Quadrupole sensitive pulse for signal filtering

Abstract

A longstanding problem in quadrupolar NMR of semi-solids is the selection of signals originating from ordered nuclei, i.e. those that experience a non-vanishing quadrupolar coupling. Established techniques, such as for example multiple-quantum filters are not adequate in situations when the radio frequency power is on the order of the quadrupolar coupling or the quadrupolar relaxation rates, such as may be the case on an MRI scanner, or in ex situ applications. In this manuscript we show a new method for the selective excitation of ordered spin-3/2 nuclei, which produces the desired results when the radio frequency power is approximately equal or smaller than quadrupolar frequency. Using a combination of simulations and experiments with 23Na in NaCl solution, Pf1-solutions, and bovine patellar cartilage samples we further show how the value of the quadrupolar frequency and global features of a quadrupolar coupling distribution can be extracted from these experiments.

Low-power suppression of fast-motion spin 3/2 signals

“…Optimal sequences for the case of selecting signals from compartments with such splittings have been described recently with a low-power pulse sequence. 5 The possibility of differentiating between intra-and extracellular sodium is of interest, since the change in intracellular sodium concentration is an accompanying factor of many diseases and pathologies 3 . Often, it is assumed that the slow-motion regime is mostly prevalent in the intracellular environment, and not in the extracellular environment, which can form the basis of a selection, although this is not always the case.…”

Modest Offset Difference Internuclear Selective Transfer via Homonuclear Dipolar Coupling

“…Here, we present a zero-quantum homonuclear dipolar recoupling method, the modest offset difference internuclear selective transfer (MODIST) pulse sequence, where selective transfer occurs between spins with small differences in their offsets. We based the MODIST sequence on the jump-return , elements of SPR pulses and modified the phase, the flip angles, and the number of pulses in the block to maximize transfer between amide spins, minimize transfer between amide and aliphatic spins, and, crucially, retain maximal total amide signal. MODIST is constructed similarly to π/4-SPR4 2 , but the modified phase cycling significantly modifies its transfer characteristics.…”