Positional lumbar imaging using a positional device in a horizontally open-configuration MR unit-Initial experience

Purpose To evaluate whether positional MR images of the lumbar spine, obtained with a horizontally open‐configuration MR unit, demonstrate positional changes of the dural sac, and to assess whether there are significant differences in positional changes between healthy volunteers and patients with chronic low back pain. Materials and Methods The study population consisted of 15 patients with chronic low back pain and 14 healthy volunteers. MR images were obtained using a horizontally open‐configuration 0.4‐T MR unit. After conventional lumbar MR examinations, images were obtained in the flexion, neutral, and extension positions, using a positioning device. The anteroposterior diameter of the dural sac at the level of each lumbar disk was measured in the three positions and quantitative data were compared. Results Our MR protocol was tolerated by all patients. In both patients and volunteers, the mean anteroposterior diameter of the dural sac was smaller in the extension positions than in the flexion positions. In the mean rate of change (RC) in the dural sac diameter at the site of the degenerated disks, the difference between the volunteers and patients was significant (P < 0.05). There was no significant difference in the mean RC between patients and volunteers without degenerative disks. Conclusion Using a horizontally open‐configuration MR unit, positional MR imaging provided position‐dependent change of the dural sac. Positional changes at the site of the degenerated disks may be different in patients with and without chronic low back pain. J. Magn. Reson. Imaging 2007. © 2007 Wiley‐Liss, Inc.