scholarly journals Comparing the signal enhancement of a gadolinium based and an iron-oxide based contrast agent in low-field MRI

PLoS ONE ◽  
2021 ◽  
Vol 16 (8) ◽  
pp. e0256252
Author(s):  
Jordy K. van Zandwijk ◽  
Frank F. J. Simonis ◽  
Friso G. Heslinga ◽  
Elfi I. S. Hofmeijer ◽  
Robert H. Geelkerken ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Contrast Agent ◽  
Spin Echo ◽  
Magnetic Behavior ◽  
Positive Contrast ◽  
Mri Contrast Agents ◽  
Signal Enhancement ◽  
Low Field ◽  
Low Field Mri ◽  
Field Strengths

Recently, there has been a renewed interest in low-field MRI. Contrast agents (CA) in MRI have magnetic behavior dependent on magnetic field strength. Therefore, the optimal contrast agent for low-field MRI might be different from what is used at higher fields. Ultra-small superparamagnetic iron-oxides (USPIOs), commonly used as negative CA, might also be used for generating positive contrast in low-field MRI. The purpose of this study was to determine whether an USPIO or a gadolinium based contrast agent is more appropriate at low field strengths. Relaxivity values of ferumoxytol (USPIO) and gadoterate (gadolinium based) were used in this research to simulate normalized signal intensity (SI) curves within a concentration range of 0–15 mM. Simulations were experimentally validated on a 0.25T MRI scanner. Simulations and experiments were performed using spin echo (SE), spoiled gradient echo (SGE), and balanced steady-state free precession (bSSFP) sequences. Maximum achievable SIs were assessed for both CAs in a range of concentrations on all sequences. Simulations at 0.25T showed a peak in SIs at low concentrations ferumoxytol versus a wide top at higher concentrations for gadoterate in SE and SGE. Experiments agreed well with the simulations in SE and SGE, but less in the bSSFP sequence due to overestimated relaxivities in simulations. At low magnetic field strengths, ferumoxytol generates similar signal enhancement at lower concentrations than gadoterate.

scholarly journals Prepolarized fast spin-echo pulse sequence for low-field MRI

2007 ◽  
Vol 57 (6) ◽  
pp. 1180-1184 ◽  
Author(s):  
C. Kegler ◽  
H.C. Seton ◽  
J.M.S. Hutchison
Keyword(s):  
Pulse Sequence ◽  
Spin Echo ◽  
Fast Spin Echo ◽  
Low Field ◽  
Low Field Mri ◽  
Echo Pulse ◽  
Fast Spin

scholarly journals GMI Effect of Ultra-Soft Magnetic Soft Amorphous Microwires

2012 ◽  
Vol 6 (1) ◽  
pp. 39-43 ◽  
Author(s):  
A. Zhukov ◽  
M. Ipatov ◽  
J. M. Blanco ◽  
V. Zhukova
Keyword(s):  
Magnetic Field ◽  
Magnetic Behavior ◽  
Bias Current ◽  
Soft Magnetic ◽  
Magnetoelastic Anisotropy ◽  
Gmi Effect ◽  
Low Field ◽  
Amorphous Microwires

In this paper we experimentally studied GMI effect and soft magnetic behavior of Co-rich microwires. Correlation between magnetoelastic anisotropy and magnetic field dependences of diagonal and off-diagonal impedance components are observed. Low field GMI hysteresis, explained in terms of magnetoelastic anisotropy of microwires, has been suppressed by the bias current.

scholarly journals Effect of Mineral Composition on Transverse Relaxation Time Distributions and MR Imaging of Tight Rocks from Offshore Ireland

Minerals ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 232
Author(s):  
Stian Almenningen ◽  
Srikumar Roy ◽  
Arif Hussain ◽  
John Georg Seland ◽  
Geir Ersland
Keyword(s):  
Magnetic Field ◽  
Relaxation Time ◽  
Mr Imaging ◽  
Field Strength ◽  
High Field ◽  
Transverse Relaxation Time ◽  
Transverse Relaxation ◽  
The Core ◽  
Low Field ◽  
Field Strengths

In this paper, we investigate the effect of magnetic field strength on the transverse relaxation time constant (T2) in six distinct core plugs from four different rock types (three sandstones, one basalt, one volcanic tuff and one siltstone), retrieved from offshore Ireland. The CPMG pulse-sequence was used at two different magnetic field strengths: high-field at 4.70 T and low-field at 0.28 T. Axial images of the core plugs were also acquired with the RAREst sequence at high magnetic field strength. Thin-sections of the core plugs were prepared for optical imaging and SEM analysis, and provided qualitative information on the porosity and quantification of the elemental composition of the rock material. The content of iron varied from 4 wt. % to close to zero in the rock samples. Nevertheless, the effective T2 distributions obtained at low-field were used to successfully predict the porosity of the core plugs. Severe signal attenuations from internal magnetic gradients resulted in an underestimation of the porosity at high-field. No definitive trend was identified on the evolution of discrete relaxation time components between magnetic field strengths. The low-field measurements demonstrate that NMR is a powerful quantitative tool for petrophysical rock analysis as compared to thin-section analysis. The results of this study are of interest to the research community who characterizes natural gas hydrates in tight heterogeneous core plugs, and who typically relies on MR imaging to distinguish between solid hydrates and fluid phases. It further exemplifies the importance of selecting appropriate magnetic field strengths when employing NMR/MRI for porosity calculation in tight rock.

scholarly journals Dynamic contrast enhanced MRI with clinical hepatospecific MRI contrast agents in pigs: initial experience

2020 ◽  
Author(s):  
Jeremy M.L. Hix ◽  
Christiane L. Mallett ◽  
Matthew Latourette ◽  
Kirk A. Munoz ◽  
Erik M. Shapiro
Keyword(s):  
Contrast Agent ◽  
Contrast Agents ◽  
Biomedical Imaging ◽  
Mri Contrast Agents ◽  
Signal Enhancement ◽  
Pig Liver ◽  
Mri Contrast ◽  
Dce Mri ◽  
Dynamic Contrast Enhanced ◽  
Contrast Enhanced

AbstractPigs are an important translational research model for biomedical imaging studies, and especially for modeling diseases of the liver. Dynamic contrast enhanced (DCE)-MRI is experimentally used to measure liver function in humans, but has never been characterized in pig liver. Here we performed DCE-MRI of pig liver following the delivery of two FDA approved hepato-specific MRI contrast agents, Gd-EOB-DTPA (Eovist) and Gd-BOPTA (Multihance), and the non-hepatospecific agent Magnevist, and optimized the anesthesia and animal handling protocol to acquire robust data. A single pig underwent 5 scanning sessions over six weeks, each time injected at clinical dosing either with Eovist (twice), Multihance (twice) or Magnevist (once). DCE-MRI was performed at 1.5T for 60 minutes. DCE-MRI showed rapid hepatic MRI signal enhancement following IV injection of Eovist or Multihance. Efflux of contrast agent from liver exhibited kinetics similar to that in humans, except for one hyperthermic animal where efflux was very fast. As expected, Magnevist was non-enhancing in the liver. The hepatic signal enhancement from Eovist matched that seen in humans and primates, while the hepatic signal enhancement from Multihance was different, similar to rodents and dogs, likely the result of differential hepatic organic anion transport polypeptides. This first experience with these agents in pigs provides valuable information on contrast agent dynamics in normal pig liver. Given the disparity in contrast agent uptake kinetics with humans for Multihance, Eovist should be used in porcine models for biomedical imaging. Proper animal health maintenance, especially temperature, seems essential for accurate and reproducible results.

scholarly journals Nano-thermometers with thermo-sensitive polymer grafted USPIOs behaving as positive contrast agents in low-field MRI

Nanoscale ◽  
2015 ◽  
Vol 7 (8) ◽  
pp. 3754-3767 ◽  
Author(s):  
Adeline Hannecart ◽  
Dimitri Stanicki ◽  
Luce Vander Elst ◽  
Robert N. Muller ◽  
Sébastien Lecommandoux ◽  
...  
Keyword(s):  
Iron Oxide ◽  
Contrast Agents ◽  
Iron Oxide Nanoparticles ◽  
Positive Contrast ◽  
Oxide Nanoparticles ◽  
Low Field ◽  
Low Field Mri

MRI signal linearity with temperature from 15 to 50 °C with thermo-sensitive chains on iron oxide nanoparticles.

Magnetic-field strengths from optical polarization data

1967 ◽  
Vol 31 ◽  
pp. 381-383
Author(s):  
J. M. Greenberg
Keyword(s):  
Magnetic Field ◽  
Optical Polarization ◽  
Polarization Data ◽  
Term Model ◽  
Source Of Information ◽  
Field Strengths

Van de Hulst (Paper 64, Table 1) has marked optical polarization as a questionable or marginal source of information concerning magnetic field strengths. Rather than arguing about this–I should rate this method asq+-, or quarrelling about the term ‘model-sensitive results’, I wish to stress the historical point that as recently as two years ago there were still some who questioned that optical polarization was definitely due to magnetically-oriented interstellar particles.

Improved Contrast in Ultra-Low-Field MRI with Time-Dependent Bipolar Prepolarizing Fields: Theory and NMR Demonstrations

2013 ◽  
Vol 20 (3) ◽  
pp. 327-336 ◽  
Author(s):  
Jaakko O. Nieminen ◽  
Jens Voigt ◽  
Stefan Hartwig ◽  
Hans Jürgen Scheer ◽  
Martin Burghoff ◽  
...  
Keyword(s):  
Field Strength ◽  
Time Course ◽  
Signal Strength ◽  
Relaxation Rates ◽  
Resonance Imaging ◽  
New Approach ◽  
Spin Lattice ◽  
Low Field ◽  
Low Field Mri ◽  
Magnetic Resonance Imaging Mri

Abstract The spin-lattice (T1) relaxation rates of materials depend on the strength of the external magnetic field in which the relaxation occurs. This T1 dispersion has been suggested to offer a means to discriminate between healthy and cancerous tissue by performing magnetic resonance imaging (MRI) at low magnetic fields. In prepolarized ultra-low-field (ULF) MRI, spin precession is detected in fields of the order of 10-100 μT. To increase the signal strength, the sample is first magnetized with a relatively strong polarizing field. Typically, the polarizing field is kept constant during the polarization period. However, in ULF MRI, the polarizing-field strength can be easily varied to produce a desired time course. This paper describes how a novel variation of the polarizing-field strength and duration can optimize the contrast between two types of tissue having different T1 relaxation dispersions. In addition, NMR experiments showing that the principle works in practice are presented. The described procedure may become a key component for a promising new approach of MRI at ultra-low fields

Sign in / Sign up

Export Citation Format

Share Document