An imaging technique that tracks a common cancer biomarker offers promise for diagnosing and monitoring cancers linked to mutations in metabolic genes. The compound 2-hydroxyglutarate (2-HG) is a biomarker of various cancers linked to mutations in IDH genes, which are central to metabolism. 2-HG is rapidly produced from the amino acid glutamine in human cells with some such mutations. Using a type of magnetic resonance imaging and an isotopically labeled form of glutamine, the authors were able to measure the production of this biomarker non-invasively in mice. They also found that inhibiting one gene that is mutated in these cancers reduced the production of 2-HG by about 40%. This could lead to new ways of diagnosing and monitoring these tumors.