An indirect method for in vivo T mapping of [1- C] pyruvate using hyperpolarized C CSI.

An indirect method for in vivo T mapping of C-labeled metabolites using T and T * information of water protons obtained a priori is proposed. The T values of C metabolites are inferred using the relationship to T ' of coexisting H and the T * of C metabolites, which is measured using routine hyperpolarized C CSI data. The concept is verified with phantom studies. Simulations were performed to evaluate the extent of T estimation accuracy due to errors in the other measurements. Also, bias in the C T * estimation from the C CSI data was studied. In vivo experiments were performed from the brains of normal rats and a rat with C6 glioma. Simulation results indicate that the proposed method provides accurate and unbiased C T values within typical experimental settings. The in vivo studies found that the estimated T of [1- C] pyruvate using the indirect method was longer in tumor than in normal tissues and gave values similar to previous reports. This method can estimate localized T relaxation times from multiple voxels using conventional hyperpolarized C CSI and can potentially be used with time resolved fast CSI.