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Result : Searchterm 'Magnetic Field' found in 5 terms [] and 219 definitions []
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Paramagnetism
 
Paramagnetic materials attract and repel like normal magnets when subject to a magnetic field. This alignment of the atomic dipoles with the magnetic field tends to strengthen it, and is described by a relative magnetic permeability greater than unity. Paramagnetism requires that the atoms individually have permanent dipole moments even without an applied field, which typically implies a partially filled electron shell. In pure Paramagnetism (without an external magnetic field), these atomic dipoles do not interact with one another and are randomly oriented in the absence of an external field, resulting in zero net moment.
Paramagnetic materials in magnetic fields will act like magnets but when the field is removed, thermal motion will quickly disrupt the magnetic alignment. In general, paramagnetic effects are small (magnetic susceptibility of the order of 10-3 to 10-5).
In MRI, gadolinium (Gd) one of these paramagnetic materials is used as a contrast agent. Through interactions between the electron spins of the paramagnetic gadolinium and the water nuclei nearby, the relaxation rates (T1 and T2) of the water protons are increased (T1 and T2 times are decreased), causing an increase in signal on T1 weighted images.

See also contrast agents, magnetism, ferromagnetism, superparamagnetism, and diamagnetism.
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Further Reading:
  Basics:
Magnet basics
   by my.execpc.com    
Paramagnetism
Wednesday, 23 November 2005   by en.wikipedia.org    
  News & More:
LEARNING CENTER FOR PARAMAGNETISM
2003   by www.naturesalternatives.com    
Searchterm 'Magnetic Field' was also found in the following services: 
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Radiology  (9) Open this link in a new windowUltrasound  (2) Open this link in a new window
5 Gauss Fringe Field
 
This line specifies the perimeter around a MR scanner within which the static magnetic fields are higher than five gauss. Five gauss and below are considered 'safe' levels of static magnetic field exposure for the general public.
Due to the physical properties of magnetic fields, the magnetic flux, which penetrates the useful volume of the magnet will return through the surroundings of the magnet to form closed field lines. Depending on the magnet construction, the returning flux will penetrate large open spaces (unshielded magnets) or will be confined largely to iron yokes or through secondary coils (shielded magnets).
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Further Reading:
  Basics:
How strong are magnets?
   by my.execpc.com    
  News & More:
Magnetic Field
   by hyperphysics.phy-astr.gsu.edu    
MRI Resources 
Software - Lung Imaging - Sequences - PACS - MRA - Patient Information
 
5 Gauss Line
 
This line specifies the perimeter around a MR scanner within which the static magnetic fields are higher than five gauss. Five gauss and below are considered 'safe' levels of static magnetic field exposure for the general public.
Portable devices requiring a separation distance between the device and the MR magnet, should not be considered 'MR Safe', 'MR Compatible', or intended for use in the MR environment. Typically the 5 gauss line is the only location where the static magnetic field strength is specified around a MR scanner. Therefore, labeling specifying a separation distance between the MR magnet and the device to ensure safe or proper operation of the device should be avoided.

See also the related poll result: 'In 2010 your scanner will probably work with a field strength of'
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Further Reading:
  News & More:
Boston Scientific and Biophan in MRI Collaboration
Friday, 21 November 2003   by www.medimaging.net    
World's First Portable MRI Cleared by FDA
Monday, 17 February 2020   by www.medgadget.com    
Searchterm 'Magnetic Field' was also found in the following services: 
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News  (76)  Resources  (16)  Forum  (18)  
 
Boltzmann Distribution
 
When a group of spins is placed in a magnetic field, each spin aligns in one of the two possible orientations. The relative numbers of spins with different alignments will be given by the Boltzmann distribution.
Definition: if a system of particles, which are able to exchange energy in collisions is in thermal equilibrium, then the relative number (population) of particles, N1 and N2, in two particular energy levels with corresponding energies, E1 and E2, is given by N1/N2 = exp [-(E1 - E2)/kT] where k is the Boltzmann constant and T is the absolute temperature.
For example, in NMR of protons at room temperature in a magnetic field of 0.25 tesla, the difference in relative numbers of spins aligned with the magnetic field and against the field is about one part in a million; the small excess of nuclei in the lower energy state is the basis of the net magnetization and the resonance phenomenon.
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Radiology  (9) Open this link in a new windowUltrasound  (2) Open this link in a new window
Electromagnet
 
A type of magnet that utilizes coils of wire, typically wound on an iron core, so that as current flows through the coil it becomes magnetized. The direction of the magnetic field is parallel to the long axis of the coil. Whole body electromagnets, used in medical imaging (also called resistive) are limited to their field strength, because the weight becomes prohibitively large at high field MRI. The magnetic field shuts down, if the current is switched of. Because this type of magnet generates heat, a good cooling system is essential.
For a stronger magnetic field, the wires must be manufactured of superconducting materials to reduce the power needed to produce the field.

See also Resistive Magnet, Superconducting Magnet and Upright™ MRI
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• View the NEWS results for 'Electromagnet' (8).Open this link in a new window.
 
Further Reading:
  Basics:
What types of magnets are there?
   by my.execpc.com    
  News & More:
'Electromagnetic Wormhole' Possible with Invisibility Technology
Monday, 15 October 2007   by www.brightsurf.com    
Superconductors Face the Future
Wednesday, 15 September 2010   by www.nanotech-now.com    
MRI Resources 
Online Books - Homepages - Breast Implant - PACS - Diffusion Weighted Imaging - General
 
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