Chapter 3.2 – Q-Space Imaging: A Model-Free Approach

This chapter will introduce the q-space theory, which describes the behavior of water molecules probing their restricted environment without assuming a specific probability function of their spatial distribution. After describing the q-space theory, the advantages of q-space in an ideal scenario will be listed, especially with reference to the potential biophysical properties of quantitative metrics based on the probability density function. The chapter will then move onto ways of dealing with the limitations of applying the q-space theory in vivo using standard imaging systems. In particular, two issues will be highlighted: hardware limitations with regard to the currently available gradient systems and time constraints when scanning in vivo subjects. Spinal cord q-space applications will be described, referring to the limited literature available, especially with reference to the spinal cord issues that are introduced, cross-referencing the discussion with other chapters. Acquisition and processing strategies will be described, with specific reference to the spinal cord structure. A protocol suggestion for acquisition and analysis will be included.