MRI blind zone: A proposed novel index for spinal implants artifacts

Background: To advocate the formulation of a new index termed MRI Blind Zone, designated to predict the dimensions of the magnetic resonance metallic artifact caused by specific spinal implants. The index may also specify the obscured organs of interest. Methods: A retrospective evaluation of post-operative MR images of patients operated for spinal instrumentation with various implants from different materials, in our institution, was performed. The MRI blind zone was described for each product, and the related obscured region of interest was discussed. A proposed 3D model was created as an example for suggested future reporting by the implants' industry. Results: Seven implant types are presented. The post-operative MR artifacts were detailed, and the clinical implications were discussed. Material type, processing methods and individual anatomical traits have a dramatic effect on the MRI blind zone and the obscured regions. Conclusion: MRI artifact is multifactorial and is influenced in part by the implant's shape, size, material and processing method. Individual products affect post-operative MR artifacts to different extents, and may carry clinical implications when post-operative imaging is required. A standardized index displaying the predicted post-operative artifact is warranted. For the manufacturers to accurately report the data to the surgeons, a parametric standardization should be performed. MRI blind zone index will allow surgeons to compare between different implants efficiently, and improve the informed decision-making process of implant selection.