Effect Of Magnetic Field Inhomogeneity Research Articles

Repeatability of image quality in very low-field MRI.

Very low-field MR has emerged as a promising complementary device to high-field MRI scanners, offering several advantages. One of the key benefits is that very low-field scanners are generally more portable and affordable to purchase and maintain, making them an attractive option for medical facilities looking to reduce costs. Very low-field MRI systems also have lower RF power deposition, making them safer and less likely to cause tissue heating or other safety concerns. They are also simpler to maintain, as they do not require cooling agents such as liquid helium. However, these portable MR scanners are impacted by temperature, lower magnetic field strength, and inhomogeneity, resulting in images with lower signal-to-noise ratio (SNR) and higher geometric distortions. It is essential to investigate and tabulate the variations in these parameters to establish bounds so that subsequent in vivo studies and deployment of these portable systems can be well informed. The aim of this work is to investigate the repeatability of image quality metrics such as SNR and geometrical distortion at 0.05 T over 10 days and three sessions per day. We acquired repeatability data over 10 days with three sessions per day. The measurements included temperature, humidity, transmit frequency, off-resonance maps, and 3D turbo spin echo (TSE) images of an in vitro phantom. This resulted in a protocol with 11 sequences. We also acquired a 3 T data set for reference. The image quality metrics included computing SNR and eccentricity (to assess geometrical distortion) to investigate the repeatability of 0.05 T image quality. The image reconstruction included drift correction, k-space filtering, and off-resonance correction. We computed the experimental parameters' coefficient of variation (CV) and the resulting image quality metrics to assess repeatability. We have explored the impact of electromagnetic interference (EMI) on image quality in very low-field MRI. The investigation involved varying both the distance and amplitude of the EMI-producing coil from the signal generator to analyze their effects on image quality. The range of temperature measured during the study was within 1.5 °C. The off-resonance maps acquired before and after the 3D TSE showed similar hotspots and were changed mainly by a global constant. The SNR measurements were highly repeatable across sessions and over the 10 days, quantified by a CV of 6.7%. The magnetic field inhomogeneity effects quantified by eccentricity showed a CV of 13.7%, but less than 5.1% in two of the three sessions over 10 days. The use of conjugate phase reconstruction mitigated geometrical distortion artifacts. Temperature and humidity did not significantly affect SNR or mean frequency drift within the ranges of these environmental factors investigated. The EMI experiment showed that as the amplitude increased the SNR decreased, and concurrently the root mean square of the background increased with a rise in EMI amplitude or a reduction in distance. We found that humidity and temperature in the range investigated did not impact SNR or frequency. Based on the CV values computed session-wise and for the overall study, our findings indicate high repeatability for SNR and magnetic field homogeneity.

Features of Self-Diffusion of Tridecane Molecules in a Porous Medium of Kaolinite Used as a Model of a Chemically Inert Membrane

The present work focused on the experimental study of the specific features of self-diffusion of tridecane molecules in macroporous kaolinite, which is used as a raw material for the production of chemically inert membranes. The measurements of self-diffusion coefficients by pulsed magnetic field gradient nuclear magnetic resonance (PMFG NMR) revealed an increased translational mobility of tridecane molecules in kaolinite with incomplete filling of the pore space. This effect was accompanied by a sharp change in the slope of the Arrhenius plot of the self-diffusion coefficients of tridecane molecules in kaolinite. An analysis of the diffusion spin echo decay in the tridecane-kaolinite system revealed a discrepancy between the experimental data and the theoretical predictions, considering the effect of the geometry of porous space on molecular mobility. It was shown that the experimental results could be interpreted in terms of a model of two phases of tridecane molecules in the pores of kaolinite, in the gaseous and adsorbed state, coexisting under the fast-exchange conditions. Within the framework of the model, the activation energies of self-diffusion were calculated, which agreed satisfactorily with the experimental data. Additionally, the effects of the internal magnetic field gradients arising in a porous medium loaded with a gas or liquid on the data of the PFG NMR measurements were calculated. It was shown that the effect of magnetic field inhomogeneities on the measured self-diffusion coefficients of tridecane in kaolinite is small and could be neglected.

Atom interferometry using σ+−σ− Raman transitions between |F=1,mF=∓1〉 and |F=2,mF=±1〉

We report on the experimental demonstration of a horizontal accelerometer based on atom interferometry using counterpropagative Raman transitions between the states $|F=1,{m}_{F}=\ensuremath{\mp}1\ensuremath{\rangle}$ and $|F=2,{m}_{F}=\ifmmode\pm\else\textpm\fi{}1\ensuremath{\rangle}$ of $^{87}\mathrm{Rb}$. Compared to the $|F=1,{m}_{F}=0\ensuremath{\rangle}\ensuremath{\leftrightarrow}|F=2,{m}_{F}=0\ensuremath{\rangle}$ transition usually used in atom interferometry, our scheme presents the advantages of having only a single counterpropagating transition allowed in a retroreflected geometry, using the same polarization configuration as the magneto-optical trap, and allowing the control of the atom trajectory with magnetic forces. We demonstrate horizontal acceleration measurement in a close-to-zero velocity regime using a single-diffraction Raman process with a short-term sensitivity of $25\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$ m ${\mathrm{s}}^{\ensuremath{-}2} {\mathrm{Hz}}^{\ensuremath{-}1/2}$ and resolution down to $3.8\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$ m ${\mathrm{s}}^{\ensuremath{-}2}$ at an integration time of 3300 s. We discuss specific features of the technique such as spontaneous emission, light shifts, and effects of magnetic field inhomogeneities. We finally give possible applications of this technique in metrology or for cold-atom inertial sensors dedicated to onboard applications.

Library-driven approach for fast implementation of the voxel spread function to correct magnetic field inhomogeneity artifacts for gradient-echo sequences.

Previously developed Voxel Spread Function (VSF) method (Yablonskiy, etal, MRM, 2013;70:1283) provides solution to correct artifacts induced by macroscopic magnetic field inhomogeneity in the images obtained by multi-Gradient-Recalled-Echo (mGRE) techniques. The goal of this study was to develop a library-driven approach for fast VSF implementation. The VSF approach describes the contribution of the magnetic field inhomogeneity effects on the mGRE signal decay in terms of the F-function calculated from mGRE phase and magnitude images. A pre-calculated library accounting for a variety of background field gradients caused by magnetic field inhomogeneity was used herein to speed up the calculation of F-function. Quantitative R2* maps from the mGRE data collected from two healthy volunteers were generated using the library as validation. As compared with direct calculation of the F-function based on a voxel-wise approach, the new library-driven method substantially reduces computational time from several hours to few minutes, while, at the same time, providing similar accuracy of R2* mapping. The new procedure proposed in this study provides a fast post-processing algorithm that can be incorporated in the quantitative analysis of mGRE data to account for background field inhomogeneity artifacts, thus can facilitate the applications of mGRE-based quantitative techniques in clinical practices.

Quantum correlation protection through spin self-rephasing in a one-dimensional Bose gas

System consisting of a number of trapped atoms evolving under the influence of external inhomogenous magnetic field undergoes spin dephasing: classically, since each atom feels different field along its trajectory, the spin rotation rates differ; as a result the average spin decays. In a quantum mechanical context this corresponds to entanglement of spin and spatial degrees of freedom and nontrivial internal spin dynamics. The spin dephasing can be prevented by tuning the interaction between the atoms. This phenomenon, called spin self-rephasing, has been observed experimentally and can increase the coherence time by a large factor. While such systems have been studied from a semiclassical point of view, a quantum mechanical description is limited, especially in the case of entangled states. In this work we provide a numerical simulation of an ab initio model and provide realistic examples of spin self-rephasing used to counteract the effect of inhomogenous magnetic field. We analyze in particular the joint effect of magnetic field inhomogeneity and interactions on the coherent and spin squeezed states evolution.

Pushing resolution limits for extracting 1H-1H scalar coupling constants by a resolution-enhanced selective refocusing method.

Nuclear magnetic resonance (NMR) spectroscopy enables one to study molecular structure and dynamics in a noninvasive manner and has long served as a versatile and indispensable analytical tool in physics, chemistry, and biology. Scalar coupling, an essential feature in NMR spectroscopy, provides rich information regarding molecular structure and conformation. The measurement of scalar coupling constants, therefore, constitutes an important issue in NMR spectroscopy. Homonuclear 2D J-resolved spectroscopy is a powerful tool for multiplet analysis and coupling measurement. Recently, a number of phase-sensitive J-resolved methods and selective measuring methods have been developed to facilitate the extraction of coupling constants. However, resolution remains a crucial challenge when extracting small coupling constants or under inhomogeneous fields. In this paper, we present a resolution-enhanced selective refocusing (RESERF) method for the extraction of coupling constants. The effect of magnetic field inhomogeneity can be eliminated, resulting in very narrow linewidths. Therefore, samples with small coupling constants or under inhomogeneous fields can be well analyzed. The RESERF method may be of great value for structural and conformational studies in chemistry and biology.

Correction of magnetic field inhomogeneity effects for fast quantitative susceptibility mapping

Magnetic Resonance in MedicineVolume 81, Issue 3 p. C1-C1 COVER IMAGEFree Access Correction of magnetic field inhomogeneity effects for fast quantitative susceptibility mapping First published: 25 January 2019 https://doi.org/10.1002/mrm.27649AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume81, Issue3March 2019Pages C1-C1 RelatedInformation

Correction of magnetic field inhomogeneity effects for fast quantitative susceptibility mapping.

Quantitative susceptibility mapping (QSM) provides information about tissue composition and organization. However, current acquisition methods can be quite time consuming, limiting the use of QSM in studies and in monitoring dynamic events. In this work, time efficient spiral acquisitions are combined with a model-based image reconstruction approach. Magnetic field inhomogeneity artifacts are corrected to obtain full brain susceptibility maps. Magnetic field maps, capturing the magnetic field inhomogeneity distribution due to non-tissue sources (background field), were estimated from a calibration scan. Tissue phase information present in the background field maps was identified using variable spherical mean value filtering and removed from the estimated field maps. The resulting background field maps were then used in the image reconstruction to correct the magnetic field inhomogeneity artifacts. Images were acquired on a 3T system with a 3D spiral-in acquisition based on a rotated stack of spirals. For comparison, standard gradient echo images were also acquired. Susceptibility maps were obtained for both acquisitions using a dipole inversion algorithm based on a compressed sensing compensated formulation with wavelet and total variation penalties. Susceptibility maps obtained with the spiral acquisition and the model-based reconstruction agree with the ones obtained with the spin-warp gradient echo acquisition. Using the 3D spiral acquisition, full brain susceptibility maps at the resolution of 1mm isotropic are obtained in 23s CONCLUSIONS: Image distortions and blurring due to magnetic field inhomogeneity are removed while maintaining tissue magnetic susceptibility information, resulting in QSM maps in much shorter acquisition time.

Enhancement and Intensity Inhomogeneity Correction of Diffusion-Weighted MR Images of Neonatal and Infantile Brain Using Dynamic Stochastic Resonance

Imaging of infantile/neonatal brain mandates tailored radio frequency coils (RF coils) to achieve a homogeneous field over a small region of interest (ROI). Most centers, however, perform pediatric imaging using adult RF coils only as procurement of tailored pediatric coils might prove quite expensive. This practice may not scientifically justified, whereas the image post-processing techniques reduces the deleterious effects of magnetic field inhomogeneity due to a small ROI being scanned in a large RF coil. Further, the eccentric placement of ROI within the RF coil perpetuates the field inhomogeneity within the scanned region. Hence, the structures closer to the coil appear brighter than those farther away giving rise to a ‘shading artefact’. The effect even more accentuates in weak signal sequences like diffusion-weighted imaging (DWI). The proposed method significantly removes shading artefact of real DWI and synthetic T1 and T2 weighted magnetic resonance images. Dynamic stochastic resonance (DSR) intelligently uses the coefficient of discrete cosine transform of an image for brightness normalization and image enhancement simultaneously. The quality of the output image depends on the bistability parameters associated with the dynamic equation. Particle swarm optimization (PSO) tunes these bistability parameters for the entropy minimization of different group of tissues individually. The proposed algorithm outperforms the post processing based homomorphic filtering, local entropy minimization with spline model and multiplicative intrinsic component optimization methods. The proposed PSO based DSR approach may be helpful in accurate diagnosis.

Mixed model phase evolution for correction of magnetic field inhomogeneity effects in 3D quantitative gradient echo-based MRI.

In 3D gradient echo magnetic resonance imaging (MRI), strong field gradients B0macro are visually observed at air/tissue interfaces. At low spatial resolution in particular, the respective field gradients lead to an apparent increase in intravoxel dephasing, and subsequently, to signal loss or inaccurate R2* estimates. If the strong field gradients are measured, their influence can be removed by postprocessing. Conventional corrections usually assume a linear phase evolution with time. For high macroscopic gradient inhomogeneities near the edge of the brain and at the paranasal sinuses, however, this assumption is often broken. Herein, we explored a novel model that considers both linear and stochastic dependences of the phase evolution with echo time in the presence of weak and strong macroscopic field inhomogeneities. We tested the performance of the model at large field gradients using simulation, phantom, and human in vivo studies. The performance of the proposed approach was markedly better than the standard correction method, providing a correction equivalent to that of the conventional approach in regions with high signal to noise ratio (SNR > 10), but appearing more robust in regions with low SNR (SNR < 4). The proposed technique shows promise to improve R2* measurements in regions of large susceptibilities. The clinical and research applications still require further investigation.

Study on magnetohydrodynamics angular rate sensor under non-uniform magnetic field

Purpose The evaluations of the magnetohydrodynamics angular rate sensor (MHD ARS) in its applications necessitate further improvements in the sensor’s dynamic measurement ability. The magnetic field of the MHD ARS is a key factor in the sensor’s modeling and error analysis. The aim of this study is to illustrate the influence of a non-uniform magnetic field on the sensor. Design/methodology/approach Numerical simulation is made using ANSYS FLUNET with the magnetic field calculated by 3D-Magnetostatic. The comparison of the simulation results between uniform and non-uniform magnetic fields is made to reveal and explain the effects of magnetic field inhomogeneity (MFI) on the flow and electric field in detail. Two different structures with different MFIs are designed to confirm the MFI effect on the sensor’s output in simulation and experiment. A cross-correlation experiment and an adaptive filter are carried out to extract the signal to identify the error of the sensor output caused by MFI. Findings The MFI effect on the flow field in MHD ARS is found to be insignificant, while its effect on the electric potential is considerable. The comparisons between two kinds of MHD ARS in numerical simulation and experiment show that the MFI effect on the sensor error can be identified by fitting the sensor output. The deviation is mainly generated at the peaks and valleys of an angular vibration. Originality/value The study of the MHD ARS under the influence of a non-uniform magnetic field can offer an understanding of the MFI effect on the sensor and an evaluation method of the sensor error caused by the MFI effect.

Demagnetization dynamics of noninteracting trapped fermions

Motivated by several experimental efforts to understand spin diffusion and transport in ultracold fermionic gases, we study the spin dynamics of initially spin-polarized ensembles of harmonically trapped non-interacting spin-1/2 fermionic atoms, subjected to a magnetic field gradient. We obtain simple analytic expressions for spin observables in the presence of both constant and linear magnetic field gradients, with and without a spin-echo pulse, and at zero and finite temperatures. The analysis shows the relevance of spin-motional coupling in the non-interacting regime where the demagnetization decay rate at short times can be faster than the experimentally measured rates in the strongly interacting regime under similar trapping conditions. Our calculations also show that particle motion limits the ability of a spin-echo pulse to remove the effect of magnetic field inhomogeneity, and that a spin-echo pulse can instead lead to an increased decay of magnetization at times comparable to the trapping period.

Effect of magnetic field inhomogeneity on ion cyclotron motion coherence at high magnetic field.

A three-dimensional code based on the particle-in-cell algorithm modified to account for the inhomogeneity of the magnetic field was applied to determine the effect of Z(1), Z(2), Z(3), Z(4), X, Y, ZX, ZY, XZ(2) YZ(2), XY and X(2)-Y(2) components of an orthogonal magnetic field expansion on ion motion during detection in an FT-ICR cell. Simulations were performed for magnetic field strengths of 4.7, 7, 14.5 and 21 Tesla, including experimentally determined magnetic field spatial distributions for existing 4.7 T and 14.5 T magnets. The effect of magnetic field inhomogeneity on ion cloud stabilization ("ion condensation") at high numbers of ions was investigated by direct simulations of individual ion trajectories. Z(1), Z(2), Z(3) and Z(4) components have the largest effect (especially Z(1)) on ion cloud stability. Higher magnetic field strength and lower m/z demand higher relative magnetic field homogeneity to maintain cloud coherence for a fixed time period. The dependence of mass resolving power upper limit on Z(1) inhomogeneity is evaluated for different magnetic fields and m/z. The results serve to set the homogeneity requirements for various orthogonal magnetic field components (shims) for future FT-ICR magnet design.

Quantum atom–light interfaces in the Gaussian description for spin-1 systems

We extend the covariance matrix description of atom–light quantum interfaces, originally developed for real and effective spin-1/2 atoms, to include ‘spin alignment’ degrees of freedom. This allows accurate modelling of optically probed spin-1 ensembles in arbitrary magnetic fields. We also include technical noise terms that are very common in experimental situations. These include magnetic field noise, variable atom number and the effect of magnetic field inhomogeneities. We demonstrate the validity of our extended model by comparing numerical simulations to a free–induction decay measurement of polarized 87Rb atoms in the f = 1 ground state. We qualitatively and quantitatively reproduce experimental results with no free parameters. The model can be easily extended to larger spin systems, and adapted to more complicated experimental situations.

P.10.19 Net muscle volumetry using MRI and CT

Muscle volumetry by MRI has been previously reported using T1 weighted images. We reported muscle volumetry using CT and compared the results obtained by CT and DIXON images. Five patients with muscular dystrophy, 3 patients with myopathy, 2 patients with myositis, and 3 patients with neurogenic amyotrophy were enrolled in this study. CT and MRI DIXON images of the 26 limbs (the thigh or lower leg) of these patients were investigated. The CT and MRI images of fourteen 1-cm and seventy 2-mm thickness slices of the mid-thigh, 7cm above and below the midpoint of the trochanter and patella, and ten 1-cm and fifty 2-mm thickness slices of the mid-lower leg, 5cm above and below the midpoint of the fibula head and lateral malleolus, were analyzed, respectively. A muscle density map was obtained using estimated linear-function. Obvious vessels and skin tissues were excluded manually from the density map and the net muscle volumes of the thighs and lower legs were calculated. Percentage water images were simultaneously calculated using DIXON images, and the sum of the %water images resulted in the net muscle volume from MRI. The results obtained by DIXON closely corresponded to those by CT, with a correlation coefficient of 0.993 and intraclass correlation coefficient of 0.993. There was a significant difference between the two results by the paired <i>t</i>-test (<i>p</i>=0.001), and the results obtained by DIXON were slightly larger than those by CT, with an SEM of 47.95cm³. The results obtained by DIXON were correlated to those by CT because these results were calculated from the division of water images by the addition of water images and fat images, and the division procedure reduced the effect of magnetic field inhomogeneity on these images. The results obtained by DIXON were larger than those by CT because the bone marrow was not able to be eliminated on %water images.

In vivo comparison of myocardial T1 with T2 and T2* in thalassaemia major

To compare myocardial T1 against T2 and T2* in patients with thalassemia major (TM) for myocardial iron characterization. A total of 106 TM patients (29 ± 10 years; 58 males) were studied on a 1.5 Tesla scanner using dedicated T1, T2*, and T2 relaxometry sequences. A single mid-ventricular short axis slice was acquired within a breath-hold. In patients with myocardial iron overload (T2* < 20 ms; n = 52), there were linear correlations between T2 and T2* (r = 0.82; P = 0.0), and between T1 and T2* (r = 0.83; P = 0.0). In patients with no myocardial iron (n = 54), T2* values were scattered with no significant correlation against T2 or T1. For all patients (n = 106) there was a strong linear correlation (r = 0.93; P = 0.0) between myocardial T1 and T2. In patients with iron overload, myocardial T2 and T1 are correlated with T2*. In patients with low or normal myocardial iron concentration, other factors become dominant in affecting T2* values as shown by scattered T2* data. Myocardial T1 correlates linearly with T2 measurements in all patients suggesting that these two relaxation parameters avoid extrinsic magnetic field inhomogeneity effects and may potentially provide improved myocardial tissue characterization.

Voxel spread function method for correction of magnetic field inhomogeneity effects in quantitative gradient-echo-based MRI.

Macroscopic magnetic field inhomogeneities adversely affect different aspects of MRI images. In quantitative MRI when the goal is to quantify biological tissue parameters, they bias and often corrupt such measurements. The goal of this article is to develop a method for correction of macroscopic field inhomogeneities that can be applied to a variety of quantitative gradient-echo-based MRI techniques. We have reanalyzed a basic theory of gradient echo MRI signal formation in the presence of background field inhomogeneities and derived equations that allow for correction of magnetic field inhomogeneity effects based on the phase and magnitude of gradient echo data. We verified our theory by mapping effective transverse relaxation rate in computer simulated, phantom, and in vivo human data collected with multi-gradient echo sequences. The proposed technique takes into account voxel spread function effects and allowed obtaining virtually free from artifacts effective transverse relaxation rate maps for all simulated, phantom and in vivo data except of the edge areas with very steep field gradients. The voxel spread function method, allowing quantification of tissue specific effective transverse relaxation rate-related tissue properties, has a potential to breed new MRI biomarkers serving as surrogates for tissue biological properties similar to longitudinal and transverse relaxation rate constants widely used in clinical and research MRI.

Quantitative T1ρ imaging using phase cycling for B0 and B1 field inhomogeneity compensation

T 1 ρ imaging is useful in a number of clinical applications. T 1 ρ preparation methods, however, are sensitive to non-uniformities of the B 0 magnetic field and the B 1 RF field. These common system imperfections can result in image artifacts and quantification errors in T 1 ρ imaging. We report on a phase-cycling method which can eliminate B 1 RF inhomogeneity effects in T 1 ρ imaging. This method does not only correct for image artifacts but also for T 2 ρ contamination caused by B 1 RF inhomogeneity. The presence of B 0 magnetic field inhomogeneity can compromise the effectiveness of this method for B 1 RF inhomogeneity correction. We demonstrate that, by combining the spin-locking scheme reported by Dixon et al. (Myocardial suppression in vivo by spin locking with composite pulses. Magn Reson Med 1996; 36:90–94) with phase cycling, we can simultaneously correct B 0 magnetic field inhomogeneity effects and B 1 RF inhomogeneity effects in T 1 ρ imaging. Phantom and in vivo data sets are used to demonstrate the proposed methods and to compare them with other existing T 1 ρ preparation methods.

Abdominal MR Imaging at 3.0 T

Magnetic resonance (MR) imaging at 3.0 T offers an improved signal-to-noise ratio compared with that at 1.5 T. However, the physics of high field strength also brings disadvantages, such as increases in the specific absorption rate, in magnetic field inhomogeneity effects, and in susceptibility artifacts. The use of 3.0-T MR imaging for abdominal evaluations, in particular, has lagged behind that for other applications because of the difficulty of imaging a large volume while compensating for respiratory motion. At a minimum, abdominal MR imaging at 3.0 T requires modifications in the pulse sequences used at 1.5 T. Such modifications may include a decrease in the flip angle used for refocusing pulses and an increase in the repetition time for T1-weighted acquisitions. In addition, parallel imaging and other techniques (hyper-echo sequences, transition between pseudo steady states) may be used to maintain a high signal-to-noise ratio while decreasing acquisition time and minimizing the occurrence of artifacts on abdominal MR images.

A New Method for High‐Resolution NMR Spectra in Inhomogeneous Fields with Efficient Solvent Suppression

AbstractHigh‐resolution nuclear magnetic resonance (NMR) is one of the most powerful tools for analyzing molecular structures and dynamics. Magnetic field homogeneity is required for conventional high‐resolution spectra. However, there are many chemical and/or biological circumstances where the spatial homogeneities of the magnetic fields are degraded. Intense solvent signal is another obstacle for obtaining high‐resolution spectra, especially in in vivo and in situ NMR spectroscopy. In this paper, a new pulse sequence based on intermolecular multiple quantum coherence (iMQC) was reported. This sequence can effectively remove the effect of magnetic field inhomogeneity and suppress the solvent signal. It can recover the spectral information such as chemical shifts, coupling constants, multiplet patterns, and relative peak areas in inhomogeneous fields. Theoretical analyses and experimental verifications are presented to demonstrate the feasibility of this method.