Postimplantation MRI with cylindric and cubic intervertebral test implants: evaluation of implant shape, material, and volume in MRI artifacting--an in vitro study.

BACKGROUND CONTEXT

Interbody spacers for anterior spine fusion are made of different materials, which can affect the postfusion magnetic resonance imaging (MRI) scans. Susceptibility artifacts specially for metallic implants can decrease the image quality.

PURPOSE

This study focused on the influence of determined implant parameters like shape, implant volume, and implant material in MRI artifacting with regard to solid geometrical titanium and carbon test spacers.

STUDY DESIGN/SETTING: A comparative study on an in vitro spine model. The study was performed at a university research facility.

METHODS

In this study we evaluated the postimplantation MRI scans of three determined cuboids and six cylinders, which were made of titanium alloy and carbon fiber reinforced polymer. MRI scans were carried out by using T1 turbo spin echo (TSE) sequences. The total artifact volume (TAV) as well as median artifact area (MAA) were calculated. Additionally the implant volume (IV)/TAV and cross-sectional area (CSA)/MAA relation were determined. Statistical analyses were calculated with the t test and Newman-Keuls test for multiple comparisons.

RESULTS

Considering all test implants with an increasing implant size, the TAV and the MAA became significantly larger (p<.001) with simultaneous reduction of the IV/TAV and CSA/MAA relation. In contrast to the carbon implant group, for titanium cylinders with an implant volume equivalent to the cuboids significant differences in MRI artifacting (p<.05) could be demonstrated.

CONCLUSIONS

Susceptibility artifacts were clearly affected by the implant material, shape, and implant volume. Independent of the implant material, with regard to a more advantageous IV/TAV and CSA/MAA relation, for larger implants the artifact rate was more limited to the implant's direct surroundings. On the basis of a high magnetizability for titanium implants with an equal IV, the range of implant-related susceptibility artifacts was influenced by the material as well as implant shape in favor of cylindric implants. According to the very low MRI artifact rate of carbon implants, the implant shape did not have any significant effect on the artifact behavior.