Medical uses of Radiation

Tracers in Medicine
1. Radioactive isotopes are injected or swallowed
  1. External detector follows its progress around the body
    1. Computer processes readings
      1. This shows where the strongest reading is coming from
2. E.g iodine-131
  1. Is absorbed by the Thyroid gland
    1. Emits radiation which can be detected
      1. Shows whether the Thyroid gland is taking in Iodine
3. Only isotopes which emit beta and gamma radiation are used
  1. These pass out of the body
    1. Reducing the damage
  2. They have short half-lifes to reduce amount of radioactivity in the body
    1. Reducing the damage
PET Scanning
1. Positron Emission Tomography
2. Used to show Organ/Tissue functions
  1. Reveals
    1. Records the blood flow
      1. Can diagnose Epilepsy
    2. Damaged/Dead heart muscle
      1. Damaged tissue in the heart is shown by detecting decreased blood flow
    3. Coronary Artery Disease
    4. Active Tumours
      1. By analysing metabolic activity of tissue
        Cancer cells have a higher metabolism
3. Method
  1. Inject a substance (e.g Glucose) with a positron-emitting radioactive isotope
    1. This acts as a tracer which moves around the body
      1. Positrons meet electrons and annihilate
        Emitting high-energy gamma rays in opposite directions which are detected
        The distribution of the radioactivity matches the metabolic activity
  2. Isotopes have a small half-life so are made on site
Tumour Treatment
1. Internally
  1. Radioactive material is inserted into/near the tumour
    1. By injecting/implanting
      1. This method gives a high dose of radiation to a small part of the body
        Damage to surrounding tissues is limited
        Whole treatment is usually 6 weeks shorter
        Reduce the number of visits
        Allows to plan for further treatment
        May have to limit contact because the radioactive source is inside the patient before it is removed
        No side effects except discomfort
2. Externally
  1. High energy x-rays or gamma rays are aimed at the tumour
    1. Radiation is aimed carefully but normal cells in the way will be damaged
      1. Sessions only last a few minutes
        Can have side effects (see below)
Associated Problems
1. Social and Ethical
  1. Radiation is useful and dangerous
    1. Using radiation to kill cells will also kill normal ones
      1. Minor
        Radiotherapy can cause hair loss, sickness & skin irritation
      2. Major
        Can lead to bowel damage & infertility
        Reduce quality of life
        In some cases a second cancer can evolve
2. Physical
  1. Ionising radiation
    1. Can kill cells
    2. Can cause mutations
    3. Can cause cells to divide uncontrollably
    4. PET scans use small doses (7 mSv)
    5. Background radiation = 2.2 mSv
    6. Prevention
      1. Low doses
      2. Short exposure time
      3. Lead shielding
      4. Increase distance
  2. Any exposure increases risk
3. Radiation Intensity & Absorbtion
  1. Intensity of radiation depends on distance squared
    Nota:
    - if you move twice as far from the source the radiation is being spread four times the area. So 1/x^2 =1/4 of the intensity
    1. Known as Inverse square relationship
  2. Thickness of materials affects absorbtion
    1. Lead and Concrete reduce such exposures because they absorb radiation
Treatment that reduces suffering without curing the illness is called palliative care

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Medical uses of Radiation

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