Objective: The aim of this study was to evaluate sequences that are established at lower magnetic field strengths for lumbar spine imaging at 7 Tesla (7 T) MR imaging.
Materials and methods: The lumbar spine of five healthy volunteers and a patient with spina bifida and meningocele were evaluated at 7 T. The examination included a T2-TSE (turbo spin echo), a 3D-DESS (double-echo steady-state sequence), a 3D-CISS (constructive interference in steady-state sequence), and a 3D-VIBE (volumetric interpolated breath hold examination) sequence. Imaging quality was evaluated by two raters on a three-level scale. The assessment included visualization of intraforaminal structures, the cauda equina, facet joints, and any abnormalities. Contrast ratios for intervertebral discs/vertebral bodies, vertebral bodies/cerebrospinal fluid (CSF) and CSF/spinal cord were calculated.
Results: The 3D-VIBE sequence provided best differentiation between intraforaminal structures. Visualization of the facet joints was reliable with VIBE, DESS, and CISS. Individual nerve roots of the cauda equina could only be delineated with the 3D-CISS sequence. CISS and DESS provided good contrast between vertebral bodies and intervertebral discs. Contrast between CSF and vertebral bodies was most pronounced for the T2-TSE sequence. Sufficient contrast between CSF and the spinal cord was only achieved with the T2-TSE sequence. VIBE and DESS sequences demonstrated best the bony malformations. Visualization of the meningocele was only possible with the 3D-CISS sequence.
Conclusion: At 7 T most structures of the lumbar spine were visualized with a combination of sequences. At present, imaging quality is not superior to 1.5 T or 3 T, precluding routine clinical use.