Singlet and Other States with Extended Lifetimes

Levitt, Malcolm H.

doi:10.1002/9780470034590.emrstm1036

Cited by 19 publications

(20 citation statements)

References 43 publications

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“…The transformation of total spin magnetization into singlet order, and back again, is an important manipulation in the NMR of long-lived states [13,14,15,16,17,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44] and in parahydrogen-enhanced NMR [18,19,20,21,22,45,46,47,48,49].…”

Section: Magnetization To Singlet Ordermentioning

confidence: 99%

Symmetry constraints on spin dynamics: Application to hyperpolarized NMR

Levitt

2016

Journal of Magnetic Resonance

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Spin dynamical evolution is constrained by the symmetries of the spin Hamiltonians that generate the quantum dynamics. The consequences of symmetry-induced constraints are examined for some common hyperpolarized NMR experiments, including the excitation of singlet order in spin-pair systems, and the transfer of parahydrogen-induced hyperpolarized singlet order to magnetization in systems displaying chemical and magnetic equivalence.

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Section: Magnetization To Singlet Ordermentioning

confidence: 99%

Symmetry constraints on spin dynamics: Application to hyperpolarized NMR

Levitt

2016

Journal of Magnetic Resonance

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“…Although it cannot be directly observed by NMR, the singlet isomer plays an active and useful role within the magnetic resonance experiment. The singlet is capable of maintaining spin order over timescales much longer (3,5) than the ''conventional'' spin-lattice relaxation time, T 1 , the upper time limit to the decay of the triplet manifold (6,7). This occurs because singlet-triplet transitions are usually slower compared to triplet-triplet transitions.…”

Section: Introductionmentioning

confidence: 99%

Hyperpolarized singlet NMR on a small animal imaging system

Laustsen

Pileio

Tayler

et al. 2012

Magnetic Resonance in Med

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Nuclear spin hyperpolarization makes a significant advance toward overcoming the sensitivity limitations of in vivo magnetic resonance imaging, particularly in the case of low-gamma nuclei. The sensitivity may be improved further by storing the hyperpolarization in slowly relaxing singlet populations of spin-1/2 pairs. Here, we report hyperpolarized 13 C spin order transferred into and retrieved from singlet spin order using a small animal magnetic resonance imaging scanner. For spins in sites with very similar chemical shifts, singlet spin order is sustained in high magnetic field without requiring strong radiofrequency irradiation. The demonstration of robust singlet-to-magnetization conversion, and vice versa, on a small animal scanner, is promising for future in vivo and clinical deployments. Magn Reson Med 000:000-000, 2012. V C 2012 Wiley Periodicals, Inc.

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“…As a result, carbonyl groups such as the C1 position in pyruvate are usually chosen for 13 C labeling because of the lack of attached protons, giving T 1 values on the order of tens of seconds and an imaging window of a few minutes. It has been shown previously that the quantum mechanical properties of two spin (or more) systems may be used to extend the hyperpolarization lifetime by exploiting the symmetry properties of singlet states in order to avoid the dominant NMR relaxation mechanisms, such as dipolar coupling (102). Transfer of hyperpolarization to a directly bonded proton or to solvent water may also provide an avenue to indirectly probe the hyperpolarized signal (103)(104)(105)(106).…”

Section: Extending Polarization Lifetimementioning

confidence: 99%

“…This first demonstration of lifetime extension using singlet states was performed using the two protons in 2,3-dibromothiophene (107): an RF pulse was applied to a sample at 9.4 T to create nonequilibrium spin-state populations, which were then converted to a long-lived singlet state by transporting the sample to the low field. Singlet-state population was converted back into a visible NMR signal when the sample was returned to high field (102). Recent advances have shown that the field cycling method may also be applied to other nuclei, such as the coupled nitrogen nuclei in 15 N 2 -nitrous oxide (113), and importantly, that the whole process can be performed outside the magnet (108), although the method has yet to be applied to 13 C-labeled hyperpolarized substrates.…”

Section: Experimental Demonstrations Of Singlet Statesmentioning

confidence: 99%

“…A number of methods are available to manipulate magnetic equivalence in a system that intrinsically lacks such a property, and these have been reviewed in detail elsewhere (102,(109)(110)(111)(112). The general principle of all such experiments involves preparation of a nonequilibrium population in the |abi and/or |bai spin states (see Fig.…”

Section: Experimental Demonstrations Of Singlet Statesmentioning

confidence: 99%

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Tumor imaging using hyperpolarized ¹³C magnetic resonance spectroscopy

Brindle¹,

Bohndiek²,

Gallagher³

et al. 2011

Magnetic Resonance in Med

236

355

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Dynamic nuclear polarization is an emerging technique for increasing the sensitivity of magnetic resonance imaging and spectroscopy, particularly for low-g nuclei. The technique has been applied recently to a number of 13 C-labeled cell metabolites in biological systems: the increase in signal-to-noise allows the spatial distribution of an injected molecule to be imaged as well as its metabolic product or products. This review highlights the most significant molecules investigated to date in preclinical cancer models, either in terms of their demonstrated metabolism in vivo or the biological processes that they can probe. Key words: hyperpolarized carbon-13; dynamic nuclear polarization; imaging; metabolism; tumor; pyruvateThe application of magnetic resonance in medicine has been dominated by imaging of tissue anatomy. However, one of the great strengths of magnetic resonance (MR) is spectroscopy, which allows imaging of tissue biochemistry; this was recognized in the earliest applications of MR to intact biological systems (1). Although magnetic resonance imaging (MRI) has become a routine clinical tool, the use of magnetic resonance spectroscopy (MRS) in patients has lagged far behind; this has been primarily due to a lack of sensitivity, which leads to long measurement times and poor image resolution (2-5). In spite of this, 1 H-MRS measurements of cellular metabolites in a variety of tumor types have been shown to provide a sensitive means to diagnose disease and detect response to treatment (2-4). However, these measurements generally give a static picture of cellular metabolism.In contrast, 13 C-MRS measurements of cellular metabolism in systems incubated with 13 C-labeled cell substrates give a dynamic, and therefore potentially more useful, measurement of tissue metabolism (6-8). For example, dynamic measurements of 13 C-labeled glucose incorporation into muscle glycogen have been used to dissect the relative importance of glucose transport and hexokinase and glycogen synthase activity in controlling muscle glycogen synthesis (9). However, the problem of low sensitivity is even more acute in the case of 13 C-MRS. Dynamic nuclear polarization (DNP or hyperpolarization) of 13 C-labeled cell substrates enhances their sensitivity to detection by >10 4 -fold (10,11). Subsequent spectroscopic imaging of their metabolism following intravenous injection offers a solution to the problem of low sensitivity and has the potential to make dynamic metabolic imaging using MRS a routine clinical application.There have been a number of recent review articles and book chapters on this subject (12-17), and therefore, the purpose of this brief review is to: highlight those DNP substrates that have shown the greatest promise for oncological applications in vivo; summarize the biochemical mechanisms responsible for label transfer from pyruvate to other metabolites in tumors; and finally provide an overview of the main challenges in label detection and imaging and how these may be addressed. PROMISING SUBSTRATES FOR HYPERPOLA...

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Singlet and Other States with Extended Lifetimes

Cited by 19 publications

References 43 publications

Symmetry constraints on spin dynamics: Application to hyperpolarized NMR

Symmetry constraints on spin dynamics: Application to hyperpolarized NMR

Hyperpolarized singlet NMR on a small animal imaging system

Tumor imaging using hyperpolarized ¹³C magnetic resonance spectroscopy

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Singlet and Other States with Extended Lifetimes

Cited by 19 publications

References 43 publications

Symmetry constraints on spin dynamics: Application to hyperpolarized NMR

Symmetry constraints on spin dynamics: Application to hyperpolarized NMR

Hyperpolarized singlet NMR on a small animal imaging system

Tumor imaging using hyperpolarized 13C magnetic resonance spectroscopy

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Tumor imaging using hyperpolarized ¹³C magnetic resonance spectroscopy