(MRS) a type of brain scan that can detect abnormalities in the brain's biochemical processes.

an MR technique wherein a sample is placed in a strong, very uniform, magnetic field, and stimulated with RF electromagnetic energy. If the field is uniform over the volume of the sample, "similar" nuclei will contribute a particular frequency component to the detected response signal irrespective of their individual positions in the sample. Since nuclei of different elements resonate at different frequencies, each element in the sample contributes a different frequency component. A chemical analysis can then be conducted by analyzing the MR response signal into its frequency components.

A technological tool similar to magnetic resonance imaging but providing chemical rather than anatomical information. MRS is most useful when evaluating trials of new treatments by measuring disease severity and progression.