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MRI scanning - how it works

• MRI stands for Magnetic Resonance Imaging.
• The magnets used are in the 0.5-tesla to 2.0-tesla range. (Compared with the Earth's magnetic field of 0.00005-tesla).
• Hydrogen is present in water and in all organic matter. Under MRI hydrogen atoms in normal and abnormal tissues show up differently.
• Hydrogen protons in the body will align with the magnetic field in one direction or the other. The vast majority cancel each other out, but a few protons in every million are unmatched.
• An RF (radio frequency) pulse that only affects hydrogen is applied.
• The RF pulse forces the one or two unmatched protons per million to spin at a particular frequency, in a particular direction.
• When the RF pulse is turned off, the hydrogen protons begin to return to their natural alignment within the magnetic field and release their excess stored energy. They give off a signal, which the coil picks up and sends to the computer system.
• This data is converted into an image.
  
  
  
• MRI is ideal for:
  - Diagnosing multiple sclerosis (MS)
  - Diagnosing tumours of the pituitary gland and brain
  - Diagnosing infections in the brain, spine or joints
  - Visualizing torn ligaments in the wrist, knee and ankle
  - Visualizing shoulder injuries
  - Diagnosing tendonitis
  - Evaluating masses in the soft tissues of the body
  - Evaluating bone tumours, cysts and bulging or herniated discs in the spine
  - Diagnosing strokes in their earliest stages.

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