Medical Physics and Radioactivity

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Medical Physics and Radioactivity
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Radioactivity
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Unstable nucleus
Electromagnetic wave
particle
Atoms which emit electromagnetic radiation or a
particle by the spontaneous transformation of
their nucleus are called radioactive.
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Types of radiation

• Alpha Particle (a)

• Beta Particle (ß)

• Gamma Ray (?)

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Uranite a rock which contains uranium
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Is radiation harmful?

• High energy radiation can damage DNA.
• This could cause
• Cancer
• Inflammation
• Cell death
• Damage to genes can lead to mutations in
  offspring
• Cells are more sensitive to radiation during cell
  division than at other times.
• Cells which divide frequently (e.g. the gut
  walls) are more sensitive than those which rarely
  divide (e.g nervous tissue).

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Detection and Measurement
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Radiation detector
Each particle or gamma ray is seen as a
deflection on the meter needle and is heard as a
click
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The detector is responding to the radiation being
emitted from the uranium ore
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Nuclear Medicine
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• Radioactive tracers can be used to see how well
  organs in your body are working or to find areas
  of disease.
• e.g. radioisotopes of iodine or technetium.
• Often these are mixed with a drug that collects
  in a particular organ in the body.
• If we then inject the drug into the body, then by
  detecting the radiation, we can examine that
  organ.

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Labelling chemicals with the radioactive isotopes
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Lead
Preparing the tracer
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The tracer is injected into the patient
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Gamma Camera
A gamma camera detects the radiation coming from
the patient and produces an image of where the
radioactivity is in the body.
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The gamma camera displays the position of each
gamma ray that it detects. This is a bone scan
made using technetium-99m.Can you see where the
patient was injected?
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Lung scan using Krypton-81m gas
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Lung scan using Krypton-81m gas
ventilation
perfusion
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Which kidney is not working properly ?

• The right one,
• How can you tell?

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Computer software enables us to look at the
kidney from all directions
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PET

• (Positron Emission Tomography)

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Cyclotron

• Used to make radionuclides for PET imaging

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The heart shows up clearly and the kidneys can be
seen. The brightest area shows that there is
cancer in a rib.
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Combined PET/CT
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Radiotherapy
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Radiotherapy

• Gamma rays can kill cancer cells, but are also
  dangerous to healthy cells
• We need to target the gamma rays to the cancer
  very precisely so that the radiation dose to
  healthy tissue is kept to a minimum.
• In particular we need to avoid any nearby organs
  such as eyes or spinal cord.

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Gamma Knife
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Planning the treatment
A medical physicist decides how to target the
gamma rays to destroy the tumour and minimise
damage to other tissue
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Summary

• Radiation can be dangerous so its use is
  carefully controlled
• In medicine, radioactive materials can be used in
  both diagnosis and treatment.
• Medical Physicists provide expert guidance and
  ensure that the radiation is controlled, measured
  and delivered to the benefit of the patient.

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Acknowledgements

• Thanks to Emily Cook, Jeff Jones, The Nuclear
  Medicine Department of The Royal Free Hospital,
  London, and The Cromwell Gamma Knife Centre,
  London for providing images
• This lesson was developed by Adam Gibson, Jeff
  Jones, David Sang, Angela Newing, Nicola Hannam
  and Emily Cook
• We have attempted to obtain permission and
  acknowledge the contributor of every image. If we
  have inadvertently used images in error, please
  contact us.