METALLIC ARTIFACTS IN MAGNETIC-RESONANCE-IMAGING OF PATIENTS WITH SPINAL-FUSION - A COMPARISON OF IMPLANT MATERIALS AND IMAGING SEQUENCES

Study Design. Devices for spinal fusion were compared with respect to their influence on magnetic resonance images. In addition, different m agnetic resonance pulse sequences were evaluated to elicit their susce ptibility to imaging artifacts. Objectives. To determine the implants with the least imaging artifacts as a recommendation for the spine sur geon and to assess the best imaging strategy for the radiologist. Summ ary of Background Data. For patients who have had surgical spinal fusi on with instrumentation, magnetic resonance imaging is the most favora ble 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 f usion devices were mounted on a simple plastic phantom in various comb inations 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 sequence s. The results of these examinations were compared with those in patie nt studies involving the same implants as well as the same pulse seque nces. Results. The least imaging artifacts were caused by titanium imp lants, especially when using shorter screws, wider implants, especiall y when using shorter screws, wider screw placement, and thinner titani um plates. Nevertheless, there were distinct image distortions that co uld lead to erroneous image interpretation. The best images were acqui red by spin echo (T1), turbo spin echo (T1, T2), and half Fourier sing le shot turbo spin echo (HASTE) sequences. Sequences containing any gr adient 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 appr opriate spinal fusion devices as well as pulse sequences, postoperativ e magnetic resonance imaging examinations can give acceptable results, in spite of the presence of metallic implants.