G485 Medical essay main points
- Created by: Alice
- Created on: 03-06-13 15:19
Medical questions
MRI
· Protons have spin
· Precess about the magnetic field produced by a strong electromagnet at a larmor frequency
· Transmitting coil produces a radio frequency equal to the larmor frequency
· Protons resonate and flip to a higher energy state
· When they relax to a lower energy state they emit radio waves
· Relaxation time depends on surrounding tissue
· Radio waves picked up by receiving coils
· Gradient coils alter magnetic flux density through the body
· Larmor frequency and radio waves given of during relaxation times varies through the body so the position of tissues can be identified
· Computer processes the signals and generates an image
PET
· A positron emitting source is used
· A positron annihilates with an electron in the patient
· This produces two gamma photons
· …
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