An indirect method for in vivo T sub(2) mapping of [1- super(13)C] pyruvate using hyperpolarized super(13)C CSI

An indirect method for in vivo T sub(2) mapping of super(13)C-labeled metabolites using T sub(2) and T sub(2)* information of water protons obtained a priori is proposed. The T sub(2) values of super(13)C metabolites are inferred using the relationship to T sub(2)' of coexisting super(1)H and the T sub(2)* of super(13)C metabolites, which is measured using routine hyperpolarized super(13)C CSI data. The concept is verified with phantom studies. Simulations were performed to evaluate the extent of T sub(2) estimation accuracy due to errors in the other measurements. Also, bias in the super(13)C T sub(2)* estimation from the super(13)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 super(13)C T sub(2) values within typical experimental settings. The in vivo studies found that the estimated T sub(2) of [1- super(13)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 sub(2) relaxation times from multiple voxels using conventional hyperpolarized super(13)C CSI and can potentially be used with time resolved fast CSI. An indirect method for in vivo T sub(2) mapping of super(13)C-labeled metabolites using T sub(2) and T sub(2)* information on water protons obtained a priori is proposed. The T sub(2) of super(13)C metabolites are inferred using the relationship to T sub(2)' of coexisting super(1)H and the T sub(2)* of super(13)C metabolites, which is measured using routine hyperpolarized super(13)C CSI data.