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Storage of magnetization as singlet order by optimal control designed pulses
Author(s) -
Laustsen Christoffer,
Bowen Sean,
Vinding Mads Sloth,
Nielsen Niels Chr.,
ArdenkjaerLarsen Jan H.
Publication year - 2014
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.24733
Subject(s) - magnetization , singlet state , order (exchange) , nuclear magnetic resonance , materials science , physics , computer science , optics , atomic physics , magnetic field , quantum mechanics , business , finance , excited state
Purpose The use of hyperpolarization to enhance the sensitivity of MRI has so far been limited by the decay of the polarization through T 1 relaxation. Recently, methods have been proposed that extend the lifetime of the hyperpolarization by storing the spin order in slowly relaxing singlet states. Methods With this aim, optimal control theory was applied to create pulses that for near‐equivalent spins accomplish transfers in and out of the singlet state with maximum efficiency while ensuring robustness toward variations in the nuclear spin system Hamiltonian (chemical shift, J ‐couplings, B 1 and B 0 magnetic field inhomogeneity). Results The pulses are designed to accomplish efficient transfer with low B 1 amplitude, essential for applications on preclinical and clinical MR scanners. Conclusion It is demonstrated that significantly improved efficiency and robustness can be obtained within the limitations of typical MR scanner performance. Magn Reson Med 71:921–926, 2014. © 2013 Wiley Periodicals, Inc.