Magnetic Resonance Imaging

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Magnetic Resonance Imaging

• Huafen Guo

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Introduction
Medical Imaging
Radiology
Part of Biomedical imaging
endoscopy
etc.
ultrasound
X-ray radiography
magnetic resonance imaging
Etc.

• Neuroimaging
• neurological cancer

• Musculoskeletal
• joint disease
• and soft tissue tumors

• Functional MRI
• brain

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Components
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Procedure

• Three field involved
• Static magnetic field (very strong one)
• gradient field
• Radio-frequency (RF) field.
• MR signal protons spin around their own axes

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Procedure

• Excitation it obtain information from the spins,
  powerful radio transmitter to generate the
  electromagnetic field to excite the spins.
• Return to equilibrium RF frequency
  transmitter-----switch off.
• Spatial encoding MR signal from the proton
  contain the information about where those protons
  are positioned in the patient ------create the
  image (three steps)
• slice selection
• frequency encoding
• phase encoding.

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Slice Selection

• Add magnetic gradient
• vertical slice the direction of gradients
  altered to an anterior-posterior gradient.

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Disadvantage

• exposure of RF field----implanted devices
• implant (level of safety)
• MR-Safe, completely nonmagnetic, non-electrically
  conductive, and non-RF reactive.
• MR-Conditional, may contain magnetic,
  electrically conductive or RF-reactive.
• MR-Unsafe contain magnetic electrically
  conductive or RF-reactive.
• projectile effect accidents
• acoustic noise---- ear protection
• Uncomfortable
• older scanner 40 minutes
• now20 minutes

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Conclusion

• Better improvement in the future.

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Question?
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Reference

• M. Lakrimi1, A.M. Thomas, G. Hutton, M. Kruip, R.
  Slade, P. Davis, A.J.Johnstone, M.J. Longfield,
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  pscience.cld.iop.orgartAbst
• Robert-Jan M. van Geuns, Piotr A. Wielopolski,
  Hein G. de Bruin, Benno J.Rensing, Peter M.A. van
  Ooijen, Marc Hulshoff,Matthijs Oudkerk, and Pim
  J.de Feyter. (1999). Basic principles of magnetic
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• Domenico F. Sergio S. (2004). Biological effects
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• Wikipedia.(2015). Medical imaging. Retrieved
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• Wikipedia.(2015). Magnetic resonance imaging.
  Retrieved from https//en.wikipedia.org/wiki/Magne
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