RADIATION PROTECTION IN RADIOTHERAPY

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RADIATION PROTECTION IN RADIOTHERAPY
IAEA Training Material on Radiation Protection in
Radiotherapy

• Part 3 Radiation BiologyPRACTICAL EXERCISE

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Objectives of Part 3

• To understand the various effects of radiation on
  human tissues
• To appreciate the difference between high and low
  dose deterministic and stochastic effects
• To gain a feel for the order of magnitude of dose
  and effects
• To appreciate the risks involved in the use of
  ionizing radiation as a starting point for a
  system of radiation protection

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Part 3 Radiation Biology
IAEA Training Material on Radiation Protection in
Radiotherapy

• Practical 1 Calculation of cancer incidence

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Contents Objective

• Appreciate the order of magnitude of radiation
  induced cancer for relatively small additional
  long term exposures
• Perform a simple calculation using information
  given in the lecture

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How many additional cancers would we expect in a
population of 1000 people exposed to 5mSv per
year for 20years?

• and how does this compare with the normal cancer
  mortality rate?

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Assumptions

• Risk of cancer mortality is 0.05 per Sv (as per
  ICRP report 60 for low dose rate exposure of the
  total population)
• 1,000 people are exposed to 5 mSv/y for 20 y

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Questions?

• Lets get started...

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Example for Risk Calculation

• Expected additional cancer deaths is
• 0.05 cancers/Svx0.005Sv/yx20yx1,000people
• 5 additional cancer deaths due to radiation

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Example for Risk Calculation

• Expected additional cancer deaths is 5 additional
  cancer deaths due to radiation
• General population 23 of all deaths due to
  cancer
• Therefore have 230 expected cancer deaths due to
  other causes...
• Can we pick 5 additional ones???

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Other interesting points...

• This assumes stochastic effects only
• Radiation induced cancer are not distinguishable
  from other cancers (at least not at present)
• Illustration of the difficulty of producing good
  epidemiological evidence
• Calculations become more complex for individual
  tissue exposures vs. whole body exposures