Diffusion tensor imaging of the pediatric spinal cord at 1.5T: preliminary results

Abstract

Background and purpose: Recent studies suggest that pediatric subjects as old as 8-years-of-age may have difficulty with the ISNCSCI examinations. Our aim was to investigate DTI parameters of healthy spinal cord in children with noncervical IS for comparison with children with SCI and to prospectively evaluate reliability measures of DTI and to correlate the measures obtained in children with SCI with the ISNCSCI.

Materials and methods: Five controls with thoracic and lumbar IS and 5 children with cervical SCI were imaged twice by using a single-shot echo-planar diffusion-weighted sequence. Axial imaging was performed to cover the entire cervical spinal cord in controls. For the SCI subjects, 2 vertebral bodies above and below the injury were imaged. FA and D values were obtained at different levels of the cervical spinal cord. All subjects with SCI had undergone ISNCSCI clinical examinations. Statistical analysis was performed to access differences of the DTI indices between the controls and SCI subjects, reproducibility measurements, and correlations between DTI and ISNCSCI.

Results: Subjects with SCI showed reduced FA and increased D values compared with controls. Test-retest reproducibility showed good ICC coefficients in all the DTI index values among controls (≥0.9), while the SCI group showed moderate ICC (≥0.77). There were statistically significant correlations between the various DTI indices and ISNCSCI scores.

Conclusions: Preliminary DTI indices in children were determined and showed good reproducibility. Reduced FA and increased D values were seen in children with SCI in comparison with controls and showed good clinical correlation with ISNCSCI examinations.

Fig 1.

Region-of-interest placement on an axial B0 image of the cervical spine used in this study.

Fig 2.

Average FA values for controls compared with FA values for each individual subject, with SCI as a function of section number.

Fig 3.

Average D values for controls compared with D values for each individual subject, with SCI as a function of section number.

Fig 4.

Average radial D values for controls compared with radial D values for each individual subject, with SCI as a function section number.

Fig 5.

Average axial D values for controls compared with D values for each individual subject, with SCI as a function of section number.

Fig 6.

A, MR tractography images of the cervical spinal cord of a child with IS derived from FA values in the white matter tracts, a measure of degree of myelination of the white matter tracts along the spinal cord. B, Conventional midline sagittal T2-weighted image of a child with SCI (complete injury, ASIA A). C, An MR tractography image based on the FACT algorithm of the cervical spinal cord of the child in B. This algorithm failed, however, to track the rest of the cervical cord well below the injury (arrow) level, even though the FA measurements for this subject 4 showed recovery of FA values as seen in Fig 2.