Synopsis

This presentation is intended to give a non-exhaustive overview of what can be done in the spinal cord using quantitative MRI. « Classical » sequences that can be robustly used will be described. For each of these sequence families, more advanced techniques will be briefly underlined. Sequences providing functional, metabolic and vascular information will also be discussed. We will finish with a brief overview of recent advances in SC MRI at 7T.

From this « soup » of sequences, attendees should be able to extract the best ingredients and recipes for their own investigation.

Target Audience

Clinicians and scientists interested in studying the spinal cord using quantitative and ultra-high field MRI

Educational Objectives

As a result of attending this course, participants should be able to:

• Describe the various optimal MR sequences for imaging the spinal cord, and the different metrics that can be derived,
• List some advanced MR techniques, not yet fully ready to study the spinal cord in a clinical context but quite promising,
• Describe the advantages/drawbacks/challenges related to ultra high field (7T) spinal cord MRI,
• List some of the remaining issues in the context of clinical improvements and when considering future methodological developments.

Presentation content

The spinal cord (SC) is a wonderful and highly organized structure. Mainly composed of white and gray matter (WM/GM), it ensures the conduction of the neural signals between the brain and the peripheral nervous system. Consequently, damage to the SC components (motor neuron degeneration such as encountered in amyotrophic lateral sclerosis (ALS), WM bundle demyelination such as induced in multiple sclerosis (MS), or tissue compression such as observed in cervicarthrosic myelopathy or spinal cord trauma), may severely impact SC function and hence the patient quality of life.
MRI is the reference imaging tool to characterize SC tissues. It plays a crucial role in detecting SC abnormalities. However, while “conventional” MR techniques (T1-weighted, T2-weighted) usually bring sufficient diagnostic information, such methods are insufficient to fully characterize the underlying pathophysiological processes and estimate patient prognosis, hence justifying the need for multimodal, quantitative and/or ultra-high field MR investigations.
In this presentation, a non-exhaustive overview of what can be done in the spinal cord in 2020 using quantitative MRI will be given. After a short description of the SC and challenges related to SC MRI, « classical » sequences that can now be routinely and robustly used to obtain quantitative information will be described: T2*-weighted sequence with good WM/GM contrast for morphological measurements, diffusion tensor imaging (DTI) and magnetization transfer (MT), which provide structural information and useful adjuncts despite pathological non specificity. For each of these sequence families, more advanced and/or promising techniques will be briefly underlined (NODDI, quantitative MT (qMT), inhomogeneous MT (ihMT), myelin water fraction (MWF), …). Sequences providing functional (fMRI, resting-state fMRI), metabolic (spectroscopy, chemical shift imaging, ..) and vascular (IVIM, DSC) information will also be discussed, highlighting their advantages with regard to the pathological descriptions as well as the methodological challenges we need to face to properly use them.
We will also look at the recent advances in SC Ultra High Field (UHF) MRI. 7T systems have indeed opened new interesting perspectives that could benefit to the characterization of SC pathologies (higher lesion conspicuousness, impaired connectivity, …) and to the collection of refine information to better assess SC myelo and cyto-architectures. While great potentialities are given thanks to increased signal-to-noise ratio (SNR), spatial resolution and contrast-to-noise ratio (CNR) compared to lower field strengths, 7T MRI also comes with numerous challenges, such as higher static (B0) and radiofrequency (B1) field inhomogeneities, higher contraindications for patient scanning and higher specific absorption rate (SAR), which are progressively explored but still need to be addressed.

Conclusion

From this « soup » of sequences, attendees should be able to extract the best ingredients and recipes for their own investigation and gain insights into the extending SC MRI field.

Acknowledgements

No acknowledgement found.

References

No reference found.