Abstract:
:A 3.0 Tesla, 0.80-m bore magnet replaced our previous 1.9 Tesla, 0.76-m magnet. The 3.0 Tesla replacement magnet had a dipole moment of 1.7 with respect to that of the 1.9 Tesla magnet. The pre-existing cylindrically symmetric passive steel shielding was modified to confine the fringe fields of the replacement magnet to match those of the previous magnet. A cylindrically symmetric inner shield insert of about 20,000 kg was designed, fabricated, and installed. Upon energization of the magnet, the combined shielding met all design criteria. Alternative designs, optimization of cylindrically symmetric designs, and costs of fabrication, are presented herein.
journal_name
Magn Reson Medjournal_title
Magnetic resonance in medicineauthors
Ewing JR,Warner R,Helpern JAdoi
10.1002/mrm.1910290319subject
Has Abstractpub_date
1993-03-01 00:00:00pages
398-401issue
3eissn
0740-3194issn
1522-2594journal_volume
29pub_type
杂志文章abstract:PURPOSE:To achieve rapid, high resolution whole-brain gray matter (GM) imaging by developing a novel, single-slab three-dimensional dual-echo fast-spin-echo pulse sequence and GM-selective reconstruction. METHODS:Unlike conventional GM imaging that uses time-consuming double-inversion-recovery preparation, the propose...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.26910
更新日期:2017-11-01 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::Leakage of Gd-DTPA through a defective blood-brain barrier is measured quantitatively using dynamic MRI scanning, in which repeated scans are made after a bolus injection. Image registration artifacts are minimized; a dose of 0.1 mM/kg and an IR sequence enable enhancement to be measured quantitatively. The triexponen...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.1910170208
更新日期:1991-02-01 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::In MRI, imaging using receiving coil arrays with a large number of elements is an area of growing interest. With increasing channel numbers for parallel acquisition, longer reconstruction times have become a significant concern. Channel reduction techniques have been proposed to reduce the processing time of channel-b...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.23048
更新日期:2012-03-01 00:00:00
abstract::Evaluation of water diffusion in the brain has revealed both fast- and slow-diffusing water populations. It has been suggested that these populations represent extra- and intracellular water, respectively. We have identified and characterized both populations in the intracellular space of the Xenopus oocyte. We have a...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.10301
更新日期:2002-11-01 00:00:00
abstract::Sinusoidal capillarization induces microcirculatory changes in liver cirrhosis and fibrosis. The purpose of this study was to assess whether contrast-enhanced MRI can be used to demonstrate the effects of sinusoidal capillarization in liver fibrosis. Dynamic MRI after injection of a low-molecular-weight contrast agent...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.10420
更新日期:2003-04-01 00:00:00
abstract::Magnetic field homogeneity is of major concern for in vivo spectroscopy, and with the increased use of volumetric chemical shift imaging (CSI) techniques, the ability to shim over a large volume of tissue is now one of the primary limiting constraints in performing these studies. In vivo shimming is routinely performe...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.1910400307
更新日期:1998-09-01 00:00:00
abstract::The purpose of this study is to examine the usefulness of histogram analysis combined with vessel size index (VSI) magnetic resonance imaging for the specific characterization of brain tumor microvasculature in a panel of six volume-matched glioma xenografts. Using a simple descriptive histogram analysis, significant ...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.22675
更新日期:2011-03-01 00:00:00
abstract:PURPOSE:Banding artifacts in images acquired by balanced steady-state free precession (bSSFP) remain a challenge in MRI as they considerably reduce image quality, and diagnostic value deteriorates accordingly. As the steady-state tolerates small shifts in frequency, it is possible to acquire frequency-modulated bSSFP. ...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.26630
更新日期:2017-12-01 00:00:00
abstract::Tumor pH is physiologically important since it influences a number of processes relevant to tumorigenesis and therapy. Hence, knowledge of localized pH within tumors would contribute to understanding these processes. The destructiveness, poor spatial resolution, and poor signal-to-noise ratio (SNR) of current technolo...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/(sici)1522-2594(199904)41:4<743::aid-mrm13
更新日期:1999-04-01 00:00:00
abstract::Coronal proton and sodium images of control rats and rats with either increased permeability edema produced by intravenous alloxan (300 mg/kg) or increased pressure edema produced by saline infusion (2 ml/min) were obtained. Axial chest CT images were used to monitor the development of pulmonary edema. Immediately aft...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.1910060403
更新日期:1988-04-01 00:00:00
abstract::The advantages of electron paramagnetic resonance (EPR) imaging at L-band frequencies are discussed. The construction and calibration of a low-field L-band EPR imaging spectrometer is described with capillary phantoms containing aqueous nitroxides as paramagnetic imaging agents. The peak separation induced by the magn...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.1910020310
更新日期:1985-06-01 00:00:00
abstract::Parallel magnetic resonance imaging in k-space such as generalized auto-calibrating partially parallel acquisition exploits spatial correlation among neighboring signals over multiple coils in calibration to estimate missing signals in reconstruction. It is often challenging to achieve accurate calibration information...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.23188
更新日期:2012-06-01 00:00:00
abstract::Comparative NMR studies of normal and pathologically altered human stomach tissues were performed on the basis of proton T1 relaxation time measurements in the presence of high external concentrations of relaxation (contrast) agents manganese ethylenediaminetetraacetic acid (Mn-EDTA) and gadolinium diethylenetriaminep...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.1910150313
更新日期:1990-09-01 00:00:00
abstract::An approach to efficiently measure three-dimensional velocity vector fields and turbulent kinetic energy of blood flow is presented. Multipoint phase-contrast imaging is used in combination with Bayesian analysis to map both mean and fluctuating velocities over a large dynamic range and for practically relevant signal...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.24370
更新日期:2013-05-01 00:00:00
abstract:PURPOSE:To investigate whether nonlinear dimensionality reduction improves unsupervised classification of (1) H MRS brain tumor data compared with a linear method. METHODS:In vivo single-voxel (1) H magnetic resonance spectroscopy (55 patients) and (1) H magnetic resonance spectroscopy imaging (MRSI) (29 patients) dat...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.25447
更新日期:2015-09-01 00:00:00
abstract:PURPOSE:A new method, called Transmit and Receive Patterns from Low-Tip-angle gradient-Echo Images (TRIPLET), is described which simultaneously maps the B1+ and B1- fields of a transmit/receive radiofrequency coil array. The input data are low-tip-angle gradient-echo images, which can be acquired in a relatively short ...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.24912
更新日期:2014-07-01 00:00:00
abstract:PURPOSE:To quantify chemical exchange saturation transfer contrast in upper extremities of participants with lymphedema before and after standardized lymphatic mobilization therapy using correction procedures for B0 and B1 heterogeneity, and T1 relaxation. METHODS:Females with (n = 12) and without (n = 17) breast canc...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.28031
更新日期:2020-05-01 00:00:00
abstract::Imaging delayed hyperenhancement of myocardial infarction is most commonly performed using an inversion recovery (IR) prepared 2D breathhold segmented k-space gradient echo (FGRE) sequence. Since only one slice is acquired per breathhold in this technique, 12-16 successive breathholds are required for complete anatomi...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.20061
更新日期:2004-05-01 00:00:00
abstract:PURPOSE:To accelerate whole-heart three-dimension MR angiography (MRA) by using a variable-density Poisson-disc undersampling pattern and a compressed sensing (CS) reconstruction algorithm, and compare the results with sensitivity encoding (SENSE). METHODS:For whole-heart MRA, a prospective variable-density Poisson-di...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.26730
更新日期:2018-02-01 00:00:00
abstract:PURPOSE:To investigate previously unreported effects of signal drift as a result of temporal scanner instability on diffusion MRI data analysis and to propose a method to correct this signal drift. METHODS:We investigated the signal magnitude of non-diffusion-weighted EPI volumes in a series of diffusion-weighted imag...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.26124
更新日期:2017-01-01 00:00:00
abstract::Cerebral metabolite concentrations and water content were measured by means of localized proton magnetic resonance spectroscopy in 50 children, while metabolite peak ratios in short echo time spectra were evaluated in 173 examinations. Normative curves for normal development were established for two cerebral locations...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.1910300405
更新日期:1993-10-01 00:00:00
abstract:PURPOSE:Because of short signal lifetimes and respiratory motion, 3D lung MRI is still challenging today. Zero-TE (ZTE) pulse sequences offer promising solutions as they overcome the issue of short T 2 ∗ ...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.28483
更新日期:2021-02-01 00:00:00
abstract::Transparent pulses are defined by the property of having no net effect on stationary spins, while selectively nutating and dephasing flowing spins. They are derived from the inverse scattering transform, a nonlinear extension of the inverse Fourier transform. They can be used as presaturation pulses to suppress select...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.1910240212
更新日期:1992-04-01 00:00:00
abstract:PURPOSE:For the application of compressive sensing to parallel MRI, Poisson disk sampling (PDS) has been shown to generate superior results compared with random sampling methods. However, due to its limited flexibility to incorporate additional constraints, PDS is not readily extendible to dynamic applications. Here, w...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.25507
更新日期:2015-11-01 00:00:00
abstract::The mechanism behind previously observed changes in the apparent diffusion coefficient (ADC) during brain activation is not well understood. Therefore, we investigated the signal source and spatial specificity of functional magnetic resonance imaging (fMRI) ADC changes systematically in the visual cortex of cats using...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.21074
更新日期:2006-12-01 00:00:00
abstract::Magnetic resonance imaging has achieved clinical importance and has become the primary tool in the investigation of head, spinal cord, pelvis, cancellous bone, pericardium (with gating), gallbladder, lymph node masses, and very soon, in the evaluation of joints. In many areas, particularly with respiratory and ECG gat...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章,评审
doi:10.1002/mrm.1910020402
更新日期:1985-08-01 00:00:00
abstract:PURPOSE:To investigate the relative gain in sensitivity of five histology coils designed in-house to accommodate tissue sections of various sizes and compare with commercial mouse head coils. METHODS:The coil set was tailored to house tissue sections ranging from 5 to1000 µm encased in either glass slides or coverslip...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.24841
更新日期:2014-05-01 00:00:00
abstract::Images of hyperpolarized 3He were acquired during breath-hold in four healthy volunteers with the use of an optimized 3D gradient-echo sequence. The images were compared with existing 2D gradient-echo methods. The average SNR from a 13-mm-thick slice in the peripheral lung was 1.4 times greater with 3D. In the airways...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.20164
更新日期:2004-09-01 00:00:00