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RADIATION PROTECTION IN RADIATION PROTECTION IN RADIOTHERAPYRADIOTHERAPY
Part 3: Radiation BiologyPart 3: Radiation BiologyPRACTICAL EXERCISEPRACTICAL EXERCISE
IAEA Training Material on Radiation Protection in Radiotherapy
Part 3, Practical 1 2Radiotherapy
Objectives of Part 3Objectives of Part 3 To understand the various effects of radiation To understand the various effects of radiation
on human tissueson human tissues To appreciate the difference between high To appreciate the difference between high
and low dose; deterministic and stochastic and low dose; deterministic and stochastic effectseffects
To gain a feel for the order of magnitude of To gain a feel for the order of magnitude of dose and effectsdose and effects
To appreciate the risks involved in the use of To appreciate the risks involved in the use of ionizing radiation as a starting point for a ionizing radiation as a starting point for a system of radiation protectionsystem of radiation protection
Part 3: Part 3: Radiation BiologyRadiation Biology
Practical 1: Calculation of cancer incidencePractical 1: Calculation of cancer incidence
IAEA Training Material on Radiation Protection in Radiotherapy
Part 3, Practical 1 4Radiotherapy
Contents + ObjectiveContents + Objective
Appreciate the order of magnitude of Appreciate the order of magnitude of radiation induced cancer for relatively radiation induced cancer for relatively small additional long term exposuressmall additional long term exposures
Perform a simple calculation using Perform a simple calculation using information given in the lectureinformation given in the lecture
Part 3, Practical 1 5Radiotherapy
How many additional cancers would we How many additional cancers would we expect in a population of 1000 people expect in a population of 1000 people
exposed to 5mSv per year for 20years?exposed to 5mSv per year for 20years?
……and how does this compare with the and how does this compare with the normal cancer mortality rate?normal cancer mortality rate?
Part 3, Practical 1 6Radiotherapy
AssumptionsAssumptions
Risk of cancer mortality is 0.05 per Sv Risk of cancer mortality is 0.05 per Sv (as per ICRP report 60 for low dose rate (as per ICRP report 60 for low dose rate exposure of the total population)exposure of the total population)
1,000 people are exposed to 5 mSv/y 1,000 people are exposed to 5 mSv/y for 20 yfor 20 y
Part 3, Practical 1 7Radiotherapy
Questions?Questions?
Let’s get started...
Part 3, Practical 1 8Radiotherapy
Example for Risk CalculationExample for Risk Calculation
Expected additional cancer deaths is0.05 [cancers/Sv]x0.005[Sv/y]x20[y]x1,000[people]
= 5 additional cancer deaths due to radiation
Part 3, Practical 1 9Radiotherapy
Example for Risk CalculationExample for Risk Calculation Expected additional cancer deaths is 5 Expected additional cancer deaths is 5
additional cancer deaths due to radiationadditional cancer deaths due to radiation
General population: 23% of all deaths due to General population: 23% of all deaths due to cancercancer
Therefore have 230 expected cancer deaths Therefore have 230 expected cancer deaths due to other causes...due to other causes...
Can we pick 5 additional ones???Can we pick 5 additional ones???
Part 3, Practical 1 10Radiotherapy
Other interesting points...Other interesting points...
This assumes stochastic effects onlyThis assumes stochastic effects only Radiation induced cancer are not Radiation induced cancer are not
distinguishable from other cancers (at least distinguishable from other cancers (at least not at present)not at present)
Illustration of the difficulty of producing good Illustration of the difficulty of producing good epidemiological evidenceepidemiological evidence
Calculations become more complex for Calculations become more complex for individual tissue exposures individual tissue exposures vs.vs. whole body whole body exposuresexposures