Inability to directly detect magnetic field changes associated with neuronal activity.

abstract：PURPOSE:We propose a constrained optimization approach for designing parallel transmit (pTx) pulses satisfying all regulatory and hardware limits. We study the trade-offs between excitation accuracy, local and global specific absorption rate (SAR), and maximum and average power for small flip-angle pTx (eight channels)...

journal_title：Magnetic resonance in medicine

authors： Guérin B,Gebhardt M,Cauley S,Adalsteinsson E,Wald LL

更新日期：2014-04-01 00:00:00

abstract：:This study investigates the potential of in vivo 31P magnetic resonance spectroscopy (MRS) to characterize musculoskeletal tumors and to determine preoperative levels of histological necrosis, which is an important clinical indicator of patient response. Pretherapy MRS was performed on 28 patients with large musculosk...

journal_title：Magnetic resonance in medicine

authors： Redmond OM,Bell E,Stack JP,Dervan PA,Carney DN,Hurson B,Ennis JT

更新日期：1992-10-01 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

authors： Cauley SF,Setsompop K,Ma D,Jiang Y,Ye H,Adalsteinsson E,Griswold MA,Wald LL

更新日期：2015-08-01 00:00:00

abstract：PURPOSE:Spiral readouts combine several favorable properties that promise superior net sensitivity for diffusion imaging. The purpose of this study is to verify the signal-to-noise ratio (SNR) benefit of spiral acquisition in comparison with current echo-planar imaging (EPI) schemes. METHODS:Diffusion-weighted in vivo...

journal_title：Magnetic resonance in medicine

authors： Lee Y,Wilm BJ,Brunner DO,Gross S,Schmid T,Nagy Z,Pruessmann KP

更新日期：2021-04-01 00:00:00

abstract：:Transmit and receive RF coil arrays have proven to be particularly beneficial for ultra-high-field MR. Transmit coil arrays enable such techniques as B(1) (+) shimming to substantially improve transmit B(1) homogeneity compared to conventional volume coil designs, and receive coil arrays offer enhanced parallel imagin...

journal_title：Magnetic resonance in medicine

authors： Adriany G,Auerbach EJ,Snyder CJ,Gözübüyük A,Moeller S,Ritter J,Van de Moortele PF,Vaughan T,Uğurbil K

更新日期：2010-06-01 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

authors： Sadleir RJ,Fu F,Chauhan M

更新日期：2019-01-01 00:00:00

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

authors： Devasahayam N,Subramanian S,Murugesan R,Hyodo F,Matsumoto K,Mitchell JB,Krishna MC

更新日期：2007-04-01 00:00:00

abstract：:This study presents the detection of [2-(13)C]glucose metabolism in the carboxylic/amide region in the human brain, and demonstrates that the cerebral metabolism of [2-(13)C]glucose can be studied in human subjects in the presence of severe hardware constraints of widely available 3 T clinical scanners and with low-po...

journal_title：Magnetic resonance in medicine

authors： Li S,Zhang Y,Wang S,Yang J,Ferraris Araneta M,Farris A,Johnson C,Fox S,Innis R,Shen J

更新日期：2009-09-01 00:00:00

abstract：:SENSE reconstruction suffers from an ill-conditioning problem, which increasingly lowers the signal-to-noise ratio (SNR) as the reduction factor increases. Ill-conditioning also degrades the convergence behavior of iterative conjugate gradient reconstructions for arbitrary trajectories. Regularization techniques are o...

journal_title：Magnetic resonance in medicine

authors： Ying L,Liu B,Steckner MC,Wu G,Wu M,Li SJ

更新日期：2008-08-01 00:00:00

abstract：PURPOSE:The primary purpose of this study is to propose a method for the simultaneous quantitative three-dimensional (3D) mapping of conductivity and susceptibility using double-echo ultrashort echo time (UTE) imaging. The secondary purpose is to investigate the changes of these properties over time during in vitro hem...

journal_title：Magnetic resonance in medicine

authors： Gho SM,Shin J,Kim MO,Kim DH

更新日期：2016-07-01 00:00:00

abstract：PURPOSE:Atherosclerotic carotid plaques can be quantified in vivo by MRI. However, the accuracy in segmentation and quantification of components such as the thin fibrous cap (FC) and lipid-rich necrotic core (LRNC) remains unknown due to the lack of a submillimeter scale ground truth. METHODS:A novel approach was take...

journal_title：Magnetic resonance in medicine

authors： Nieuwstadt HA,Geraedts TR,Truijman MT,Kooi ME,van der Lugt A,van der Steen AF,Wentzel JJ,Breeuwer M,Gijsen FJ

更新日期：2014-07-01 00:00:00

abstract：:Although promising for visualizing the structure of ordered tissues, MR diffusion tensor imaging (DTI) has been hampered by long acquisition time and low spatial resolution associated with its inherently low signal-to-noise ratio (SNR). Moreover, the uncertainty in the DTI measurements has a direct impact on the accur...

journal_title：Magnetic resonance in medicine

authors： Chen B,Hsu EW

更新日期：2005-08-01 00:00:00

abstract：PURPOSE:To assess the feasibility of using dissolved hyperpolarized xenon-129 (129 Xe) MRI to study renal physiology in humans at 3 T. METHODS:Using a flexible transceiver RF coil, dynamic and spatially resolved 129 Xe spectroscopy was performed in the abdomen after inhalation of hyperpolarized 129 Xe gas with 3 healt...

journal_title：Magnetic resonance in medicine

authors： Chacon-Caldera J,Maunder A,Rao M,Norquay G,Rodgers OI,Clemence M,Puddu C,Schad LR,Wild JM

更新日期：2020-01-01 00:00:00

abstract：PURPOSE:To develop and evaluate a novel 2D phase-unwrapping method that works robustly in the presence of severe noise, rapid phase changes, and disconnected regions. THEORY AND METHODS:The MR phase map usually varies rapidly in regions adjacent to wraps. In contrast, the phasors can vary slowly, especially in regions...

journal_title：Magnetic resonance in medicine

authors： Cheng J,Mei Y,Liu B,Guan J,Liu X,Wu EX,Feng Q,Chen W,Feng Y

更新日期：2018-01-01 00:00:00

abstract：PURPOSE:Anesthesia is necessary for most animal studies requiring invasive procedures. It is well documented that various types of anesthesia modulate a wide variety of important metabolic and functional processes in the body, and as such, represent a potential limitation in the study design. In the present study, we a...

journal_title：Magnetic resonance in medicine

authors： Qi H,Mariager CØ,Lindhardt J,Nielsen PM,Stødkilde-Jørgensen H,Laustsen C

更新日期：2018-11-01 00:00:00

abstract：:The time evolution of water diffusion, perfusion, T1, and T2 is investigated at high magnetic field (8.5 T) following permanent middle cerebral artery occlusion in the rat. Cerebral blood flow maps were obtained using arterial spin tagging. Although the quantitative perfusion measurements in ischemic tissue still pose...

journal_title：Magnetic resonance in medicine

authors： Calamante F,Lythgoe MF,Pell GS,Thomas DL,King MD,Busza AL,Sotak CH,Williams SR,Ordidge RJ,Gadian DG

更新日期：1999-03-01 00:00:00

abstract：:Uncertainty regarding the intracellular/extracellular distribution of inorganic phosphate (P(i)) in tumors has raised concerns that pH calculated from the tumor P(i) chemical shift may not accurately represent the intracellular pH (pHin). This issue was addressed in subcutaneously transplanted murine radiation induced...

journal_title：Magnetic resonance in medicine

authors： Soto GE,Zhu Z,Evelhoch JL,Ackerman JJ

更新日期：1996-11-01 00:00:00

abstract：PURPOSE:Quantitative myocardial perfusion mapping has advantages over qualitative assessment, including the ability to detect global flow reduction. However, it is not clinically available and remains a research tool. Building upon the previously described imaging sequence, this study presents algorithm and implementat...

journal_title：Magnetic resonance in medicine

authors： Xue H,Brown LAE,Nielles-Vallespin S,Plein S,Kellman P

更新日期：2020-02-01 00:00:00

abstract：:Rapid MR imaging using the stimulated echo acquisition mode (STEAM) technique yields single-shot images without any sensitivity to resonance offset effects. However, the absence of susceptibility-induced signal voids or geometric distortions is at the expense of a somewhat lower signal-to-noise ratio than EPI. As a co...

journal_title：Magnetic resonance in medicine

authors： Block KT,Frahm J

更新日期：2008-04-01 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

authors： Feldman RE,Scholl TJ,Alford JK,Handler WB,Harris CT,Chronik BA

更新日期：2011-12-01 00:00:00

abstract：:For diffusion-weighted magnetic resonance imaging and under circumstances where patient movement can be modeled as rigid body motion, it is shown both theoretically and experimentally that translations and rotations produce phase errors which are zero- and first-order, respectively, in position. While a navigator echo...

journal_title：Magnetic resonance in medicine

authors： Anderson AW,Gore JC

更新日期：1994-09-01 00:00:00

abstract：:MRI of myocardial perfusion observed with an extracellular contrast agent has proven valuable for the detection of coronary artery disease. During contrast enhancement transient dark rim artifacts are sometimes visible, complicating diagnosis and quantification. In this work a quantification of the frequency offsets c...

journal_title：Magnetic resonance in medicine

authors： Ferreira P,Gatehouse P,Bucciarelli-Ducci C,Wage R,Firmin D

更新日期：2008-10-01 00:00:00

abstract：:Aim of the study was to determine distribution and depletion patterns of intramyocellular lipids (IMCL) in leg muscles before and after two types of standardized endurance exercise. ¹H-magnetic resonance spectroscopic imaging was performed (1) in the thigh of eight-trained cyclists after exercising on an ergometer for...

journal_title：Magnetic resonance in medicine

authors： Vermathen P,Saillen P,Boss A,Zehnder M,Boesch C

更新日期：2012-11-01 00:00:00

abstract：:Fitting a model to an experimental spectrum is a difficult nonlinear estimation problem. The solution presented here is to start an iterative search procedure sufficiently close to the optimal model parameter set. This is achieved by providing tissue-dependent a priori peak information and by a novel correlation metho...

journal_title：Magnetic resonance in medicine

authors： Burger C,McKinnon G,Buchli R,Boesiger P

更新日期：1991-10-01 00:00:00

abstract：PURPOSE:In this work, 22 configurations for remote radiofrequency (RF) coil arrays consisting of different transmit element designs for 7 Tesla (T) ultrahigh-field MRI are compared by numerical simulations. METHODS:Investigated transmit RF element types are rectangular loops, micro striplines, micro striplines with me...

journal_title：Magnetic resonance in medicine

authors： Rietsch SHG,Orzada S,Bitz AK,Gratz M,Ladd ME,Quick HH

更新日期：2018-02-01 00:00:00

abstract：:MR oximetry requires a T2 measurement that is accurate within 5% in vivo. Simple methods are susceptible to signal loss and tend to underestimate T2. Current methods utilize RF pulses or RF cycling patterns that prevent signal loss at each data acquisition. However, using these methods with imperfect pulses, T2 tends ...

journal_title：Magnetic resonance in medicine

authors： Foltz WD,Stainsby JA,Wright GA

更新日期：1997-11-01 00:00:00

abstract：:A receive-only phased-array coil was designed to image the lower extremities. The array consists of four volume coils placed on two cylindrical formers. The coil array has the ability to image both legs simultaneously over a 40 cm longitudinal field of view (FOV). Experiments using phantoms show an increase in signal-...

journal_title：Magnetic resonance in medicine

authors： Brown R,Mareyam A,Reid E,Wang Y

更新日期：2004-03-01 00:00:00

abstract：:The Shinnar-Le Roux (SLR) radiofrequency (RF) pulse design algorithm is widely used for designing slice-selective RF pulses due to its intuitiveness, optimality, and speed. SLR is limited, however, in that it is only capable of designing one-dimensional pulses played along constant gradients. We present a nonuniform S...

journal_title：Magnetic resonance in medicine

authors： Grissom WA,McKinnon GC,Vogel MW

更新日期：2012-09-01 00:00:00

abstract：:Two single-shot volume imaging techniques are described. The first, single-echo echo-volume imaging, is essentially the echo-volume imaging (EVI) sequence suggested by Mansfield (J. Phys. C. 10, L55 (1977)). The second is a multi-spin-echo approach in which one plane of k-space is collected during each spin echo. In b...

journal_title：Magnetic resonance in medicine

authors： Song AW,Wong EC,Hyde JS

更新日期：1994-11-01 00:00:00

abstract：:A common type of motion present in clinical magnetic resonance imaging examinations is rotational motion, such as that due to voluntary motion during head examinations. The correction scheme presented in this work offers a method for eliminating the effects of rotations within the imaging plane. Integral to the implem...

journal_title：Magnetic resonance in medicine

authors： Korin HW,Felmlee JP,Riederer SJ,Ehman RL

更新日期：1995-05-01 00:00:00