Study design: Devices for spinal fusion were compared with respect to their influence on magnetic resonance images. In addition, different magnetic resonance pulse sequences were evaluated to elicit their susceptibility to imaging artifacts.
Objectives: To determine the implants with the least imaging artifacts as a recommendation for the spine surgeon and to assess the best imaging strategy for the radiologist.
Summary of background data: For patients who have had surgical spinal fusion with instrumentation, magnetic resonance imaging is the most favorable diagnostic method. Unfortunately, metallic implants lead to severe degradation of image quality. These artifacts depend on the material of the implant and on the choice of the pulse sequence.
Methods: The fusion devices were mounted on a simple plastic phantom in various combinations and were imaged on 1.5-T magnetic resonance units. Frequently used types of plates and screws made of titanium or steel in various alloys were examined on the phantom with routinely used pulse sequences. The results of these examinations were compared with those in patient studies involving the same implants as well as the same pulse sequences.
Results: The least imaging artifacts were caused by titanium implants, especially when using shorter screws, wider screw placement, and thinner titanium plates. Nevertheless, there were distinct image distortions that could lead to erroneous image interpretation. The best images were acquired by spin echo (T1), turbo spin echo (T1, T2), and half Fourier single shot turbo spin echo (HASTE) sequences. Sequences containing any gradient echo components (gradient echo or turbo gradient and spin echo sequence or frequency-selective fat saturation techniques) resulted in the highest amount of image degradation.
Conclusion: By choosing appropriate spinal fusion devices as well as pulse sequences, postoperative magnetic resonance imaging examinations can give acceptable results, in spite of the presence of metallic implants.