Basic radiation protection

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Basic radiation protection radiobiology

• By
• Dr. Mohsen Dashti
• Patient care management 202
• 14-3-10

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Discussion issues

• Ionizing radiation.
• Protecting the patient.
• Protecting the radiographer.
• Radiation monitoring.

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Ionizing radiation

• What are the sources of ionizing radiation?
• Natural radiation.
• - What is natural radiation?
• -- Sources of radiation that occur spontaneously
  in nature and can be affected by human activity.
• Examples
• -- Cosmic radiation.. The sun and other
  planets.
• -- Radioactive substances on earth. Uranium and
  radium.
• Natural radiation sources are given less
  attention to their hazardous potential.

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Ionizing radiation

• What are the sources of ionizing radiation?
• Manmade radiation.
• - What is manmade radiation?
• -- Sources of radiation that are developed by
  humans and used in different fields of
  technology.
• Examples
• -- Nuclear industry. Weapons nuclear power
  stations.
• -- Radionuclide. Radioactive elements
  radiopharmaceuticals.
• -- Medical radiation. Medical imaging dental
  exposure.

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Ionizing radiation

• Manmade radiation.
• It is known as x-rays, which is a form of
  electromagnetic radiation that travels at the
  speed of light depositing energy randomly.
• How can we produce x-rays?
• Source of electrons.
• Force to move electrons rapidly.
• Element to stop this movement rapidly.

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Ionizing radiation

• Manmade radiation.
• What happens to x-rays when they are produced?
• Absorbed.
• Scatter.
• Pass through undistributed.

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Ionizing radiation

• Manmade radiation.
• How do x-rays interact with matter?
• Classic coherent scattering.
• -- Interaction with matter in which a low-energy
  photon (below 10 keV) is absorbed and released
  with its same energy, frequency and wavelength
  but with change of direction.
• Photoelectric interaction.
• -- Interaction with matter in which proton
  strikes an inner shell electron, causing its
  ejection from orbit with complete absorption of
  the photons energy.

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Ionizing radiation

• Manmade radiation.
• How do x-rays interact with matter?
• Compton scattering.
• -- Interaction with matter in which a
  higher-energy photon strikes a loosely bound
  outer electron, removing it from its shell, and
  the remaining energy is released as scatter
  photon.
• Pair production.
• -- Interaction between matter and photon
  possessing a minimum of 1.02 MeV of energy,
  producing two oppositely charged particles.
• Photodisintegration.
• -- Interaction directly with the nucleus of
  photon possessing a minimum of 10 MeV, causing
  excitement followed by emission of nuclear
  fragment.

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Ionizing Radiation

• Standards for regulation of exposure
• What guidelines available to limit radiation
  dose?
• No-threshold.
• -- No dose exists below which the risk of damage
  does not exist.
• 2. Risk versus benefit.
• -- The benefit to the patient performing
  radiographic procedure far outweigh the risk of
  possible biologic damage.

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Ionizing radiation

• Radiation risk.

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Ionizing radiation

• ALARA
• To keep radiation dose as low as reasonably
  achievable.
• -- The annual whole-body dose-equivalent limit
  for the occupational worker is 50mSv (5 rem).
• -- The whole-body dose-equivalent limit for the
  general population is one tenth the occupational
  workers annual limit or 5 msv (0.5 rem).
• Sv unit in the SI system to measure the
  dose-equivalent or biologic effectiveness of
  differing radiation 1 Sv is equal to 100 rems.

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Ionizing radiation
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Protecting the patient

• ALARA concept can be practiced with the patient
  by utilizing 3 methods
• Time
• Time minimization is the most important element
  to protect the patient from radiation dose. How?
• -- Applying the rules of radiographic
  techniques.
• -- Using the exposure chart to determine the
  correct amount of radiation to produce an image.
• -- Minimizing repeat rates to reduce the
  patients time in the path of the x-ray beam.

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Protecting the patient

• Distance
• Distance maximization is another element to
  reduce patient radiation dose. Why?
• -- This serve to lessens the skin or entrance
  dose to the patient.
• -- Increasing the distance should be kept to a
  reasonable range so radiation dose will not be
  affected. How?
• -- For you to answer???
• Shielding
• Use of shield to protect sensitive or unexposed
  region of the patients body is another method to
  protect the patient from radiation dose.

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Protecting the patient

• Shielding
• The rule indicates that patients should be
  shielded whenever they are 4-5 cm from the
  primary x-ray beam.
• -- Shields are made of lead, which absorbs
  x-rays through the process of photoelectric
  effect, thereby minimizing patient exposure.
• Types of shield
• Flat contact shield made of a combination of
  vinyl and lead. Placed directly over the gonads
  of the patient.
• Shaped shield cup shaped and made specifically
  for male patients.

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Protecting the patient

• Shadow shield mounted on the side of the
  collimator of the x-ray tube and can be
  manipulated to extend into the path of the beam.

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Protecting the radiographer

• The same methods are used to protect the
  radiographer from extra radiation dose.
• The radiographer should spend the least amount of
  time possible in a room when a source of
  radiation is active.
• Fluoroscopy requires the radiographer to spend
  longer time in an active radiation room,
  therefore extra protection should be considered.
• Distance is the best measure to protect the
  radiographer from radiation dose.
• Inverse square law should be applied to reduce
  the impact of radiation dose.

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Protecting the radiographer

• Inverse square law The intensity of radiation
  varies inversely with the square of the distance.
  What does it mean?
• -- For you to answer???
• Submit your answer next
• week ?

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Protecting the patient

• Lead shield and aprons must be used by the
  radiographer whenever radiation is active.
• Aprons and lead shields must in in good
  conditions and crack free to avoid passing
  radiation into the radiographer.
• The minimum permissible amount of lead
  equivalency for aprons used where the peak
  kilovoltage is 100 should be 0.25 mm.

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Radiation monitoring

• Discuss the four main radiation monitoring
  methods used in x-rays film badges,
  thermoluminescent dosimeters, pocket dosimeters,
  and field survey instruments.

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See you next week