Meng Law

Diffusion tensor imaging of the brain and spine has been a hot topic for a number of years now. We chose to investigate DTI in the spinal cord because of the challenges of doing DTI in the cord, as well as the many potential clinical applications of DTI in multiple sclerosis, spinal cord tumors, degenerative myelopathy, HIV-related spinal cord changes, spinal cord injury, and vascular diseases of the spinal canal including AVMs and cord infarct.^1–4 Many of these diseases are devastating clinically, and applying novel imaging techniques may help in diagnosing earlier, triaging therapy, and predicting prognosis. We also spent many years optimizing the methodology for doing spinal cord DTI, which requires a balance between imaging time, reducing artifacts, obtaining reproducible data with good SNR, and novel postprocessing techniques.⁵

In multiple sclerosis, most of the central nervous system is affected by demyelination, even areas of normal-appearing white matter in the brain and spinal cord. We know that with conventional MRI, spinal cord lesions typically occur in the posterior and lateral columns of the human spinal cord. In this paper, Dr. Hesseltine was able to demonstrate regional changes in fractional anisotropy (FA) in the posterior and lateral columns of the normal-appearing spinal cord (NASC) in relapsing-remitting MS (RRMS). These microscopic changes in the NASC may correlate with disease status, progression, and response to therapy. Since then, we have continued to investigate DTI in the spinal cord and feel there have been significant improvements in the acquisition methodology towards achieving high-quality spinal cord DTI data.

There has been much recent interest in mapping the human connectome, which, incidentally, extends beyond the brain to the spinal cord and peripheral nerves. A repository of high-quality, high-gradient connectomics of the brain is being created. We are working on the MRI acquisition and processing methodology with Dr. Yonggang Shi and Dr. John Van Horn (USC Institute of Neuroimaging and Informatics – USC INI), to determine if we can map the connectome structurally into the spinal cord and even beyond, to the spinal nerves. This undertaking is immensely challenging, but we feel it is a natural extension towards mapping the entire human nervous system.

References

1. Hesseltine SM, Law M, Babb J, et al. Diffusion tensor imaging in multiple sclerosis: assessment of regional differences in the axial plane within normal-appearing cervical spinal cord. AJNR Am J Neuroradiol 2006;27:1189–93
2. Jones J, Lerner A, Kim PE, et al. Diffusion tensor imaging in the assessment of ossification of the posterior longitudinal ligament: a report on preliminary results in 3 cases and review of the literature. Neurosurg Focus 2011;30:E14
3. Jones JGA, Cen SY, Lebel RM, et al. Diffusion tensor imaging correlates with the clinical assessment of disease severity in cervical spondylotic myelopathy and predicts outcome following surgery. AJNR Am J Neuroradiol 2013;34:471–78, 10.3174/ajnr.A3199
4. Mueller-Mang C, Law M, Mang T, et al. Diffusion tensor MR imaging (DTI) metrics in the cervical spinal cord in asymptomatic HIV-positive patients. Neuroradiology 2011;53:585–92, 10.1007/s00234-010-0782-6
5. Thurnher MM, Law M. Diffusion-weighted imaging, diffusion-tensor imaging, and fiber tractography of the spinal cord. Magn Reson Imaging Clin N Am 2009;17:225–44, 10.1016/j.mric.2009.02.004

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