Neurography of the Spinal Nerve Roots by Diffusion Tensor Scanning Applying Motion-Probing Gradients in Six Directions

Abstract

Diffusion-weighted (DW) magnetic resonance (MR) imaging of the nerve roots and peripheral nerves has been reported. We applied a sequence similar to brain diffusion tensor (DT) tractography to such a technique and assessed its feasibility. On a 1.5-T MR system, we acquired DW images in the axial plane using a single-shot echo-planar short tau inversion-recovery (STIR)-based sequence. Motion-probing gradients (MPGs) were applied in 6 directions with a b-value of 500 s/mm(2). For postprocessing, we performed maximum-intensity projection to reconstruct the images. We obtained cervical spine images from 3 volunteers and 8 patients and thoracolumbar spine images from 3 volunteers and 6 patients. On the source images of the cervical spine obtained from the volunteers, we compared the signal-to-noise ratios (SNRs) of the neural structures between images obtained applying MPG in 6 directions and in 3 directions. We visually assessed the nerve roots and proximal portions of the contiguous peripheral nerves in the images from volunteers and patients. The SNRs were significantly superior in the images obtained with the application of MPGs in 6 directions to those obtained with the application of MPGs in 3 directions (P<0.01). Visual assessment demonstrated the nerve roots as well as the nerve ganglia and the contiguous peripheral nerves up to 3 cm or more from the respective neural foramina in each subject. Image distortion was minimal. Our technique provides neurographic images of the nerve roots and proximal portions of the contiguous peripheral nerves, and images obtained using our sequence applying MPGs in 6 directions are superior to those obtained in 3 directions.