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

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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

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Questions?Questions?

Let’s get started...

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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???

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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