Storage of magnetization as singlet order by optimal control designed pulses

Area of Science:

• Magnetic Resonance Imaging (MRI)
• Quantum Spin Physics

Background:

• Hyperpolarization significantly enhances MRI sensitivity but is limited by T1 relaxation decay.
• Storing spin order in long-lived singlet states offers a strategy to extend hyperpolarization lifetime.

Purpose of the Study:

• To develop efficient and robust methods for transferring spin order into and out of singlet states.
• To enable hyperpolarization preservation for enhanced MRI sensitivity.

Main Methods:

• Optimal control theory was employed to design novel radiofrequency pulses.
• Pulses were optimized for near-equivalent spins, maximizing transfer efficiency.
• Robustness was ensured against variations in chemical shift, J-couplings, and magnetic field inhomogeneity (B1 and B0).

Main Results:

• Efficient spin transfer into and out of singlet states was achieved.
• The designed pulses operate with low B1 amplitude, suitable for clinical MRI scanners.
• Demonstrated significant improvements in efficiency and robustness.

Conclusions:

• The developed method effectively extends hyperpolarization lifetime by utilizing singlet states.
• This technique overcomes T1 relaxation limitations, paving the way for more sensitive MRI.
• The approach is compatible with standard preclinical and clinical MRI scanner performance.