MRS (MR spectroscopy)
This is different than a regular MRI or fMRI because it does not study the brain structure or function, but rather studies the metabolites (small chemical compounds produced by the brain). The three main compounds measured are NAA (n-acetyl aspartate) which gives a reading of brain cell amounts and choline and creatine which give a measure of the amount of scar tissue (gliosis) in the brain. If there is no damage to the brain, the amount of NAA will be greater than the choline and creatine amounts. Conversely, in parts of the brain where there is scar tissue, there will be less NAA and more choline and creatine.
Technically, NAA, choline and creatine are measured as peaks in what is called spectral analysis.