Radiation

1. Radiation 

2. Radiation Origin of Radiation and History Nature of Radiation Radiation and Life Radiation Detection and Safety 

3. Radiation Origin of Radiation and History Nature of Radiation Radiation and Life Radiation Detection and Safety 

4. Origin of Radiation and History Sources of radiation doses (UK) 

5. Cosmic radiation Origin of Radiation and History Radiation doses depending on where we are Background radiation in Europe 

6. Origin of Radiation and History 1895 Wilhelm Roentgen discovered X-rays 1896 Henri Becquerel discovered natural radioactivity in uranium 1998 Marie and Pierre Curie identified elemental radium, thorium and polonium 1901 First recorded medical use of a radioactive substance (radium on TB lesion) 1918 Ernest Rutherford observed constituents of the atomic nucleus 1930 Lawrence and Livingstone constructed the first cyclotron 1934 Enrico Fermi produced artificial radioactivity 1942 First controlled uranium fission reaction 1945 Bombs dropped on Hiroshima and Nagasaki 1954 First industrial scale nuclear power reactor in Russia 1964 Hal Anger invented the gamma camera for radionuclide imaging 1972 First patients underwent CT scanning 1986 Chernobyl reactor incident 

7. Radiation Origin of Radiation and History Nature of Radiation Radiation and Life Radiation Detection and Safety 

8. Nature of Radiation Composition of matter • Matter is composed of molecules • Molecules are composed of atoms • Atoms are composed of subatomic particles 

9. Nature of Radiation Atom model electron (-) nucleus neutron proton (+) atom 

10. Nature of Radiation Standard atomic notation atomic mass (Z+N) X A Z N (number of neutrons) atomic number (number of protons) 

11. Nature of Radiation Stability of atoms depending on the proton/neutron ratio unstable stable very unstable Unstable atoms decay into stable atoms, emitting α-,β-,γ-radiation 

12. Nature of Radiation Radioactive decay Unstable atoms decay into stable atoms, emitting either α-,β- or γ-radiation radiation unstable stable They are - what we call – radioactive! 

13. Nature of Radiation Alpha decay nucleus (helium atom nucleus) Very large unstable atoms can transform themselves into smaller atoms by emitting alpha radiation 

14. Nature of Radiation Beta decay electron positron Too many neutrons result in a negatron decay Too many protons result in a positron decay 

15. Nature of Radiation Gamma decay If the ratio of neutron and protons is within a stable range, but the energy of the nucleus is greater than the resting level, the excess nuclear energy is emitted as a gamma ray. 

16. Nature of Radiation Gamma ray Wavelength [m] low energy high energy Gamma ray is a photon (energy) with a much higher energy than visible light. 

17. Nature of Radiation Penetrating properties of radiation α β γ lead / concrete copper / perspex paper 

18. Nature of Radiation Bremsstrahlung (‘braking radiation’) γ β lead / perspex The intensity depends on the density of the material; the denser the material the more Bremsstrahlung. 

19. The half-life of a radioactive material is the time taken for an arbitrary sample to halve its original amount of activity Nature of Radiation Half-life time (t½) 

20. One Becquerel (Bq) is defined as 1 radioactive decay per second One Curie (Ci) is defined as 3.7x1010 radioactive decays per second Nature of Radiation Measurement of radioactivity The amount of any radionuclide may be expressed as the number of decays per unit time. The SI unit is Becquerel, but Curie is also still used. 1 Ci = 3.7x1010 Bq = 3.7x104 MBq = 37 GBq (M=Mega; G=Giga) 1 Bq = 2.7x10-11 Ci = 27 pCi (p=pico) 

21. One Becquerel (Bq) is defined as 1 radioactive decay per second One Curie (Ci) is defined as 3.7x1010 radioactive decays per second Nature of Radiation Measurement of radioactivity The amount of any radionuclide may be expressed as the number of decays per unit time. The SI unit is Becquerel, but Curie is also still used. Describes the activity of the PRODUCT 

22. One Gray (Gy) is equivalent to an absorbed radiation energy of 1 joule per kilogram of tissue Nature of Radiation Measurement of absorbed dose The unit of absorbed radiation dose is the gray (Gy) named after L.H.Gray, one of the first radiobiologist. The absorbed dose is a measure of the energy imparted per unit mass of tissue. In the US the unit rad is still in use. 100 rads being equivalent to 1 Gy 

23. One Gray (Gy) is equivalent to an absorbed radiation energy of 1 joule per kilogram of tissue Nature of Radiation Measurement of absorbed dose The unit of absorbed radiation dose is the gray (Gy) named after L.H.Gray, one of the first radiobiologist. The absorbed dose is a measure of the energy imparted per unit mass of tissue. Describes the intensity of the TREATMENT 

24. dose in Sievert = dose in Gray x QF Nature of Radiation Measurement of dose equivalent The dose equivalent is the unit of absorbed energy that takes into account the estimated biologic effect of the type of radiation that imparts the energy to the tissue. The SI unit is Sievert (Sv). The relative damage for each type of radiation is referred to as its quality factor (QF) QF (alpha)=10-20, QF (protons, neutrons)=10, QF (beta, gamma)=1 

25. dose in Sievert = dose in Gray x QF Nature of Radiation Measurement of dose equivalent The dose equivalent is the unit of absorbed energy that takes into account the estimated biologic effect of the type of radiation that imparts the energy to the tissue. The SI unit is Sievert (Sv). The relative damage for each type of radiation is referred to as its quality factor (QF) Describes the amount of personal EXPOSURE 

26. Radiation Origin of Radiation and History Nature of Radiation Radiation and Life Radiation Detection and Safety 

27. Radiation and Life The biological effects of radiation depend upon • Type of radiation (α,β,γ) • Amount of radiation (dose) • Time of exposure 

28. Radiation and Life Radiation penetration skin muscle Radiation Distance Energy α-radiation: 0.04mm 5Mev β-radiation: 7mm 1MeV γ-radiation: 65cm 1MeV 

29. Radiation and Life Radiation effect after short time exposure Less than 0.5 Sv temporary blood effects 0.8-1.2 Sv 10% Nausea and vomiting 4-5 Sv 50% lethal 5.5-7.5Sv 100% lethal 50 Sv Death within 1 week 

30. Radiation and Life The sequence of events resulting in radiation damage Initial Interaction Ionization and excitation 10-17 to 10-15 seconds Chemical Damage Free radical production 10-14 to 10-3 seconds Biomolecular Damage Proteins and nucleic acid damage Seconds to hours Biological Damage Cell mutation, cell death and animal death Hours to decades 

31. Radiation and Life Cellular effects All radiation injury results primarily from radiation induced chemical changes in one or more of the complex molecules (mainly DNA) which are present in living cells 

32. Radiation and Life Radiosensitivity and cell cycle The greatest amount of damage occurs during the period of mitosis where one cell divides into two individual cells 

33. Radiation and Life Tissue sensitivity Different organs of the body vary in their sensitivity to absorbed doses of radiation The most sensitive organs are generally those with the highest rate of cellular replication These are bone marrow, lung, thyroid, bone, gonads and female breast 

34. Radiation Origin of Radiation and History Nature of Radiation Radiation and Life Radiation Detection and Safety 

35. Radiation Detection and Safety Monitors used for detection of radioactivity reading multiplier scintillation probe (β- and γ-radiation) high sensitivity monitor pancake probe (α-, β- and γ-radiation) 

36. Radiation Detection and Safety Personal dosimetry electronic dosimeter film badge thermo luminescent dose meter (TLD) finger ring (TLD) Dose limits recommended by the ICRP (1991): Occupational: 100mSv in 5 years, 50mSv maximum in any year Public: 5mSv in any 5 consecutive years 

37. Radiation Detection and Safety Dose calibrator ionization chamber electrometer The exact amount of radioactivity can be assayed in a dose calibrator. A factor appropriate for the energy of the radionuclide is entered and the amount of radioactivity can be read directly. 

38. Radiation Detection and Safety Radiation protection The 3 methods of reducing external exposure relate to: • Time of exposure (the less the better) • Distance to the source (the more the better) • Appropriate Shielding (the more the better) 

39. Radiation Origin of Radiation and History Nature of Radiation Radiation and Life Radiation Detection and Safety 

40. Radiation What is most important to remember? α-,β-,γ-radiation and Bremsstrahlung radioactive decay and half-life time absorbed dose and dose equivalent biological effects of radiation principles of radiation protection 