Multiquantum Coherences Research Articles

Low-rank reconstruction for simultaneous double half-echo 23Na and undersampled 23Na multi-quantum coherences MRI.

To develop a new sequence to simultaneously acquire Cartesian sodium (23Na) MRI and accelerated Cartesian single (SQ) and triple quantum (TQ) sodium MRI of in vivo human brain at 7 T by leveraging two dedicated low-rank reconstruction frameworks. The Double Half-Echo technique enables short echo time Cartesian 23Na MRI and acquires two k-space halves, reconstructed by a low-rank coupling constraint. Additionally, three-dimensional (3D) 23Na Multi-Quantum Coherences (MQC) MRI requires multi-echo sampling paired with phase-cycling, exhibiting a redundant multidimensional space. Simultaneous Autocalibrating and k-Space Estimation (SAKE) were used to reconstruct highly undersampled 23Na MQC MRI. Reconstruction performance was assessed against five-dimensional (5D) CS, evaluating structural similarity index (SSIM), root mean squared error (RMSE), signal-to-noise ratio (SNR), and quantification of tissue sodium concentration and TQ/SQ ratio in silico, in vitro, and in vivo. The proposed sequence enabled the simultaneous acquisition of fully sampled 23Na MRI while leveraging prospective undersampling for 23Na MQC MRI. SAKE improved TQ image reconstruction regarding SSIM by 6% and reduced RMSE by 35% compared to 5D CS in vivo. Thanks to prospective undersampling, the spatial resolution of 23Na MQC MRI was enhanced from mm3 to mm3 while reducing acquisition time from min to min. The proposed sequence, coupled with low-rank reconstructions, provides an efficient framework for comprehensive whole-brain sodium MRI, combining TSC, T2*, and TQ/SQ ratio estimations. Additionally, low-rank matrix completion enables the reconstruction of highly undersampled 23Na MQC MRI, allowing for accelerated acquisition or enhanced spatial resolution.

Multidimensional compressed sensing to advance 23 Na multi-quantum coherences MRI.

Sodium (23 Na) multi-quantum coherences (MQC) MRI was accelerated using three-dimensional (3D) and a dedicated five-dimensional (5D) compressed sensing (CS) framework for simultaneous Cartesian single (SQ) and triple quantum (TQ) sodium imaging of in vivo human brain at 3.0 and 7.0 T. 3D 23 Na MQC MRI requires multi-echo paired with phase-cycling and exhibits thus a multidimensional space. A joint reconstruction framework to exploit the sparsity in all imaging dimensions by extending the conventional 3D CS framework to 5D was developed. 3D MQC images of simulated brain, phantom and healthy brain volunteers obtained from 3.0 T and 7.0 T were retrospectively and prospectively undersampled. Performance of the CS models were analyzed by means of structural similarity index (SSIM), root mean squared error (RMSE), signal-to-noise ratio (SNR) and signal quantification of tissue sodium concentration and TQ/SQ ratio. It was shown that an acceleration of three-fold, leading to less than min of scan time with a resolution of at 3.0 T, are possible. 5D CS improved SSIM by 3%, 5%, 1% and reduced RMSE by 50%, 30%, 8% for in vivo SQ, TQ, and TQ/SQ ratio maps, respectively. Furthermore, for the first time prospective undersampling enabled unprecedented high resolution from to MQC images of in vivo human brain at 7.0 T without extending acquisition time. 5D CS proved to allow up to three-fold acceleration retrospectively on 3.0 T data. 2-fold acceleration was demonstrated prospectively at 7.0 T to reach higher spatial resolution of 23 Na MQC MRI.

High-resolution absorptive intermolecular multiple-quantum coherence NMR spectroscopy under inhomogeneous fields

Intermolecular multiple-quantum coherence (iMQC) is capable of improving NMR spectral resolution using a 2D shearing manipulation method. A pulse sequence termed CT-iDH, which combines intermolecular double-quantum filter (iDQF) with a modified constant-time (CT) scheme, is designed to achieve fast acquisition of high-resolution intermolecular zero-quantum coherences (iZQCs) and intermolecular double-quantum coherences (iDQCs) spectra without strong coupling artifacts. Furthermore, double-absorption lineshapes are first realized in 2D intermolecular multi-quantum coherences (iMQCs) spectra under inhomogeneous fields through a combination of iZQC and iDQC signals to double the resolution without loss of sensitivity. Theoretically the spectral linewidth can be further reduced by half compared to original iMQC high-resolution spectra. Several experiments were performed to test the feasibility of the new method and the improvements are evaluated quantitatively. The study suggests potential applications for in vivo spectroscopy.

On the damping of multiquantum coherences with an increase in their order. An asymptotic behavior

Expressions describing the asymptotic (as a function of the order n) damping of multispin multiquantum coherences in systems with an infinite-range interaction (van der Waals model) have been obtained. The results coincide with the results of the numerical experiment for nanocavities.

Measurement of glutathione in human brain at 3T using an improved double quantum filter in vivo

A single voxel proton NMR double quantum filter (DQF) for measurement of glutathione (GSH) in human brain at 3T is reported. Yield enhancement for the CH 2 resonances of the cysteine moiety at 2.95 ppm has been achieved by means of dual encoding. After the preparation of double quantum and zero quantum coherences (DQC and ZQC) at equal magnitude, the first DQC encoding was followed by interchange of DQC and ZQC, and another DQC encoding. The multi-quantum coherences were fully utilized to generate a GSH target signal at ∼2.95 ppm. The optimal echo time and the editing efficiency were obtained with numerical analysis of the filtering performance and phantom measurements. The dual-DQC encoding method provided GSH yield greater by a factor of 2.1 than single-DQC encoding for identical slice-selective RF pulses in phantom tests. Using the phantom relaxation times and the ratio of edited GSH to N-acetylaspartate (NAA) 2.0-ppm peak areas, the concentration of GSH in the medial parietal cortex of the healthy human brain in vivo was estimated to be 1.0 ± 0.3 mM (mean ± SD, n = 7), with reference to NAA at 10 mM.

About the CRAZED sequence

AbstractIn this article we report a detailed and understandable analysis of the evolution of various coherence orders in a Correlated 2D spectroscopy Revamped by Asymmetric Z‐gradient Echo Detection (CRAZED) like pulse sequence, used to select a signal from intermolecular Multi Quantum Coherences (iMQCs). Because the signal to‐noise‐ratio of iMQC is much lower than the signal from conventional single quantum coherence (SQC), an optimization of experimental parameters is a necessity when measurements are made with iMQC. For this purpose a phase cycle is shown that not only allows a simpler selection of a particular quantum coherence order, but also removes receiver artifacts. © 2004 Wiley Periodicals, Inc. Concepts Magn Reson Part A 21A: 22–36, 2004

Effects of pulse strength, width, and sample spinning speed on the spectral spin diffusion of multiquantum coherences of spin-3/2 quadrupolar nuclei.

The effects of radio-frequency pulse strength, width, and sample spinning speed on the spin-diffusion spectrum of half-integer quadrupolar spins in solids have been studied by theoretical, numerical, and experimental investigations. It is revealed that the line shape of the cross peaks changes nonmonotonically with respect to the change of pulse strength, pulse width, or sample spinning speed. It is also found that the sample spinning speed has much more pronounced influence on the spin diffusion spectral line shape. In many cases of practical importance, the effect of sample spinning must be included in spectral analysis, in contrast to the practice of previous studies. Moreover, this effect can be exploited to further improve the precision in the determination of relative orientation of the electric-field gradient tensors of the exchange partners.

Relaxation mechanisms of multi-quantum coherences in the Zeeman structure of atomic Cs trapped in solid He

This paper extends our previous work on near-degenerate magnetic resonance transitions in alkali ground states involving the simultaneous absorption of multiple radio-frequency quanta. New experimental results with an improved spectral resolution were obtained with cesium atoms trapped in the cubic phase of a helium crystal. The main objective of the paper is a theoretical study of the influence of stochastic perturbations of given multipole orders on the various multi-photon coherences. Algebraic and numerical results for perturbations of both dipolar and quadrupolar symmetry are presented. The present experimental resolution does not yet allow us to distinguish between these two most likely relaxation mechanisms. Nonetheless, the experimental spectra are very well described when allowing in the calculations for a magnetic field inhomogeneity of 2×10-5.

Intensities of coherences in multiquantum NMR

The intensities of multiquantum coherences are calculated for the ZZ-model Hamiltonian. The simple analytical expressions are in agreement with the experimental data.

Gradient selection of coherences in experiments with carbon detection

Coherence pathway selection with gradients in carbon-detected experiments is demonstrated. Gradient selection (gs) offers excellent suppression of artifacts and unwanted magnetization, and in practice the signal-to-noise ratio is at least as good as for the equivalent phase cycled experiment. A selective gs-1D-13C-COSY is used to correlate one carbon resonance with its neighbours. The gs-INADEQUATE is used to select multi-quantum coherences; this can be performed as a 1D or a 2D experiment. Complete elimination of t1 noise is obtained in the gs version only. Applications to labelled glucose, 3-phenylpropan-1-ol and natural abundance menthol are presented. Interference from high-frequency stray radiation in the gradient cable is removed by inserting a low-pass filter between the gradient wiring and the probe.

Solomon Echoes Extended to Soft Pulse Excitation

Abstract Solomon echoes, produced by two in-phase pulses separated by a delay τ2, are derived in taking into account the first-order quadrupolar interaction during the pulses. Consequently, the results are valid for any ratio of the quadrupolar coupling, ωQ, to the amplitude of the radiofrequency pulse, ωRF. Six echoes are predicted after the second pulse: three, detected as inner satellite signals, occur at τ4 = τ2, τ4 =2 τ2 and τ4 = 3 τ2/2; the other three, detected as outer satellite signals, occur at τ4=τ2/2, τ4 =τ2 , and τ4=3τ2/2. These echoes originate from the refocusing of single- and multi-quantum offresonance coherences developed during the first pulse. Four of them are allowed echoes, the other two are forbidden ones. However, there is no echo for the central transition. From a practical point of view this means that τ2 must be short compared to τFID, the duration of the FID of the central transition. The behavior of the echo amplitude versus the second pulse length is discussed for several ratios of ωQ/ωRF.

Determination of [formula omitted] quadrupolar coupling with two-pulse sequences

The density matrix of a spin- 5 2 system excited by two in-phase pulses separated by a delay τ 2 is calculated from the equilibrium state to the end of the second pulse. The interaction involved throughout the computation is the first-order quadrupolar interaction. Consequently, the results are valid for any ratio of the quadrupolar coupling to the amplitude of the radio-frequency pulse. It is shown that single- and multi-quantum coherences developed during the first pulse are detected at the end of the second pulse through single-quantum coherences. Other two-pulse sequences with various phase cyclings as well as the rotary echo sequence are also discussed and illustrated with the nuclei 27Al in a single crystal of corundum Al 2O 3.

Proton NMR detection of long-range heteronuclear multiquantum coherences in proteins: the complete assignment of the quaternary aromatic carbon-13 chemical shifts in lysozyme

Proton NMR detection of long-range heteronuclear multiquantum coherences in proteins: the complete assignment of the quaternary aromatic carbon-13 chemical shifts in lysozyme

Creation of multiquantum coherences from equilibrium spin systems

Recently it has been suggested that zero quantum coherence in scalar coupled spin systems at thermal equilibrium can be created by a single non-selective pulse. In this note, it is shown that the proposed effect will be masked as a consequence of the failure of the conventional high-temperature approximation normally applied to the equilibrium spin density operator. For exacting experiments, its appears that the approximation ϱ(eq) ≈ 1- Hħ/kT may not suffice.

ChemInform Abstract: OBSERVATION OF 1000‐FOLD ENHANCEMENT OF NITROGEN‐15 NMR VIA PROTON‐DETECTED MULTIQUANTUM COHERENCES: STUDIES OF LARGE PEPTIDES

Chemischer InformationsdienstVolume 16, Issue 3 Physical Organic Chemistry ChemInform Abstract: OBSERVATION OF 1000-FOLD ENHANCEMENT OF NITROGEN-15 NMR VIA PROTON-DETECTED MULTIQUANTUM COHERENCES: STUDIES OF LARGE PEPTIDES D. H. LIVE, D. H. LIVESearch for more papers by this authorD. G. DAVIS, D. G. DAVISSearch for more papers by this authorW. C. AGOSTA, W. C. AGOSTASearch for more papers by this authorD. COWBURN, D. COWBURNSearch for more papers by this author D. H. LIVE, D. H. LIVESearch for more papers by this authorD. G. DAVIS, D. G. DAVISSearch for more papers by this authorW. C. AGOSTA, W. C. AGOSTASearch for more papers by this authorD. COWBURN, D. COWBURNSearch for more papers by this author First published: January 22, 1985 https://doi.org/10.1002/chin.198503051AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume16, Issue3January 22, 1985 RelatedInformation

Observation of 1000-fold enhancement of nitrogen-15 NMR via proton-detected multiquantum coherences: studies of large peptides

Observation of 1000-fold enhancement of nitrogen-15 NMR via proton-detected multiquantum coherences: studies of large peptides