5351006 Method and apparatus for correcting spatial distortion in magnetic resonance images due to magnetic field inhomogeneity including inhomogeneity due to susceptibility variations

1995 ◽  
Vol 13 (5) ◽  
pp. XX ◽  
Author(s):  
Thilaka Sumanaweera ◽  
H Glover Gary ◽  
R Adler John
Keyword(s):  
Magnetic Field ◽  
Magnetic Resonance ◽  
Magnetic Resonance Images ◽  
Magnetic Field Inhomogeneity ◽  
Field Inhomogeneity ◽  
Spatial Distortion

scholarly journals Characterization and Relaxation Properties of a Series of Monodispersed Magnetic Nanoparticles

Sensors ◽  
2019 ◽  
Vol 19 (15) ◽  
pp. 3396 ◽  
Author(s):  
Yapeng Zhang ◽  
Jingjing Cheng ◽  
Wenzhong Liu
Keyword(s):  
Magnetic Field ◽  
Magnetic Nanoparticles ◽  
Magnetic Resonance ◽  
Relaxation Rate ◽  
Correlation Coefficient ◽  
Transverse Relaxation Rate ◽  
Magnetic Field Inhomogeneity ◽  
Field Inhomogeneity ◽  
Relaxation Rates ◽  
Correlation Relationship

Magnetic iron oxide nanoparticles are relatively advanced nanomaterials, and are widely used in biology, physics and medicine, especially as contrast agents for magnetic resonance imaging. Characterization of the properties of magnetic nanoparticles plays an important role in the application of magnetic particles. As a contrast agent, the relaxation rate directly affects image enhancement. We characterized a series of monodispersed magnetic nanoparticles using different methods and measured their relaxation rates using a 0.47 T low-field Nuclear Magnetic Resonance instrument. Generally speaking, the properties of magnetic nanoparticles are closely related to their particle sizes; however, neither longitudinal relaxation rate r 1 nor transverse relaxation rate r 2 changes monotonously with the particle size d . Therefore, size can affect the magnetism of magnetic nanoparticles, but it is not the only factor. Then, we defined the relaxation rates r i ′ (i = 1 or 2) using the induced magnetization of magnetic nanoparticles, and found that the correlation relationship between r 1 ′ relaxation rate and r 1 relaxation rate is slightly worse, with a correlation coefficient of R 2 = 0.8939, while the correlation relationship between r 2 ′ relaxation rate and r 2 relaxation rate is very obvious, with a correlation coefficient of R 2 = 0.9983. The main reason is that r 2 relaxation rate is related to the magnetic field inhomogeneity, produced by magnetic nanoparticles; however r 1 relaxation rate is mainly a result of the direct interaction of hydrogen nucleus in water molecules and the metal ions in magnetic nanoparticles to shorten the T 1 relaxation time, so it is not directly related to magnetic field inhomogeneity.

Effects of static and radiofrequency magnetic field inhomogeneity in ultra-high field magnetic resonance imaging

2006 ◽  
Vol 24 (2) ◽  
pp. 103-112 ◽  
Author(s):  
Trong-Kha Truong ◽  
Donald W. Chakeres ◽  
David Q. Beversdorf ◽  
Douglas W. Scharre ◽  
Petra Schmalbrock
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Field ◽  
Magnetic Resonance ◽  
High Field ◽  
Magnetic Field Inhomogeneity ◽  
Field Inhomogeneity ◽  
Resonance Imaging ◽  
Ultra High Field

NMR measurement of magnetic field inhomogeneity

1991 ◽  
Vol 34 (6) ◽  
pp. 610-613
Author(s):  
Ya. Weis ◽  
I. Frollo ◽  
L. Budinsk�
Keyword(s):  
Magnetic Field ◽  
Magnetic Field Inhomogeneity ◽  
Field Inhomogeneity

scholarly journals Nanosized T1 MRI Contrast Agent Based on a Polyamidoamine as Multidentate Gd Ligand

Molecules ◽  
2021 ◽  
Vol 27 (1) ◽  
pp. 174
Author(s):  
Paolo Arosio ◽  
Davide Cicolari ◽  
Amedea Manfredi ◽  
Francesco Orsini ◽  
Alessandro Lascialfari ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Resonance ◽  
Contrast Agent ◽  
Potentiometric Titration ◽  
Molecular Model ◽  
Repeat Unit ◽  
Magnetic Resonance Images ◽  
Mri Contrast Agent ◽  
Size Exclusion ◽  
Molar Ratio

A linear polyamidoamine (PAA) named BAC-EDDS, containing metal chelating repeat units composed of two tert-amines and four carboxylic groups, has been prepared by the aza-Michael polyaddition of ethylendiaminodisuccinic (EDDS) with 2,2-bis(acrylamido)acetic acid (BAC). It was characterized by size exclusion chromatography (SEC), FTIR, UV–Vis and NMR spectroscopies. The pKa values of the ionizable groups of the repeat unit were estimated by potentiometric titration, using a purposely synthesized molecular ligand (Agly-EDDS) mimicking the structure of the BAC-EDDS repeat unit. Dynamic light scattering (DLS) and ζ-potential analyses revealed the propensity of BAC-EDDS to form stable nanoaggregates with a diameter of approximately 150 nm at pH 5 and a net negative charge at physiological pH, in line with an isoelectric point <2. BAC-EDDS stably chelated Gd (III) ions with a molar ratio of 0.5:1 Gd (III)/repeat unit. The stability constant of the molecular model Gd-Agly-EDDS (log K = 17.43) was determined as well, by simulating the potentiometric titration through the use of Hyperquad software. In order to comprehend the efficiency of Gd-BAC-EDDS in contrasting magnetic resonance images, the nuclear longitudinal (r1) and transverse (r2) relaxivities as a function of the externally applied static magnetic field were investigated and compared to the ones of commercial contrast agents. Furthermore, a model derived from the Solomon–Bloembergen–Morgan theory for the field dependence of the NMR relaxivity curves was applied and allowed us to evaluate the rotational correlation time of the complex (τ = 0.66 ns). This relatively high value is due to the dimensions of Gd-BAC-EDDS, and the associated rotational motion causes a peak in the longitudinal relaxivity at ca. 75 MHz, which is close to the frequencies used in clinics. The good performances of Gd-BAC-EDDS as a contrast agent were also confirmed through in vitro magnetic resonance imaging experiments with a 0.2 T magnetic field.

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