T 1 ρ $$ {}_{1\rho } $$ as a Biomarker for IDH1 Mutation Status in a Glioma Mouse Model

Glioma is a common and often aggressive malignant brain cancer for which treatment is in part dependent on the mutation status of the IDH gene. Current diagnostic methods require a biopsy and genetic analysis to obtain IDH status, which can have lengthy wait times. T ${}_{1\rho }$ , the spin-lattice relaxation in the rotating frame, has shown potential to serve as a faster, non-invasive means of IDH1-typing that could be implemented at clinically relevant field strengths; however, there have been few studies to date that have explored its utility. This study consisted of three groups of five mice: naïve controls, IDH1-wild-type glioma bearing and IDH1-mutant glioma bearing, imaged once weekly with a T ${}_{1\rho }$ -prepped EPI sequence. It was found that IDH1-mutant gliomas exhibited significantly higher T ${}_{1\rho }$ values in the tumour compared with the brain, while IDH1-wild-type gliomas presented similar T ${}_{1\rho }$ values in the tumour and brain. T ${}_{1\rho }$ was found to be sensitive to whole-brain changes linked to glioma and IDH status, although further investigations into the confounding effects related to T ${}_1$ and T ${}_2$ differences are needed. A measurement of tumour T ${}_{1\rho }$ normalised to the brain ( $\Delta$ T ${}_{1\rho }$ ) was able to distinguish between IDH1-mutant and -wild-type glioma, with IDH1-mutant mice exhibiting an average $\Delta$ T ${}_{1\rho }$ of $\sim$ 29% and IDH1-wild-type mice having an average $\Delta$ T ${}_{1\rho }$ of only $\sim$ 3%. $\Delta$ T ${}_{1\rho }$ may thus have the capacity to serve as a non-invasive biomarker for IDH1 typing.