A recent update of the World Health Organization (WHO) classification of brain tumors introduced molecular markers that add greater prognostic accuracy than histopathologic findings alone (1,2). Isocitrate dehydrogenase (IDH) genotype and epigenetic 1p/19q codeletion are two key molecular markers. Patients with IDH wildtype gliomas have a worse prognosis than those with IDHmutant gliomas. Patients with 1p/19q uncodeleted gliomas have a worse prognosis than those with codeleted IDH-mutant gliomas (3). The establishment of in vivo biomarkers that enable prediction of IDH and 1p/19q status would thus be relevant for patient management (4) and clinical trials. Diffusion MRI is a potential method for providing such in vivo biomarkers. It enables assessment of the microstructure of the whole tumor at a relatively high spatial resolution and is easily accessible. Diffusion-tensor imaging (DTI) is currently the most used method (5). DTI parameters such as mean diffusivity (MD) and fractional anisotropy (FA) correlate with changes in cellular density and in extracellular matrix features induced by glioma infiltration and growth. Several studies aimed to grade gliomas with use of DTI. Most of these have demonstrated significantly lower MD values in high-grade gliomas (6-12), but the majority failed to differentiate WHO grade II gliomas from grade III gliomas due to overlapping MD and FA values. A limitation of the above studies is that the authors did not stratify patients according to IDH

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