Medical Physics and Radioactivity

Transcription

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 (α) - Beta Particle (β) Gamma Ray (γ)

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 Preparing the tracer Lead

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 A blood clot in the right lung is preventing blood from reaching the lower lobe of the right lung, although the ventilation image shows that air is filling that region.

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

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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. tumour heart kidney

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 The radiation has to be precisely targeted. Metal windows restrict the gamma ray beam size This is the Gamma Knife in position. A patient s eye view A polystyrene model shows the position that the patients head would occupy.

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.

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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.