Corresponding midsagittal CT (left), MR (middle), and registered (right) images of the cervical spine show proper alignment and the relationship between the margin of the spinal canal (solid arrow) and its contents. Corresponding midsagittal CT (left), MR (middle), and registered (right) images of the cervical spine show proper alignment and the relationship between the margin of the spinal canal (solid arrow) and its contents. The images were registered using external fiducial landmarks. Subject 4 from figure 3B is represented Ashok Panigrahy et al. AJNR Am J Neuroradiol 2000;21:282-289 ©2000 by American Society of Neuroradiology