In vivo hyperpolarization transfer in a clinical MRI scanner

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