petri dish under vibration and floating on rubber-sponge (RS) in a water bath.

Results: No significant warming of the implants was observed with any of the used sequences at either 3 or 1.5 Tesla field strength (TF). With 3 TF, all 17 implants changed their position on the surface of the water and moved at a slow speed (0.0004–0.0014 m/s) towards the magnetic field. With 1.5 TF, the tested ME implants moved at a maximum speed of 0.0002 m/s and in the case of the ventilation tubes at 0.0005 m/s.

Conclusion: No warming occurred in any of the tested middle ear implants at either 1.5 or 3 TF. The attractive forces exerted through the static magnetic field were overall low at 1.5 and 3 TF, indicating that no dislocation is to be expected if intraoperative anchoring is correctly conducted. Nevertheless, the indication for examination at 3 TF should be carefully considered due to the anatomically sensitive region.

Magnetresonanztomografie - Mittelohrimplantate - Titan-Implantate

Magnetic resonance imaging - middle ear implants - titanium implants

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