LUMBAR SPINE - QUANTITATIVE AND QUALITATIVE ASSESSMENT OF POSITIONAL (UPRIGHT FLEXION AND EXTENSION) MR-IMAGING AND MYELOGRAPHY

PURPOSE: To compare measurements of the sagittal diameter of the lumba r dural sac obtained at positional magnetic resonance (MR) imaging and at functional myelography acid to assess the influence of various bod y positions on the dural sac and the intervertebral foramina. MATERIAL S AND METHODS: Thirty consecutive patients referred for lumbar myelogr aphy were examined with an open 0.5-T MR imager. Sagittal T2-weighted fast spin-echo images were acquired with patients in the supine, uprig ht flexion, and upright extension positions. The midsagittal diameter of the dural sac was measured at the level disks on MR images and myel ograms. Foraminal sizes on the MR images were scored independently by two observers. RESULTS: Correlation between MR imaging and myelographi c measurements was high (r =.81-.97). A small but statistically signif icant positional dependence of the dural sac diameter was found in the lower lumbar spine. Position-dependent differences in foraminal score s were uncommon. CONCLUSION: Quantitative assessment of sagittal dural sac diameters is comparable between lumbar myelography and positional MR imaging. In a selected patient population, only small changes in t he sagittal diameter of the dural sac and foramina I size can be expec ted between various body positions, and the information gained with st andard MR imaging is limited.