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DOI: 10.1055/s-0028-1109882
© Georg Thieme Verlag KG Stuttgart · New York
Adjustable Cerebrospinal Fluid Shunt Valves in 3.0-Tesla MRI: a Phantom Study using Explanted Devices
Verstellbare Hydrozephalus-Shuntventile im 3,0 Tesla-MRT: Phantommessungen an explantierten VentilenPublikationsverlauf
received: 14.10.2009
accepted: 16.10.2009
Publikationsdatum:
02. Dezember 2009 (online)
![](https://www.thieme-connect.de/media/roefo/201007/lookinside/thumbnails/10.1055-s-0028-1109882-1.jpg)
Zusammenfassung
Ziel: Die Zahl klinischer Hochfeld-MR-Tomografen nimmt stark zu. Es liegen nur wenige Daten zu Wechselwirkungen zwischen Magneten von 3,0 Tesla-Feldstärke und magnetisch einstellbaren Hydrozephalus-Shunt-Ventilen vor. Diese wurden ausschließlich an fabrikneuen Ventilen erhoben; die Aussagekraft für In-vivo-Bedingungen ist daher eingeschränkt. In dieser Studie am Messphantom wurden explantierte Ventile als realistischeres Modell verwendet, um die sicherheitsrelevante Funktionalität der Ventile zu prüfen und um Bildgebungsartefakte, Scherkräfte und Erhitzung der metallischen Implantate systematisch zu erfassen. Material und Methoden: 16 explantierte Codman-Medos- und Sophy-SU8-Shunt-Ventile, alle funktionstüchtig, wurden dem statischen Magnetfeld des 3,0 T MRT-Geräts ausgesetzt. Die Artefakt- und Auslöschungsuntersuchung als auch die Erwärmungsuntersuchung wurden unter Verwendung von standardisierten diagnostischen MR-Sequenzen mit unterschiedlichen SAR-Werten durchgeführt. Die translatorische Anziehungskraft für die verstellbaren Ventile wurde anhand des Ablenkungs-Winkel-Tests bestimmt. Um die Verstellbarkeit und die Funktion der Ventile zu testen, wurde das sphärische Phantom mit dem Ventil ins Isocenter des MR-Geräts platziert und dem statischen Magnetfeld des 3,0 T für 0,25 bis zu 12 h (wiederholte Exposition: 1- bis 12-mal) einschließlich der Ein- und Ausfahrprozeduren ausgesetzt. Ergebnisse: Der Durchmesser der MRT-Artefakte betrug 10 – 70 mm und waren besonders ausgeprägt in T 2*w-Sequenzen. Eine durch das MRT induzierte relevante Erwärmung der Ventile ergab sich nicht. Die auf das Ventil wirkenden magnetischen Kräfte waren im Normbereich. Reproduzierbare Einstellungsfehler wurden bei 6 Ventilen festgestellt. Schlussfolgerung: Bis Empfehlungen bezüglich Untersuchungen von Hydrozephalus-Patienten in 3,0T-MRT möglich sind, sind größer angelegten Studien notwendig.
Abstract
Purpose: Considering the rapidly increasing number of clinical high-field MR imagers and the lack of data regarding interference with magnetically adjustable cerebrospinal fluid (CSF) shunt valves, valve safety was assessed with regard to magnetic field interactions: imaging artifacts, heating, magnetic forces, and functional changes in a phantom study at 3.0 Tesla using explanted devices as a realistic model for in vivo conditions. Materials and Methods: Sixteen explanted Codman-Medos and Sophy-SU8 shunt valves, all in perfect working order, were selected and exposed to a 3.0 T static magnetic field. Valve-induced imaging artifacts and signal drop-outs and the heating experiments were evaluated using standard diagnostic MR sequences with different SAR values. Translational attraction for the adjustable valves was assessed using the deflection angle method. To test adjustability and function, the spherical phantom containing the valve was placed in the isocenter of the MR scanner and exposed to a static magnetic field of 3.0 T for 0.25 to 12 hours (repeated exposure 1 – 12 times), including typical entrance and move-out procedures. Results: The diameters of imaging artifacts ranged from 10 – 70 mm and were most prominent on T 2*w sequences. There was no relevant MR-imaging-related heating. Magnetic forces were not critical. Reproducible adjustment failures occurred in 6 valves. Conclusion: Until suggestions can be made concerning the exposure of hydrocephalic patients to 3.0T-MRI, further testing is necessary.
Key words
adjustable cerebrospinal fluid shunt valves - Codman-Medos valves - hydrocephalus - 3.0-T MRI - failure of adjustability
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Dr. Michael Akbar
Stiftung Orthopädische Universitätsklinik Heidelberg
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Germany
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