Purpose
In spinal surgery, metallic implants are regularly used to treat deformities, degeneration, destruction and traumas. The MRI compatibility of these implants has not yet been sufficiently investigated. The aim of this study was to systematically evaluate susceptibility artifacts and radio frequency (RF) induced heating on spinal implants with different configurations and lengths at 1.5 T and 3 T.
Methods and materials
In the present study a pedicle-screw-rod system (CD HORIZON® SOLERATM Spinal System, Medtronic) for a full spine sawbone with up to 14 segments (Fig. 1) was systematically evaluated with standardized test methods of the ASTM at 1.5T (Magnetom Avanto and Aera, Siemens, Germany) and 3T (Magnetom Skyra and Prisma, Siemens, Germany). The rods are fabricated from titanium (Ti) with cobalt-chromium (CoCr) alloy. The screw head consists of CoCr and the thread of Ti. A spine model was used to bend the rods and position the...
Results
The maximum artifact extent (distance between implant surface and end of signal extinction) ranged between 37 to 48 mm (TSE) and 35 to 57 mm (GRE) for the titanium rod with cobalt-chromium-alloy (Fig. 2), between 25 to 30 mm (TSE) and 36 to 38 mm (GRE) for the screws (Fig. 3), and 13 to 14 mm (TSE) and between 21 to 29 mm (GRE) for the cross-links. The maximum RF induced heating was 0.90 °C for 1.5T and 1.30 °C for 3T (Fig. 4).
Conclusion
Large spinal implants are not necessarily a contraindication for MRI. Although susceptibility artifacts can severely limit the diagnostic close by the implants (Fig. 5), the examination of other regions is possible. The RF induced heating on the implant is at an acceptable level in supine position.
Personal information and conflict of interest
Andreas Heinrich, medical physicists
Department of Radiology, University Hospital Jena, Friedrich Schiller University, Germany
Am Klinikum 1
07747 Jena, Germany
e-mail:
[email protected]
A. Heinrich; Jena/DE - nothing to disclose M. Reinhold; Jena/DE - nothing to disclose F. Güttler; Jena/DE - nothing to disclose T. Zippelius; Eisenberg/DE - nothing to disclose P. Strube; Eisenberg/DE - nothing to disclose U. K. M. Teichgräber; Jena/DE - nothing to disclose
References
ASTM F2182-11a,Standard Test Method for Measurement of Radio Frequency Induced Heating On or Near Passive Implants During Magnetic Resonance Imaging. 2011, ASTM International: West Conshohocken, PA.
ASTM F2119-07, Standard Test Method for Evaluation of MR Image Artifacts from Passive Implants. 2013, ASTM International: West Conshohocken, PA.
Heinrich, A., U.K. Teichgräber, and F.V. Güttler, Measurement of susceptibility artifacts with histogram-based reference value on magnetic resonance images according to standard ASTM F2119. Biomedical Engineering/Biomedizinische Technik, 2015. 60(6): p. 541-549.