IDH1 and glioma: In particular, for monitoring the treatment in mutant IDH1 glioma patients the non-invasive MRS detection of 2HG is more feasible27,28 and has clear advantages, compared to biopsies: (1) there are no associated risks, (2) the technique can be repeated multiple times, (3) the technique can probe multiple tumor regions, and (4) MRS can investigate normal appearing brain as internal control.