Abstract:
PURPOSE:To improve imaging performance for body MRI with a local transmit array at 10.5T, the geometry of a dipole antenna was optimized to achieve lower peak specific absorption rate (SAR) levels and a more uniform transmit profile. METHODS:Electromagnetic simulations on a phantom were used to evaluate the SAR and B 1 + -performance of different dipole antenna geometries. The best performing antenna (the snake antenna) was simulated on human models in a 12-channel array configuration for safety assessment and for comparison to a previous antenna design. This 12-channel array was constructed after which electromagnetic simulations were validated by B 1 + -maps and temperature measurements. After obtaining approval by the Food and Drug Administration to scan with the snake antenna array, in vivo imaging was performed on 2 volunteers. RESULTS:Simulation results on a phantom indicate a lower SAR and a higher transmit efficiency for the snake antenna compared to the fractionated dipole array. Similar results are found on a human body model: when comparing the trade-off between uniformity and peak SAR, the snake antenna performs better for all imaging targets. Simulations and measurements are in good agreement. Preliminary imaging result were acquired in 2 volunteers with the 12-channel snake antenna array. CONCLUSION:By optimizing the geometry of a dipole antenna, peak SAR levels were lowered while achieving a more uniform transmit field as demonstrated in simulations on a phantom and a human body model. The array was constructed, validated, and successfully used to image 2 individuals at 10.5T.
journal_name
Magn Reson Medjournal_title
Magnetic resonance in medicineauthors
Steensma B,van de Moortele PF,Ertürk A,Grant A,Adriany G,Luijten P,Klomp D,van den Berg N,Metzger G,Raaijmakers Adoi
10.1002/mrm.28297subject
Has Abstractpub_date
2020-11-01 00:00:00pages
2885-2896issue
5eissn
0740-3194issn
1522-2594journal_volume
84pub_type
杂志文章abstract:PURPOSE:To develop histology-informed simulations of diffusion tensor cardiovascular magnetic resonance (DT-CMR) for typical in-vivo pulse sequences and determine their sensitivity to changes in extra-cellular space (ECS) and other microstructural parameters. METHODS:We synthesised the DT-CMR signal from Monte Carlo r...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.27561
更新日期:2019-04-01 00:00:00
abstract::For protons diffusing among a system of magnetic particles, the process by which initial phase coherence is lost depends substantially on particle size. In this article, evidence for three dephasing mechanisms is presented: an incremental process at small particle sizes (motional averaging regime), a discrete process ...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.22966
更新日期:2011-12-01 00:00:00
abstract::When using tracer kinetic modeling to analyze dynamic contrast-enhanced MRI (DCE-MRI) it is necessary to identify an appropriate arterial input function (AIF). The measured AIF is often poorly sampled in both clinical and preclinical MR systems due to the initial rapid increase in contrast agent concentration and the ...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.21959
更新日期:2009-05-01 00:00:00
abstract::Designing multidimensional radiofrequency pulses for clinical application must take into account the local specific absorption rate (SAR) as controlling the global SAR does not guarantee suppression of hot spots. The maximum peak SAR, averaged over an N grams cube (local NgSAR), must be kept under certain safety limit...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.23049
更新日期:2012-03-01 00:00:00
abstract:PURPOSE:The aim of this work was to quantify the extent of lipid-rich necrotic core (LRNC) and intraplaque hemorrhage (IPH) in atherosclerotic plaques. METHODS:Patients scheduled for carotid endarterectomy underwent four-point Dixon and T1-weighted magnetic resonance imaging (MRI) at 3 Tesla. Fat and R2* maps were gen...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.26359
更新日期:2017-07-01 00:00:00
abstract::Phase-contrast MRI can provide high-resolution angiographic velocity images, especially in conjunction with non-Cartesian k-space sampling. However, acquisitions can be sensitive to errors from artifacts from main magnetic field inhomogeneities and chemical shift from fat. Particularly in body imaging, fat content can...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.22355
更新日期:2010-06-01 00:00:00
abstract::Measurement of myocardial and brain perfusion when using exogenous contrast agents (CAs) such as gadolinium-DTPA (Gd-DTPA) and MRI is affected by the diffusion of water between compartments. This water exchange may have an impact on signal enhancement, or, equivalently, on the longitudinal relaxation rate, and could t...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.1188
更新日期:2001-08-01 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::A MultiEcho Segmented EPI with z-shimmed BAckground gradient Compensation (MESBAC) pulse sequence is proposed and validated for functional MRI (fMRI) study in regions suffering from severe susceptibility artifacts. This sequence provides an effective tradeoff between spatial and temporal resolution and reduces image d...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.10219
更新日期:2002-08-01 00:00:00
abstract:PURPOSE:It has been shown, theoretically and in vivo, that using the Stejskal-Tanner pulsed-gradient, or linear tensor encoding (LTE), and in tissue exhibiting a "stick-like" diffusion geometry, the direction-averaged diffusion-weighted MRI signal at high b-values ( ...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.28191
更新日期:2020-09-01 00:00:00
abstract:PURPOSE:To develop and evaluate a neural network-based method for Gibbs artifact and noise removal. METHODS:A convolutional neural network (CNN) was designed for artifact removal in diffusion-weighted imaging data. Two implementations were considered: one for magnitude images and one for complex images. Both models we...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.28395
更新日期:2021-01-01 00:00:00
abstract::Assuming that the SSFP magnetization response maintains a steady state which is periodic in the presence of diffusion, we can solve for the diffusion effect in such sequences. Formulating a Fourier series decomposition solution to the Bloch-Torrey equation and imposing the steady-state condition, analytical expression...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.1910190209
更新日期:1991-06-01 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: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::Gadobutrol (Gd-Bt; Gadovist(R), Schering AG) is a 1-M Gadolinium (Gd)-based contrast agent. Its higher Gd concentration allows for reduction of injection volumes in first pass contrast-enhanced MR angiography (CE-MRA) and should increase bolus sharpness and image quality. However, ambivalent results were reported. In ...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.21345
更新日期:2008-01-01 00:00:00
abstract::This study characterizes gains in sensitivity and spectral resolution of proton echo-planar spectroscopic imaging (PEPSI) with increasing magnetic field strength (B(0)). Signal-to-noise ratio (SNR) per unit volume and unit time, and intrinsic linewidth (LW) of N-acetyl-aspartate (NAA), creatine (Cr), and choline (Cho)...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.21067
更新日期:2006-12-01 00:00:00
abstract:PURPOSE:Magnetic susceptibility is a physical property of matter that varies depending on chemical composition and abundance of different molecular species. Interest is growing in mapping of magnetic susceptibility in the human brain using magnetic resonance imaging techniques, but the influences affecting the mapped v...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.26281
更新日期:2017-05-01 00:00:00
abstract:PURPOSE:Quantitative susceptibility mapping can be performed through the minimization of a function consisting of data fidelity and regularization terms. For data consistency, a Gaussian-phase noise distribution is often assumed, which breaks down when the signal-to-noise ratio is low. A previously proposed alternative...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.27073
更新日期:2018-08-01 00:00:00
abstract::Hyperpolarized gases ((129)Xe and (3)He) are being used increasingly in both MRI and NMR spectroscopy studies. However, it has been shown that carrier agents are required to preserve the long relaxation times of gases in biological fluids. Optimized gas transport can be achieved through controlled T(1) and T(2) measur...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.10476
更新日期:2003-06-01 00:00:00
abstract:PURPOSE:To present a time-efficient technique for banding reduction in balanced steady-state free precession (bSSFP) imaging using phase-cycled simultaneous multislice (SMS) acquisition with CAIPIRINHA (controlled aliasing in parallel imaging results in higher acceleration). THEORY:The proposed technique exploits the ...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.26076
更新日期:2016-12-01 00:00:00
abstract::The ability to directly detect neuronal magnetic fields by MRI would help investigators achieve the "holy grail" of neuroimaging, namely both high spatial and temporal resolution. Both positive and negative findings have been reported in the literature, with no clear consensus as to the feasibility of direct detection...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.21129
更新日期:2007-02-01 00:00:00
abstract::Advances in modern magnetic resonance imaging (MRI) pulse sequences have enabled clinically practical cortical bone imaging. Human cortical bone is known to contain a distribution of T(1) and T(2) components attributed to bound and pore water, although clinical imaging approaches have yet to discriminate bound from po...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.24186
更新日期:2012-12-01 00:00:00
abstract::The spin-lattice relaxation time T1 of multicomponent tissues is often determined by fitting relaxation data to monoexponential functions. This process can lead to large errors in the relaxation time. We describe a procedure using chemical-shift imaging (CSI) which separates the NMR signal into water and lipid compone...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.1910130307
更新日期:1990-03-01 00:00:00
abstract::A modified inversion-recovery sequence is introduced which performs subtraction angiography by varying time-of-flight effects of blood flowing into an imaged slab. The selective 180 degrees excitation inverts different regions between measurements to isolate arterial and/or venous blood. On normal human subjects, high...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.1910040214
更新日期:1987-02-01 00:00:00
abstract::A cerebrospinal fluid (CSF)-suppressed flow-attenuated inversion recovery (FLAIR) double-shot diffusion echo-planar imaging (EPI) sequence was developed and used, along with a non-CSF-suppressed version of the sequence, to determine the extent of the contribution of CSF partial-volume averaging to the apparent diffusi...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.1910370117
更新日期:1997-01-01 00:00:00
abstract::A novel method for reducing the rf power requirements of selective pulses employed for z magnetization slice inversion in localized NMR spectroscopy is presented. Following slice preparation by the use of frequency-incremented sinc pulses, the slice gradient is reduced, which narrows the frequency width of the slice. ...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.1910050610
更新日期:1987-12-01 00:00:00
abstract::A multimodal MR study including relaxometry, diffusion tensor imaging (DTI), and MR spectroscopy was performed on patients with classical phenylketonuria (PKU) and matched controls, to improve our understanding of white matter (WM) lesions. Relaxometry yields information on myelin loss or malformation and may substant...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.21422
更新日期:2007-12-01 00:00:00
abstract::In active catheter tracking, small RF coils are attached to the catheter for localization. For interactive catheter steering at vessel branchings, it is necessary to visualize not only a single point near the catheter tip but also the entire shape and orientation of the catheter's distal end. Therefore, a 35-mm-long t...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.20108
更新日期:2004-07-01 00:00:00
abstract::Phosphorus-31 nuclear magnetic resonance spectroscopy (31P NMR) was used to assess the temporal changes of high-energy phosphate metabolites in the region of acute myocardial ischemia of open-chest cats. Eight anesthetized cats were studied following ligation of the left anterior descending coronary artery. Creatine p...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.1910030209
更新日期:1986-04-01 00:00:00
abstract:PURPOSE:Oscillating gradient spin-echo (OGSE) diffusion MRI provides information about the microstructure of biological tissues by means of the frequency dependence of the apparent diffusion coefficient (ADC). ADC dependence on OGSE frequency has been explored in numerous rodent studies, but applications in the human b...
journal_title:Magnetic resonance in medicine
pub_type: 杂志文章
doi:10.1002/mrm.28083
更新日期:2020-06-01 00:00:00