Singlet NMR methodology in two-spin-1/2 systems

Pileio, Giuseppe

doi:10.1016/j.pnmrs.2016.11.002

Cited by 54 publications

(33 citation statements)

References 74 publications

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“…This feature of LLSs offers an additional MRI contrast [32]. An alternative background suppression technique is a specialized singlet spin order filter (T 00 -filters) [51,52].…”

Section: Pulse Sequencementioning

confidence: 99%

In vitro singlet state and zero-quantum encoded magnetic resonance spectroscopy: Illustration with N-acetyl-aspartate

2020

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Magnetic resonance spectroscopy (MRS) allows the analysis of biochemical processes non-invasively and in vivo. Still, its application in clinical diagnostics is rare. Routine MRS is limited to spatial, chemical and temporal resolutions of cubic centimetres, mM and minutes. In fact, the signal of many metabolites is strong enough for detection, but the resonances significantly overlap, exacerbating identification and quantification. Besides, the signals of water and lipids are much stronger and dominate the entire spectrum. To suppress the background and isolate selected signals, usually, relaxation times, J-coupling and chemical shifts are used. Here, we propose methods to isolate the signals of selected molecular groups within endogenous metabolites by using long-lived spin states (LLS). We exemplify the method by preparing the LLSs of coupled protons in the endogenous molecules N-acetyl-L-aspartic acid (NAA). First, we store polarization in long-lived, double spin states, followed by saturation pulses before the spin order is converted back to observable magnetization or double quantum filters to suppress background signals. We show that LLS and zero-quantum coherences can be used to selectively prepare and measure the signals of chosen metabolites or drugs in the presence of water, inhomogeneous field and highly concentrated fatty solutions. The strong suppression of unwanted signals achieved allowed us to measure pH as a function of chemical shift difference.

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“…This feature of LLSs offers an additional MRI contrast [32]. An alternative background suppression technique is a specialized singlet spin order filter (T 00 -filters) [51,52].…”

Section: Pulse Sequencementioning

confidence: 99%

In vitro singlet state and zero-quantum encoded magnetic resonance spectroscopy: Illustration with N-acetyl-aspartate

2020

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“…Experiments with long-lived singlet order are drawing increased attention, as they allow one to investigate various slow processes and to preserve non-thermal spin order from relaxation losses (Levitt, 2012;. Presently, there is a number of NMR methods, 435 reviewed in detail by Pileio (Pileio, 2017), known to convert magnetization into singlet order and to perform backward conversion of such a long-lived order into detectable magnetization. In strict terms, the long-lived order is given by the expectation value of the singlet order operator ⟨SO⟩.…”

Section: Singlet Ordermentioning

confidence: 99%

Representation of population exchange at level anti-crossings

Rodin¹,

Ivanov²

2020

Preprint

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Abstract. A theoretical framework is proposed to describe the spin dynamics driven by coherent spin mixing at Level Anti-Crossings (LACs). We briefly introduce the LAC concept and propose to describe the spin dynamics using a vector of populations of the diabatic eigenstates. In this description, each LAC gives rise to a pairwise redistribution of eigenstate populations, allowing one to construct the total evolution operator of the spin system. Additionally, we take into account that in the course of spin evolution a “rotation” of the eigenstate basis case take place. The approach is illustrated by a number of examples, dealing with magnetic field inversion, cross-polarization, singlet-state NMR and parahydrogen induced polarization.

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“…This state is neither directly observable in MRI, nor can it be manipulated by radiofrequency (rf) pulses. Additionally, the proton singlet state is immune to certain relaxation mechanisms 36,37 , and can have a much longer lifetime. Thus, the hyperpolarization can be stored in the singlet state until the molecule undergoes a chemical reaction that renders the protons chemically or magnetically inequivalent.…”

Section: Introductionmentioning

confidence: 99%

Singlet-Contrast Magnetic Resonance Imaging

Eills

Cavallari²,

Kircher³

et al. 2020

Preprint

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Hyperpolarization-enhanced magnetic resonance imaging can be used to study biomolecular processes in the body, but typically requires nuclei such as 13C, 15N, or 129Xe due to their long spin‑polarization lifetimes and the absence of a proton‑background signal from water and fat in the images. Here we present a novel type of 1H imaging, in which hyperpolarized spin order is locked in a nonmagnetic long-lived correlated (singlet) state, and is only liberated for imaging by a specific biochemical reaction. In this work we produce hyperpolarized fumarate via chemical reaction of a precursor molecule with para-enriched hydrogen gas, and the proton singlet order in fumarate is released as antiphase NMR signals by enzymatic conversion to malate in D2O. Using this model system we show two pulse sequences to rephase the NMR signals for imaging and suppress the background signals from water. The hyperpolarization-enhanced 1H‑imaging modality presented here can allow for hyperpolarized imaging without the need for low‑abundance, low‑sensitivity heteronuclei.

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Singlet NMR methodology in two-spin-1/2 systems

Cited by 54 publications

References 74 publications

In vitro singlet state and zero-quantum encoded magnetic resonance spectroscopy: Illustration with N-acetyl-aspartate

In vitro singlet state and zero-quantum encoded magnetic resonance spectroscopy: Illustration with N-acetyl-aspartate

Representation of population exchange at level anti-crossings

Singlet-Contrast Magnetic Resonance Imaging

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