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Research output: Contribution to Journal/Magazine › Journal article › peer-review
Research output: Contribution to Journal/Magazine › Journal article › peer-review
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TY - JOUR
T1 - Double-quantum filtered 23Na NMR and MRI
T2 - Selective detection of ordered sodium in an inhomogeneous B0 field
AU - Wimperis, Stephen
AU - Pavlovskaya, Galina E
PY - 2025/2/28
Y1 - 2025/2/28
N2 - Double-quantum filtered Na NMR experiments with one or two "magic angle" (54.7°) pulses in the filter step are widely used for selective observation of sodium ions that are interacting with ordered biological structures ("ordered sodium") and hence exhibit a distribution of quadrupolar splittings in their NMR spectrum. This approach has recently been extended to Na MRI where the conventional experiment has been modified, omitting the 180° pulse to reduce the absorption of radiofrequency energy during human studies. Here, the "magic angle" double-quantum filtered Na NMR experiment (without a 180° pulse) is analysed in terms of coherence pathways that lead to refocusing in an inhomogeneous B field ("echoes") and those that do not ("antiechoes"). It is shown that the echo and antiecho pathways can be separated by phase cycling and that the antiecho pathway contributes very little to the overall signal in an inhomogeneous B field. Hence, a double-quantum filtered Na NMR experiment that utilises just the echo pathway and so achieves complete refocusing of the effects of B inhomogeneity without making use of a 180° pulse is proposed. The new method is demonstrated both in Na NMR spectroscopy in an inhomogeneous B field and in Na MRI of a three-component phantom. [Abstract copyright: Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.]
AB - Double-quantum filtered Na NMR experiments with one or two "magic angle" (54.7°) pulses in the filter step are widely used for selective observation of sodium ions that are interacting with ordered biological structures ("ordered sodium") and hence exhibit a distribution of quadrupolar splittings in their NMR spectrum. This approach has recently been extended to Na MRI where the conventional experiment has been modified, omitting the 180° pulse to reduce the absorption of radiofrequency energy during human studies. Here, the "magic angle" double-quantum filtered Na NMR experiment (without a 180° pulse) is analysed in terms of coherence pathways that lead to refocusing in an inhomogeneous B field ("echoes") and those that do not ("antiechoes"). It is shown that the echo and antiecho pathways can be separated by phase cycling and that the antiecho pathway contributes very little to the overall signal in an inhomogeneous B field. Hence, a double-quantum filtered Na NMR experiment that utilises just the echo pathway and so achieves complete refocusing of the effects of B inhomogeneity without making use of a 180° pulse is proposed. The new method is demonstrated both in Na NMR spectroscopy in an inhomogeneous B field and in Na MRI of a three-component phantom. [Abstract copyright: Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.]
KW - Coherence pathways
KW - B(0) inhomogeneity
KW - Magic angle
KW - Ordered sodium
KW - Spin echo
KW - (23)Na MRI
KW - Double-quantum filter
U2 - 10.1016/j.jmr.2024.107810
DO - 10.1016/j.jmr.2024.107810
M3 - Journal article
C2 - 39740531
VL - 371
JO - Journal of Magnetic Resonance
JF - Journal of Magnetic Resonance
SN - 1090-7807
M1 - 107810
ER -