In vivo hyperpolarization transfer in a clinical MRI scanner

Abstract

Purpose: The purpose of this study was to investigate the feasibility of in vivo ¹³ C->¹ H hyperpolarization transfer, which has significant potential advantages for detecting the distribution and metabolism of hyperpolarized ¹³ C probes in a clinical MRI scanner.

Methods: A standalone pulsed ¹³ C RF transmit channel was developed for operation in conjunction with the standard ¹ H channel of a clinical 3T MRI scanner. Pulse sequences for ¹³ C power calibration and polarization transfer were programmed on the external hardware and integrated with a customized water-suppressed ¹ H 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 [2-¹³ C]glycerol, and ¹ H detection of [2-¹³ C]lactate generated from hyperpolarized [2-¹³ C]pyruvate in rat liver in vivo.

Results: Operation of the custom pulsed ¹³ C RF channel resulted in effective ¹³ C->¹ H hyperpolarization transfer, as confirmed by the characteristic antiphase appearance of ¹ H-detected, ¹ J_CH -coupled doublets. In conjunction with a pulse sequence providing 190-fold water suppression in vivo, ¹ H detection of hyperpolarized [2-¹³ C]lactate generated in vivo was achieved in a rat liver slice.

Conclusion: The results show clear feasibility for effective ¹³ C->¹ H hyperpolarization transfer in a clinical MRI scanner with customized heteronuclear RF system.

Keywords: INEPT; dynamic nuclear polarization; lactate; pyruvate.