Genotype/imaging phenotype correlation analysis with relative cerebral blood volume (rCBV) MRI – a robust and non-invasive estimate of tumor angiogenesis – in 73 treatment-naive patients with low-grade and anaplastic gliomas showed that a one-unit increase in rCBV corresponded to a two-third decrease in the odds for an IDH mutation and correctly predicted IDH mutation status in 88% of patients. The gene discussed is IDH1; the disease is grade III glioma.