Abstract
It has recently been shown that a bolus of hyperpolarized nuclear spins can yield stimulated emission signals similar in nature to maser signals, potentially enabling new ways of sensing hyperpolarized contrast media, including most notably [1-13C]pyruvate that is under evaluation in over 50 clinical trials for metabolic imaging of cancer. The stimulated NMR signal emissions lasting for minutes do not require radio-frequency excitation, offering unprecedented advantages compared to conventional MR sensing. However, creating nuclear spin maser emission is challenging in practice due to stringent fundamental requirements, making practical in vivo applications hardly possible using conventional passive MR detectors. Here, we demonstrate the utility of a wireless NMR maser detector, the quality factor of which was enhanced 22-fold (to 1,670) via parametric pumping. This active-feedback technique breaks the intrinsic fundamental limit of NMR detector circuit quality factor. We show the use of parametric pumping to reduce the threshold requirement for inducing nuclear spin masing at 300 MHz resonance frequency in a preclinical MRI scanner. Indeed, stimulated emission from hyperpolarized protons was obtained under highly unfavorable conditions of low magnetic field homogeneity (T2* of 3 ms). Greater gains of the quality factor of the MR detector (up to 1 million) were also demonstrated.
| Original language | English |
|---|---|
| Article number | e202406551 |
| Journal | Angewandte Chemie - International Edition |
| Volume | 63 |
| Issue number | 37 |
| DOIs | |
| State | Published - Sep 9 2024 |
Funding
This material is based upon work supported by the U.S. Department of Energy, Office of Biological and Environmental Research (BER) under Award Number(s) DE‐SC0023334. Disclaimer: This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency. This work was also supported by the National Institutes of Health grant R21EB025313 (T.T.), R01EB029829 (T.T.), R01 EB034197 (M.R.S. & E.Y.C.), R21EB033872 (E.Y.C.), R21HL154032 (E.Y.C.). The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. M.S.R. acknowledges the generous support of the Kiyomi and Ed Baird MGH Research Scholar Award. Research reported in this publication was also supported by the Mallinckrodt Foundation, NSF CHE‐1904780, WSU Rumble fellowship (I.A.), NC Biotechnology Center in the form of a Translational Research Grant, WSU PD award, DKTK, and the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation)—SCHM3694/1, SCHM3694/2, SFB 1527/1—project‐ID 454252029.
Keywords
- hyperpolarization
- NMR spectroscopy
- parahydrogen
- parametric pumping
- RASER