Analysis of multisite 2D relaxation exchange NMR

Landeghem, Maxime Van; Haber, Agnes; Lacaillerie, Jean-Baptiste d’Espinose de; Blümich, Bernhard

doi:10.1002/cmr.a.20157

Cited by 78 publications

(66 citation statements)

References 29 publications

(72 reference statements)

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“…The complexity of the problem increases, when moving from a model two-site exchange system to a real one, in which multi-site exchange is very likely to occur. It has been recently pointed out that in the case of multi-site exchange the effect of longitudinal relaxation leads to asymmetric exchange maps and the attenuation or even the disappearance of some of the signals [26]. Moreover, the ill-conditioned nature of the multi-exponential inversion used in the data processing poses additional problems in the interpretation of the results, e.g.…”

Section: The T 2 -T 2 Exchange Pulse Sequencementioning

confidence: 99%

“…11) may not necessarily reflect the true structure of the system. Second, in the case of intermediate exchange, for which it was previously proven that the magnetization is not conserved or follows many single relaxation paths [26], the interpretation of relaxation time distributions is complicated furthermore by the effects of outflow and dispersion. If the outflow can be mathematically represented as a simple subtractive term, dispersion affects the magnetization vector in a similar way as the exchange and relaxation matrices, making it extremely difficult to distinguish between the effects of diffusive exchange on one hand and the ones of slow dispersive flow on the other hand.…”

Section: Superimposed Effects Of Exchange and Advectionmentioning

confidence: 99%

“…the ''pearling effect'' [27]. Model development and computer simulations are therefore an essential next step for correct data interpretation [26].…”

Section: The T 2 -T 2 Exchange Pulse Sequencementioning

confidence: 99%

“…As mentioned at the beginning of this section, this simulation set was performed only as a validity check for the behavior of the model, so its results will not be interpreted in detail. An extensive discussion on the effects the ratio relaxation time/exchange constant has on the output of a CPMG experiment is presented in [26], including more complex simulations of 1D decays recorded following an encoding and an evolution period.…”

Section: Effects Of Exchange In Zero Flow Conditionsmentioning

confidence: 99%

“…(10) has the same general structure as the Hahn/Maxwell/McConnell model for exchange spectroscopy [33]. It has been applied and analyzed with respect to relaxation exchange in [26]. The innovative part in this work is to consider advection within a mathematical model for signal evolution of a relaxation site discretization.…”

Section: Discrete Signal Evolutionmentioning

confidence: 99%

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Exchange relaxometry of flow at small Péclet numbers in a glass bead pack

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Sethi

et al. 2012

Journal of Magnetic Resonance

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Section: The T 2 -T 2 Exchange Pulse Sequencementioning

confidence: 99%

Section: Superimposed Effects Of Exchange and Advectionmentioning

confidence: 99%

“…the ''pearling effect'' [27]. Model development and computer simulations are therefore an essential next step for correct data interpretation [26].…”

Section: The T 2 -T 2 Exchange Pulse Sequencementioning

confidence: 99%

Section: Effects Of Exchange In Zero Flow Conditionsmentioning

confidence: 99%

Section: Discrete Signal Evolutionmentioning

confidence: 99%

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Exchange relaxometry of flow at small Péclet numbers in a glass bead pack

Olaru

Kowalski

Sethi

et al. 2012

Journal of Magnetic Resonance

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Desktop NMR and Its Applications From Materials Science To Organic Chemistry

2017

Self Cite

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NMR spectroscopy is an indispensable method of analysis in chemistry, which until recently suffered from high demands for space, high costs for acquisition and maintenance, and operational complexity. This has changed with the introduction of compact NMR spectrometers suitable for small-molecule analysis on the chemical workbench. These spectrometers contain permanent magnets giving rise to proton NMR frequencies between 40 and 80 MHz. The enabling technology is to make small permanent magnets with homogeneous fields. Tabletop instruments with inhomogeneous fields have been in use for over 40 years for characterizing food and hydrogen-containing materials by relaxation and diffusion measurements. Related NMR instruments measure these parameters in the stray field outside the magnet. They are used to inspect the borehole walls of oil wells and to test objects nondestructively. The state-of-the-art of NMR spectroscopy, imaging and relaxometry with compact instruments is reviewed.

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Closed‐form solution for multisite 2D relaxation exchange NMR

Dortch¹,

Does²

2010

Concepts Magnetic Resonance

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Recently, Landeghem et al. (1) reviewed T 2 -T 2 relaxation exchange spectroscopy (REXSY), which is an attractive means for studying exchange in porous media and biological tissue. This detailed review of REXSY data analysis will be a valuable resource for many wishing to perform such experiments. However, for the sake of thoroughness, we wish to point out one key omission that may be of interest to the readers of this journal.In their review, the authors note ''there is no published analytical solution for the case of relaxation and exchange between more than two sites'' for the T 2 -T 2 spectral peak amplitudes; therefore, ''only numerical simulations that take relaxation and exchange into account at all time periods of the 2D exchange experiment can support the interpretation of experimental data.'' However, a recent article by Dortch et al. (2) proposed and validated such an expression:[1]where P(t m ) is a general N-pool expression for the peak amplitudes derived from 2D inverse Laplace transform (ILT) of T 2 -T 2 data. Other terms in this equation are defined as follows: U L 2 is a matrix whose columns are the eigenvectors of L 2 ; L 1,2 ¼ ÀR 1,2 þ K, where R 1,2 is a diagonal matrix of R 1 s or R 2 s for each pool and K is a matrix of exchange rates; M 0 is a vector of equilibrium magnetizations; t m is the mixing time; 1 1 Â N is a 1 Â N vector of ones; represents element-wise matrix multiplication; and the superscript T represents the matrix transpose. This expression can be expressed analytically for two-pool systems, although in practice we typically compute it numerically. However, unlike numerical 2D ILT methods, this is a very stable and computationally inexpensive task.

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Analysis of multisite 2D relaxation exchange NMR

Cited by 78 publications

References 29 publications

Exchange relaxometry of flow at small Péclet numbers in a glass bead pack

Exchange relaxometry of flow at small Péclet numbers in a glass bead pack

Desktop NMR and Its Applications From Materials Science To Organic Chemistry

Closed‐form solution for multisite 2D relaxation exchange NMR

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