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What does MRI stand for?
Magnetic Resonance Imaging
What is the procedure of MRI scans?
Strong magnetic fields and radio waves are used when a person lies under a powerful scanner. The body is made up of water molecules. At the centre of these molecules are protons. When a person lies under the powerful scanner, the protons are knocked out of alignment. The scanner is then turned off and the protons realign. A detector picks up this movement.
What parts of the body can be examined using MRI?
Brain, spinal cord, bones, joints, breasts, heart and blood vessels and other internal organs.
What are the advantages and disadvantages of MRI?
- Used in soft tissue diagnosis
- Non invasive
- 3D imagery
- Cannot be used on people with pacemakers
- Procedure takes a long time
What are lasers?
Lasers are used to removed any unwanted parts of the body using light energy. They are used in surgery to burn away tissue so that unwanted organs can be removed.
What are the precautions when using lasers?
- Use eye protection
- Use short bursts of energy
- Use a steady grip/hand
Advantages and Disadvantages of lasers
- Advantages - quick procedure and accurate to use for burning away flesh etc.
- Disadvantages - very expensive procedure, risk of surgeon cutting through a vital organ.
What tool is usually used during keyhole surgery? (laproscopy)
How does an endoscope/optical fibre work?
Endoscopes need to have a high refractive index, therefore a low critical angle. Total internal reflection relies on a low critical angle. Optical fibres need total internal reflection in order for the light to reach the end of the fibre effectively.
How many incisions are usually needed for keyhole surgery?
Three. One for the endoscope and two others for the tools/lasers.
What can keyhole surgery be used for?
- Removing a diseased or damaged organ (e.g. gall bladder)
- Removing a tissue for testing (biopsy)
What are the advantages of keyhole surgery when compared with traditional surgery?
- Shorter hospital stay
- Less pain
- Less scarring
- Less skin needs cutting open
Draw how light travels down an optical fibre.
What is the equation for refractive index?
n = sinI / sinR
What is the equation for critical angle?
C = sin-1 x (1/n)