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Deville, G.; Bernier, M.; Delrieux, J. M.

doi:10.1103/physrevb.19.5666

Cited by 315 publications

(286 citation statements)

References 29 publications

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“…Various aspects of signal evolution in the HOMOGE-NIZED experiment were treated theoretically in previous publications (3,13,(15)(16)(17)(18)(19)(20)(21)(22). Under the assumption that the gradient imposes a 1D modulation, and that diffusion and radiation damping can be neglected, an analytical solution of Bloch's equation including the DDF can be obtained.…”

Section: Theory Of the Homogenized Experimentsmentioning

confidence: 99%

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Spatially localized intermolecular zero‐quantum coherence spectroscopy for in vivo applications

Balla

Melkus

Faber

2006

Magnetic Resonance in Med

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Magnetic resonance spectroscopy (MRS) techniques that use the distant dipolar field (DDF) to locally refocus inhomogeneous line-broadening promise improved spectral resolution in spatially varying fields. We investigated three possible implementations of localized DDF spectroscopy. Theoretical analysis and phantom experiments at 17.6 T showed that only localization immediately prior to acquisition provides sufficient spatial selectivity and sensitivity for in vivo applications. Spectra from an (8 mm) 3 voxel of the rat brain were acquired in 25 min, and three major metabolites were resolved. In a tumor mouse model, DDF spectra with well-resolved lines can be obtained from significantly larger voxels compared to conventional localized spectroscopy. From an inhomogeneous voxel, improved spectral resolution can be obtained with DDF techniques when a sufficient number of increments are sampled along the second spectral dimension. With fewer increments, measurement time is significantly shortened, and DDF techniques can provide higher signal-to-noise ratio ( Key words: iZQC; HOMOGENIZED; localized spectroscopy; inhomogeneous broadening; resolution enhancementIn vivo magnetic resonance spectroscopy (MRS) can be used to resolve spectral patterns to analyze the biochemical composition of tissue. High spectral resolution can be achieved when the magnetic field is extremely homogeneous over the region studied. Such field homogeneity is usually achieved with localized shimming procedures (1,2). If the region of interest (ROI) is strongly structured or includes air/tissue boundaries, homogeneous magnetic fields cannot be obtained and spectral resolution is often poor. One way to avoid inhomogeneous line-broadening caused by small-scale field variations is to use experimental techniques that exploit the effect of the distant dipolar field (DDF) originating from the sample magnetization (3-6). The homogeneity enhancement by intermolecular zeroquantum echo detection (HOMOGENIZED) experiment has been shown to produce narrow line shapes even under temporarily unstable magnetic fields (7), linear inhomogeneities across the sample volume (3-5), and field distortions in living organisms (8,9). Efficient water suppression (WS) and localization of the acquired signal are essential for in vivo applications. While different combinations of WS modules have been described and compared (5,10), the inherently low sensitivity of these methods has hampered the development of localization techniques in vivo (11).In this study we investigate three possible ways to combine localization with the HOMOGENIZED experiment, and demonstrate that high-quality spectra can be obtained in vivo. THEORY Theory of the HOMOGENIZED ExperimentThe HOMOGENIZED pulse sequence is a 2D NMR experiment derived from correlation spectroscopy (COSY) (3,12):The values in brackets indicate the flip angle of RF pulses with pulse phase given in subscript; t 1 is the incremented delay, CG is the correlation magnetic field gradient, and t 2 the acquisition period. The acquire...

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Section: Theory Of the Homogenized Experimentsmentioning

confidence: 99%

“…A theoretical description has been given in terms of a mean field treatment (13)(14)(15), and in the quantum mechanical density matrix formalism (17,18), leading to the commonly used term "intermolecular zero-quantum coherence" (iZQC) spectroscopy.…”

Section: Theory Of the Homogenized Experimentsmentioning

confidence: 99%

Spatially localized intermolecular zero‐quantum coherence spectroscopy for in vivo applications

Balla

Melkus

Faber

2006

Magnetic Resonance in Med

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“…This was shown by analyzing the sequence using product operator formalism in the work of He et al (5,6) and further by de Graaf et al (8). In both publications, an incomplete suppression of the water signal can be seen, and this is attributed by de Graaf et al to so-called multiple spin-echoes of water, which originate from high-intensity water signal in an inhomogeneous magnetic field after two or more 90°pulses are applied on this resonance (18,19). By acquiring the 1 H spectrum with the classic CSI experiment, the residual water resonance at 4.7 ppm is well separated from the metabolite of interest and does not interfere with the quantification in most cases.…”

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confidence: 92%

Sensitive J‐coupled metabolite mapping using Sel‐MQC with selective multi‐spin‐echo readout

Melkus

Mörchel

Behr

et al. 2009

Magnetic Resonance in Med

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The selective multiple quantum coherence technique is combined with a read gradient to accelerate the measurement of a specific scalar-coupled metabolite. The sensitivities of the localization using pure phase encoding and localization with the read gradient are compared in experiments at high magnetic field strength (17.6 T). Multiple spin-echoes of the selective multiple quantum coherence edited metabolite are acquired using frequency-selective refocusing of the specified molecule group. The frequency-selective refocusing does not affect the J-modulation of a coupled spin system, and the echo time is not limited to a multiple of 1/J to acquire pure in-phase or antiphase signal. The multiple echoes can be used to accelerate the metabolite imaging experiment or to measure the apparent transverse relaxation T 2 . A simple phase-shifting scheme is presented, which enables the suppression of editing artifacts resulting from the multiple spin-echoes of the water resonance. In 1 H NMR spectroscopy, the spectral overlap of resonances is a common problem when information about a specific metabolite (e.g., lactate [Lac]) is desired in vivo. In the last decades, several types of spectral editing schemes were developed to filter the metabolite of interest from coresonant or overlapping signals (1-4). The class of multiple quantum coherence (MQC) filters using magnetic field gradients for editing provides robust single-shot editing techniques. One of the single-shot editing filters is the frequency selective multiple quantum coherence editing scheme (Sel-MQC) proposed by He et al. (5). This selective MQC filter enables editing of a single scalar-coupled spin system with simultaneous suppression of water and other resonances in one scan.Successful applications of the Sel-MQC editing sequence have been shown in several studies in which the metabolite of interest is overlapped by other spins with a similar chemical shift. For instance, in extracranial tumor tissues, the Lac CH 3 resonance (at 1.33 parts per million [ppm]) has been filtered from overlapping methylene groups of mobile lipids (5,6). A recent preliminary study on healthy and cancerous human breast tissue has shown a robust application of the Sel-MQC editing sequence to detect polyunsaturated fatty acids (PUFA) (7). The olefinic methylene protons of PUFA at 5.3 ppm that are coupled with the allylic methylene protons of unsaturated acyl chains at 2.8 ppm were detected in breast tissue, and the PUFA pattern is sensitive to breast tissue changes, including cancerous alterations. An adiabatic version of the Sel-MQC scheme was used by de Graaf et al. (8) to detect the ␤H1-glucose resonance at 4.63 ppm in rat brain in vivo. Executing the Sel-MQC sequence with adiabatic radiofrequency pulses allows optimal sensitivity when surface coils are used. In recent years, several extensions of the Sel-MQC editing scheme have been developed, such as Hadamard encoding for localization (9,10), multislice selection using spatial-spectral selective pulses (11), T 1 and T 2 relaxation ...

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“…The signals induced by dipolar couplings between distant spins can be analyzed with either the distant dipolar field (DDF) effect [1], or alternatively, with the theory of intermolecular multiple-quantum coherences (iMQC) [2]. Compared to conventional NMR signals, the signals originated from the DDF (or iMQC) contain some unique properties, the utility of which have been explored in a wide variety of applications, including contrast enhancement or novel contrast in MRI [3][4][5] and fMRI [6,7], suppression of inhomogeneous broadening [8,9], and measurements of magnetization structure [10][11][12].…”

Section: Introductionmentioning

confidence: 99%

Numerical simulations of motion-insensitive diffusion imaging based on the distant dipolar field effects

Lin

Sun

Chen

et al. 2007

Magnetic Resonance Imaging

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Diffusion weighting in MRI is commonly achieved with the pulsed-gradient spin-echo (PGSE) method. When combined with spin-warping image formation, this method often results in ghosts due to the sample's macroscopic motion. It has been shown experimentally (Kennedy and Zhong, MRM 2004;52:1−6) that these motion artifacts can be effectively eliminated by the distant dipolar field (DDF) method, which relies on the refocusing of spatially modulated transverse magnetization by the DDF within the sample itself. In this report, diffusion weighted images (DWIs) using both DDF and PGSE methods in the presence of macroscopic sample motion were simulated. Numerical simulation results quantify dependence of signals in DWI on several key motion parameters, and demonstrate that the DDF DWIs are much less sensitive to the macroscopic sample motion than the traditional PGSE DWIs. The results also show that the dipolar correlation distance (d c ) can alter contrast in DDF DWIs. The simulated results are in good agreement with the experimental results reported previously.

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NMR multiple echoes observed in solidHe3

Cited by 315 publications

References 29 publications

Spatially localized intermolecular zero‐quantum coherence spectroscopy for in vivo applications

Spatially localized intermolecular zero‐quantum coherence spectroscopy for in vivo applications

Sensitive J‐coupled metabolite mapping using Sel‐MQC with selective multi‐spin‐echo readout

Numerical simulations of motion-insensitive diffusion imaging based on the distant dipolar field effects

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