# Direct detection of SABRE-SHEATH hyperpolarization and spin-lattice relaxation of [1-13C]pyruvate

## TL;DR

The paper shows how to directly detect hyperpolarization and relaxation in [1-13C]pyruvate using SABRE-SHEATH and SQUID sensors, offering new insights into polarization dynamics.

## Contribution

Direct detection of hyperpolarization and spin-lattice relaxation in [1-13C]pyruvate using SABRE-SHEATH and SQUID sensors at ultra-low magnetic fields.

## Key findings

- Hyperpolarization build-up times (TB) of 36 s and 26 s were observed at 150 nT and 500 nT.
- Spin-lattice relaxation times (T1) of 40 s and 43 s were measured at the same field strengths.
- The results suggest a shift in dominant polarization transfer mechanisms at different field strengths.

## Abstract

Nuclear magnetism is typically investigated by perturbing the spin system with radio frequency pulses, but low polarization and detection using induction coils limit direct access to the longitudinal magnetization. The hyperpolarization technique SABRE-SHEATH requires ultra-low magnetic fields for spin order transfer; consequently, SQUID sensors with a frequency-independent sensitivity are well-suited for unperturbed detection in this regime. We demonstrate direct observation of hyperpolarization build up (TB) and spin lattice relaxation (T1) in [1-13C]pyruvate, hyperpolarized with SABRE-SHEATH at 150 nT and 500 nT. The values for TB of 36 s and 26 s and T1 of 40 s and 43 s, respectively, suggests a shift in dominant polarization transfer efficacy or complexes, highlighting the method’s merit in characterizing hyperpolarization pathways. Moreover, as demand for hyperpolarized probes in metabolic imaging continues to grow, the exceptional time resolution makes direct detection a valuable tool for understanding and optimizing polarization dynamics and reactor designs.

Traditional nuclear magnetism studies are hindered by low polarization and limited detection methods. Here, the authors utilize the hyperpolarization technique SABRE-SHEATH at 150 nT and 500 nT as well as SQUID sensors to directly detect longitudinal nuclear magnetization to characterize hyperpolarization build-up and spin lattice relaxation in [1-13C]-pyruvate, revealing insights into polarization pathways.