IDH1 and oligodendroglioma: The duration of the progression-free interval did not correlate with the maximal rCBV in any glioma group (IDH-mutant astrocytic tumors r = − 0.8, p = 0.83, IDH wild-type astrocytic tumors r = 0.14, p = 0.59, oligodendrogliomas r = − 0.18, p = 0.59, respectively).