Double-quantum filtered 23Na NMR and MRI: Selective detection of ordered sodium in an inhomogeneous B0 field
Year: 2024
Type: article
Abstract: • “Magic angle” double-quantum filtered 23 Na NMR experiment is analysed theoretically. • Coherence pathways that lead to refocusing in inhomogeneous B 0 fields are identified. • These pathways can be selected by phase cycling, forming basis of a new experiment. • “Magic angle” double-quantum filtered echo tested in 23 Na NMR of xanthan/NaCl(aq) • New echo experiment used for selective detection of ordered sodium in 23 Na MRI. Double-quantum filtered 23 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 23 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 23 Na NMR experiment (without a 180° pulse) is analysed in terms of coherence pathways that lead to refocusing in an inhomogeneous B 0 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 0 field. Hence, a double-quantum filtered 23 Na NMR experiment that utilises just the echo pathway and so achieves complete refocusing of the effects of B 0 inhomogeneity without making use of a 180° pulse is proposed. The new method is demonstrated both in 23 Na NMR spectroscopy in an inhomogeneous B 0 field and in 23 Na MRI of a three-component phantom.
Source: Journal of Magnetic Resonance
Authors: Stephen Wimperis, Galina E. Pavlovskaya
Institutions: Lancaster University, University of Nottingham
Language: English
Subfield: Spectroscopy
Field: Chemistry
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $3,660
Funder: Medical Research Council
OpenAlex ID: W4404625890