Abstract:
:A gradient technique to measure electron paramagnetic resonance spectra simultaneously at several different locations is described. The technique is based on the use of point probes containing paramagnetic centers. The value of the magnetic field gradient is chosen to be sufficient to separate the EPR signals from the different paramagnetic probes yet at the same time small enough to change only minimally the shape of individual signals. The conditions to apply this technique are considered in detail. When experimental data have a high signal-to-noise ratio, the lineshape distortion induced by the gradient can be corrected with the aid of a known distribution function of paramagnetic centers within the probe. The maximum entropy deconvolution algorithm is successfully applied for the correction of significantly distorted lines. The technique is experimentally tested and applied to measure the concentration of oxygen in hypertrophied rat myocardium and normal rat kidney in vivo by low frequency EPR (L-band, 1.2 GHz). Two types of EPR oxygen-sensitive probes--lithium phthalocyanine crystals and synthetic carbohydrate chars--were used.
journal_name
Magn Reson Medjournal_title
Magnetic resonance in medicineauthors
Smirnov AI,Norby SW,Clarkson RB,Walczak T,Swartz HMdoi
10.1002/mrm.1910300210subject
Has Abstractpub_date
1993-08-01 00:00:00pages
213-20issue
2eissn
0740-3194issn
1522-2594journal_volume
30pub_type
杂志文章abstract:PURPOSE:Spectrally selective "prewinding" radiofrequency pulses can counteract B0 inhomogeneity in steady-state sequences, but can only prephase a limited range of off-resonance. We propose spectral-spatial small-tip angle prewinding pulses that increase the off-resonance bandwidth that can be successfully prephased by...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.26794
更新日期:2018-03-01 00:00:00
abstract:PURPOSE:The purpose of this project was to construct a physical brain phantom for MRI, mimicking structure and T1 relaxation properties of white matter (WM) and gray matter (GM). METHODS:The phantom design comprised 2 compartments, 1 resembling the WM and 1 resembling the GM. Their T1 relaxation times, as assessed usi...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.27464
更新日期:2019-02-01 00:00:00
abstract::We used high-field (13)C NMR (18.8 T) to assign unambiguously the isotopic shifts induced by the deuterium substitutions of the H3(proR) and H3(proS) hydrogens of (2-(13)C) glutamate in extracts of the brain from deuterated animals. Monodeuterated H3R or H3S glutamate diastereoisomers were produced stereospecifically ...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.22277
更新日期:2010-04-01 00:00:00
abstract::Variations in T(1ρ) with locking-field strength (T(1ρ) dispersion) may be used to estimate proton exchange rates. We developed a novel approach utilizing the second derivative of the dispersion curve to measure exchange in a model system of cross-linked polyacrylamide gels. These gels were varied in relative compositi...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.22947
更新日期:2011-12-01 00:00:00
abstract::A technique for reconstructing dynamic undersampled MRI data, termed "x-f choice," was developed and applied to dynamic contrast-enhanced MR angiography (DCE-MRA). Regular undersampling in k-t space (a hybrid of k-space and time) creates aliasing in the conjugate x-f space that must be resolved. When regions in the ob...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.21008
更新日期:2006-10-01 00:00:00
abstract::The accurate assessment of pulmonary perfusion is especially important in the evaluation of patients with suspected pulmonary embolism, a common and potentially lethal disorder that can be treated by aggressive anticoagulation. In this study, we demonstrate for the first time the use of MR to image pulmonary perfusion...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.1910360402
更新日期:1996-10-01 00:00:00
abstract::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 anis...
journal_title:Magnetic resonance in medicine
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doi:10.1002/mrm.21925
更新日期:2009-04-01 00:00:00
abstract::Among previous analyses of the steady-state free-precession (SSFP) signal in rapid MRI, one treatment resulted in equations that require the evaluation of infinite binomial series. Here, an analytical solution is derived by a transformation into the power series expansion of the derivative of the inverse sine function...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.10410
更新日期:2003-04-01 00:00:00
abstract:PURPOSE:MR fingerprinting (MRF) is a technique for quantitative tissue mapping using pseudorandom measurements. To estimate tissue properties such as T1 , T2 , proton density, and B0 , the rapidly acquired data are compared against a large dictionary of Bloch simulations. This matching process can be a very computation...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.25439
更新日期:2015-08-01 00:00:00
abstract::Experiments have been performed to demonstrate and quantify cross-relaxation between water and methylene resonances in a simple model system. Inversion recovery experiments on aqueous solutions of polyethylene glycol produce a transient nuclear Overhauser effect that alters the recovery of the methylene resonance. The...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.1910090305
更新日期:1989-03-01 00:00:00
abstract::Dynamic MRI tracking of rat T-cells in vivo is performed in rat testicles after labeling isolated rat T-cells in vitro with superparamagnetic dextran-coated iron-oxide particles, BMS180549. Tissue inflammation induced by the local injection of the calcium ionophore, A23187, is used to attract labeled T-cells. Gradient...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.1910330209
更新日期:1995-02-01 00:00:00
abstract::Volume-localized proton NMR spectroscopy was used to estimate bone marrow cellularity in the posterior iliac crests of patients undergoing treatment with hematopoietic growth factors for a variety of hematologic and neoplastic disorders. Twelve patients were accrued, six of whom were studied more than once, yielding a...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.1910190108
更新日期:1991-05-01 00:00:00
abstract::Chemical shifts were extracted from in vivo 3-dimensional 31P NMR CSI data and pH images were constructed. The images could spatially resolve tissue pH ranging from 5.8 to 7.2 (with uncertainty of 0.11-0.17 pH unit) in an ischemia-reperfusion model of diabetic rat calf muscles. ...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.1910290214
更新日期:1993-02-01 00:00:00
abstract::The combination of a frequency nonselective excitation suppression method (1331 sequence) with selective excitation followed by gradient-induced dephasing of water transverse magnetization yielded suppression ratios of greater than 10,000:1. The need for gradient preemphasis and correction of B0 field shifts is discus...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.1910090114
更新日期:1989-01-01 00:00:00
abstract:PURPOSE:To develop a deep learning-based Bayesian estimation for MRI reconstruction. METHODS:We modeled the MRI reconstruction problem with Bayes's theorem, following the recently proposed PixelCNN++ method. The image reconstruction from incomplete k-space measurement was obtained by maximizing the posterior possibili...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.28274
更新日期:2020-10-01 00:00:00
abstract::Phased-array coils distribute the high signal-to-noise ratio (SNR) performance of their small component surface coils over the larger area covered by the entire array. The inhomogeneous sensitivity profiles of the component surface coils result in images with very high signal near the phased-array and decreased signal...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.1910350419
更新日期:1996-04-01 00:00:00
abstract:PURPOSE:To propose a phase error correction scheme for monopolar time-interleaved multi-echo gradient echo water-fat imaging that allows accurate and robust complex-based quantification of the proton density fat fraction (PDFF). METHODS:A three-step phase correction scheme is proposed to address a) a phase term induce...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.26485
更新日期:2017-09-01 00:00:00
abstract:PURPOSE:Sensitivity encoding (SENSE) reconstruction of multiband echo planar imaging (EPI) may cause artifacts when simultaneously excited slices require different phase correction to remove the EPI-specific ghost shifted by half of the matrix size (N). We propose a simplified solution of this problem that combines SEN...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.25915
更新日期:2016-09-01 00:00:00
abstract:PURPOSE:Develop and test an analytic correction method to correct the signal intensity variation caused by the inhomogeneous reception profile of an eight-channel phased array for hyperpolarized (13) C imaging. THEORY AND METHODS:Fiducial markers visible in anatomical images were attached to the individual coils to pr...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.26042
更新日期:2016-02-01 00:00:00
abstract:PURPOSE:To systematically evaluate the dependence of intravoxel-incoherent-motion (IVIM) parameters on the b-value threshold separating the perfusion and diffusion compartment, and to implement and test an algorithm for the standardized computation of this threshold. METHODS:Diffusion weighted images of the upper abdo...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.25506
更新日期:2015-11-01 00:00:00
abstract:PURPOSE:To perform quantitative susceptibility mapping (QSM) in negligible acquisition time and apply it to measuring iron-rich subcortical gray matter. METHODS:Whole brain QSM was performed using single-shot gradient echo-planar imaging (EPI) in under 7 seconds on a standard 1.5 T system for imaging brain iron in sub...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.25316
更新日期:2015-05-01 00:00:00
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journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.28413
更新日期:2021-01-01 00:00:00
abstract::The concept of temporal echo multiplexing is defined and used to develop rapid biphasic spin-echo sequences for imaging the heart. Three imaging sequences, based on four-echo and two-echo multiplexing and rapid single echo (i.e., conventional spin-echo imaging), are compared. Preliminary results indicate that two-echo...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.1910110109
更新日期:1989-07-01 00:00:00
abstract:PURPOSE:To improve quantification of myocardial blood flow using a fast T1 mapping technique using highly constrained back projection reconstruction (HYPR)-accelerated acquisition. METHODS:A major source of error in the measurement of myocardial blood flow (MBF) using MRI is the nonlinear relationship between image si...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.24958
更新日期:2014-09-01 00:00:00
abstract::The combination of an in-plane B(1) sensitivity encoding (SENSE) technique with a simultaneous multiple-slice B(0) field step technique (multiple-acquisition micro B(0) array (MAMBA)) has produced high scan time reduction factors (R < or = 8). In this study, two slices were acquired simultaneously in combination with ...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.10464
更新日期:2003-06-01 00:00:00
abstract::The equal-phase line (EPL) algorithm is proposed as a means of allowing rapid Fourier transform (FT) reconstruction of MR image data acquired on a non-Cartesian grid. The pixels on the image are grouped according to their positions. The pixels in a group have the same phase in the complex exponential function -exp[j2p...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.10165
更新日期:2002-06-01 00:00:00
abstract::A computer simulation program capable of demonstrating various artifacts, such as image distortion caused by metallic implants in MR imaging, is presented. The structure of the program allows for the implementation of various imaging situations as long as spins only experience weak interaction, i.e., the Bloch equatio...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.1910340418
更新日期:1995-10-01 00:00:00
abstract::This work aimed to investigate the effects of administering Gd-DTPA on the BOLD effect, and to determine the feasibility of using this approach to measure fractional changes in blood volume and blood oxygenation on neuronal activation during a visual paradigm. A linear relationship between cortical R(2)(*) and the int...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.10340
更新日期:2003-01-01 00:00:00
abstract::A 3-T study is presented, comparing the ability of two (1) H spectroscopy pulse sequences, Carr-Purcell point resolved spectroscopy (CPRESS; TE = 45 msec), and conventional PRESS (TE = 35 msec), to separate between groups of 20 normal control (NC) and 20 mild cognitive impairment (MCI) subjects. Both sequences showed ...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.22749
更新日期:2011-06-01 00:00:00
abstract:PURPOSE:Anisotropic transverse R2 (1/T2 ) relaxation of water proton is sensitive to cartilage degenerative changes. The purpose is to develop an efficient method to extract this relaxation metric in clinical studies. METHODS:Anisotropic R2 can be measured inefficiently by standard R2 mapping after removing an isotrop...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.27621
更新日期:2019-06-01 00:00:00