Abstract:
:It is demonstrated that the stability of the Carr-Purcell-Meiboom-Gill (CPMG) sequence reflects the existence of a steady state solution to the Bloch equations in the absence of T2 and T1 decay. The steady state theory is then used to evaluate the performance of low flip angle RARE imaging sequences with both constant and optimally varied refocusing flip angles. The theory is experimentally verified in phantoms and then optimized, single shot, low flip angle RARE is used to obtain artifact-free images from the brain of a normal volunteer.
journal_name
Magn Reson Medjournal_title
Magnetic resonance in medicineauthors
Alsop DCdoi
10.1002/mrm.1910370206subject
Has Abstractpub_date
1997-02-01 00:00:00pages
176-84issue
2eissn
0740-3194issn
1522-2594journal_volume
37pub_type
杂志文章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:PURPOSE:We aimed to develop a novel free-breathing cardiac diffusion tensor MRI (DT-MRI) approach, M2-MT-MOCO, capable of whole left ventricular coverage that leverages second-order motion compensation (M2) diffusion encoding and multitasking (MT) framework to efficiently correct for respiratory motion (MOCO). METHODS...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.28611
更新日期:2020-11-30 00:00:00
abstract::NMR relaxation times (T1 and T2) and the water content (WC) of in vitro rat lungs were measured during the course of endotoxin lung injury in rats. Measurements of normal lungs, untreated endotoxin-injured lungs, and endotoxin-injured lungs treated with methylprednisolone (MPSL) were compared. The untreated endotoxin ...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.1910150204
更新日期:1990-08-01 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:To determine whether neurochemical concentrations obtained at two MRI sites using clinical 3T scanners can be pooled when a highly optimized, nonvendor short-echo, single-voxel proton MRS pulse sequence is used in conjunction with identical calibration and quantification procedures. METHODS:A modified semi-LAS...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.25295
更新日期:2015-05-01 00:00:00
abstract:PURPOSE:Magnetic resonance imaging (MRI)-based techniques for assessing liver iron concentration (LIC) have been limited by single scanner calibration against biopsy. Here, the calibration of spin-density projection-assisted (SDPA) R2-MRI (FerriScan®) in iron-overloaded β-thalassemia patients treated with the iron chel...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章,多中心研究
doi:10.1002/mrm.24854
更新日期:2014-06-01 00:00:00
abstract:PURPOSE:Magnetic resonance imaging is a promising alternative to computed tomography for lung imaging. However, organ motion and poor signal-to-noise ratio, arising from short T2*, impair image quality. To alleviate these issues, a new retrospective gating method was implemented and tested with an ultra-short echo time...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.26891
更新日期:2018-04-01 00:00:00
abstract::Parallel imaging presents a promising approach for MRI of hyperpolarized nuclei, as the penalty in signal-to-noise ratio typically encountered with (1)H MRI due to a reduction in acquisition time can be offset by an increase in flip angle. The signal-to-noise ratio of hyperpolarized MRI generally exhibits a strong dep...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.22962
更新日期:2011-12-01 00:00:00
abstract::Quantification of peak velocity is important in the assessment of stenotic flow jets in patients with congenital heart disease. Phase-contrast magnetic resonance underestimates peak velocities. Hence, clinically Doppler ultrasound is used as the reference standard for assessing stenoses. It is possible to accurately m...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.24293
更新日期:2012-06-01 00:00:00
abstract:PURPOSE:To evaluate the use of variable flip angle refocusing pulse trains in single-shot three-dimensional gradient and spin-echo (3D-GRASE) to reduce blurring and increase the spatial coverage for high spatial resolution T2 -weighted functional MRI at 7 Tesla. METHODS:Variable flip angle refocusing schemes in 3D-GRA...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.25979
更新日期:2016-09-01 00:00:00
abstract::Multiple receivers can be utilized to enhance the spatiotemporal resolution of MRI by employing the parallel imaging technique. Previously, we have reported the L-curve Tikhonov regularization technique to mitigate noise amplification resulting from the geometrical correlations between channels in a coil array. Nevert...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.21356
更新日期:2007-10-01 00:00:00
abstract::High polarization of nuclear spins in liquid state through hyperpolarized technology utilizing dynamic nuclear polarization has enabled the direct monitoring of (13)C metabolites in vivo at a high signal-to-noise ratio. Acquisition time limitations due to T(1) decay of the hyperpolarized signal require accelerated ima...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.22233
更新日期:2010-02-01 00:00:00
abstract::A pulse sequence is presented for obtaining a single image with combined T1/T2 weighting. T2 relaxation is made to increase intensity, in cooperation with the effect of T1 relaxation, by providing T2 weighting with a 90 degrees-180 degrees-90 degrees driven inversion pulse triplet in an inversion recovery method. Unli...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.1910150307
更新日期:1990-09-01 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:PURPOSE:Applications of dynamic shimming require high field fidelity, and characterizing the shim field dynamics is therefore necessary. Modeling the system as linear and time-invariant, the purpose of this work was to measure the impulse response function with optimal sensitivity. THEORY AND METHODS:Frequency-swept p...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.24934
更新日期:2014-08-01 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:PURPOSE:A direct method of imaging neural activity was simulated to determine typical signal sizes. METHODS:An active bidomain finite-element model was used to estimate approximate perturbations in MR phase data as a result of neural tissue activity, and when an external MR electrical impedance tomography imaging curr...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.27351
更新日期:2019-01-01 00:00:00
abstract::Nuclear Overhauser effect (NOE) enhancements and relaxation times of 31P metabolites in human calf were measured in 12 volunteers (4 men and 8 women) at 1.5 T using a dual tuned four-ring birdcage. The NOE enhancements of inorganic phosphate (Pi), phosphocreatine (PCr), gamma-, alpha-, and beta-nucleoside triphosphate...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.1910330316
更新日期:1995-03-01 00:00:00
abstract::This note considers the anomolous contrast in inversion recovery images produced by NMR scanners if a map of [My] is reconstructed, rather than a map of My'. ...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.1910020110
更新日期:1985-02-01 00:00:00
abstract::Three-dimensional MRI is typically performed with the same orientation for radiofrequency slab excitation and slab select phase encoding. We introduce independent slab excitation and encoding to create a new degree of freedom in three-dimensional MRI, which is the angular relationship between the prescribed excitation...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.23043
更新日期:2012-02-01 00:00:00
abstract::The potential of quantitative parameter images of the relaxation times T1 and T2, the proton density rho and the apparent diffusion coefficient (ADC) to characterize three different experimental rat brain tumors (F98 glioma, RN6 Schwannoma, and E376 neuroblastoma) was studied. All parameter values, as determined in hi...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.1910340608
更新日期:1995-12-01 00:00:00
abstract::A novel multiple quantum filtering method is proposed that uses a doubly selective pulse termed Delays Alternating with Nutations for Tailored Excitation (DANTE) for multiple quantum preparation. This method selectively prepares GABA-3 and GABA-4 into a multiple quantum state and suppresses all other resonances at 3.0...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.10104
更新日期:2002-03-01 00:00:00
abstract:PURPOSE:To demonstrate feasibility of transceive phase mapping with the PLANET method and its application for conductivity reconstruction in the brain. METHODS:Accuracy and precision of transceive phase (ϕ± ) estimation with PLANET, an ellipse fitting approach to phase-cycled balanced steady state free precession (bSS...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.27958
更新日期:2020-02-01 00:00:00
abstract::Quantitative MRI assessment of leukoencephalopathy is difficult because the MRI properties of leukoencephalopathy significantly overlap those of normal tissue. This report describes the use of an automated procedure for longitudinal measurement of tissue volume and relaxation times to quantify leukoencephalopathy. Ima...
journal_title:Magnetic resonance in medicine
pub_type: 临床试验,杂志文章,随机对照试验
doi:10.1002/mrm.10124
更新日期:2002-05-01 00:00:00
abstract::Optimization of experimental settings of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI), like the contrast administration protocol, is of great importance for reliable quantification of the microcirculatory properties, such as the volume transfer-constant K(trans). Using system identification theory an...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.21575
更新日期:2008-05-01 00:00:00
abstract:PURPOSE:Multiple nonlinear gradient fields offer many potential benefits for spatial encoding including reduced acquisition time, fewer artefacts and region-specific imaging, although designing a suitable trajectory for such a setup is difficult. This work aims to optimize encoding trajectories for multiple nonlinear g...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.25859
更新日期:2016-07-01 00:00:00
abstract:PURPOSE:To obviate online slice-by-slice RF shim optimization and reduce B1+ mapping requirements for patient-specific RF shimming in high-field magnetic resonance imaging. THEORY AND METHODS:RF Shim Prediction by Iteratively Projected Ridge Regression (PIPRR) predicts patient-specific, SAR-efficient RF shims with a m...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.27192
更新日期:2018-11-01 00:00:00
abstract::A new fully automatic algorithm for the segmentation of the brain and total intracranial cerebrospinal fluid (CSF) from T(1)-weighted volume MRI scans of the head, called Exbrain v.2, is described. The algorithm was developed in the context of serial intracranial volumetry. A brain mask obtained using a previous versi...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.10436
更新日期:2003-05-01 00:00:00
abstract::Minimally invasive cardiac surgery requires arresting and emptying of the heart, which compromises visualization of the surgical field. In this feasibility study a novel surgical procedure is demonstrated in which real-time MRI is used to guide the placement of a prosthetic aortic valve in the beating heart via direct...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.21044
更新日期:2006-11-01 00:00:00
abstract::Mathematical models are required to estimate kinetic parameters of [1-(13)C] pyruvate-lactate interconversion from magnetic resonance spectroscopy data. One- or two-way exchange models utilizing a hypothetical approximation to the true arterial input function (AIF), (e.g. an ideal 'box-car' function) have been used pr...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.24546
更新日期:2013-10-01 00:00:00