The current state-of-the-art of spinal cord imaging: methods

Abstract

A first-ever spinal cord imaging meeting was sponsored by the International Spinal Research Trust and the Wings for Life Foundation with the aim of identifying the current state-of-the-art of spinal cord imaging, the current greatest challenges, and greatest needs for future development. This meeting was attended by a small group of invited experts spanning all aspects of spinal cord imaging from basic research to clinical practice. The greatest current challenges for spinal cord imaging were identified as arising from the imaging environment itself; difficult imaging environment created by the bone surrounding the spinal canal, physiological motion of the cord and adjacent tissues, and small cross-sectional dimensions of the spinal cord, exacerbated by metallic implants often present in injured patients. Challenges were also identified as a result of a lack of "critical mass" of researchers taking on the development of spinal cord imaging, affecting both the rate of progress in the field, and the demand for equipment and software to manufacturers to produce the necessary tools. Here we define the current state-of-the-art of spinal cord imaging, discuss the underlying theory and challenges, and present the evidence for the current and potential power of these methods. In two review papers (part I and part II), we propose that the challenges can be overcome with advances in methods, improving availability and effectiveness of methods, and linking existing researchers to create the necessary scientific and clinical network to advance the rate of progress and impact of the research.

Keywords: Artifacts; Human; Imaging; Magnetic resonance; Physiological motion; Positron emission tomography; Spectroscopy; Spinal cord; Susceptibility.

Fig. 1

Spatial distortions caused by bone/tissue interfaces in the spine with A) a half-Fourier single-shot fast spin-echo (HASTE), B) a spin-echo EPI, and C) a gradient-echo EPI imaging sequence.

Fig. 2

An example of spinal cord and brainstem fMRI results obtained from a group of healthy participants, with thermal stimulation of the right and left hands. The left panel shows the approximate rostral–caudal locations of the axial slices on the right side of the figure. Results are shown for selected contiguous 1-mm thick transverse slices through the C8 spinal cord segment and the rostral medulla. Areas of activity are displayed in axial slices from spatially normalized functional MRI data, with colors corresponding to the T-value determined with a GLM analysis. The results are shown separately for analyses with paradigms corresponding to right-hand stimulation and left-hand stimulation, and demonstrate spatial specificity.

Fig. 3

The panel on the left shows a color-coded representation of diffusion parameters in an axial plane through the level of the medulla oblongata, as well as a selective reconstruction of the corticospinal tracts in a healthy participant. The panel on the right shows the reconstructed fiber tracts overlaid on a sagittal reference image. The decussation of the corticospinal tracts in the medulla is clearly identified in this example.