Magnetic resonance spectroscopy (MRS) can non-invasively detect IDH mutant glioma by demonstrating elevated 2-D-HG levels (Branzoli et al., 2018) as it can accumulate to very high (1–50 mM) concentration in the tumor (Zhou et al., 2018; Andronesi et al., 2012). Here, IDH1 is linked to glioma.