Optimal control NMR differentiation between fast and slow sodium

Sodium ions in tissues and organs may experience motion on a variety of timescales, leading to NMR relaxation effects with quadrupolar coupling as the primary mechanism. The various effects that this fluctuating interaction has on spin dynamics can be exploited for distinguishing slow sodium ions from fast ones. Techniques such as triple-quantum filtering have been used for this purpose in the past. In this work we present optimal pulses which significantly improve the selectivity towards slow-tumbling sodium. These pulses can also be modified for robustness against magnetic field inhomogeneities, and could hence also become useful as MRI contrast methods.

62Research highlights► Optimal control theory is used to design MRI contrast. ► Optimal pulse sequences discriminate between slow and fast sodium ions. ► Higher contrast was achieved compared to inversion recovery and triple-quantum filter. ► Slow sodium selectivity is important for detecting cell dysfunction via spectroscopy and imaging.