P4 - Treatment using radiation

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  • Created by: Naomi
  • Created on: 21-01-13 21:50
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  • Treatment using radiation
    • Using radiation
      • Radiation emitted from the nucleus of an unstable atom can be alpha, beta or gamma
        • Alpha radiation is absorbed by the skin, so is of no use for diagnosis or therapy
        • Beta radiation passes through the skin, but not bone. Its medical applications are limited but it is used
        • Gamma radiation is very penetrating and is used in medicine. Cobalt-60 is a gamma-emitting radioactive material that is used to treat cancers
      • When nuclear radiation passes through a material, it causes ionisation
        • Ionising radiation damages living cells, increasing the risk of cancer
      • Cancer cells within the body can be destroyed by exposing the affected area to large amounts of radiation
    • Comparing x-rays and gamma rays
      • When x-rays pass through the body the tissue absorbs some of the ionising radiation
        • The amount absorbed depends on the thickness and the density of the absorbing material
      • Gamma rays and x-rays have similar wavelengths but are produced in different ways
        • X-rays are made by firing high speed electrons at metal targets
          • An x-ray machine allows the rate of production and energy of the x-rays to be controlled
            • You can't change the gamma radiation emitted from a particular source
        • When the nucleus of an atom of a radioactive substance decays, it emits an alpha or beta particle and loses any surplus energy by emitting gamma rays
          • You can't change the gamma radiation emitted from a particular source
    • A radioactive tracer is used to investigate inside a patient's body without surgery
      • The radioctive tracer is mixed with food or drink or injected into the body
      • Its progress through the body is monitored using a detector such as a gamma camera connected to a computer
    • Treating cancer
      • 3 sources of radiation, each providing one third of the required dose, are arranged around the patient with the tumour at the centre
        • The healthy tissue only receives one third of the dose, which limits the damage to it
      • Each radiation source is rotated around the patient
        • The tumour receives a constant dose, but the healthy tissue only receives intermittent doses


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