DDF and iMQC News

Fast high-resolution 2D correlation spectroscopy in inhomogeneous fields via Hadamard intermolecular multiple quantum coherences technique

2011-06-24T11:42:00.001-05:00

Congbo Cai, Fenglian Gao, Shuhui Cai, Yuqing Huang and Zhong Chen
Journal of Magnetic Resonance
Article in Press, Corrected Proof

Recently, a method based on intermolecular multiple quantum coherences (iMQCs) has been proposed to obtain high-resolution 2D COSY spectra in inhomogeneous fields via 3D acquisitions. However, the very long acquisition time prevents its practical application. To overcome this shortage, the Hadamard technique was applied for the iMQC method in this paper. For the new pulse sequence, the direct frequency-domain excitation is used in the first indirect detection dimension, so the 3D acquisition was replaced by an array of 2D acquisitions. The acquisition time can be reduced to 10 min. The resulting spectra retain useful structural information including chemical shifts and multiplet patterns of J coupling even when the inhomogeneous line broadening leads to overlap of neighboring diagonal resonances in the conventional COSY spectrum. The experimental results are consistent with the theoretical predictions and computer simulations. The new sequence may provide a time-efficient way for the studies of chemical solution in inhomogeneous fields.

Nearly 106-fold enhancements in intermolecular 1H double-quantum NMR experiments by nuclear hyperpolarization

2010-09-29T11:10:00.001-05:00

Mor Mishkovsky, Uzi Eliav, Gil Navon and Lucio Frydman
Journal of Magnetic Resonance
Volume 200, Issue 1, September 2009, Pages 142-146

Abstract

Intermolecular Multiple-Quantum Coherences (iMQCs) can yield interesting NMR information of high potential usefulness in spectroscopy and imaging – provided their associated sensitivity limitations can be overcome. A recent study demonstrated that ex situ dynamic nuclear polarization (DNP) could assist in overcoming sensitivity problems for iMQC-based experiments on 13C nuclei. In the present work we show that a similar approach is possible when targeting the protons of a hyperpolarized solvent. It was found that although the DNP procedure enhances single-quantum 1H signals by about 600, which is significantly less than in optimized low-γ liquid-state counterparts, the non-linear dependence of iMQC-derived signals on polarization can yield very large enhancements approaching 106. Cleary no practical amount of data averaging can match this kind of sensitivity gains. The fact that DNP endows iMQC-based 1H NMR spectra with a sensitivity that amply exceeds that of their thermally polarized single-quantum counterpart, is confirmed in a number of simple single-scan 2D imaging experiments.

Intermolecular single-quantum coherence sequences for high-resolution NMR spectra in inhomogeneous fields

2010-09-29T11:06:00.001-05:00

Yuqing Huang, Shuhui Cai, Xi Chen and Zhong Chen
Journal of Magnetic Resonance
Volume 203, Issue 1, March 2010, Pages 100-107

Abstract

A new pulse sequence based on intermolecular single-quantum coherences (iSQCs) is proposed to obtain high-resolution NMR spectroscopy in inhomogeneous magnetic fields via fast 2D acquisition. Taking the intrinsic properties of iSQCs, the sequence is time-efficient with a narrow spectral width in the indirect dimension. It can recover useful information of chemical shifts, relative peak areas, J coupling constants, and multiplet patterns even when the field inhomogeneity is severe enough to erase almost all spectroscopic information. Moreover, good solvent suppression efficiency can be achieved by this sequence even with imperfect radio-frequency pulse flip angles. Spatially localized iSQC spectroscopy was performed on a sample packed with pig brain tissue and cucumber to show the feasibility of the sequence in in vivo magnetic resonance spectroscopy (MRS). This sequence may provide a promising way for the applications on in vivo and in situ high-resolution NMR spectroscopy.

Highly efficient square wave distant dipolar field and its application for in vivo MRI

2010-05-25T14:25:00.000-05:00

Congbo Cai, Fenglian Gao , Shuhui Cai, Jianhui Zhong, Zhong Chen

Intermolecular multiple quantum coherences generated by distant dipolar field (DDF) have some attractive properties, but the intrinsic weak signal intensity prevents their widespread applications. Recently, Branca et al. (J Chem Phys 2008;129:054502) suggested that square wave DDF was more efficient than conventional sinusoidal DDF because it could simultaneously produce intermolecular multiple quantum coherences signal with various major orders. In this article, instead of a series of adiabatic inversion pulses proposed previously, a more efficient composite adiabatic inversion pulse was applied to create square wave DDF. The square wave DDF was applied to in vivo MRI for the first time, and the corresponding simulations were performed. Both experimental and simulated results show that square wave DDF with composite adiabatic inversion pulse improves over the original Z-modulation enhanced to binary for self-refocused acquisition implementation and can enhance the signal intensity to about 2-fold of that from conventional correlation spectroscopy (COSY) revamped with asymmetric Z-gradient echo detection sequence for in vivo MRI, close to the theoretical prediction. Magn Reson Med, 2010. © 2010 Wiley-Liss, Inc.

Fast acquisition scheme for achieving high-resolution MRS with J-scaling under inhomogeneous fields

2009-03-25T17:16:00.001-05:00

Xi Chen, Meijin Lin, Zhong Chen, and Jianhui Zhong
Magnetic Resonance in Medicine
Volume 61 Issue 4, Pages 775 - 784
Published Online: 2 Feb 2009

Intermolecular multiple-quantum coherences (iMQCs) can refocus the phase dispersion caused by magnetic field inhomogeneities while preserving the chemical shift, so they have been applied to achieve high-resolution MR spectroscopy free of line broadening caused by susceptibility gradients. However, previous iMQC high-resolution methods all require two-dimensional spectra sampling of the full range of chemical shifts of solute evolutions in both F1 and F2 dimensions, resulting in a prolonged scanning time for data acquisition. In this work, sparse sampling in the t1 dimension and subsequent fold-over correction are used to speed up the intermolecular zero-quantum coherence spectroscopy by up to 50 times on high-field MR systems. Furthermore, three types of spectra with homo-decoupling, original J-coupling constants, and doubled J-coupling constants respectively are obtained with manipulation of the t1 period. The water suppression is also improved by the combined use of intermolecular double-quantum filter and excitation sculpting. The feasibilities of this group of new sequences are demonstrated by experiments using an agar gel phantom with an air bubble, in vitro pig brain tissues and an intact postmortem mudskipper. Magn Reson Med, 2009. © 2009 Wiley-Liss, Inc.

iDQC anisotropy map imaging for tumor tissue characterization in vivo

2009-02-13T09:29:00.001-06:00

Rosa T. Branca, Yuming M. Chen, Vladimir Mouraviev, Gigi Galiana, Elizabeth R. Jenista, Challa Kumar, Carola Leuschner, Warren S. Warren

Intermolecular double quantum coherences (iDQCs), signals that result from simultaneous transitions of two or more separated spins, are known to produce images that are highly sensitive to subvoxel structure, particularly local anisotropy. Here we demonstrate how iDQCs signal can be used to efficiently detect the anisotropy created in breast tumor tissues and prostate tumor tissues by targeted (LHRH-conjugated) superparamagnetic nanoparticles (SPIONs), thereby distinguishing the necrotic area from the surrounding tumor tissue. Magn Reson Med, 2009. © 2009 Wiley-Liss, Inc.

Hyperpolarized carbon–carbon intermolecular multiple quantum coherences

2008-10-21T10:41:00.000-05:00

Journal of Magnetic Resonance
Article in Press, Corrected Proof

Hyperpolarized carbon–carbon intermolecular multiple quantum coherences

Elizabeth R. JenistaCorresponding Author Contact Information, a, E-mail The Corresponding Author, Rosa T. Brancaa and Warren S. Warrena
aCenter for Molecular and Biomolecular Imaging, 2220 French Family Science Center, Duke University, Durham, NC 27708, USA

Received 17 July 2008;
revised 17 September 2008.
Available online 2 October 2008.

Abstract

Intermolecular multiple quantum coherences (iMQCs) can provide unique contrast with sub-voxel resolution. However, the characteristic growth rate of iMQCs mostly limits these effects to either hydrogen or hydrogen-coupled systems for thermally polarized samples. Hyperpolarization techniques such as dynamic nuclear polarization (DNP) allow for significant increases in the carbon signal (even more signal than that from hydrogen), making carbon iMQCs achievable. We present the first intermolecular multiple quantum signal between two carbon nuclei.

Keywords: Intermolecular multiple quantum coherence; 13C hyperpolarization; Dynamic nuclear polarization; MultiCRAZED; CRAZED

Accurate Temperature Imaging Based on Intermolecular Coherences in Magnetic Resonance

2008-10-21T08:23:00.001-05:00

Science 17 October 2008:
Vol. 322. no. 5900, pp. 421 - 424
DOI: 10.1126/science.1163242

Accurate Temperature Imaging Based on Intermolecular Coherences in Magnetic Resonance
Gigi Galiana, Rosa T. Branca, Elizabeth R. Jenista, and Warren S. Warren

Conventional magnetic resonance methods that provide interior temperature profiles, which find use in clinical applications such as hyperthermic therapy, can develop inaccuracies caused by the inherently inhomogeneous magnetic field within tissues or by probe dynamics, and work poorly in important applications such as fatty tissues. We present a magnetic resonance method that is suitable for imaging temperature in a wide range of environments. It uses the inherently sharp resonances of intermolecular zero-quantum coherences, in this case flipping up a water spin while flipping down a nearby fat spin. We show that this method can rapidly and accurately assign temperatures in vivo on an absolute scale.

Innovations Improve Accuracy Of MRI As Internal 'Thermometer'; Technique Can Enhance Cancer Therapy

2008-10-21T08:14:00.001-05:00

ScienceDaily (Oct. 21, 2008) — Duke University chemists say they have developed a new way to measure temperature changes inside the body with unprecedented precision by correcting a subtle error in the original theory underlying Magnetic Resonance Imaging (MRI)...

BOLD imaging in the mouse brain using a turboCRAZED sequence at high magnetic fields

2008-09-25T09:58:00.000-05:00

Johannes T. Schneider, Cornelius Faber

Functional MRI (fMRI) based on the detection of intermolecular double-quantum coherences (iDQC) has previously been shown to provide pronounced activation signal. For fMRI in small animals at very high magnetic fields, the essential fast gradient echo-based readout methods become problematic. Here, rapid intermolecular double-quantum coherence (iDQC) imaging was implemented, combining the iDQC preparation sequence with a Turbo spin echo-like readout. Four-step phase cycling and a novel intensity-ordered k-space encoding scheme with separate acquisition of odd and even echoes were essential to optimize signal to noise ratio efficiency. Compared with a single echo readout of iDQC signal, acceleration of factor 16 was achieved in phantoms using the novel method at 17.6 Tesla. In vivo, echo trains consisting of 32 echoes were possible and images of the mouse brain were obtained in 30 s. The blood oxygen level dependent (BOLD) effect in the mouse brain upon change of breathing gas was observed as average signal change of (6.3 ± 1.1)% in iDQC images. Signal changes in conventional multi spin echo images were (4.4 ± 2.3)% and (8.3 ± 3.8)% with gradient echo methods. Combination of T2*-weighting with the fast iDQC sequence may yield higher signal changes than with either method alone, and establish fast iDQC imaging a robust tool for high field fMRI in small animals. Magn Reson Med 60:850-859, 2008. © 2008 Wiley-Liss, Inc.

Enhanced nonlinear magnetic resonance signals via square wave dipolar fields

2008-08-13T00:19:00.001-05:00

R. T. Branca,1 G. Galiana,1,2 and W. S. Warren1
1Center for Molecular and Biomolecular Imaging, Duke University, Durham, North Carolina 27708, USA
2Chemistry Department, Princeton University, Princeton, New Jersey 08544, USA
J. Chem. Phys. 129, 054502 (2008)

This report introduces a new approach that enhances nonlinear solution magnetic resonance signals from intermolecular dipolar interactions. The resulting signals can theoretically be as large as the full equilibrium magnetization. Simple, readily implemented pulse sequences using square-wave magnetization modulation simultaneously refocus all even order intermolecular multiple quantum coherences, leading to a substantial net signal enhancement, complex nonlinear dynamics, and improved structural sensitivity under realistic conditions. ©2008 American Institute of Physics

Appendices A and B with mathematical derivations as referred to in the text (10 pages)

2008-07-24T18:22:00.002-05:00

ARTICLE INFORMATION

EPAPS Document No.: E-JCPSA6-129-617827

Journal: J. Chem. Phys. 129, 044505 (2008)

All Authors: Stefan Kirsch, William E. Hull

Title: Quantitative time- and frequency-domain analysis of the two-pulse
CRAZED NMR experiment; theoretical and experimental aspects, time-zero
data truncation artefacts, and radiation damping

Deposit Information

Description: Appendices A and B with mathematical derivations as referred
to in the text (10 pages)

Total No. of Files: 2

File Names: Readme.txt, 617827JCP appendices.pdf

File Types: .txt and .pdf

Contact:
Dr. William E. Hull (PhD)
Core Facility: Molecular Structure Analysis (W160)
German Cancer Research Center (DKFZ)
Im Neuenheimer Feld 280
Postfach 101949
D-69009 Heidelberg

Fax: +49-6221-42-4554
Tel: +49-6221-42-4515 / -4544 / -4542

Quantitative time- and frequency-domain analysis of the two-pulse COSY revamped by asymmetric Z-gradient echo detection NMR experiment: Theoretical an

2008-07-24T18:16:00.000-05:00

Stefan Kirsch and William E. Hull
J. Chem. Phys. 129, 044505 (2008)

Thetwo-pulse COSY revamped by asymmetric Z-gradient echo detection (CRAZED) NMRexperiment has the basic form 90°−G−t_rec−−nG−t_rec-FID, with a phase-encoding gradientpulse G of length applied during the evolution time for transverse magnetization, readout pulse , rephasing gradient nG,and recovery time t_rec prior to acquisition of the free-inductiondecay. Based on the classical treatment of the spatially modulateddipolar demagnetizing field and without invoking intermolecular multiple-quantum coherence, anew formulation of the first-order approximation for the theoretical solutionof the nonlinear Bloch equations has been developed. The nth-orderCRAZED signal can be expressed as a simple product ofa scaling function C_n(,) and a signal amplitude function A_n(t),where the domain t begins immediately after the pulse.Using a single-quantum coherence model, a generalized rf phase shiftfunction has also been developed, which explains all known phasebehavior, including nth-order echo selection by phase cycling. Details ofthe derivations are provided in two appendices as supplementary material.For n>1, A_n(t) increases from zero to a maximum valueat t=t_max before decaying and can be expressed as aseries of n exponential decays with antisymmetric binomial coefficients. Fouriertransform gives an antisymmetric binomial series of Lorentzians, where thecomposite lineshape exhibits negative wings, zero integral, and a linewidththat decreases with n. Analytical functions are presented for t_maxand A_n(t_max) and for estimating the maximal percent error incurredfor A_n(t_max) when using the first-order model. The preacquisition delay=+t_rec results in the loss of the data points fort=0 to . Conventional Fourier transformation produces time-zero truncation artifacts(reduced negative wing amplitude, nonzero integral, and reduced effective T2^*" align="middle" border="0">),which can be avoided by time-domain fitting after right shiftingthe data by . A doped water sample (9.93 mMNiSO₄, 10 mm sample tube) was used to study thebehavior of the CRAZED signal for n=1–4 with =90° at7 T (300 MHz ¹H frequency) as a function of, with and without radiation damping. Pulse-acquire experiments were usedto determine the relaxation times (T₁=61.8 ms and T2^*" align="middle" border="0">=29.7 ms), and theradiation damping time constant T_rd=18.5 ms. When experimental CRAZED data setswere right shifted by , excellent least-squares fits to thefirst-order model function were obtained for all n using aminimal set of free variables. Without radiation damping the fittedT2^*" align="middle" border="0">values (29.7–30.2 ms) agreed with the reference value. With radiationdamping the fitted effective T2^*" align="middle" border="0"> values were 16.2 ms fora 90° pulse-acquire experiment and 18.8–20.2 ms for the CRAZEDexperiment with n=1–4 and signal amplitudes spanning a range of10⁵. ©2008 American Institute of Physics

Diffraction-like phenomena in a periodic magnetization distribution at 1.5 T using the distant dipolar field (DDF)

2008-05-19T11:52:00.002-05:00

Stefan Kirsch and Peter Bachert
Journal of Magnetic Resonance
Volume 185, Issue 2, April 2007, Pages 183-190

In the CRAZED experiment (COSY revamped by asymmetric Z-gradient echo detection, Warren et al.), a spatially anisotropic magnetization distribution is created by application of a magnetic field gradient (strength G, duration τ) which in turn generates a response called the distant dipolar field (DDF). The DDF is a source of intermolecular multiple-quantum coherences (iMQC) which contain information on the distance d = π/(γGτ) between pairs of dipolar-coupled spins. Diffraction-like phenomena may result for periodically structured samples. In this study, we report the observation of diffraction owing to the DDF at 1.5 T using a clinical whole-body tomograph. Based on the semi-classical treatment of the problem by Robyr and Bowtell, diffraction conditions were obtained for a CRAZED-type pulse sequence that selects iMQC of order N. The predicted distinct difference in N = 2 and N ≠ 2 coherences, i.e., a dominant continuous course as a function of τ (N = 2) and prominent diffraction peaks otherwise, could be verified in CRAZED experiments in a periodically structured sample selecting coherence orders N = 2 and N = 3. The diffractive signal component contains information on the geometric structure of the sample. Applications of this technique may permit the detection of changes in composition and geometry of periodic structures. Keywords: CRAZED; Distant dipolar field (DDF); Intermolecular multiple-quantum coherence; Diffraction

Localized intermolecular zero-quantum coherence spectroscopy in vivo

2008-05-15T10:32:00.002-05:00

David Z. Balla , Cornelius Faber
Concepts in Magnetic Resonance Part A
Volume 32A, Issue 2 , Pages 117 - 133

Resolution enhancement in NMR spectra, acquired in spatially or temporally varying magnetic fields, can be achieved with 2D pulse sequences detecting intermolecular zero-quantum coherences (iZQC). The insensitivity towards long range field distortions renders these methods particularly appealing for in vivo NMR spectroscopy, where ample sources of field inhomogeneities are encountered. This article provides a comprehensive description of iZQC spectroscopy, following a classical treatment. A pictorial explanation is given of how iZQC signal is formed under the action of the distant dipolar field in the sample and how this local refocusing process leads to line narrowing in the indirect dimension of 2D spectra. Signal evolution and peak positions in the spectra are analyzed by solving the modified Bloch equations. Finally, it is explained how water suppression and localization can be combined with the iZQC preparation sequence, and recent in vivo applications are discussed. The given examples illustrate that iZQC spectroscopy can provide either resolution or sensitivity enhancement in vivo. © 2008 Wiley Periodicals, Inc. Concepts Magn Reson Part A 32A: 117-133, 2008.

Intermolecular zero-quantum coherence NMR spectroscopy in the presence of local dipole fields spectroscopy in vivo

2008-05-13T10:04:00.002-05:00

David Z. Balla and Cornelius Faber
Department of Experimental Physics 5, University of Würzburg, 97074 Würzburg, Germany
J. Chem. Phys. 128, 154522 (2008); DOI:10.1063/1.2904564

NMRexperiments detecting intermolecular zero-quantum coherences (iZQCs) allow for observation ofhomogeneous line shapes under inhomogeneous magnetic fields. Local dipole fieldsimpair the refocusing capacity of such experiments and render theavailable theoretical description of signal evolution invalid. In this article,the impact of local dipole fields on two-dimensional iZQC spectroscopyexperiments was assessed by performing extensive numerical simulations, which solvedthe nonlinear Bloch equations for a binary solution in amagnetization array of 64³ spatial points. Local dipole fields weresimulated using spherical volumes with different magnetic susceptibility values correspondingto either a glass sphere or an air inclusion witha diameter of 100 µm. The local field resulted in abroadened distribution of difference frequencies between locally interacting spins andled to the dominating effect of decreasing the amplitude ofthe solute peak, before line broadening was observed in thespectra. From simulations using a magnetic field strength of 17.6 T,the smallest ratio of sample to inclusion volume that stillallowed for observation of the solute peak was determined tobe _limit=215 and _limit=392 for glass and air inclusions, respectively.Experimental data acquired with a 100 µm diameter glass sphere embeddedin agar gel yielded a value of _limit=252 and confirmedthe order of magnitude obtained from the simulations. From thesedata, it was concluded that iZQC spectroscopy is possible aslong as the relative volume occupied by air inclusions doesnot exceed the order of 0.1% of the sample volume.This limit, in contrast to the previous speculations, strongly excludesmaterials or tissues with high density of strong inhomogeneities fromthe investigation by iZQC spectroscopy. ©2008 American Institute of Physics

In vivo intermolecular zero-quantum coherence MR spectroscopy in the rat spinal cord at 17.6 T: a feasibility study

2008-05-13T10:02:00.001-05:00

David Z. Balla^{1, 2} and Cornelius Faber¹

(1)	Department of Experimental Physics 5, University of Würzburg, Am Hubland, 97074 Würzburg, Germany

(2)	Present address: Max-Planck-Institute for Biological Cybernetics, 72076 Tübingen, Germany

Received: 5 April 2007 Revised: 14 August 2007 Accepted: 17 August 2007 Published online: 18 September 2007

Abstract

Objective: The feasibility of in vivo magnetic resonance spectroscopy of the healthy rat spinal cord at 17.6 T using conventional methods and intermolecular zero-quantum coherence (iZQC) spectroscopy is explored and the performance of both approaches is compared.

Methods: Localised spectra were acquired at 17.6 T from three healthy Fisher rats and phantoms with injected iron-oxide particles using the PRESS and a modified HOMOGENIZED sequence.

Results: Well-resolved in vivo spectra showing the four singlet resonances of creatine, choline, and N-acetyl aspartate were obtained with both approaches. iZQC spectra were acquired from larger voxels, but did not provide higher sensitivity or resolution in the healthy spinal cord. In the presence of paramagnetic iron-oxide particles, the quality of in vitro spectra acquired with PRESS declined and was strongly dependent on the quality of the local shim. iZQC spectra were not affected by the presence of iron-oxide particles and provided narrow lines (9 Hz) independent of the shim.

Conclusion: In vivo iZQC spectroscopy of the rat spinal cord is possible. The robustness in presence of local field distortions makes iZQC methods a promising alternative for the investigation of tissue containing labelled cells, implants, or clotted blood. New application of MRS to tissue inaccessible using conventional methods may thus become possible.

Keywords MR spectroscopy - Resolution enhancement - iMQC - DDF - SPIO

Understanding intra- and intermolecular multiple quantum coherences

2008-05-11T00:02:00.002-05:00

This was in the weekend educational program.
Somebody registered for the weekend must login...

_____________________________________

MR Physics for Physicists
Organizer: Michael H. Buonocore, M.D., Ph.D.
Skill Level: Intermediate – Advanced
Saturday, 3 May, 08:30 – 18:15, Room 801 A/B

Spin Physics
09:30 Understanding intra- and intermolecular multiple quantum coherences
Jianhui Zhong, Ph.D.
University of Rochester, USA

Nuclear magnetic resonance (NMR), after all, is a quantum mechanical phenomenon.
Even though in the imaging community, we are mostly familiar and use in most times the
so-called vector model which describes the MR signal as from a precessing bar magnet
inside the magnetic field (not too much different from a spinning toy top in the earth’s
gravitation field), at a more fundamental level quantum mechanics should be used for
NMR. The phenomena of multiple-quantum coherence (MQC) not only provides a nice
demonstration of the true quantum mechanical nature of NMR, applications of various
MQC techniques also reveal many interesting structural and functional information in
MRS and MRI...

ISMRM 2008 DDF/iMQC

2008-05-10T22:53:00.010-05:00

Here are the iMQC/DDF related abstracts that I found. Please email me if I missed one (especially yours!) corum@cmrr.umn.edu

Hopefully you, or a colleague has access to the login.

Curt

______________________________________

1407.
Intermolecular Zero-Quantum Coherence Imaging in Structured Samples
Bernard Siow1, Li Sun1, Andrew M. Blamire1
1Newcastle University, Newcastle upon Tyne, UK

Intermolecular multiple quantum coherence imaging sequences have recently been shown to provide a fundamentally different contrast mechanism to conventional MRI. A numerical study of intermolecular zero-quantum coherence imaging has shown sensitivity to susceptibility gradients at selected distance scales. In this study, an iZQC sequence was implemented and iZQC signal verified. The sequence was used to investigate sensitivity to susceptibility gradients at selected distance scales in structured samples. Images show contrast in areas where susceptibility gradients are present. Furthermore, contrast was modulated by the distance scale selected. Further results suggest that contrast is modulated by specific resonant frequency difference at distance scale selected.

1454.
Fast Relaxation Induced by SPIO Compromises Contrast from Intermolecular Double–quantum Coherence in CRAZED–MRI
Elvira Mehlin1, Stefan Kirsch1, Peter Bachert1
1German Cancer Research Center (DKFZ), 69120 Heidelberg, Germany

The CRAZED sequence permits detection of signal generated by intermolecular double–quantum coherence (iDQC). When applied to 1H MRI, a novel type of contrast is obtained, in particular, a positive contrast when superparamagnetic iron oxide particles (SPIOs) are present. We demonstrate that the high T1–relaxivity of SPIOs can cause spurious signal in CRAZED MRI which cannot be attributed to iDQC.

1458.
Optimization of Parameters for the Distant Dipolar Field Signal Acquired in CRAZED-Multiecho Pulse Sequence
Chung Ki K. Wong1, Jianhui Zhong1
1University of Rochester, Rochester, New York, USA

The decrease of dipolar signal with refocusing pulses of finite duration in a CRAZED-multiecho acquisition was investigated previously. It was found that the rephasing of the dipolar signal during the refocusing pulses in the multiecho sequence depends substantially on the phase of the pulses. In this abstract, the total signal acquired from the multiecho sequence was optimized with the parameters of the sequence. The results show that the attenuation of the signal due to the finite duration of the refocusing pulses can be compensated with a longer τ2 and a proper choice of the phase of the pulses.

1562.
Time-Zero Signal Truncation in CRAZED Experiments Due to Rephasing Gradient Delays Leads to Incorrect Frequency-Domain Lineshapes
Stefan Kirsch1, William Edmund Hull1
1German Cancer Research Center (DKFZ), Heidelberg, Germany

In contrast to the decay of a conventional pulse-acquire FID, the time-domain signal from of a CRAZED-type pulse sequence for coherence order n > 1 increases from initially zero to a maximum, followed by an exponential decay. We show that the finite duration of the coherence rephasing gradient and any subsequent recovery delays lead to loss of the initial portion of the time-domain signal. This so-called “time-zero truncation artefact” results in an altered frequency-domain lineshape with incorrect integral and linewidth. Correct analysis requires time-domain fitting of right-shifted data.

1563.
In Vivo Human Whole Cerebellum MRS Under Severe Field Inhomogeneity with IDQC Method
Tianliang Gu1, 2, Zhong Chen1, Xiaoxu Liu1, Ling-chih Lin1, Jianhui Zhong1
1University of Rochester, Rochester, New York, USA

An intermolecular double quantum coherence (iDQC) 2D MRS pulse sequence was created and implemented on a 3T scanner for acquisition of human brain 1H spectra in regions susceptible to field inhomogeneity such as the cerebellum. High resolution 1D MRS could be obtained in a few minutes with iDQC over the whole cerebellum, whereas conventional single voxel 1D MRS was working successfully only when regions much smaller were covered. NAA/Cr and Cho/Cr measured with both methods in 5 healthy subjects agreed well with each other.

2361.
Enhanced BOLD Effect in the Mouse Brain with Fast CRAZED Imaging at High Magnetic Fields
Johannes Thomas Schneider, Cornelius Faber

A fast CRAZED sequence detecting the signal from intermolecular multiple-quantum coherences (iMQC) was implemented at 17.6 T to observe the BOLD effect in the mouse brain. Signal readout as echo train employing a four-step phase cycle for the refocusing pulses and an intensity-ordered k-space sampling allowed for acquisition of CRAZED images in 30 seconds. In the CRAZED images the BOLD effect was more pronounced than in RARE images but smaller than in gradient echo images. Combination of iMQC with T2*-effects may provide larger signal changes than conventional BOLD methods.

3063.
Enhanced Contrast in CEST MRI Via Intermolecular Double Quantum Coherences
Shengchun Zhang1, Huijun Sun1, Zhong Chen1, Congbo Cai1, Jianhui Zhong2
1Xiamen University, Xiamen, People's Republic of China; 2University of Rochester, Rochester, New York, USA

A CEST imaging technique based on intermolecular double quantum coherence (iDQC) is proposed. Quantitative analysis and experiments in glucose agarose-gel phantoms demonstrate that, in CEST MRI, iDQC signal is more sensitive to RF saturation than the conventional SQC signal, and thus needs RF saturation pulses of lower power to achieve similar CEST image contrast. Consequently, the method can reduce the potential RF burning in clinic applications, and is expected to facilitate the study of the CEST effect in the system with exchangeable protons of low concentrations.

3125.
High-Resolution MR Spectroscopy in Inhomogeneous and Unstable Fields Via Intermolecular Zero-Quantum Coherences
Xi Chen1, Meijin Lin1, Tao Lin1, Zhong Chen1, Jianhui Zhong2
1Xiamen University, Xiamen, People's Republic of China; 2University of Rochester, Xiamen, New York, USA

A new iZQC pulse sequence with stroboscopic acquisition is designed to achieve high-resolution magnetic resonance spectroscopy in inhomogeneous and unstable fields. Primary results suggest potential applications for suppressions of motion-caused t1 noises and inhomogeneous broadenings in in vivo studies.

3186.
High Resolution NMR Spectra in Inhomogeneous Fields Via Intermolecular Multiple Quantum Coherences Without Coherence Selection Gradients
Zhong Chen1, Congbo Cai1, Yanqin Lin1, Shuhui Cai1, Jianhui Zhong2
1Xiamen University, Xiamen, People's Republic of China; 2University of Rochester, Rochester, New York, USA

Coherence selection gradient has been thought to be essential for high resolution NMR spectra in inhomogeneous field based on intermolecular multiple quantum coherences (iMQC). However, our experimental results show that it can be omitted if correct phase cycling is applied. This means that the measured line-width of high resolution spectral peaks is not determined by the dipolar correlation distance caused by coherence selection gradient, but only affected by the effects of diffusion and T2 relaxation. This result prompts us to reconsider the iMQC high resolution mechanism.

3188.
An Effective Fast Acquisition Scheme to Achieve High-Resolution MRS with J-Coupling Scaling Via Intermolecular Multiple-Quantum Coherences
Xi Chen1, Meijin Lin1, Jincan Chen1, Tao Lin1, Zhong Chen1
1Xiamen University, Xiamen, People's Republic of China

A series of intermolecular double-quantum filtered (iDQF) sequence with efficient solvent suppression and different scaling factors of J-coupling constants, named iDQF-HOMOGENIZED II (abbreviated as iDH2), are designed to achieve fast acquisition of high-resolution spectra in inhomogeneous fields. Experiments on swine brain tissues were performed to test the feasibility of the new method. The results suggest potential applications for in vivo spectroscopy.

3189.
A Flexible IMQC Method for Accurate Determination of J-Coupling Constants in Inhomogeneous Fields
Yanqin Lin1, Shuhui Cai1, Yuqing Huang1, Zhong Chen1, Jianhui Zhong2
1Xiamen University, Xiamen, People's Republic of China; 2University of Rochester, Rochester, New York, USA

An improved pulse sequence was developed to scale apparent J coupling constants by a scaling factor ranging theoretically from zero (completely decoupled) to infinity under inhomogeneous fields via intermolecular multiple-quantum coherences. Scaling up the apparent J coupling constants allows more accurate measurement of small J coupling constants, and a completely decoupled homonuclear spectrum can be of considerable help for improving signal separation and thus peak assignment in MRS. The resulting spectrum retains conventional high-resolution NMR spectral information.

3351.
Apparent Diffusion Behaviors Modulated by Distant Dipolar Field in Solution NMR
Shuhui Cai1, Guiping Shen1, Congbo Cai1, Zhong Chen1
1Xiamen University, Xiamen, People's Republic of China

A modified CRAZED sequence was designed to observe and characterize apparent diffusion behaviors of signals from intermolecular double-quantum coherences during the mixing period. It is found that their apparent diffusion behaviors are different from conventional single-quantum coherences, and different orientation of diffusion weighting gradients relative to coherence selection gradients results in different apparent diffusion behaviors. This indicates
that the apparent diffusion behavior is influenced by the distant dipolar field.

3647.
Enhancement of MT, CEST and NOE Contrast Via Intermolecular Multiple Quantum Coherences
Wen Ling1, Uzi Eliav1, Xu Yang2, Gil Navon1, Alexej Jerschow2
1Tel Aviv University, Israel; 2New York University, New York, New York, USA

We demonstrate that using intermolecular multiple-quantum coherences can enhance contrast in MTC/CEST/NOE experiments in proportion to (Mz/Mo)p, where Mz is the the saturated level of the z-component of the magnetization, Mo its value in equilibrium and l is the coherence order used. These methods are demonstrated on a series of glycosaminoglycan (GAG) samples, and also for a piece of bovine articular cartilage.

High-resolution NMR spectra in inhomogeneous fields utilizing the CRAZED sequence without coherence selection gradients

2008-05-10T22:43:00.002-05:00

Congbo Cai, Yanqin Lin, Shuhui Cai, Zhong Chen, , and Jianhui Zhong

Journal of Magnetic Resonance
Article in Press, Corrected Proof

Abstract: Coherence selection gradients have been considered as indispensable for high-resolution NMR spectroscopy in inhomogeneous fields utilizing the CRAZED-type sequences. However, our experimental results demonstrate that these gradients can be omitted if an appropriate phase cycling is applied. The measured linewidth of reconstructing 1D high-resolution spectral peaks does not depend on the dipolar correlation distance determined by the coherence selection gradients, but is only affected by diffusion and T2 relaxation. This finding suggests the need to reconsider the mechanism for the iMQC-based high-resolution spectroscopy.

Keywords: High-resolution spectra; Intermolecular multiple-quantum coherences; Inhomogeneous fields; Dipolar correlation distance; Coherence selection gradients

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

2008-02-28T00:09:00.001-06:00

Tao Lin, Huijun Sun, Zhong Chen, Rongyi You, Jianhui Zhong
Magnetic Resonance Imaging 25 (2007) 1409–1416

Abstract
Diffusion weighting in MRI is commonly achieved with the pulsed-gradient spin-echo (PGSE) method. When combined with spinwarping
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 the dependence of signals in DWI on several key motion parameters and demonstrate that the DDF
DWIs are much less sensitive to macroscopic sample motion than the traditional PGSE DWIs. The results also show that the dipolar
correlation distance (dc) can alter contrast in DDF DWIs. The simulated results are in good agreement with the experimental results
reported previously.
D 2007 Elsevier Inc. All rights reserved.

Keywords: DDF; Motion; Diffusion; Image contrast; Computer simulation

Functional MRI at 3T using intermolecular double-quantum coherence (iDQC) with spin-echo (SE) acquisitions

2007-12-12T08:53:00.000-06:00

Functional MRI at 3T using intermolecular double-quantum coherence (iDQC) with spin-echo (SE) acquisitions
T. Gu, S. D. Kennedy, Z. Chen, K. A. Schneider and J. Zhong
Magnetic Resonance Materials in Physics, Biology and Medicine
Published online: 5 December 2007

Abstract

Object To reinvestigate the dependence of the signal and contrast on sequence parameters and tissue relaxation times for intermolecular double-quantum coherence (iDQC) signals, and to explore the possibility to use a spin-echo (SE)-iDQC sequence for detecting activation signals at 3T.

Materials and methods Brain activations were detected in five human volunteers in a visual simulation study using a SE-iDQC sequence, in addition to a GE-iDQC and a conventional single-quantum coherence (SQC) blood-oxygenation-level-dependent (BOLD) sequence. A brain phantom was also used for some quantitative measurements.

Results By choosing an optimal echo time TE (~T2) and iDQC evolution time τ(~20 ms), robust brain activations were detected using the SE-iDQC sequence, in addition to the GE-iDQC and a conventional single-quantum coherence (SQC) BOLD sequence. A higher percentage signal change due to activation was observed for both the iDQC-based measurements in comparison to the conventional SQC acquisition.

Conclusion Even though a phenomenological analysis consistent with the experimental results was provided, a detailed model is still needed for the contrast mechanism at microscopic level to guide potential applications of brain functional imaging based on the SE-iDQC.

Keywords fMRI - Intermolecular double-quantum coherence (iDQC) - Distant dipolar field (DDF) - Spin echo (SE)

Thanks to Andreas Schaefer for sending...cac

Enhancement of magnetization transfer effects by inter-molecular multiple quantum filtered NMR

2007-10-24T17:53:00.000-05:00

Uzi Eliav^a and Gil Navon ^,^a^,
^aSchool of Chemistry, Tel Aviv University, Ramat Aviv, Tel Aviv 69978, Israel
Received 10 May 2007. Available online 28 September 2007.

Abstract

There are a number of methods that give MRI contrasts based on changes of the water M_z magnetization as a result of magnetization transfer to macromolecules. In the present work we report that a combination of these methods with inter-molecular multiple quantum coherences (iMQC) gives enhanced effects. For the magnetization transfer contrast (MTC) method an effect of (M_z/M₀) becomes (M_z/M₀)^l where l is the rank of the tensors constituting the iMQC. A similar trend was found upon combining iMQC with the Goldman–Shen experiment. It is pointed out that the method is general for all magnetization transfer methods, including the nuclear Overhauser effect.

Keywords: iMQC; Intermolecular dipolar interaction; Magnetization transfer; MTC; Goldman–Shen

NMR Time Reversal as a Probe of Incipient Turbulent Spin Dynamics

2007-10-12T05:41:00.000-05:00

NMR Time Reversal as a Probe of Incipient Turbulent Spin Dynamics
M. E. Hayden,1 E. Baudin,2 G. Tastevin,2 and P. J. Nacher2

1Physics Department, Simon Fraser University, 8888 University Drive, Burnaby BC, Canada V5A 1S6
2Laboratoire Kastler Brossel, Ecole Normale Supérieure; CNRS; UPMC; 24 rue Lhomond, F75005 Paris, France
Phys. Rev. Lett. 99, 137602 (2007)
(Received 23 April 2007; published 27 September 2007)

Wedemonstrate time reversal of nuclear spin dynamics in highly magnetizeddilute liquid ³He-⁴He mixtures through effective inversion of long-range dipolarinteractions. These experiments, which involve using magic sandwich NMR pulsesequences to generate spin echoes, probe the spatiotemporal development ofturbulent spin dynamics and promise to serve as a versatiletool for the study and control of dynamic magnetization instabilities.We also show that a repeated magic sandwich pulse sequencecan be used to dynamically stabilize modes of nuclear precessionthat are otherwise intrinsically unstable. To date, we have extendedthe effective precession lifetimes of our magnetized samples by morethan three orders of magnitude.

(Thanks to Louis Bouchard for sending...Curt)

Functional contrast based on intermolecular double-quantum coherences: Influence of the correlation distance

2007-09-28T12:42:00.000-05:00

Andreas Schäfer^{1 2}, Harald E. Möller^{1 *}

¹Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
²University of Nottingham, School of Physics and Astronomy, Sir Peter Mansfield Magnetic Resonance Centre, University Park, Nottingham, United Kingdom

email: Harald E. Möller (moeller@cbs.mpg.de)

^*Correspondence to Harald E. Möller, Max Planck Institute for Human Cognitive and Brain Sciences, Stephanstr. 1a, 04103 Leipzig, Germany

Keywords

BOLD contrast • correlation distance • distant dipolar field • intermolecular double-quantum coherence (iDQC)

Abstract

A functional MRI (fMRI) study with visual stimulation of healthy subjects was performed at 3T exploiting intermolecular double-quantum coherences. The correlation distance, d_c, was varied between 60 and 300 m for different evolution times, . Robust activation was obtained in all experiments with average signal changes ([bar S₂ ]) = 8.4 ± 0.7% and 9.4 ± 0.8% for = 15 and 20 ms, respectively) exceeding those normally associated with conventional blood oxygen level-dependent (BOLD) fMRI. Relaxation-rate changes (R₂ = 0.33 ± 0.36 s^-1 and R₂* = 0.77 ± 0.54 s^-1) were similar to those commonly obtained for the extravascular BOLD effect. The number of activated voxels increased with increasing d_c until a plateau was reached at 120 m. Similar trends were observed for the activation-induced percent signal change and for the maximal Z-scores. These effects were quantitatively explained by a reduced sensitivity at short d_c due to increasing signal attenuation related to diffusion and an increasing amount of signal fluctuations in the fMRI time series due to imperfect suppression of unwanted coherence pathways. Consistent indications of a preferential selection of susceptibility changes in blood vessels of a particular size were not obtained. Magn Reson Med 58:696-704, 2007. © 2007 Wiley-Liss, Inc.

Received: 16 March 2007; Revised: 30 July 2007; Accepted: 6 August 2007

Assessing signal enhancement in distant dipolar field-based sequences

2007-08-30T10:40:00.000-05:00

Wilson Barros Jr., Daniel F. Gochberg and John C. Gore

Abstract
The possibility of improving the signal-to-noise efficiency of NMR signal refocused by long-range dipolar interactions has been discussed recently [Branca et al., JMR 187 (2007) 38-43]. For systems where T1<< T2, by including an extra radio-frequency pulse in a standard CRAZED sequence, it is possible to increase the available signal by exploiting its sensitivity to T1 relaxation. Here, we use analytical calculations to investigate the source of this improved signal and determine the maximum enhancement provided by the method.

Apparent Longitudinal Relaxation in Solutions with Intermolecular Dipolar Interactions and Slow Chemical Exchange

2007-08-30T10:37:00.000-05:00

Shengchun Zhang, Xiaoqin Zhu, Zhong Chen, Shuhui Cai and Jianhui Zhong

Abstract
A modified CRAZED sequence with selective inversion before excitation was designed to investigate the longitudinal relaxation under the effects of slow chemical exchange and distant dipolar interactions in highly polarized spin systems. Analytical expressions for the apparent longitudinal relaxation time of such systems were derived from a combination of the dipolar field theory and product operator formalism. The result shows that the signal intensity follows a multi-exponential function of the inversion-recovery time. Experimental results support the theoretical predictions.

Finite Element Formulation of the Bloch Equations with Dipolar Field Effects

2007-08-23T13:33:00.000-05:00

Louis-S. Bouchard
(Submitted on 24 Jun 2007)
arXiv.org

A Galerkin finite element (FEM) formulation for the Bloch equations with dipolar field is presented which makes possible the derivation of weak solutions to the Bloch equations. The FEM formulation has the advantage that the equations of motion are local in real space, eliminating the global truncation errors associated with calculations of the dipolar field in Fourier space. The dipolar field and other geometric parameters are calculated only once, before the simulation, and used as an initial condition rather than re-calculated at every time step of some numerical integration.

Numerical simulations of contribution of chemical shift in novel magnetic resonance imaging

2007-04-30T23:46:00.000-05:00

Huijun Sun, Tao Lin, Shuhui Cai and Zhong Chen
Lecture Notes in Computer ScienceVolume 4222/2006
Advances in Natural Computation

Abstract
Contribution of chemical shift to intermolecular multiple-quantum coherence (iMQC) imaging signals in two-component systems was simulated and discussed using an efficient numerical algorithm based on the Bloch equations with an additional nonlinear term describing distant dipolar field. Numerical simulation switches back and forth between real and Fourier spaces to handle dipolar field effects in three-dimensional sample. The iMQC signals of each component of two-component systems can be obtained respectively when the second pulse of the CRAZED pulse sequence is selective. Simulation results show that chemical shift provides an edge detection method to regions containing spins with chemical shift offset and selected by the second RF pulse, and different gray value is related to different chemical shift in detected regions. These results indicate that chemical shift may provide new imaging information helpful for iMQC magnetic resonance imaging.

Multiple quantum correlated spectroscopy revamped by asymmetric z-gradient echo detection signal intensity as a function of the read pulse flip angle

2007-04-30T23:36:00.000-05:00

Bin Jiang, Huili Liu, China Maili Liu, Chaohui Ye, and China Xi-an Mao
J. Chem. Phys. 126, 054502 (2007)

(Received 28 August 2006; accepted 5 December 2006; published online 1 February 2007)

Heteronuclearmultiple quantum (n=±0 and n=±2) correlated spectroscopy revamped by asymmetricz-gradient echo detection (CRAZED) experiments were performed on the spins³¹P and ¹H in a H₃PO₄ solution in order todetermine the optimum flip angle for the read pulse. Ithas been shown that for the negative quantum signals, themaximum signals appear at =0, and for the positive quantumsignals, the maximum signals appear at =. The CRAZED signalswere compared to the single quantum signals in two-pulse two-gradientexperiments. It is found that the CRAZED signals can alsobe distinguished into gradient echoes and spin echoes. The gradient-echo-typeCRAZED signal requires =0 and the spin-echo-type CRAZED signal requires= for maximum echo intensities, in the same way asin single quantum experiments. ©2007 American Institute of Physics

Simultaneous acquisition and effective separation of intermolecular multiple-quantum signals of different orders

2007-04-30T23:31:00.000-05:00

Xiaoqin Zhu, Song Chen, Zhong Chen, Shuhui Cai and Jianhui Zhong
Chemical Physics Letters
Volume 438, Issues 4-6, 20 April 2007, Pages 308-314

Abstract
A three-pulse sequence was designed to simultaneously acquire intermolecular multiple-quantum coherence (iMQC) signals of coherence order n = 2, 1, 0, −1, −2. Analytical expressions were derived from modified Bloch equations. Signal of a specific order was obtained by optimal combinations of data from different acquisition steps. This allows a time saving of 5/7 compared to the phase cycling designs targeted for individual coherence orders. The method also results in pure iMQC signal of all the above five orders which are insensitive to radio-frequency flip angle errors, in contrast to some previous methods. Theoretical predictions are supported by the experimental observations and numerically simulated results.

Magnetic resonance microscopic imaging based on high-order intermolecular multiple-quantum coherences

2007-04-30T23:23:00.000-05:00

Jee-Hyun Cho, Sangdoo Ahn, Chulhyun Lee, Kwan Soo Hong, Kee-Choo Chung, Suk-Kyu Chang, Chaejoon Cheong and Warren S. Warren
Magnetic Resonance Imaging
Article in Press, Corrected Proof

Abstract

Most imaging studies using intermolecular multiple-quantum coherences (iMQCs) have focused on the two-spin dipolar interactions — zero and double quantum coherences. Here, we report the results of various experimental studies to assess the feasibility of magnetic resonance microscopy with high-order iMQCs in model systems at 7 and 14 T. Experimental results demonstrated that the iMQC microscopic images with high coherence orders are readily observable at high field and have unique contrast depending on the sample microstructure and coherence order.

Keywords: Intermolecular multiple-quantum coherence; iTQC; iQQC; MR microscopy

Signal enhancement in CRAZED experiments

2007-04-28T22:30:00.000-05:00

Signal enhancement in CRAZED experiments
Rosa T. Branca, Gigi Galiana and Warren S. Warren
Journal of Magnetic Resonance
Article in Press, Corrected Proof

Many of the promising applications of the CRAZED (COSY Revamped with Asymmetric Z-gradient Echo Detection) experiments are in biomedical and clinical technologies. In tissue, however, signal from the typical CRAZED experiment is largely limited by transverse relaxation. When relaxation is included, the maximum achievable signal from a prototypical CRAZED sequence, in the linear regime, is proportional to T2/τd. This means that for samples with a short T2, as encountered in vivo, signals from intermolecular multiple-quantum coherences (iMQCs) reach very diminished signal intensities. While relaxation is generally regarded as a fundamental constraint, we show here that when T2 is short but T1 is long, as in tissue, there are simple sequence modifications that can increase signal beyond the T2 limit. To better utilize the available signal intensity from iMQCs we propose a method to substitute part of the transverse magnetization with the longitudinally modulated magnetization. In this paper we show, with both simulations and experimental results, that in the presence of strong transverse relaxation the standard CRAZED scheme is not the optimal method for observing iMQCs, and can be improved upon with simple modifications.

Keywords: CRAZED; iZQC; iDQC; Dipolar demagnetization time

Gradient-echo and CRAZED imaging for minute detection of Alzheimer plaques in an APPV717I × ADAM10-dn mouse model

2007-03-27T14:43:00.000-05:00

Cornelius Faber, Benjamin Zahneisen, Frank Tippmann, Anja Schroeder, Falk Fahrenholz
Magnetic Resonance in Medicine
Published Online: 27 Mar 2007

Different strategies to visualize amyloid plaques with MRI at 17.6 Tesla were investigated in a novel mouse model of Alzheimer's disease (AD). Large iron-containing plaques were observed in the thalamus, but cortical plaques did not show iron deposits. Plaques in the thalamus were visualized in vivo with the use of low-resolution, 3D gradient-echo (GRE) imaging in 82 s, and with 94-m resolution in 34 min. The feasibility of obtaining bright contrast from plaques using the COSY revamped with asymmetric z-GRE detection (CRAZED) technique was investigated in experiments on fixed brains. The original CRAZED approach provided reduced signal near the plaques (similarly to GRE imaging) and additionally emphasized small structures in the brain. In CRAZED images acquired with mismatched gradients, elevated signal near the plaques was obtained, while background signal was suppressed almost to the noise level. Bright-contrast images were acquired in 2.6 min with the use of a 2D GRE sequence with slightly mismatched slice refocusing gradients. For future detection of plaques in patients, such bright-contrast visualization protocols may be of particular value when contrast agents that allow labeling of early plaques with iron oxide nanoparticles become available. Magn Reson Med 57:696-703, 2007. © 2007 Wiley-Liss, Inc.

Indirect detection of NMR via geometry-dependent dipolar fields, revisited

2007-03-15T23:16:00.000-05:00

Journal of Magnetic Resonance
In Press, Accepted Manuscript, Available online 1 March 2007,
Wei Dong and CA. Meriles

We explore the dipolar interactions between two separate nuclear spin ensembles in a mixture containing oil and water. Here we expand initial results (C.A. Meriles and W. Dong, J. Magn. Reson. 181, 331 (2006)) to the case in which both systems have the shape of flat, stacked disks. We find that - spite of the strong inhomogeneity of thecoupling dipolar field - the signal encoded in one of the components can be made approximately proportional to the magnetization in the other. This allows us to use one of these systems as a ‘sensor’ to indirectly reconstruct the resonance spectrum or to determine the relaxation time of the ‘sample’ system. In the regime in which dipolar interactions are sufficiently strong, our method can be set to scale-up weaker signals in a non-linear fashion, which, potentially, could allow one to introduce contrast or to improve detection sensitivity of less magnetized samples.

Theoretical studies of the effect of the dipolar field in multiple spin-echo sequences with refocusing pulses of finite duration

2007-02-09T18:37:00.000-06:00

Chung Ki Wong, Scott D. Kennedy, Edmund Kwok and Jianhui Zhong

Journal of Magnetic Resonance
Article in Press, Corrected Proof

It has been observed recently that the finite duration of refocusing rf pulses in a multiecho acquisition of the signal formed under the influence of the dipolar field leads to significant signal attenuation [S. Kennedy, Z. Chen, C.K. Wong, E.W.-C. Kwok, J. Zhong, Investigation of multiple-echo spin-echo signal acquisition under distant dipole–dipole interactions, Proc. Int. Soc. Magn. Reson. Med. 13 (2005) 2288]. Hereto, we quantify the phenomenon by evaluating analytically the influences of both the distant dipolar field (DDF) and transverse relaxation T2 on the magnetization in a multiecho pulse sequence based on correlation spectroscopy revamped by asymmetric z-gradient echo detection (CRAZED). Analytic expressions for the magnetization were obtained, which demonstrate explicitly the origin of rephased signal in the presence of the finite π pulses in the multiecho train. The expressions also explain the effects of the DDF and T2 during the refocusing pulses on the signal strength, and show the substantial signal dependence on the phase of the rf pulses. We show that when the DDF effect during the pulse is canceled, the signal rises primarily during the free evolution time in the acquisition period. This elucidates the signal attenuation when the rf pulses cover a significant proportion of time in the sequence. In addition, we performed an optimization on the number of refocusing pulses that maximizes the total acquired signal using parameters for water, brain white matter, and muscle. We found that maximal signal-to-noise ratio is obtained when the pulse duration approximately equals the free evolution time in the samples with a wide range of T2.

Keywords: Distant dipolar field; Multiple spin-echo sequence; Finite pulse; Intermolecular double-quantum coherence

Yahoo Group ddf_imqc

2007-01-09T17:50:00.000-06:00

Here is the link to the new yahoo discussion group.

This is to facillitate more interactive technical discussion on DDF and iMQC related magnetic resonance.

Curt

Contrast Enhancement by Feedback Fields in Magnetic Resonance Imaging

2006-11-29T13:04:00.000-06:00

Sandip Datta, Susie Y. Huang, and Yung-Ya Lin*

Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095

Received: January 31, 2006

In Final Form: April 25, 2006

Abstract:

A conceptually new approach giving rise to contrast enhancement by feedback fields in magnetic resonance imaging is proposed, and the detailed mechanism is described. Nonlinear spin dynamics under the feedback fields of the distant dipolar field and/or radiation damping are examined and shown to amplify contrast due to small variations in spin density and precession frequency. Feedback-based contrast enhancement depends on the instability of the initial magnetization configuration and is propagated by positive feedback, as shown through numerical simulations and experimental results on simple phantom samples. On the basis of a theoretical understanding of contrast enhancement, insight into pulse sequence design and optimal contrast attainable under the individual and joint feedback fields is provided.

Direct enhancement of any solution NMR signal using the distant dipolar fields created by highly polarized and concentrated nuclear spin systems

2006-11-29T12:59:00.000-06:00

H. Desvaux, D.J. Marion, G. Huber, L. Dubois and P. Berthault

Laboratoire Structure et Dynamique par Résonance Magnétique, Service de Chimie Moléculaire, URA CEA/CNRS 331 Claude Fréjacques, CEA/Saclay, 91191 Gif-sur-Yvette, France
hdesvaux@cea.fr

(Received: 9 May 2006 / Accepted: 26 July 2006 / Published online: 6 October 2006)

Abstract
Peculiar nuclear spin systems can be polarized at a level of thousands times the value obtained at thermal equilibrium, for instance by optical pumping. When concentrated, these systems create a sizeable average dipolar field which is experienced by any nuclear spin. We propose to use these distant dipolar fields for performing a polarization transfer in the Hartmann-Hahn conditions. We report the maximum enhancement value calculated using the spin temperature approach and first theoretical insights on the polarization transfer rate. Using, as an example, dissolved laser-polarized xenon, we show that by spin-locking both xenon spins and a proton spin of a solute, the polarization of the latter is enhanced. This is obtained without the existence of chemical interaction between the two entities and with characteristic rising time not directly correlated to the proton self-relaxation time. By its generality and its non-local feature, this approach could make possible nuclear magnetic resonance spectroscopy on very dilute systems.

PACS
82.56.-b - Nuclear magnetic resonance.
76.70.-r - Magnetic double resonances and cross effects.
82.56.Jn - Pulse sequences in NMR.
32.80.Bx - Level crossing and optical pumping.

© EDP Sciences 2006

Diffraction-like phenomena in a periodic magnetization distribution at 1.5 T using the distant dipolar field (DDF)

2006-11-15T20:30:00.000-06:00

In the CRAZED experiment (COSY revamped by asymmetric Z-gradient echo detection, Warren et al.), a spatially anisotropic magnetization distribution is created by application of a magnetic field gradient (strength G, duration τ) which in turn generates a response called the distant dipolar field (DDF). The DDF is a source of intermolecular multiple-quantum coherences (iMQC) which contain information on the distance d = π/(γGτ) between pairs of dipolar-coupled spins. Diffraction-like phenomena may result for periodically structured samples. In this study, we report the observation of diffraction owing to the DDF at 1.5 T using a clinical whole-body tomograph. Based on the semi-classical treatment of the problem by Robyr and Bowtell, diffraction conditions were obtained for a CRAZED-type pulse sequence that selects iMQC of order N. The predicted distinct difference in N = 2 and N ≠ 2 coherences, i.e., a dominant continuous course as a function of τ (N = 2) and prominent diffraction peaks otherwise, could be verified in CRAZED experiments in a periodically structured sample selecting coherence orders N = 2 and N = 3. The diffractive signal component contains information on the geometric structure of the sample. Applications of this technique may permit the detection of changes in composition and geometry of periodic structures.
Keywords: CRAZED; Distant dipolar field (DDF); Intermolecular multiple-quantum coherence; Diffraction

Fast single-gradient simultaneous measurement of D and T2 in liquids via the distant dipolar field

2006-09-26T17:05:00.000-05:00

Wilson Barros, Jr , a, and Daniel F. Gochberg
a aVanderbilt University Institute of Imaging Science (VUIIS), Vanderbilt University Medical Center, R-1302 Medical Center North, Nashville, TN 37232-2310

Here we show that simultaneous measurement of the self-diffusioncoefficient D and the relaxation time T2 using the NMR signal in the presence of long-range dipolar interactions can be performed using a single-square gradient pulse. Furthermore, during acquisition, a train of 180 radio-frequency pulses is utilized in order to improve signal-to-noise efficiency and to reduce the diffusion-attenuation associated with local field inhomogeneities. The new approach can determine D and T2 in a single-shot acquisition. The results obtained for water protons show good agreement when compared to standard techniques. Finally, this method offers a new possibility for monitoring fast processes.

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

2006-09-26T16:59:00.000-05:00

David Z. Balla, Gerd Melkus, Cornelius Faber *
Department of Experimental Physics 5, University of Würzburg, Würzburg, Germany
email: Cornelius Faber (faber@physik.uni-wuerzburg.de)
*Correspondence to Cornelius Faber, Experimentelle Physik 5, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
setDOI("ADOI=10.1002/mrm.21007")
Funded by: Deutsche Forschungsgemeinschaft; Grant Number: Fa474/1, Ha1232/13
Keywords
iZQC • HOMOGENIZED • localized spectroscopy • inhomogeneous broadening • resolution enhancement
Abstract
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 (SNR) efficiency. Magn Reson Med, 2006. © 2006 Wiley-Liss, Inc.

iDQC MRI weighted by longitudinal relaxation in the rotating frame

2006-09-06T13:10:00.000-05:00

Bingwen Zheng, Zhong Chen, Scott D. Kennedy, and Jianhui Zhong

A long-duration, low-power, off-resonance spin-locking pulse was incorporated into the COSY revamped by asymmetric z gradient-echo detection (CRAZED) pulse sequence in order to evaluate the effects of intermolecular double-quantum longitudinal relaxation in the tilted rotating frame (T[stack 1,DQeff ]). This modified CRAZED sequence was followed by a standard fast spin-echo imaging sequence to form images with T[stack 1,DQeff ]-weighted contrast. Imaging experiments were performed on an agarose-gel phantom and mouse-tail tissue at 600 MHz. Experimental results demonstrated the feasibility of imaging applications based on T[stack 1,DQeff ] as a novel contrast mechanism, and showed that iDQC off-resonance longitudinal relaxation in the rotating frame T[stack 1,DQeff ] is sensitive to the tilt angle and the effective spin-locking field e. Imaging based on T[stack 1,DQeff ] has reduced RF power deposition compared to on-resonance spin-locking, which is advantageous for human applications. Magn Reson Med, 2006. © 2006 Wiley-Liss, Inc.

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

2006-08-24T16:19:00.000-05:00

Magnetic Resonance in Medicine
Early View (Articles online in advance of print)
David Z. Balla, Gerd Melkus, Cornelius Faber

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 (SNR) efficiency. Magn Reson Med, 2006. © 2006 Wiley-Liss, Inc.

Sensitivity to local dipole fields in the CRAZED experiment: An approach to bright spot MRI

2006-05-23T09:43:00.001-05:00

doi is not active yet, for now try this...

Sensitivity to local dipole fields in the CRAZED experiment: An approach to bright spot MRI

2006-05-23T09:25:00.000-05:00

Cornelius Faber, Carolin Heil, Benjamin Zahneisen, David Z. Balla and Richard Bowtell
Journal of Magnetic Resonance
Article in Press, Corrected Proof

Local dipole fields such as those created by small iron-oxide particles are used to produce regions of low intensity (dark contrast) in many molecular magnetic resonance imaging applications. We have investigated, with computer simulations and experiments at 17.6 T, how the COSY revamped with asymmetric z-gradient echo detection (CRAZED) experiment that selects intermolecular double-quantum coherences can also be used to visualize such local dipole fields. Application of the coherence-selection gradient pulses parallel to the main magnetic field produced similar, dark contrast as conventional gradient echo imaging. Application of the gradient along the magic angle leads to total loss of signal intensity in homogeneous samples. In the presence of local dipole fields, the contrast was inverted and bright signals from the dipoles were observed over a very low background. Both simulations and experiments showed that the signal strongly decreased when a phase-cycle suppressing single-quantum coherences was employed. Therefore, we conclude that most of the signal comes from directly refocused magnetization or intermolecular single-quantum coherences. Finally, we demonstrate that bright contrast from local dipole fields can also be obtained, when the pair of coherence-selection gradient pulses is deliberately mismatched. Both methods allowed visualization of local dipole fields in phantoms in experimental times of about 3 min.

Indirect detection of nuclear magnetic resonance via geometrically induced long-range dipolar fields

2006-05-13T09:10:00.000-05:00

by C.A. Meriles and Wei Dong
Department of Physics, CUNY—City College of New York, 138th Street and Convent Avenue, New
York, NY 10031, USA

In press on the Journal of Magnetic Resonance

We report the indirect detection of the magnetization of one spin species via the NMR signal of a second species. Our method relies on the control of long-range dipolar fields between two separate objects, in this case, a water droplet (sensor) immersed in a tube containing mineral oil (sample). Unlike prior experiments, no gradient pulses are used; rather, the setup geometry is exploited to select the part of the sample to be probed and modulate the spin alignment in the sensor. Our results are discussed in the context of Dipolar Field Microscopy, a proposed strategy in which the detector is a hyperpolarized tip.

A new approach to bright spot MRI: visualizing local dipolar fields with the CRAZED sequence

2006-04-26T08:37:00.000-05:00

At ISMRM...

2478. A new approach to bright spot MRI: visualizing local dipolar fields with the CRAZED sequence

Cornelius Faber, Carolin Heil, Benjamin Zahneisen, David Balla, Richard Bowtell

EP5, University of Wuerzburg, Germany
SPMMRC, University of Nottingham, UK

The transient dynamics leading to spin turbulence in high-field solution magnetic resonance: A numerical study

2006-04-20T12:12:00.000-05:00

The transient dynamics leading to spin turbulence in high-field solution magnetic resonance: A numerical study
Sandip Datta, Susie Y. Huang, and Yung-Ya Lin
Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095
(Received 16 September 2005; accepted 7 February 2006; published online 17 April 2006)
The dynamics under the joint action of radiation damping and the distant dipolar field in high-field solution magnetic resonance are investigated. Different dynamical regimes during the evolution are identified and their individual features are discussed. In the steady state, the dynamics can be associated with a strange attractor in phase space on which the motion is chaotic. The possibility of the observed chaotic motion being spatiotemporal is examined. ©2006 American Institute of Physics

DDF/iZQC at ISMRM in Seattle

2006-04-16T13:50:00.000-05:00

Please post if I missed one...Thanks, Curt

Room 4E Monday 14:00 - 16:00
1032. Simulations of Motion-Insensitive Diffusion Imaging Based on the Distant Dipolar Field

Tao Lin¹, Huijun Sun¹, Congbo Cai¹, Zhong Chen¹,², Shuhui Cai¹, Jianhui Zhong²

¹Xiamen University, Xiamen, Fujian, People’s Republic of China; ²University of Rochester, Rochester, New York, USA

Room 4E Tuesday 13:30 - 15:30

2423. MR Imaging of Intermolecular Double-Quantum-Filtered Zero-Quantum Coherence

Zhong Chen¹,², Bingwen Zheng¹, Xiaoqin Zhu¹, Tianliang Gu², Jianhui Zhong²

¹Xiamen University, Xiamen, Fujian, People’s Republic of China; ²University of Rochester, Rochester, New York, USA

Room 4E Wednesday 14:00 - 16:00
2479. Effect of Distant Dipolar Field and T₂ on Magnetization in CRAZED-Multiecho Pulse Sequence

Chung Ki Wong¹, Edmund Kwok¹, Jianhui Zhong¹

¹University of Rochester, Rochester, New York, USA

Room 4E Thursday 13:30 - 15:30
3020. Spectroscopic and Imaging Observations of Intermolecular Single-Quantum Coherence

Shuhui Cai¹, Zhong Chen¹,², Xiaoqin Zhu¹, Bingwen Zheng¹, Jianhui Zhong²

¹Xiamen University, Xiamen, Fujian, People’s Republic of China; ²University of Rochester, Rochester, New York, USA

3040. Intermolecular Double-Quantum-Filtered Zero-Quantum Coherence in Liquid NMR

Xiaoqin Zhu¹, Zhong Chen¹,², Shuhui Cai¹, Jianhui Zhong²

¹Xiamen University, Xiamen, Fujian, People’s Republic of China; ²University of Rochester, Rochester, New York, USA

3046. POM: A Simulation Program for NMR Under Inter- And Intramolecular Interactions

Congbo Cai¹, Zhong Chen¹,², Shuhui Cai¹, Jianhui Zhong²

¹Xiamen University, Xiamen, Fujian, People’s Republic of China; ²University of Rochester, Rochester, New York, USA

3047. Simultaneous Acquisition of Signals of Different Orders of Intermolecular
Multiple-Quantum Coherences

Song Chen¹, Xiaoqin Zhu¹, Zhong Chen¹,², Shuhui Cai¹, Jianhui Zhong²

¹Xiamen University, Xiamen, Fujian, People’s Republic of China; ²University of Rochester, Rochester, New York, USA

ENC next week

2006-04-16T03:21:00.000-05:00

Spin Locking SQCs in an iMQC Experiment

Gigi Galiana1; Rosa T. Branca2; Warren S. Warren2;
1Princeton University, Princeton, NJ; 2Duke University, Durham, NC;

While iMQCs present a wide range of promising applications, dephasing during t2 competes with signal buildup, and limits the maximum attainable signal. Previous work has explored signal with T1ρ decay during t1, where iMQC terms like IxSx can be locked with a steady RF field along x. In reality, many Cartesian terms that do not lie along the locking axis can also be conserved with a spinlocking pulse. For example, antiphase terms such as IxSz–IzSx, are perfectly locked with a spinlock along y, and continue to be locked when they evolve into observable magnetization. Based on this principle, we present a method to slow the effective dephasing rate during the signal build up period to enhance the iMQC signal.

Distant Dipolar Field Effects in Polymer Melts: A new Approach
Towards Structural Investigations Of Complex Fluids

Priyanga Bandara; Marcel Utz;
University of Connecticut, Storrs, CT, United States

We report the observation of distant dipolar field (DDF) effects in polymer melts. Using the CRAZED sequence, we have succeeded in obtaining DDF double quantum echos in melts of poly(isobutylene). In this system, T2is about 2ms. This requires the use of very strong gradient pulses, which are generated using a home-built gradient probe assembly with a car battery as current source. Experiments of this type could be very useful to investigate the structure of polymer systems. Motivated by such applications, we report pilot measurements using a suspension of PTFE spheres of various diameters in PIB.

Intermolecular Zero Quantum Spectroscopy in the Live Mouse Brain Using a MR Imager
Benoit M. Boulat; P.T. Narasimhan; Russell E. Jacobs;
Caltech, Pasadena, CA

We have utilized the effects of the distant dipolar field to obtain one-dimensional high-resolution NMR spectra in the full head or a localized region in the brain of live mice. Experiments were conducted on a 11.7T magnetic resonance imager. The method uses techniques of two-dimensional NMR spectroscopy and can be well described within the formalism known as “Intermolecular Zero Quantum (IZQ) spectroscopy”. Based on HOMOGENIZED class of pulse sequences, IZQ spectra of good resolution and signal to noise ratio could be obtained in as little as 18 minutes. The method was utilized to study mice of various genetic background.

In vivo multiple quantum imaging of prostatic ductal structure by MR: preliminary results

Albert P Chen1; Charles H Cunningham2; Louis-S Bouchard3; Janine Lupo1; John M
Pauly2; Danial B Vigneron1;

1University of California, San Francisco, San Francisco, CA; 2Stanford University, Stanford, CA; 3University of California, Berkeley and LBNL, Berkeley, CA;

The glandular prostate consists of a duct system that can not be resolved by conventional MRI at lower or moderate field strength (1.5T-3T). Intermolecular multiple quantum coherence (iMQC) that arises from long-range nuclear dipole-dipole couplings has been shown to have the ability to encode spatial heterogeneity on an intermediate length scale using a CRAZED sequence. With this method, structural anisotropy of a given material not detected by MR diffusion methods have been observed in heterogeneous media. This preliminary study demonstrates for the first time the feasibility of obtaining CRAZED images from the prostate in vivo. Potentially, CRAZED may provide a unique image contrast based on the ductal structural anisotropy.

Fast simultaneous measurement of D and T2 using the distant dipolar field

Wilson Barros Jr; Daniel F. Gochberg;
Vanderbilt University Institute of Imaging Science, Nashville, TN

Recently, we reported the simultaneous measurement of the self-diffusion coefficient D and the
spin-spin relaxation time T2 via the NMR signal refocused by long-range dipolar field interactions. Typically the signal available for this methodology is a fraction of the full equilibrium magnetization density. Here, we incorporated a train of equally spaced π pulses into the standard CRAZED (COSY Revamped by Asymmetric Z-gradient Echo Detection) sequence in order to improve the signal-to-noise ratio as well as to perform fast acquisition. A reduction of undesirable diffusion-attenuation caused by local magnetic-field inhomogeneities is also realized. In a series of experiments, the parameters D and T2 are extracted by this method and then compared to values obtained by conventional techniques.

iMQC Discussion at ISMRM

2006-03-29T11:23:00.000-06:00

I'd like to propose a discussion group, get together at ISMRM in Seattle.

Maybe a dinner or lunch as well if folks are interested?

What do you think?

-Curt

Formation and identification of pure intermolecular zero-quantum coherence signal in liquid NMR

2006-02-13T15:29:00.000-06:00

Xiaoqin Zhu, Zhong Chen, Shuhui Cai and Jianhui Zhong

A new pulse sequence with three radio-frequency pulses was designed to detect NMR signals originating from pure intermolecular zero-quantum coherence (iZQC) in isolated spin-1/2 samples such as water. Analytical expressions were derived from the modified Bloch equations with dipolar fields. All the experimental observations and simulated results demonstrate that the iZQC signals can be selectively detected, mostly free of contamination of other coherences and conventional signals. Compared to the two-pulse CRAZED sequence, the new sequence is insensitive to the imperfection of flip angles.

International Symposium on Biomedical Magnetic Resonance Imaging and Spectroscopy at Very High Fields

2006-02-06T16:36:00.000-06:00

University of Wuerzburg
Institute of Physics
Am Hubland
97074 Wuerzburg
Germany
2/16-2/18
Two sessions on IMQC
Intermolecular Multiple-quantum Coherences
Intermolecular Multiple-quantum Coherences II

Ultrafast Intermolecular Zero Quantum Spectroscopy

2005-11-25T06:22:00.000-06:00

Gigi Galiana, Rosa T. Branca, and Warren S. Warren

J. Am. Chem. Soc., in press (2005)

Clinical magnetic resonance spectroscopy is typically limited by magnetic inhomogeneities which destroy spectral resolution, but intermolecular zero quantum coherences (iZQCs) are insensitive to such inhomogeneities. iZQC resolution in vivo, however, has been hampered by physiological fluctuations over the time scale of the two-dimensional acquisition. A faster iZQC sequence will allow us to average away these fluctuations, and thus we present a new approach to ultrafast two-dimensional spectroscopy. This communication reports iZQC experiments acquiring up to 31 t1-points per scan, as well as extensions to a broad range of other 2D sequences.

Intermolecular multiple quantum coherences at high magnetic field: The nonlinear regime

2005-11-14T10:49:00.000-06:00

J. P. Marques, S. Grant, S. Blackband, R. W. Bowtell
J. Chem. Phys. 123, 164311 (2005) (10 pages)

Experimentshave been carried at magnetic-field strengths of 9.4, 14.1, and17.6 T to explore the evolution of intermolecular multiple quantumcoherences in the nonlinear regime where the system evolves fortimes that are much greater than the characteristic time ofaction of the long-range dipolar field, _d. The results showthe expected Bessel function form of the recorded signal asa function of time of evolution, with evident zeros andsign changes. As expected, the rate of signal evolution increasesat higher-field strengths as a result of the increased equilibriummagnetization. A numerical method for calculating the evolution of magnetizationunder the action of the distant dipolar field, relaxation, anddiffusion that is based on Fourier analysis of the magnetizationdistribution has been applied to the correlated two-dimensional spectroscopy revampedby asymmetric z-gradient echo detection sequence in the nonlinear regimeand shown to produce results that are in good agreementwith experimental data acquired at different magnetic fields and ratesof spatial modulation. Experiments and simulations have also been usedto explore the evolution of magnetization in a mixture oftwo interacting spin species in the nonlinear regime. ©2005 American Institute of Physics

Simultaneous measurement of D and T2 using the distant dipolar field

2005-11-09T11:31:00.000-06:00

Wilson Barros, Jr., John C. Gore and Daniel F. Gochberg
Journal of Magnetic Resonance
Article in Press, Corrected Proof

The presence of long-range dipolar fields in liquids is known to introduce a non-linear term in the Bloch–Torrey equations which is responsible for many interesting effects in nuclear magnetic resonance as well as in magnetic resonance imaging. We show here, for the first time, that the diffusion coefficient D and the spin–spin relaxation time T₂ can be obtained simultaneously from the time evolution profile of the long-range dipolar field refocused signal. In a COSY Revamped by Z-asymmetric Echo Detection sequence, the analytical first-order approximation solution of the Bloch–Torrey equations modified to include the effect of the distant dipolar field is used to demonstrate the technique in an experiment using doped water.

Structural anisotropy and internal magnetic fields in trabecular bone: Coupling solution and solid dipolar interactions

2005-09-21T19:59:00.000-05:00

Louis-S. Boucharda, Felix W. Wehrlib, Chih-Liang Chinb and Warren S. Warrena, , aDepartment of Chemistry, Princeton University, Princeton, NJ 08544, USAbDepartment of Radiology, University of Pennsylvania, Philadelphia, PA 19104, USA Received 19 February 2005; revised 27 April 2005. Available online 13 June 2005.
Abstract
We investigate the use of intermolecular multiple-quantum coherence to probe structural anisotropy in trabecular bone. Despite the low volume fraction of bone, the bone–water interface produces internal magnetic field gradients which modulate the dipolar field, depending on sample orientation, choice of dipolar correlation length, correlation gradient direction, and evolution time. For this system, the probing of internal magnetic field gradients in the liquid phase permits indirect measurements of the solid phase dipolar field. Our results suggest that measurements of volume-averaged signal intensity as a function of gradient strength and three orthogonal directions could be used to non-invasively measure the orientation of structures inside a sample or their degree of anisotropy. The system is modeled as having two phases, solid and liquid (bone and water), which differ in their magnetization density and magnetic susceptibility. A simple calculation using a priori knowledge of the material geometry and distribution of internal magnetic fields verifies the experimental measurements as a function of gradient strength, direction, and sample orientation.
Keywords: Distant dipolar field; Intermolecular multiple-quantum coherence; Porous materials; Trabecular bone; Material anisotropy; Microstructure
PACS: 76.60.Jx

Multiple-quantum vector field imaging by magnetic resonance

2005-09-18T02:16:00.000-05:00

Louis-S. Bouchard and Warren S. Warren

Published in J. Magn. Res. 177, 9-21 (2005)

We introduce a method for non-invasively mapping fiber orientation in materials and biological tissues using intermolecular multiple-quantum coherences. The nuclear magnetic dipole field of water molecules is configured by a CRAZED sequence to encode spatial distributions of material heterogeneities. At any given point r in space, we obtain the spherical coordinates of fiber orientation (θ,ϕ) with respect to the external field by comparing three signals G_X, G_Y, and G_Z (modulus), acquired with linear gradients applied along the X, Y, and Z axes, respectively. For homogeneous isotropic materials, a subtraction G_Z − G_X − G_Y gives zero. With anisotropic materials, we find an empirical relationship relating G_Z − G_X − G_Y/(G_X + G_Y + G_Z) to the polar angle θ, while G_X − G_Y/(G_X + G_Y + G_Z) is related to the azimuthal angle ϕ. Experiments in structured media confirm the structural sensitivity. This technique can probe length scales not accessible by conventional MRI and diffusion tensor imaging.

Nuclear Magnetic Resonance with the Distant Dipolar Field

2005-07-26T12:17:00.000-05:00

C. A. Corum
186 pages, 43 figures, Ph.D. Dissertation, University of Arizona, Optical Sciences Center

Distant dipolar field (DDF)-based nuclear magnetic resonance is an active research area with many fundamental properties still not well understood. Already several intriguing applications have developed, like HOMOGENIZED and IDEAL spectroscopy, that allow high resolution spectra to be obtained in inhomogeneous fields, such as in-vivo. The theoretical and experimental research in this thesis concentrates on the fundamental signal properties of DDF-based sequences in the presence of relaxation (T1 and T2) and diffusion. A general introduction to magnetic resonance phenomenon is followed by a more in depth introduction to the DDF and its effects. A novel analytical signal equation has been developed to describe the effects of T2 relaxation and diffusing spatially modulated longitudinal spins during the signal build period of an HOMOGENIZED cross peak. Diffusion of the longitudinal spins results in a lengthening of the effective dipolar demagnetization time, delaying the re-phasing of coupled anti-phase states in the quantum picture. In the classical picture the unwinding rate of spatially twisted magnetization is no longer constant, but decays exponentially with time. The expression is experimentally verified for the HOMOGENIZED spectrum of 100mM TSP in H2O at 4.7T. Equations have also been developed for the case of multiple repetition steady state 1d and 2d spectroscopic sequences with incomplete magnetization recovery, leading to spatially varying longitudinal magnetization. Experimental verification has been accomplished by imaging the profile. The equations should be found generally applicable for those interested in DDF-based spectroscopy and imaging.

Multiple-Quantum Vector Imaging

2005-07-26T11:55:00.000-05:00

Abstract of talk 420 from ISMRM 2005 Meeting (need password for access)
L-S. Bouchard, W. S. Warren

A novel methodology based on measurements of the distant dipolar field, or intermolecular multiple-quantum coherences, is presented for tracking the vector orientation of parallel fiber bundles or other anisotropic structures in materials or biological tissues. The method uses a CRAZED sequence (Warren et al., Science 262:2005-9, 1993) with correlation gradient applied along the X, Y and Z axes. A subtraction |Gx|+|Gy|-|Gz| gives a signal when structural anisotropy is present and zero when the material is isotropic. For a material consisting of oriented fibers, the strength of the subtraction is related to the polar angle of the directional vector of the fibers. A comparison of X and Y gradients is related to the azimuthal angle. Experimental results in the petiole of celery show that anisotropy can be readily detected by this method. Tilting the sample with respect to the applied field, and rotating the sample in the transverse plane allow gave subtraction results that are consistent with theoretical calculations and demonstrate its applicability. The method can clearly detect structural anisotropy even for very weak gradient pulses well outside any diffusion-weighted regime. The structure sizes that can be detected are on the order of the length of the correlation distance. Thus, material heterogeneities can be detected on the tens of microns to millimeters scales and the method nicely complements currently existing techniques such as diffusion tensor imaging or high resolution MRI. This method finds potential applications in the materials and biomedical sciences. It could perhaps be of use in detecting tumor vascularity or for mapping trabecular bone anisotropy.

Effect of Hypercapnia on the iDQC Response

2005-07-26T11:50:00.000-05:00

Abstract of talk 117 from ISMRM 2005 Meeting (need password for access)
A. Schäfer, S. Zysset, W. Heinke, H. E. Möller

To date the origin of the fMRI signal change based on intermolecular double quantum coherences (iDQC) is not well understood. The aim of this work was to investigate the sensitivity to global changes of the cerebral blood flow (CBF) of this method. Global CBF changes can be induced by changing the arterial partial pressure of carbon dioxide due to hypercapnia. While the number of activated voxels was significantly decreased, the percentage signal change was roughly seven-fold increased in iDQC-based imaging as compared to conventional BOLD contrast.

Selection of intra- or inter-molecular multiple-quantum coherences in NMR of highly polarized solution

2005-07-14T02:00:00.000-05:00

Xiaoqin Zhu, Zhong Chen, Shuhui Cai and Jianhui Zhong
published in the Physica B, Condensed matter [0921-4526] yr:2005 vol:362 iss:1-4
pg: 286 -294

Abstract
In highly polarized scalar-coupled liquid systems, nuclear magnetic resonance signals from multiple-quantum coherences (MQCs) may be formed by inter-molecular dipolar and/or intra-molecular scalar couplings. Selection of specific signals can simplify the spectra, which may help us understand the underlying physical mechanisms in complex coupled spin systems. In this paper, a pulse sequence with three selective radio-frequency (RF) pulses and phase cycling was designed for this purpose. For an IpSq (p, q=1,2,3,…) spin system, there are three kinds of MQC signals, which originate from intra-molecular I–S, inter-molecular I–S, and inter-molecular S–S (or I–I) coherences. These three kinds of signals can be detected separately by proper phase cycling of RF pulses, which is independent of coupling constants. The intra- and inter-molecular MQC signals can also be detected separately with specific preparation periods, but this method is sensitive to coupling constants. Our theoretical predictions are in good agreement with experimental observations. The method proposed herein can be extended to heteronuclear cases.
Keywords: NMR; Inter-molecular MQCs; Intra-molecular MQCs; Dipolar couplings; Scalar couplings; Phase cycling
PACS: 76.60.−k; 76.80.+y; 75.40.Gb; 39.30.+w

Nuclear Magnetic Resonance Studies of Quadrupolar Nuclei and Dipolar Field Effects

2005-07-12T18:43:00.000-05:00

Jeffry Todd Urban
Ph.D. Dissertation
Doctor of Philosophy in Chemistry
University of California, Berkeley
Advisor: Professor Alexander Pines
2004

Experimental and theoretical research conducted in two areas in the field of nuclear magnetic resonance (NMR) spectroscopy is presented: (1) studies of the coherent quantum-mechanical control of the angular momentum dynamics of quadrupolar (spin I > 1/2) nuclei and its application to the determination of molecular structure; and (2) applications of the long-range nuclear dipolar field to novel NMR detection methodologies. The dissertation is organized into six chapters. The first two chapters and associated appendices are intended to be pedagogical and include an introduction to the quantum-mechanical theory of pulsed NMR spectroscopy and the time dependent theory of quantum mechanics. The third chapter describes investigations of the solid-state multiple-quantum magic angle spinning (MQMAS) NMR experiment applied to I = 5/2 quadrupolar nuclei. This work reports the use of rotary resonance-matched radiofrequency irradiation for sensitivity enhancement of the I = 5/2 MQMAS experiment. These experiments exhibited certain selective line narrowing effects which were investigated theoretically. The fourth chapter extends the discussion of multiple quantum spectroscopy of quadrupolar nuclei to a mostly theoretical study of the feasibility of enhancing the resolution of nitrogen-14 NMR of large biomolecules in solution via double-quantum spectroscopy. The fifth chapter continues to extend the principles of multiple quantum NMR spectroscopy of quadrupolar nuclei to make analogies between experiments in NMR/nuclear quadrupolar resonance (NQR) and experiments in atomic/molecular optics (AMO). These analogies are made through the Hamiltonian and density operator formalism of angular momentum dynamics in the presence of electric and magnetic fields. The sixth chapter investigates the use of the macroscopic nuclear dipolar field to encode the NMR spectrum of an analyte nucleus indirectly in the magnetization of a sensor nucleus. This technique could potentially serve as an encoding module for the recently developed NMR remote detection experiment. The feasibility of using hyperpolarized xenon-129 gas as a sensor is discussed. This work also reports the use of an optical atomic magnetometer to detect the nuclear magnetization of Xe-129 gas, which has potential applicability as a detection module for NMR remote detection experiments.

NMR detection using laser-polarized xenon as a dipolar sensor

2005-07-12T17:12:00.000-05:00

J. Granwehr, J.T. Urban, A.H. Trabesinger and A. Pines
Journal of Magnetic Resonance
Article in Press, Corrected Proof

Hyperpolarized ¹²⁹Xe can be used as a sensor to indirectly detect NMR spectra of heteronuclei that are neither covalently bound nor necessarily in direct contact with the Xe atoms, but coupled through long-range intermolecular dipole–dipole interactions. To reintroduce long-range dipolar couplings the sample symmetry has to be broken. This can be done either by using an asymmetric sample arrangement, or by breaking the symmetry of the spin magnetization with field gradient pulses. Experiments are performed where only a small fraction of the available ¹²⁹Xe magnetization is used for each point, so that a single batch of xenon suffices for the point-by-point acquisition of a heteronuclear NMR spectrum. Examples with ¹H as the analyte nucleus show that these methods have the potential to obtain spectra with a resolution that is high enough to determine homonuclear J couplings. The applicability of this technique with remote detection is discussed.

Solvent-localized NMR spectroscopy using the distant dipolar field: A method for NMR separations with a single gradient

2005-06-30T08:02:00.000-05:00

Cornelius Faber
Journal of Magnetic Resonance
Article in Press, Corrected Proof

Solvent-localized NMR (SOLO) is a new method which allows the separation of NMR spectra of substances dissolved in different solvents. It uses the selective HOMOGENIZED pulse sequence to produce a two-dimensional NMR spectrum resulting from intermolecular zero-quantum coherences in one distinct solvent. The detected signal is locally refocused by the action of the distant dipolar field, which is created by a frequency selective pulse only in regions containing the selected solvent. The prerequisites are that the different solvents have sufficiently different chemical shifts to be excited separately and that compartments with different solvents are spatially separated by more than the typical diffusion distance. Here, the method is demonstrated for the solvents water and DMSO on a length scale of 0.5 mm. Because signal in the spectra is refocused locally, SOLO is insensitive to variations in the magnetic field which may result from inhomogeneities or structures in the sample. This makes applications in strongly structured samples possible. SOLO is the first method that achieves localization of NMR signal with a single gradient pulse. Therefore, it can be used in conventional NMR spectrometers with one-axis gradient systems and lends itself to a wide range of applications including in vivo NMR.

Structural anisotropy and internal magnetic fields in trabecular bone: Coupling solution and solid dipolar interactions

2005-06-22T07:38:00.000-05:00

Louis-S. Bouchard, Felix W. Wehrli, Chih-Liang Chin and Warren S. Warren
Journal of Magnetic Resonance
Article in Press, Corrected Proof

We investigate the use of intermolecular multiple-quantum coherence to probe structural anisotropy in trabecular bone. Despite the low volume fraction of bone, the bone–water interface produces internal magnetic field gradients which modulate the dipolar field, depending on sample orientation, choice of dipolar correlation length, correlation gradient direction, and evolution time. For this system, the probing of internal magnetic field gradients in the liquid phase permits indirect measurements of the solid phase dipolar field. Our results suggest that measurements of volume-averaged signal intensity as a function of gradient strength and three orthogonal directions could be used to non-invasively measure the orientation of structures inside a sample or their degree of anisotropy. The system is modeled as having two phases, solid and liquid (bone and water), which differ in their magnetization density and magnetic susceptibility. A simple calculation using a priori knowledge of the material geometry and distribution of internal magnetic fields verifies the experimental measurements as a function of gradient strength, direction, and sample orientation.

Finite difference simulation of diffusion behaviors under inter- and intra-molecular multiple-quantum coherences in liquid NMR

2005-06-15T15:39:00.000-05:00

Congbo Cai, Zhong Chen, Shuhui Cai, Lian-Pin Hwang and Jianhui Zhong
Chemical Physics Letters
Volume 407, Issues 4-6 , 27 May 2005, Pages 438-443

The behaviors of molecular self-diffusion were simulated in complex spin systems with both intra-molecular scalar couplings and inter-molecular dipolar couplings in liquid nuclear magnetic resonance (NMR). The simulation algorithm was based on a combination of the non-linear Bloch equations, product operator matrix, and finite difference method. The simulated results reveal different diffusion behaviors of inter- and intra-molecular multiple-quantum coherences, coincident with theoretical predictions and experimental measurements. Compared with the Monte Carlo method, the finite difference method is more precise and efficient for simulating diffusion behaviors of multiple-quantum coherences.

Orientational dependence of intermolecular double quantum coherence (iDQC) signal from tendon tissue

2005-06-07T10:51:00.000-05:00

Bahadir Ozus, Geoffrey D. Clarke, Stephen J. Dodd, Gary D. FullertonThe proton signal changes as the long axis of tendon tissue is rotated with respect to the main magnetic field (B₀). The orientational changes in the tendon signal obtained using the correlation spectroscopy revamped by asymmetric z-gradient echo detection (CRAZED) sequence, which allows the effects of intermolecular dipolar interactions to be observed, were investigated and compared with the orientational changes of the signals produced using correlation spectroscopy (COSY), spin-echo (SE), and one-pulse sequences. The intermolecular double quantum coherence (iDQC) signal obtained using the CRAZED sequence showed a variation in the signal from tendon tissue, with sharper peaks and greater relative differences between minimum and maximum signal values compared to the variations in the signal obtained from the COSY, SE, and one-pulse sequences. This result is attributed to the orientational dependence of the transverse relaxation rate of single (SQC) and double (DQH) quantum coherences R₂ and R_2,2, respectively. Magn Reson Med 53:1183-1186, 2005. © 2005 Wiley-Liss, Inc.

Functional magnetic resonance imaging with intermolecular double-quantum coherences at 3 T

2005-05-19T12:18:00.000-05:00

Andreas Schäfer, Thies H. Jochimsen, Harald E. Möller

Functional magnetic resonance imaging (fMRI) based on the selection of intermolecular double-quantum coherences (iDQC) was performed with a standard birdcage coil at 3 T in a group of normal human volunteers. Suppression of spurious signal contributions from unwanted coherence-transfer pathways was achieved by combining a two-step phase cycle and a long repetition time of 5 s. A gradient-recalled echo iDQC sequence (echo time, T_E = 80 ms) yielded robust activation with a visual paradigm. Maximum z-scores were about half of those observed with conventional blood-oxygen level dependent fMRI, whereas the functional signal change increased by more than a factor of 5. No activation was obtained with a spin-echo iDQC sequence (T_E = 160 ms), in which dephasing accumulated during the evolution period was fully rephased by an appropriate delay time. It is hypothesized that substantial inherent diffusion weighting of the iDQC technique efficiently suppresses intravascular contributions to the functional contrast. A consistent quantitative explanation of the observed amount of signal change currently remains speculative. Magn Reson Med 53:1402-1408, 2005. © 2005 Wiley-Liss, Inc.

Dipolar field effects described by boson operators techniques: The case of intermolecular multiple-quantum coherences in liquids

2005-05-15T13:27:00.000-05:00

W. Nosel, T. Gili, S. Capuani and B. Maraviglia
Chemical Physics Letters
Volume 406, Issues 4-6 , 2 May 2005, Pages 452-456

Dipolar couplings between macroscopically distant spins in solution nuclear magnetic resonance (NMR) are treated. We propose a novel technique to calculate the intermolecular multiple-quantum coherences (iMQCs) based on a boson operators approach. The choice of an annihilation and creation operator basis set allows us to produce a general expression of the NMR signal depending on local inhomogeneities of magnetic field. The general expression we derive fits into the well known background of iMQCs signal descriptions [J. Jeener, J. Chem. Phys. 112 (2000) 5091] and turns into the conventional quantum-mechanical Warren formulation [S. Lee, W. Richter, S. Vathyam, W.S. Warren, J. Chem. Phys. 105 (1996) 874] by means of appropriate approximations.

Application of a Fourier-based method for rapid calculation of field inhomogeneity due to spatial variation of magnetic susceptibility

2005-05-15T13:24:00.000-05:00

J.P. Marques, R. Bowtell

Inhomogeneous B₀-magnetic fields generate distortion in magnetic resonance images, particularly those produced using echo planar imaging, and are responsible for signal reduction due to intravoxel dephasing in gradient echo experiments. Such effects increase in magnitude in proportionality with the static field strength, and with the growing use of high-field (3 T and above) systems in medical imaging, it is increasingly important to be able to quantify field inhomogeneities. Here, we describe the implementation and use of a method for rapidly calculating frequency shifts due to spatially varying magnetic susceptibility that is based on an approach previously used to calculate long-range dipolar field effects. The method relies on a simple expression that relates the three-dimensional Fourier transforms of the magnetization distribution and the field, and can naturally include the effect of the sphere of Lorentz. It has been used to evaluate field inhomogeneity in the head due to the variation of magnetic susceptibility with tissue type and to calculate the change in field inhomogeneity that occurs due to small rotations of the head. In addition, this approach has been used to simulate the effect of lung volume changes in generating respiration induced resonant offsets in the brain. © Wiley Periodicals, Inc. Concepts Magn Reson Part B (Magn Reson Engineering) 25B: 65-78, 2005

ISMRM 2005 Abstracts on DDF/iMQC

2005-05-05T14:55:00.000-05:00

Here are the DDF/iMQC related abstracts at ISMRM, let me know if I missed any...

Quantitative Investigation of Rotating-Frame Intermolecular
Simulation of Diffusion Behaviors under Scalar and Dipolar Couplings
Selection and Suppression of Intra- and Inter-Molecular MQCs
Investigation of multiple-echo spin-echo signal acquisition under distant dipole-dipole interactions
Issues and Artifacts in Intermolecular Double Quantum Imaging
Sensitivity enhancement in breast tumor imaging with MultiCRAZED experiments
Contrast Enhancement by the Butterfly Effect and Chaos Control in High-Field MRI

At the moment one needs their registration password to get to these links, this should change after the conference.

Curt

LASER and iZQC meet at ENC...

2005-04-09T10:49:00.000-05:00

session information

abstracts:
Localized Intermolecular Zero-Quantum Coherence Spectroscopy in vivo
David Balla and Cornelius Faber

First Results with "LASER" localized HOMOGENIZED sequence
Curtis A Corum and Michael Garwood

Rotating-frame intermolecular double-quantum spin-lattice relaxation T1rho, DQC-weighted magnetic resonance imaging

2005-03-29T11:39:00.000-06:00

Rotating-frame intermolecular double-quantum spin-lattice relaxation T1rho, DQC-weighted magnetic resonance imaging
Bingwen Zheng, Dennis W. Hwang, Zhong Chen, Lian-Pin Hwang
Magnetic Resonance in Medicine, Volume 53, Issue 4, p 930-936 (April 2005)
http://dx.doi.org/10.1002/mrm.20432

Nonlinear Amplification of Small Spin Precession Using Long-Range Dipolar Interactions

2005-03-20T13:34:00.000-06:00

M. P. Ledbetter, I. M. Savukov, and M. V. Romalis

Nonlinear Amplification of Small Spin Precession Using Long-Range Dipolar Interactions
Phys. Rev. Lett. 94, 060801 (2005)

DDF and iMQC News

2005-03-20T12:47:00.000-06:00

First Post...

DDF and iMQC Researchers,

Here is an opportunity to share news, new publications, preprints, and comments with the community.

Enjoy,

Curt