Diffusion imaging of the human spinal cord and the vertebral column

During the last decade, diffusion-weighted imaging (DWI) has matured from an experimental tool to a clinically useful modality that has not only significantly impacted the diagnosis of (acute) cerebral stroke but has also shown utility in other abnormalities of the brain. Although DWI should be equally sensitive to changes in the spine, it has been used far less frequently in this region of the body. This is mainly because of the inhomogeneous magnetic environment, the small size of the spinal cord, and increased motion in and around the spine. However, once these limitations are overcome, a whole range of applications can be envisioned. Already now, DWI promises to be able to differentiate between benign and malignant vertebral compression fractures. As in the brain, the immediate reduction of diffusivity following ischemic damage in the spinal cord may provide an early identification of patients with infarction. The study of diffusion anisotropy may open new avenues for the detection and better understanding of damage to the long fiber tracts with important clinical implications for disorders like multiple sclerosis and amyotrophic lateral sclerosis. It may also be possible to address, in a more refined manner, mechanisms of damage such as occur with spondylotic myelopathy. To lay the basis for future research in these areas, we will discuss the most appropriate DWI methods for the spine. Following an overview of the basic principles of DWI and associated pitfalls, the most commonly used imaging methods are addressed. Finally, experimental and clinical applications in the spinal cord and the vertebral column and their clinical relevance thus far are reviewed.