The authors recently found that 80% of lower-grade gliomas (LGGs) harbored a mutation in IDH1. Intraoperative detection of the mutated IDH1 helps not only differentiate LGGs from other type of brain tumors, but determine the resection border. In the current study, the authors have applied an automated genetic typing involving a quenching probe to detect the mutated IDH1. If tumor cells with the mutated IDH1 contained 10% or more in the mixture of normal and tumor cells, the device could detect it sensitively. The intraoperative assessment of IDH1 mutation is useful in brain tumor surgeries.