ABSTRACT
Magnetisation transfer (MT) contrast originates from the exchange of magnetisation occurring between protons in free water and those attached to macromolecules, such as proteins and lipids. As the latter protons are virtually invisible on conventional MRI, MT provides an indirect way of probing them. This is of particular interest for neuroscientific applications, as myelin, the insulating material wrapped around axons, is believed to dominate the MT process in the brain. Several methods have been proposed to quantify MT: from the simplest MT ratio to analytical models that can relate the MRI signal to biologically meaningful parameters. This chapter will review the different approaches available for quantifying the MT phenomenon, providing instructions for their implementation and highlighting advantages and limitations of each of them. The chapter will also provide theoretical and practical background to the most recently reported contrast mechanism based on MT, namely inhomogeneous MT. Finally, phantoms and strategies for quality assurance will be reviewed.
