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Medical Physics and Radioactivity

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Title: Medical Physics and Radioactivity


1
Medical Physics and Radioactivity
2
Radioactivity
3
Unstable nucleus
Electromagnetic wave
particle
Atoms which emit electromagnetic radiation or a
particle by the spontaneous transformation of
their nucleus are called radioactive.
4
Types of radiation
  • Alpha Particle (a)
  • Beta Particle (ß)
  • Gamma Ray (?)

5
Uranite a rock which contains uranium
6
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).

7
Detection and Measurement
8
Radiation detector
Each particle or gamma ray is seen as a
deflection on the meter needle and is heard as a
click
9
The detector is responding to the radiation being
emitted from the uranium ore
10
Nuclear Medicine
11
  • 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.

12
Labelling chemicals with the radioactive isotopes
13
Lead
Preparing the tracer
14
The tracer is injected into the patient
15
Gamma Camera
A gamma camera detects the radiation coming from
the patient and produces an image of where the
radioactivity is in the body.
16
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?
17
Lung scan using Krypton-81m gas
18
Lung scan using Krypton-81m gas
ventilation
perfusion
19
Which kidney is not working properly ?
  • The right one,
  • How can you tell?

20
Computer software enables us to look at the
kidney from all directions
21
PET
  • (Positron Emission Tomography)

22
Cyclotron
  • Used to make radionuclides for PET imaging

23
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24
The heart shows up clearly and the kidneys can be
seen. The brightest area shows that there is
cancer in a rib.
25
Combined PET/CT
26
Radiotherapy
27
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.

28
Gamma Knife
29
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30
Planning the treatment
A medical physicist decides how to target the
gamma rays to destroy the tumour and minimise
damage to other tissue
31
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.

32
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33
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.
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