Abstract：
:An NMR technique is described which allows the observation of ionic charge carriers moving in the electric field within a porous system saturated with electrolyte solution. This method, which was recently developed in our laboratory, gives experimental access to the study of electric transport in disordered media on a microscopic level and offers new potential for morphology studies. We performed 1H NMR PFG self-diffusion measurements on ions combined with ionic drift velocity measurements by electrophoretic NMR (ENMR), each as a function of observation time Delta. In this way we obtained time-dependent self-diffusion coefficients D(+/-) (Delta) and time-dependent electric mobilities mu(+/-) (Delta) of polyatomic cations and anions in porous media. The porous media used were gels and glass bead packs. From the behaviour of D(+/-) (Delta) and mu(+/-) (Delta) at long observation times the tortuosities T(p) (D(+/-)) and T(p) (mu(+/-)) are derived, allowing a direct experimental check of the validity of the Einstein relation (D(+/-) is proportional to mu(+/-)) in a disordered medium. The tortuosities obtained via the diffusivity of ions are compared with those obtained via the diffusivity of water molecules. We also make a first attempt to derive the specific surface S/V(p) from the time-dependence of the ionic mobility at short observation times and discuss possible advantages of those measurements in morphology studies of porous media.
journal_name
Magn Reson Imagingjournal_title
Magnetic resonance imagingauthors
Holz M,Heil SR,Schwab IAdoi
10.1016/s0730-725x(01)00267-3subject
Has Abstractpub_date
2001-04-01 00:00:00pages
457-63issue
3-4eissn
0730-725Xissn
1873-5894pii
S0730-725X(01)00267-3journal_volume
19pub_type
杂志文章abstract：:Water content is the dominant chemical compound in the brain and it is the primary determinant of tissue contrast in magnetic resonance (MR) images. Water content varies greatly between individuals, and it changes dramatically over time from birth through senescence of the human life span. We hypothesize that the effe...
journal_title：Magnetic resonance imaging
pub_type： 杂志文章
doi：10.1016/j.mri.2013.07.017
更新日期：2013-12-01 00:00:00
abstract：PURPOSE:To determine the diagnostic performance of diffusion-weighted MRI and MR volumetry for the assessment of tumor response after preoperative chemoradiotherapy (CRT) in patients with locally advanced rectal cancer. MATERIALS AND METHODS:Forty-three patients with rectal cancer who underwent preoperative CRT were p...
journal_title：Magnetic resonance imaging
pub_type： 杂志文章
doi：10.1016/j.mri.2014.08.041
更新日期：2015-02-01 00:00:00
abstract：:In vivo spin-lattice relaxation times, T1, of water and lipid protons of normal and atrophic muscles were measured, using the spatially resolved spectroscopy (SPARS) sequence, in a genetic avian model of myopathy. These T1 values were compared with those of the hypertrophic muscles. Although the water T1 values of mus...
journal_title：Magnetic resonance imaging
pub_type： 杂志文章
doi：10.1016/0730-725x(89)90550-x
更新日期：1989-05-01 00:00:00
abstract：PURPOSE:The purpose of this study was to determine the pre- and postpubertal 1H magnetic resonance spectroscopic characteristics of the normal testis to establish baseline values for further clinical studies. MATERIALS AND METHODS:The subjects consisted of male volunteers, of whom 19 were prepubertal with ages between...
journal_title：Magnetic resonance imaging
pub_type： 杂志文章
doi：10.1016/j.mri.2007.06.008
更新日期：2008-02-01 00:00:00
abstract：:Quantifying the intracranial tissue volume changes in magnetic resonance imaging (MRI) assists specialists to analyze the effects of natural or pathological changes. Since these changes can be subtle, the accuracy of the automatic compartmentalization method is always criticized by specialists. We propose and then eva...
journal_title：Magnetic resonance imaging
pub_type： 杂志文章
doi：10.1016/j.mri.2019.11.002
更新日期：2020-01-01 00:00:00
abstract：:Ten patients with biopsy-proved synovial sarcoma were evaluated by magnetic resonance (MR) imaging on a 1.5-T unit. The lesions showed intermediate signal intensity on T1-weighted images and heterogeneous high signal intensity on T2-weighted images. Tumors were well-demarcated from normal tissues. Additional informati...
journal_title：Magnetic resonance imaging
pub_type： 杂志文章
doi：10.1016/0730-725x(89)90706-6
更新日期：1989-03-01 00:00:00
abstract：:The objective of this study was to determine the value of magnetic resonance (MR) imaging in diagnosing local recurrence of Ewing sarcoma. We retrospectively reviewed radiographs, Tc99m-methylene diphosphonate (MDP) skeletal scintigraphy, computed tomography scans, and MR studies of 11 patients who had local recurrenc...
journal_title：Magnetic resonance imaging
pub_type： 杂志文章
doi：10.1016/0730-725x(94)90079-7
更新日期：1994-01-01 00:00:00
abstract：:Various analogs of NMR and MRI are now technically possible in optics; specifically, high-resolution laser-pulse shaping and complex pulse sequence generation with well-defined phase shifts has been demonstrated. Here we summarize this technology and discuss the potential for these methods to enhance optical functiona...
journal_title：Magnetic resonance imaging
pub_type： 杂志文章
doi：10.1016/j.mri.2003.08.024
更新日期：2003-12-01 00:00:00
abstract：PURPOSE:A direct correlation between T(1ρ), T(2) and quantified proteoglycan and collagen contents in human osteoarthritic cartilage has yet to be documented. We aimed to investigate the orientation effect on T(1ρ) and T(2) values in human osteoarthritic cartilage and to quantify the correlation between T(1ρ), T(2) vs....
journal_title：Magnetic resonance imaging
pub_type： 杂志文章
doi：10.1016/j.mri.2010.09.004
更新日期：2011-04-01 00:00:00
abstract：:It is a big challenge to segment magnetic resonance (MR) images with intensity inhomogeneity. The widely used segmentation algorithms are region based, which mostly rely on the intensity homogeneity, and could bring inaccurate results. In this paper, we propose a novel region-based active contour model in a variationa...
journal_title：Magnetic resonance imaging
pub_type： 杂志文章
doi：10.1016/j.mri.2012.10.010
更新日期：2013-05-01 00:00:00
abstract：:Retained sponges after laparotomy may cause a broad spectrum of clinical symptoms and present a difficult diagnostic problem. We report a case of retained surgical sponge in a dog to illustrate the MRI findings of this infrequent but important cause of postoperative complications. ...
journal_title：Magnetic resonance imaging
pub_type： 杂志文章
doi：10.1016/0730-725x(85)90358-3
更新日期：1985-01-01 00:00:00
abstract：PURPOSE:To develop a method for estimating metabolite concentrations using phased-array coils and sensitivity-encoded (SENSE) magnetic resonance spectroscopic images (MRSI) of the human brain. MATERIALS AND METHODS:The method is based on the phantom replacement technique and uses receive coil sensitivity maps and body...
journal_title：Magnetic resonance imaging
pub_type： 杂志文章
doi：10.1016/j.mri.2009.11.003
更新日期：2010-04-01 00:00:00
abstract：:We studied 26 cases of abdominal aortic aneurysm with magnetic resonance imaging (MRI), computed tomography (CT), ultrasonography (US), and angiography. Data acquired were compared to those obtained at surgery. Diameter of the aneurysm was correctly defined in all cases by CT and MRI, while angiography underestimated ...
journal_title：Magnetic resonance imaging
pub_type： 杂志文章
doi：10.1016/0730-725x(90)90089-k
更新日期：1990-01-01 00:00:00
abstract：:Flattened representations are a useful approach to represent the convoluted complex surface of the neocortex of primates and other large-brained mammals. In this study, we compared the flattened representation of neocortical areas obtained from the recently published MRI and histology atlas of the rhesus monkey brain ...
journal_title：Magnetic resonance imaging
pub_type： 杂志文章
doi：10.1016/j.mri.2010.03.023
更新日期：2010-10-01 00:00:00
abstract：:In this contribution, we explore the potential of proton electron double resonance imaging (PEDRI) in environmental science (hydrogeological) applications. After a discussion of the hydrogeological motivation for studies of free radical transport in environmental matrices, we present results from first experiments tha...
journal_title：Magnetic resonance imaging
pub_type： 杂志文章
doi：10.1016/j.mri.2004.11.027
更新日期：2005-02-01 00:00:00
abstract：:NMR spectroscopy is applied to study microstructure of calcium silicate hydrates present in cement and concrete. It is shown that 29Si NMR gives information on the siliceous skeleton of the hydrates. 1H NMR, using CRAMPS techniques, allows to discriminate between protons linked to silicon atoms or to calcium atoms. A ...
journal_title：Magnetic resonance imaging
pub_type： 杂志文章
doi：10.1016/s0730-725x(96)00211-1
更新日期：1996-01-01 00:00:00
abstract：:In the present work, we reported a new nuclear Overhauser enhancement (NOE)-mediated magnetization transfer (MT) signal at around -1.6ppm (NOE(-1.6)) in rat brain and investigated its application in the detection of acute ischemic stroke in rodent model. Using continuous wave (CW) MT sequence, the NOE(-1.6) is reliabl...
journal_title：Magnetic resonance imaging
pub_type： 杂志文章
doi：10.1016/j.mri.2016.05.002
更新日期：2016-10-01 00:00:00
abstract：:To demonstrate the feasibility of a novel MR elastography (MRE) technique based on a conventional gradient-echo type multi-echo MR sequence which does not need additional bipolar magnetic field gradients (motion encoding gradient: MEG), yet is sensitive to vibration. In a gradient-echo type multi-echo MR sequence, sev...
journal_title：Magnetic resonance imaging
pub_type： 杂志文章
doi：10.1016/j.mri.2014.10.002
更新日期：2015-01-01 00:00:00
abstract：:A new pulse sequence for estimating cerebral blood flow called UNFAIR, which uses a combination of sequential hyperbolic secant preparatory pulses, is introduced. This sequence is based on the same generalized conditions as previously introduced inversion recovery techniques except that the spins in the image slice of...
journal_title：Magnetic resonance imaging
pub_type： 杂志文章
doi：10.1016/s0730-725x(96)00353-0
更新日期：1997-01-01 00:00:00
abstract：:Resting fluctuations in arterial CO2 (a cerebral vasodilator) are believed to be an important source of low-frequency blood oxygenation level dependent (BOLD) signal fluctuations. In this study we focus on the two commonly used resting-states in functional magnetic resonance imaging experiments, eyes open and eyes clo...
journal_title：Magnetic resonance imaging
pub_type： 杂志文章
doi：10.1016/j.mri.2012.06.013
更新日期：2013-04-01 00:00:00
abstract：:We compared the efficacy of rapidly acquired magnetization prepared gradient-echo (MP-GRE) sequences with CT and standard MRI pulse sequences for the detection of focal liver lesions. Fourteen patients with 28 focal liver lesions were scanned. TI times of 300, 450, and 600 ms were used. MP-GRE lesion conspicuity was c...
journal_title：Magnetic resonance imaging
pub_type： 杂志文章
doi：10.1016/0730-725x(94)92198-9
更新日期：1994-01-01 00:00:00
abstract：:A series of direct shear and nuclear magnetic resonance (NMR) tests were performed on a compacted weakly expansive clay saturated by sodium chloride (NaCl) solutions with different concentrations to study the effect of NaCl solution on the shear strength and its mechanism. Results from the direct shear tests show that...
journal_title：Magnetic resonance imaging
pub_type： 杂志文章
doi：10.1016/j.mri.2019.01.002
更新日期：2019-05-01 00:00:00
abstract：:High density barium sulphate suspension was investigated as an oral contrast on MRI. On 30 consecutive subjects, the stomach (in all cases) and the two first portions of the duodenum (in 21 cases) were filled with the suspension. This oral contrast behaved as a negative contrast, being hypointense on all pulse sequenc...
journal_title：Magnetic resonance imaging
pub_type： 杂志文章
doi：10.1016/0730-725x(91)90019-i
更新日期：1991-01-01 00:00:00
abstract：:In magnetic resonance elastography (MRE), shear waves at a certain frequency are encoded through bipolar gradients that switch polarity at a controlled encoding frequency and are offset in time to capture wave propagation using a controlled sampling frequency. In brain MRE, there is a possibility that the mechanical a...
journal_title：Magnetic resonance imaging
pub_type： 杂志文章
doi：10.1016/j.mri.2011.09.017
更新日期：2012-02-01 00:00:00
abstract：:A regularization strategy is described for generalized autocalibrating partially parallel acquisition (GRAPPA) that allows successful calibration using a small number of autocalibration signals (ACS). The approach requires certain nonlinear relationships between the GRAPPA coefficients to be satisfied, which increases...
journal_title：Magnetic resonance imaging
pub_type： 杂志文章
doi：10.1016/j.mri.2008.05.005
更新日期：2009-01-01 00:00:00
abstract：:Magnetic field inhomogeneities like eddy current-related gradient fields cause geometric distortions in echo-planar imaging (EPI). This in particular affects diffusion-weighted imaging where these distortions vary with the direction of the diffusion weighting and hamper the accurate determination of diffusion paramete...
journal_title：Magnetic resonance imaging
pub_type： 杂志文章
doi：10.1016/j.mri.2009.12.004
更新日期：2010-04-01 00:00:00
abstract：:A dextran-Gd-DTPA compound has been recently synthesized utilizing 70,800 Da molecular weight dextran. This polymeric contrast agent for magnetic resonance imaging has been found chemically to be very stable and to demonstrate in vitro improved relaxivities of 1.5 to 2.3 times that of monomeric Gd-DTPA at 100 MHz. Thi...
journal_title：Magnetic resonance imaging
pub_type： 杂志文章
doi：10.1016/0730-725x(92)90515-2
更新日期：1992-01-01 00:00:00
abstract：:Our purpose was to investigate three-dimensional (3D) gadolinium-enhanced magnetic resonance angiography (Gd-MRA) in the evaluation of renal transplant arteries. Eleven MR angiography examinations were performed in nine renal transplant patients. Gd-MRA, three-dimensional phase contrast (3D-PC) post-gadolinium, and tw...
journal_title：Magnetic resonance imaging
pub_type： 杂志文章
doi：10.1016/s0730-725x(96)00348-7
更新日期：1997-01-01 00:00:00
abstract：:Primary epiploic appendagitis (PEA) occurs secondary to inflammation of an epiploic appendage, and is considered to be a rare cause of acute abdomen. In this case report, we describe the magnetic resonance imaging (MRI) findings of PEA correlated with computed tomographic (CT) findings. MRI findings included an oval s...
journal_title：Magnetic resonance imaging
pub_type： 杂志文章
doi：10.1016/s0730-725x(02)00478-2
更新日期：2002-01-01 00:00:00
abstract：:Quantitative longitudinal brain magnetic resonance (MR) studies may be confounded by scanner-related drifts in voxel sizes. Total intracranial volume (TIV) normalisation is commonly used to correct serial cerebral volumetric measurements for these drifts. We hypothesised that automated rigid-body registration of whole...
journal_title：Magnetic resonance imaging
pub_type： 杂志文章
doi：10.1016/j.mri.2004.01.057
更新日期：2004-09-01 00:00:00
