Abstract:
:A method is presented that improves the effectiveness of RF-spoiling whenever an image consists of the averaging of several identical single acquisitions. Using this method, it becomes possible to reduce the necessary moment of the spoiler gradient by a factor equal to the number of averages. The idea is to perform the collection of k-space lines such that the averaging takes over a part of the spoiling process. The number of sequence cycles played out between two acquisitions of a certain k-space line is adjusted based on both the number of total averages of this line and the phase-cycling pattern of the RF-pulse train of a RF-spoiled gradient echo sequence. In this way, ghost artifacts visible in the single images add to zero in the averaged image while the depiction of the object experiences normal averaging with enhanced signal-to-noise ratio.
journal_name
Magn Reson Medjournal_title
Magnetic resonance in medicineauthors
Leupold J,Hennig Jdoi
10.1002/mrm.22882subject
Has Abstractpub_date
2011-10-01 00:00:00pages
1123-8issue
4eissn
0740-3194issn
1522-2594journal_volume
66pub_type
杂志文章abstract::A radiofrequency (RF) time-domain electron paramagnetic resonance (EPR) instrument operating at 300, 600, and 750 MHz was used to image tumor hypoxia with high spatial and temporal resolution. A high-speed signal-averaging Peripheral Component Interconnect (PCI) board with flexibility in the input signal level and the...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.21194
更新日期:2007-04-01 00:00:00
abstract::The fate of the 13C label arising from [U-13C]succinate in rabbit renal proximal convoluted tubular (PCT) cells, incubated with [U-13C]succinate, was investigated by 13C NMR spectroscopy of the perchloric acid extracts of the cell pellets. The 13C label of [U-13C]succinate was predominantly metabolized into glutamate,...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.1910140114
更新日期:1990-04-01 00:00:00
abstract::Iron-mediated tissue damage is present in cerebrovascular and neurodegenerative diseases and neurotrauma. Brain microbleeds are often present in these maladies and are assuming increasing clinical importance. Because brain microbleeds present a source of pathologic iron to the brain, the noninvasive quantification of ...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.22185
更新日期:2010-01-01 00:00:00
abstract:PURPOSE:Single-scan two-dimensional MRI has been generally constrained to acquisitions in high quality magnets. This study introduces a methodology, cross-term spatiotemporal encoding (xSPEN), that delivers such images under much poorer external field conditions. METHODS:xSPEN departs from conventional k-space scannin...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.26145
更新日期:2017-02-01 00:00:00
abstract::The suppression of water signals in in vivo proton spectra by means of multiple-quantum filtering can be brought about in several ways. This communication exposes the shortcomings of using purely subtractive filtering techniques to observe signals from metabolites that contain proton couplings of the form AX3. ...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.1910110314
更新日期:1989-09-01 00:00:00
abstract:PURPOSE:A method for the quantification of perfusion in murine myocardium is demonstrated. The method allows for the reconstruction of perfusion maps on arbitrary time points in the heart cycle while addressing problems that arise due to the irregular heart beat of mice. METHODS:A flow-sensitive alternating inversion ...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.25526
更新日期:2015-12-01 00:00:00
abstract::The authors describe a method for accurate in vivo multislice imaging of the active component of the B1 field which is based on a previously proposed method, which uses the signal intensity ratio of two images measured with different excitation angles, and a repetition time TR 5 > or = 5 T1. The new method essentially...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.1910350217
更新日期:1996-02-01 00:00:00
abstract::The most widely-used functional magnetic resonance imaging (fMRI) technique is based on the blood oxygenation level dependent (BOLD) effect, which requires at least partial uncoupling between cerebral blood flow (CBF) and oxygen consumption changes during increased mental activity. To compare BOLD and CBF effects duri...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.1910380110
更新日期:1997-07-01 00:00:00
abstract:PURPOSE:To introduce a new outer volume suppression (OVS) technique that uses a single pulse and rotating gradients to accomplish frequency-swept excitation. This new technique, which is called gradient rotating outer volume excitation (GROOVE), produces a circular or elliptical suppression band rather than suppressing...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.25101
更新日期:2015-01-01 00:00:00
abstract::Parallel imaging reconstructions result in spatially varying noise amplification characterized by the g-factor, precluding conventional measurements of noise from the final image. A simple Monte Carlo based method is proposed for all linear image reconstruction algorithms, which allows measurement of signal-to-noise r...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.21728
更新日期:2008-10-01 00:00:00
abstract:PURPOSE:Diabetic nephropathy (DN) is the leading cause of renal failure; however, current clinical tests are insufficient for assessing this disease. DN is associated with changes in renal metabolites, so we evaluated the utility of chemical exchange saturation transfer (CEST) imaging to detect changes characteristic o...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.26045
更新日期:2016-11-01 00:00:00
abstract:PURPOSE:In this study, an iterative k-t principal component analysis (PCA) algorithm with nonrigid frame-to-frame motion correction is proposed for dynamic contrast-enhanced three-dimensional perfusion imaging. METHODS:An iterative k-t PCA algorithm was implemented with regularization using training data corrected for...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.24894
更新日期:2014-07-01 00:00:00
abstract::For MR applications such as contrast-enhanced MR angiography, it is desirable to achieve simultaneously high spatial and temporal resolution. The current clinical standard uses view-sharing methods combined with parallel imaging; however, this approach still provides limited spatial and temporal resolution. To improve...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.22814
更新日期:2011-08-01 00:00:00
abstract::Regional values of fractional anisotropy (FA) and mean diffusivity (D(av)) of in vivo and excised rat spinal cords were measured using an iscosahedral encoding scheme that is based on 21 uniformly distributed and alternating gradient directions with an echo planar imaging (EPI) readout. Based on the water phantom stud...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.20304
更新日期:2005-01-01 00:00:00
abstract::Dual labeled liposomes, carrying both paramagnetic and fluorescent lipids, were recently proposed as potent contrast agents for MR molecular imaging. These nanoparticles are coated with poly(ethylene glycol) (PEG) to increase their blood circulation half-life, which should allow extensive accumulation at the targeted ...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.21780
更新日期:2008-12-01 00:00:00
abstract::The reconstruction of non-Cartesian k-space trajectories often requires the estimation of nonuniform sampling density. Particularly for 3D, this calculation can be computationally expensive. The method proposed in this work combines an iterative algorithm previously proposed by Pipe and Menon (Magn Reson Med 1999;41:1...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.23041
更新日期:2012-03-01 00:00:00
abstract:PURPOSE:Despite the increasing understanding of major depressive disorder (MDD) using neuroimaging techniques, the topological organization of anatomical networks underlying MDD remains unclear. METHODS:The topological organization of brain anatomical networks was explored using complex network approaches. Diffusion t...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.25036
更新日期:2014-11-01 00:00:00
abstract::Wavelet packet analysis is a mathematical transformation that can be used to post-process images, for example, to remove image noise ("denoising"). At a very low signal-to-noise ratio (SNR <5), standard magnitude magnetic resonance images have skewed Rician noise statistics that degrade denoising performance. Since th...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/(sici)1522-2594(199903)41:3<631::aid-mrm29
更新日期:1999-03-01 00:00:00
abstract:PURPOSE:To characterize the q-space truncation and sampling on the spin-displacement probability density function (PDF) in diffusion spectrum imaging (DSI). METHODS:DSI data were acquired using the MGH-USC connectome scanner (Gmax = 300 mT/m) with bmax = 30,000 s/mm2 , 17 × 17 × 17, 15 × 15 × 15 and 11 × 11 × 11 gri...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.26071
更新日期:2016-12-01 00:00:00
abstract::The hypothesis was tested that the intravoxel distribution of water diffusion rates, as measured with a stretched-exponential model of diffusion-weighted imaging (DWI), is a marker of brain tumor invasion. Eight rats underwent intracerebral inoculation of C6 glioma cells. In three rats, cells were labeled with a fluor...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.20286
更新日期:2004-11-01 00:00:00
abstract:PURPOSE:To measure the apparent diffusion coefficients (ADC) of five main metabolites in the human brain at 3T with PRESS and STEAM, avoiding measurement biases because of cross-terms. Cross-terms arise from interactions between slice-selection and spoiler gradients in the localized spectroscopy sequence and the diffus...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.26969
更新日期:2018-06-01 00:00:00
abstract::To detect perfusion abnormalities in areas of high magnetic susceptibility in the brain, an arterial spin-labeling MRI technique utilizing flow-sensitive alternating inversion recovery (FAIR) and half-Fourier single shot turbo spin-echo (HASTE) for spin preparation and image acquisition, respectively, was developed. I...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/1522-2594(200103)45:3<431::aid-mrm1056>3.0
更新日期:2001-03-01 00:00:00
abstract::Techniques are described for the (31)P NMR analysis of glycerophospholipid (PL) headgroup and molecular species in brain. The (31)P NMR spectrum of PLs from human temporal cortex, solubilized in aqueous Na cholate, typically showed 3 major resonances, assigned to phosphatidylcholine (PC) molecular species containing 0...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/1522-2594(200008)44:2<215::aid-mrm8>3.0.co
更新日期:2000-08-01 00:00:00
abstract::Rapid flow imaging was achieved with a partial field of view (pFOV) spiral motion-encoded technique. The FOV and the acquisition time were reduced by a factor of 2 by undersampling k-space. The pFOV spiral k-space trajectory aliased signals from outside a circular ring whose radius was inversely proportional to the di...
journal_title:Magnetic resonance in medicine
pub_type: 临床试验,杂志文章
doi:10.1002/mrm.20975
更新日期:2006-09-01 00:00:00
abstract::Diffusion-weighted imaging suffers from motion artifacts and relatively low signal quality due to the long echo times required to permit the diffusion encoding. We investigated the inclusion of a noncylindrical fourth gradient coil, dedicated entirely to diffusion encoding, into the imaging system. Standard three-axis...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.22971
更新日期:2011-12-01 00:00:00
abstract::A method is presented for the detection of quadrupole splitting in tissue, where the spectral line splittings are typically unobservable. The method used is a study of the rate of rotation of the flip angle as a function of radiofrequency (rf) amplitude. Our results with samples of skeletal muscle and cat brain indica...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.1910040108
更新日期:1987-01-01 00:00:00
abstract::To quantify metabolite and cation concentrations using NMR spectroscopy, the volumes of intracellular and extracellular spaces must be known. We describe a simple 31P NMR spectroscopic method that employs dimethyl methylphosphonate (DMMP) as a marker of total water space and phenylphosphonate (PPA) as a marker of extr...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.1910320206
更新日期:1994-08-01 00:00:00
abstract::Recently, a technique based on arterial spin labeling, called dynamic arterial spin labeling (DASL (Magn Reson Med 1999;41:299-308)), has been introduced to measure simultaneously the transit time of the labeled blood from the labeling plane to the exchange site, the longitudinal relaxation time of the tissue, and the...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.1136
更新日期:2001-06-01 00:00:00
abstract:PURPOSE:To demonstrate the feasibility of imaging the first passage of a bolus of hyperpolarized (13)C urea through the rodent heart using flow-sensitizing gradients to reduce signal from the blood pool. METHODS:A flow-sensitizing bipolar gradient was optimized to reduce the bright signal within the cardiac chambers, ...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.25713
更新日期:2016-04-01 00:00:00
abstract::When developing new techniques for NMR imaging and in vivo spectroscopy it is a major advantage to be able to calculate the magnetization slice profiles, at any point during a pulse sequence in the presence of a field gradient. While this has frequently been done by treating the problem as a number of discrete resonan...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.1910050511
更新日期:1987-11-01 00:00:00