Hazards & protection

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Hazards & protection

  1. 1. Radiation Hazards and Protection 30 January 2015 1Dr Saad Wahby Al Bayatti
  2. 2. X- ray Dose Measurements X- ray Dose Units 30 January 2015 2Dr Saad Wahby Al Bayatti
  3. 3. Radiation Absorbed Dose • This is a measure of the amount of energy absorbed from the radiation beam per unit mass of tissue • Unit of measurement: • SI unit : Gray, (Gy) measured in joules/kg • original unit : rad, measured in ergs/gm • 1 Gray = 100 rads 30 January 2015 3Dr Saad Wahby Al Bayatti
  4. 4. Equivalent Dose • A measure which allows comparison between different types of radiation in regard to their absorbed doses in the body (RBE radiobiological effectiveness) • Unit of measurement (SI unit) : Sievert (Sv) • subunits : millisievert (mSv) ( ×1/1 000) • : microsievert ( µSv) ( ×1/1 000 000) • original unit : rem • 1 Sievert = 100 rems 30 January 2015 4Dr Saad Wahby Al Bayatti
  5. 5. Quality Factor (Q) • Represents the biological effects of each type of radiation: • X- rays, gamma rays and beta particles Q = 1 • Fast neutrons protons Q = 10 • Alpha particles Q = 20 30 January 2015 5Dr Saad Wahby Al Bayatti
  6. 6. Equivalent Dose • equivalent dose = radiation absorbed dose (Gy)× Q • Since Q for x -ray = 1, then equivalent dose = radiation absorbed dose (Sv) = (Gy) 30 January 2015 6Dr Saad Wahby Al Bayatti
  7. 7. Effective Dose • Each body tissue is affected differently by radiation • Effective dose: This is a measure that allows doses from different investigations of different parts of the body to be compared , by converting all doses to an equivalent whole body dose 30 January 2015 7Dr Saad Wahby Al Bayatti
  8. 8. Weighing Factor (W) • Measures the radiosensitivity, i.e.the risk of the tissue being damaged by radiation. • The higher the damage, the higher is W 30 January 2015 8Dr Saad Wahby Al Bayatti
  9. 9. Weighing factors for different body tissues Tissue Weighing factor Testes and ovaries 0.20 Red bone marrow, colon, lung, stomach 0.12 Breast, bladder, liver, thyroid 0.05 Bone surfaces , skin 0.01 Remainder 0.01 30 January 2015 9Dr Saad Wahby Al Bayatti
  10. 10. Effective Dose • Effective dose = equivalent dose × weighing factor = radiation absorbed dose(Gy)×Q ×W • SI unit : Sievert (Sv) • subunit : millisievert (mSv) • Effective dose (whole body) = sum of W 30 January 2015 10Dr Saad Wahby Al Bayatti
  11. 11. Absorbed dose Multiplied by a factor to reflect harm by a specific radiation Equivalent dose Multiplied by a factor to reflect sensitivity of a specific tissue Effective dose, commonly called “dose” 30 January 2015 11Dr Saad Wahby Al Bayatti
  12. 12. Effective doses X -ray examination X- ray exam. Effective dose (mSv) • CT cest 8.0 • barium meal 7.7 • lumbar spine 2.2 • CT head 2.0 • skull 0.1 • chest 0.04 • OPG 0.007 • 2 intra oral films (E speed) 0.002 30 January 2015 12Dr Saad Wahby Al Bayatti
  13. 13. The frequency of taking films is based on the following factors: 1. Patient’s oral hygiene 2. Caries activity 3. Dental history 4. Reliability of patient 5. ADA Guidelines
  14. 14. ADA Guidelines Full-mouth Series 1 - 5 years Bitewings 6 months - 3 years Panoramic 1 - 5 years
  15. 15. Biological Effects of X-ray 30 January 2015 15Dr Saad Wahby Al Bayatti
  16. 16. Radiobiology The response of living systems to ionizing radiation
  17. 17. Biological Effects of X-ray • X-Rays interact with living tissues and can cause biological changes. • These changes are mediated directly by excitation or ionization of atoms or indirectly as a result of chemical changes occurring near the cells. • Affected cells may be damaged or killed. 30 January 2015 17Dr Saad Wahby Al Bayatti
  18. 18. Biological Effects of X-ray (cont’d) • Genetic effects involve chromosomal damage or mutation in the reproductive cells and will affect future generations. • Somatic effects involve damage to other tissues and result in changes within the individual’s lifetime (e.g. radiation burns, leukemia). • Radiation is a particular hazard because its effects are painless, latent and cumulative 30 January 2015 18Dr Saad Wahby Al Bayatti
  19. 19. Incoming photon Excited electron Excitation 30 January 2015 19Dr Saad Wahby Al Bayatti
  20. 20. Incoming photon Ejected electron Photon Positive Ion Ionization Photon 30 January 2015 20Dr Saad Wahby Al Bayatti
  21. 21. Ionization The process of removing an electron from an electrically neutral atom to produce an ion. An ion is an atom or subatomic particle with a positive or negative charge.
  22. 22. Ionization negative ion positive ion
  23. 23. Attenuation Reduction of x-ray beam intensity (that reaches film) by interaction with matter. 1. Coherent scattering 2. Compton scattering 3. Photoelectric absorption
  24. 24. Coherent Scattering Low-energy x-ray interacts with outer- shell electron and causes it to vibrate briefly. Scattered x-ray of same energy as primary x-ray is then emitted, going in a different direction than primary x- ray. Electron not ejected from atom. (No ionization).
  25. 25. Coherent Scattering
  26. 26. Compton Scattering Outer shell electron ejected (Ionization) Scatter radiation results Occurs majority of the time 30% of scatter exits head
  27. 27. recoil electron scattered x-ray Compton Scattering primary x-ray The primary x-ray strikes an outer-shell electron, knocking it out of its orbit (ionization). The primary x- ray loses some of its energy and continues in a different direction as a scattered x-ray.
  28. 28. Inner-shell electron ejected (Ionization) Complete absorption Photoelectric Absorption
  29. 29. photoelectron primary x-ray Photoelectric Absorption The primary x-ray strikes an inner-shell electron, knocking it out of its orbit (ionization). The x-ray loses all of its energy and disappears. There is no scatter.
  30. 30. Dose-Response Curves threshold linear non-linear non-threshold Response Dose Linear: the response is directly related to the dose. Non-linear: the response is not proportionate to the dose. Threshold: the dose at which effects are produced; below this dose, there are no obvious effects. Non-threshold: any dose produces a response.
  31. 31. Critical Molecule (Target) DNA
  32. 32. Radical Atom or molecule that has an unpaired electron in the valence shell, making it highly reactive. (Most damaging).
  33. 33. Mutations Cell death Sublethal injury Biologic Effects
  34. 34. DNA altered; cell function altered or development changed. It is unclear which critical lesion/s in DNA may lead to cancer. Mutation Normal Mutation
  35. 35. Loss of capacity for mitosis Cell Death
  36. 36. Cellular Repair 1. Damage to biologic molecules (single-strand break of DNA) 2. Removal of damaged section by cell enzymes 3. Placement of new material by other cell enzymes
  37. 37. Radiation Effects Influenced by: Total dose Dose rate Total area covered Type of tissue Age
  38. 38. Sources of Radiation 30 January 2015 39Dr Saad Wahby Al Bayatti
  39. 39. Sources of Radiation • Natural background radiation - cosmic rays - gamma rays from rocks & soil 87% - ingested radioisotops in certain foods - radon decay products (granite ) • Artificial background radiation - fallout from nuclear explosions > 1% - radioactive waste • Medical and dental diagnostic radiation 12% • Occupational exposure > 1% 30 January 2015 40Dr Saad Wahby Al Bayatti
  40. 40. 30 January 2015 41Dr Saad Wahby Al Bayatti
  41. 41. Biologic Effects Of Ionizing Radiation Stochastic • The probability of occurrence of the change, rather than its severity, is dose dependant • All or non, the person either has the condition, or not • No threshold e.g. • Radiation induced cancer, greater exposure of population to radiation increases cancer probability, but not its severity Deterministic • The severity of response is proportional to the dose • Occur in all people when the dose is large enough • There is a dose threshold below which the response is not seen e.g. • Oral effects after radiation therapy • Radiation sickness after whole body radiation 30 January 2015 42Dr Saad Wahby Al Bayatti
  42. 42. Radiation Hazards 30 January 2015 43Dr Saad Wahby Al Bayatti
  43. 43. Radiation Hazards Nuclerar boms nueclear reactors leaks Whole body radiation Medical (diagnostic & theraputic) Dental X- rays Specific area radiation Radiation exposure 30 January 2015 44Dr Saad Wahby Al Bayatti
  44. 44. Specific Versus Whole-Body Radiation 30 January 2015 45Dr Saad Wahby Al Bayatti
  45. 45. Radiation Hazards Indirect Direct Somatic Affects individual No effect on offspring Genetic Do not affect individuial Offspring is affected Radiation damage 30 January 2015 46Dr Saad Wahby Al Bayatti
  46. 46. Radiation Hazards Direct Damage RH +Radiation R + + H + + e - R + Dissociation R + X + Y Cross-linking R + + S RS 30 January 2015 47Dr Saad Wahby Al Bayatti
  47. 47. Radiation Hazards Direct Damage Radiation • DNA /RNA molecule nuclear acid breakdown • Nuclear acid breakdown Somatic cells radiation induced malignancy Genetic cells radiation induced congenital abnormality 30 January 2015 48Dr Saad Wahby Al Bayatti
  48. 48. Radiation Hazards (indirect damage) Water Hydrolysis • H 2 O H + + OH - • H + + H + H2 • OH - + OH - H 2 O 2 Radiation 30 January 2015 49Dr Saad Wahby Al Bayatti
  49. 49. • H2O2 + DNA Molecular breakdown • H2O2 + Proteins • Molecular breakdown Cell damage Radiation Hazards (indirect damage) Water Hydrolysis 30 January 2015 50Dr Saad Wahby Al Bayatti
  50. 50. Radiation Hazards Direct DNA /RNA hit Radiation induced malignancy Indirect H2O2 formation TOXIC breakdown of large molecules(protiens/DNA) Somatic Radiation damage 30 January 2015 51Dr Saad Wahby Al Bayatti
  51. 51. Radiation Hazards Direct DNA/RNA hit Radiation induced congenital abnormality Indirect H2O2 formation TOXIC breakdown large molecules ( proteins/ DNA) Genetic Radiation damage 30 January 2015 52Dr Saad Wahby Al Bayatti
  52. 52. 30 January 2015 53Dr Saad Wahby Al Bayatti
  53. 53. 30 January 2015 54Dr Saad Wahby Al Bayatti
  54. 54. Factors Affecting Radiosensitvity • Dose: the amount of radiation received. The higher the dose, the greater is the effect (consider the threshold) • Dose rate: the rate of exposure. e.g. a total dose of 5Gy can be given as - 5Gy/min (single dose) is more destructive - 5mGy/min(fractionized), less destructive, injured cells can recover • Oxygen: the higher the O2 level in irradiated cells, the greater is the damage. (H2O2 formation) • Linear Energy Transfer (LET): the rate of loss of energy from a particle as it moves in its track through matter (tissue) e.g. alpha particles vs. X-ray 30 January 2015 55Dr Saad Wahby Al Bayatti
  55. 55. X- ray Protection 30 January 2015 56Dr Saad Wahby Al Bayatti
  56. 56. X- ray Protection Follow ALARA , keep exposure A = As L = Low A = As R = Reasonably A = Achievable 30 January 2015 57Dr Saad Wahby Al Bayatti
  57. 57. Patient Staff public X- ray protection 30 January 2015 58Dr Saad Wahby Al Bayatti
  58. 58. X- ray Protection Patient • Radiographs are only taken when necessary • Number, frequency and type of radiographs is the responsibility of the dentist • Use high output DC x- ray generators • Minimum kilovoltage should be 60kV • Minimum milliamperage should be 8 mA • Minimum filtration should be 1.5 mm Al 30 January 2015 59Dr Saad Wahby Al Bayatti
  59. 59. X- ray Protection Patient • Maximum Beam diameter should be 7 cm (circular beams) • Use rectangular collimation for intra oral films • Minimum target – skin distance should be 20 cm • Accurate timer • Use open- ended lead lined cylindrical cones (PID) • Do not use close ended pointed plastic cones 30 January 2015 60Dr Saad Wahby Al Bayatti
  60. 60. X- ray Protection Patient • Use high speed films (D or E ) • Use film holders and beam-aiming devices • Avoid retakes, master radiographic techniques • Avoid retakes, master film processing techniques • Use lead aprons • Use thyroid collars30 January 2015 61Dr Saad Wahby Al Bayatti
  61. 61. Lead Aprons 30 January 2015 62Dr Saad Wahby Al Bayatti
  62. 62. Lead Apron/Thyroid Collar Psychology Protection
  63. 63. Adult Patient’ s Lead apron with a thyroid collar Separate thyroid collar 30 January 2015 64Dr Saad Wahby Al Bayatti
  64. 64. Child Patient’ s Lead apron with and without thyroid collar 30 January 2015 65Dr Saad Wahby Al Bayatti
  65. 65. Operator’s Lead apron 30 January 2015 66Dr Saad Wahby Al Bayatti
  66. 66. Proper placement of the Lead apron with a thyroid collar 30 January 2015 67Dr Saad Wahby Al Bayatti
  67. 67. Correct way of hanging the Lead apron 30 January 2015 68Dr Saad Wahby Al Bayatti
  68. 68. Lead apron Without a thyroid collar 30 January 2015 69Dr Saad Wahby Al Bayatti
  69. 69. Correct way of hanging lead apron and thyroid collars 30 January 2015 70Dr Saad Wahby Al Bayatti
  70. 70. Lead apron hangers 30 January 2015 71Dr Saad Wahby Al Bayatti
  71. 71. X- ray Protection Staff • Never hold the x- ray head during exposure • Never hold the film during exposure • Never stand in the path of the primary beam • Stand behind a lead barrier (2 mm thickness) • Watch the patient through leaded glass during exposure • Stand minimum 2 M from the x-ray beam behind the patient’s head 30 January 2015 72Dr Saad Wahby Al Bayatti
  72. 72. X- ray Protection Public • Warning/Informative signals to indicate hazardous x- radiation • Patients should be seated away from x- ray rooms • Patients are not allowed to wait in corridors next to x- ray rooms 30 January 2015 73Dr Saad Wahby Al Bayatti
  73. 73. 30 January 2015 74Dr Saad Wahby Al Bayatti
  74. 74. Open –ended cylindrical Close ended plastic 7 cm 7 cm 30 January 2015 75Dr Saad Wahby Al Bayatti
  75. 75. Mobile lead barriers 30 January 2015 76Dr Saad Wahby Al Bayatti
  76. 76. Open-end cylindrical coneClose-end pointed cone √X 30 January 2015 77Dr Saad Wahby Al Bayatti
  77. 77. Rectangular modifications for an Open-end cylindrical cone 30 January 2015 78Dr Saad Wahby Al Bayatti
  78. 78. 30 January 2015 79Dr Saad Wahby Al Bayatti
  79. 79. Rectangular collimatorsCircular collimators Area of exit of the x-ray beam Area of exit of the x-ray beam Metal shield 30 January 2015 80Dr Saad Wahby Al Bayatti
  80. 80. Long cylindrical Open-end cone Short cylindrical Open-end cone Long rectangular cone Short rectangular cone 30 January 2015 81Dr Saad Wahby Al Bayatti
  81. 81. Patient 90-135 o o 90-135 X- ray head 90 o 90 o 180 o Operator Safe position Operator Safe position Scattered rays Scattered rays DangerDanger Safe operator’s position No barrier used 30 January 2015 82Dr Saad Wahby Al Bayatti
  82. 82. Patient 90-135 o o 90-135 90 o 90 o 180 o Operator’s Safe position Operator Safe position Scattered rays Scattered rays Danger Danger Safe operator’s position No barrier used 30 January 2015 83Dr Saad Wahby Al Bayatti
  83. 83. 30 January 2015 85Dr Saad Wahby Al Bayatti
  84. 84. 1 M 2 M A B Source Inverse square law I 1/D Intensity of radiation at B =1/4 at A 2 30 January 2015 86Dr Saad Wahby Al Bayatti
  85. 85. Inverse-square law states that the intensity (quantity) of X-ray is inversely proportional to the square of the distance from the source of radiation 30 January 2015 87Dr Saad Wahby Al Bayatti
  86. 86. 2 M minimum . Operator ` Patient Danger X -ray Safe operator’s position 30 January 2015 88Dr Saad Wahby Al Bayatti
  87. 87. Operator ` Lead barrier Using a lead barrier allows less than 2 M distance X- ray Patient Danger 30 January 2015 89Dr Saad Wahby Al Bayatti
  88. 88. Patient Operator ` Leaded wall room Leaded glass Danger X- ray 30 January 2015 90Dr Saad Wahby Al Bayatti
  89. 89. Patients’ Waiting rooms X- ray room X- ray room Restricted areas Restrictedareas Safe patients waiting rooms 30 January 2015 91Dr Saad Wahby Al Bayatti

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