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Result : Searchterm 'Radio Frequency' found in 12 terms [] and 63 definitions []
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Coil LoadingInfoSheet: - Coils - 
Intro, 
Overview, 
etc.
 
The interaction of the patient with the RF coil, which causes shifts of the resonance frequency and damping of the coil's resonance and hence reduction of the quality factor because of magnetic induction and dielectric losses in the patient.
The design and construction of a MRI coil is determined by the load on the coil. The load is either a phantom or the actual sample being imaged.

See also Radio Frequency Coil.
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Radiology  (2) Open this link in a new window
Data Clipping (Artifact)InfoSheet: - Artifacts - 
Case Studies, 
Reduction Index, 
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 - Artifacts -
 
Data clipping artifacts give images a washed-out, non-uniform appearance. If the receiver gain increase, so that the signal level is larger than the maximum ADC value, the reconstructed image brightness was scaled to compensate this. The overall intensity loss as well as the extensive signal is reconstructed outside of the object. This effect is called 'clipping' because on a plot of signal amplitude vs. time, it looks like the top and bottom of the echo has been 'clipped off' with scissors.

See Radio Frequency Overflow Artifact.
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MRI Resources 
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Electron Spin Resonance
 
(ESR) Electron spin resonance is a spectroscopic technique to identify paramagnetic substances. This magnetic resonance phenomenon investigates the nature of the bonding within molecules by identifying unpaired electrons, e.g. in free radicals and their interaction with their immediate surroundings. The Larmor frequency are much higher than corresponding NMR frequencies in the same static magnetic field.
Nuclei with an odd number of neutrons and/or protons, because of their spin, react like tiny magnets and can be lined up in an applied magnetic field. Energy applied by alternating radio frequency radiation is absorbed when its frequency coincides with that of precession of the electron magnets. The spectrum of radiation absorbed as the field changes gives information valuable in chemistry, biology, and medicine since over 50 years.
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Further Reading:
  Basics:
Electron Spin Resonance
   by hyperphysics.phy-astr.gsu.edu    
  News & More:
After merging resources, chemist, retina surgeon see melanin's value in new light
Thursday, 18 August 2005   by chronicle.uchicago.edu    
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Excitation
 
Sent (inducing, transferring) energy into the 'spinning' nuclei via radio frequency pulse, which puts the nuclei into a higher energy state. By producing a net transverse magnetization a MRI system can observe a response from the excited system.
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Further Reading:
  Basics:
Musculoskeletal MRI at 3.0 T: Relaxation Times and Image Contrast
Sunday, 1 August 2004   by www.ajronline.org    
IMAGE CONTRAST IN MRI(.pdf)
   by www.assaftal.com    
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Radiology  (2) Open this link in a new window
Faraday Shield
 
In electromagnetism, the Faraday cage or shield is an application of Gauss's law, one of Maxwell's equations. Gauss's law describes the distribution of electrical charge on a conducting form, such as a sphere, a plane, a torus, etc. Intuitively, since like charges repel each other, charge will "migrate" to the surface of the conducting form, as described below. The application is named after physicist Michael Faraday, who built the first Faraday cage in 1836, to demonstrate his finding. A Faraday shield is used generally for any kind of electrostatic shielding.
In MRI, one use of the Faraday shield is the shielding of the scanning room, to block incoming radio frequency (RF) signals which would contaminate the send and received signals of the MRI scanner, and it suppresses RF signals, which would else pollute the environment around.
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Further Reading:
  Basics:
Faraday's Law
   by hyperphysics.phy-astr.gsu.edu    
Faraday_shield
   by en.wikipedia.org    
  News & More:
Electrical eddy currents in the human body: MRI scans and medical implants
   by www.phy.olemiss.edu    
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