In vivo hyperpolarization transfer in a clinical MRI scanner

PurposeThe purpose of this study was to investigate the feasibility of in vivo C-13->H-1 hyperpolarization transfer, which has significant potential advantages for detecting the distribution and metabolism of hyperpolarized C-13 probes in a clinical MRI scanner. MethodsA standalone pulsed C-13 RF transmit channel was developed for operation in conjunction with the standard H-1 channel of a clinical 3T MRI scanner. Pulse sequences for C-13 power calibration and polarization transfer were programmed on the external hardware and integrated with a customized water-suppressed H-1 MRS acquisition running in parallel on the scanner. The newly developed RF system was tested in both phantom and in vivo polarization transfer experiments in (1)J(CH)-coupled systems: phantom experiments in thermally polarized and hyperpolarized [2-C-13]glycerol, and H-1 detection of [2-C-13]lactate generated from hyperpolarized [2-C-13]pyruvate in rat liver in vivo. ResultsOperation of the custom pulsed C-13 RF channel resulted in effective C-13->H-1 hyperpolarization transfer, as confirmed by the characteristic antiphase appearance of H-1-detected, (1)J(CH)-coupled doublets. In conjunction with a pulse sequence providing 190-fold water suppression in vivo, H-1 detection of hyperpolarized [2-C-13]lactate generated in vivo was achieved in a rat liver slice. ConclusionThe results show clear feasibility for effective C-13->H-1 hyperpolarization transfer in a clinical MRI scanner with customized heteronuclear RF system.