Parahydrogen-induced polarization of13C nuclei by side-arm hydrogenation (PHIP-SAH) for [1-13C]acetate and [1-13C]pyruvate esters with application of PH-INEPT-type pulse sequences for1H to13C polarization transfer is reported, and its efficiency is compared with that of polarization transfer based on magnetic field cycling (MFC). The pulse-sequence transfer approach may have its merits in some applications because the entire hyperpolarization procedure is implemented directly in an NMR or MRI instrument, whereas MFC requires a controlled field variation at low magnetic fields. Optimization of the PH-INEPT-type transfer sequences resulted in13C polarization values of 0.66 ± 0.04% and 0.19 ± 0.02% for allyl [1-13C]pyruvate and ethyl [1-13C]acetate, respectively, which is lower than the corresponding polarization levels obtained with MFC for1H to13C polarization transfer (3.95 ± 0.05% and 0.65 ± 0.05% for allyl [1-13C]pyruvate and ethyl [1-13C]acetate, respectively). Nevertheless, a significant13C NMR signal enhancement with respect to thermal polarization allowed us to perform13C MR imaging of both biologically relevant hyperpolarized molecules which can be used to produce useful contrast agents for the in vivo imaging applications.
- Award ID(s):
- 1904780
- NSF-PAR ID:
- 10274320
- Date Published:
- Journal Name:
- Physical Chemistry Chemical Physics
- Volume:
- 23
- Issue:
- 3
- ISSN:
- 1463-9076
- Page Range / eLocation ID:
- 2320 to 2330
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract -
Purpose The purpose of this study was to investigate the feasibility of in vivo13C‐>1H hyperpolarization transfer, which has significant potential advantages for detecting the distribution and metabolism of hyperpolarized13C probes in a clinical MRI scanner.
Methods A standalone pulsed13C RF transmit channel was developed for operation in conjunction with the standard1H channel of a clinical 3T MRI scanner. Pulse sequences for13C power calibration and polarization transfer were programmed on the external hardware and integrated with a customized water‐suppressed1H MRS acquisition running in parallel on the scanner. The newly developed RF system was tested in both phantom and in vivo polarization transfer experiments in1JCH‐coupled systems: phantom experiments in thermally polarized and hyperpolarized [2‐13C]glycerol, and1H detection of [2‐13C]lactate generated from hyperpolarized [2‐13C]pyruvate in rat liver in vivo.
Results Operation of the custom pulsed13C RF channel resulted in effective13C‐>1H hyperpolarization transfer, as confirmed by the characteristic antiphase appearance of1H‐detected,1JCH‐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 effective13C‐>1H hyperpolarization transfer in a clinical MRI scanner with customized heteronuclear RF system.
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Abstract We introduce a Spin Transfer Automated Reactor (STAR) that produces continuous parahydrogen induced polarization (PHIP), which is stable for hours to days. We use the PHIP variant called signal amplification by reversible exchange (SABRE), which is particularly well suited to produce continuous hyperpolarization. The STAR is operated in conjunction with benchtop (1.1 T) and high field (9.4 T) NMR magnets, highlighting the versatility of this system to operate with any NMR or MRI system. The STAR uses semipermeable membranes to efficiently deliver parahydrogen into solutions at nano to milli Tesla fields, which enables1H,13C, and15N hyperpolarization on a large range of substrates including drugs and metabolites. The unique features of the STAR are leveraged for important applications, including continuous hyperpolarization of metabolites, desirable for examining steady‐state metabolism in vivo, as well as for continuous RASER signals suitable for the investigation of new physics.
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