Feasibility of in vivo N-15 MRS detection of hyperpolarized N-15 labeled choline in rats

The increase of total choline in tumors has become an important biomarker in cancer diagnosis. Choline and choline metabolites can be measured in vivo and in vitro using multinuclear MRS. Recent in vivo C-13 MRS studies using labeled substrates enhanced via dynamic nuclear polarization demonstrated the tremendous potential of hyperpolarization for real-time metabolic studies. The present study demonstrates the feasibility of detecting hyperpolarized N-15 labeled choline in vivo in a rat head at 9.4 T. We furthermore report the in vitro (172 +/- 16 s) and in vivo (126 +/- 15 s) longitudinal relaxation times. We conclude that with appropriate infusion protocols it is feasible to detect hyperpolarized N-15 labeled choline in live animals.