Training Module 2 – Version 1.1

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Radiation

Training Module 2 – Version 1.1

For Internal Use Only

®

Radiation

Origin of Radiation and History

Nature of Radiation

Radiation and Life

Radiation Detection and Safety

Training Module 2 – Version 1.1

For Internal Use Only

®

Radiation

Origin of Radiation and History

Nature of Radiation

Radiation and Life

Radiation Detection and Safety

Training Module 2 – Version 1.1

For Internal Use Only

®

Origin of Radiation and History

Sources of radiation doses (UK)

Training Module 2 – Version 1.1

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Cosmic radiation

Origin of Radiation and History

Radiation doses depending on where we are

Background radiation in Europe

Training Module 2 – Version 1.1

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Origin of Radiation and History

1895 Wilhelm Roentgen discovered X-rays

1896 Henri Becquerel discovered natural radioactivity in uranium

1998 Marie and Pierre Curie identified elemental radium, thorium and polonium

1901 First recorded medical use of a radioactive substance (radium on TB lesion)

1918 Ernest Rutherford observed constituents of the atomic nucleus

1930 Lawrence and Livingstone constructed the first cyclotron

1934 Enrico Fermi produced artificial radioactivity

1942 First controlled uranium fission reaction

1945 Bombs dropped on Hiroshima and Nagasaki

1954 First industrial scale nuclear power reactor in Russia

1964 Hal Anger invented the gamma camera for radionuclide imaging

1972 First patients underwent CT scanning

1986 Chernobyl reactor incident

Training Module 2 – Version 1.1

For Internal Use Only

®

Radiation

Origin of Radiation and History

Nature of Radiation

Radiation and Life

Radiation Detection and Safety

Training Module 2 – Version 1.1

For Internal Use Only

®

Nature of Radiation

Composition of matter

Matter is composed of molecules

Molecules are composed of atoms

Atoms are composed of subatomic particles

Training Module 2 – Version 1.1

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Nature of Radiation

Atom model

atom

electron (-)

neutron

proton (+)

nucleus

Training Module 2 – Version 1.1

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Nature of Radiation

Standard atomic notation

XA

Z N

atomic mass (Z+N)

atomic number(number of protons)

(number of neutrons)

Training Module 2 – Version 1.1

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Nature of Radiation

Stability of atoms depending on the proton/neutron ratio

very unstable

unstable

stab

le

Unstable atoms decay into stable atoms, emitting α-,β-,γ-radiation

Training Module 2 – Version 1.1

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Nature of Radiation

Radioactive decay

Unstable atoms decay into stable atoms, emitting either α-,β- or γ-radiation

radiation

They are - what we call – radioactive!

unstable stable

Training Module 2 – Version 1.1

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Nature of Radiation

Alpha decay

nucleus (helium atom nucleus)

Very large unstable atoms can transform themselves into smaller atoms by emitting alpha radiation

Training Module 2 – Version 1.1

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Nature of Radiation

Beta decayelectron

Too many neutrons result in a negatron decay

Too many protons result in a positron decay

positron

Training Module 2 – Version 1.1

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Nature of Radiation

Gamma decay

If the ratio of neutron and protons is within a stable range, but the energy of the nucleus is greater than the resting level, the excess nuclear energy is emitted as a gamma ray.

Training Module 2 – Version 1.1

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Nature of Radiation

Gamma ray

Gamma ray is a photon (energy) with a much higher energy than visible light.

Wavelength [m]

low energy

high energy

Training Module 2 – Version 1.1

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Nature of Radiation

Penetrating properties of radiation

α

β

γ

paper copper / perspex

lead / concrete

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Nature of Radiation

Bremsstrahlung (‘braking radiation’)

β

lead / perspex

γ

The intensity depends on the density of the material; the denser the material the more Bremsstrahlung.

Training Module 2 – Version 1.1

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Nature of Radiation

Half-life time (t½)

The half-life of a radioactive material is the time taken for an arbitrary sample to halve its original amount of activity

Training Module 2 – Version 1.1

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Nature of Radiation

Measurement of radioactivity

The amount of any radionuclide may be expressed as the number of decays per unit time. The SI unit is Becquerel, but Curie is also still used.

One Becquerel (Bq) is defined as 1 radioactive decay per second

One Curie (Ci) is defined as 3.7x1010 radioactive decays per second

1 Ci = 3.7x1010 Bq = 3.7x104 MBq = 37 GBq (M=Mega; G=Giga)

1 Bq = 2.7x10-11 Ci = 27 pCi (p=pico)

Training Module 2 – Version 1.1

For Internal Use Only

®

Nature of Radiation

Measurement of radioactivity

The amount of any radionuclide may be expressed as the number of decays per unit time. The SI unit is Becquerel, but Curie is also still used.

One Becquerel (Bq) is defined as 1 radioactive decay per second

One Curie (Ci) is defined as 3.7x1010 radioactive decays per second

Describes the activity of the PRODUCT

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Nature of Radiation

Measurement of absorbed dose

The unit of absorbed radiation dose is the gray (Gy) named after L.H.Gray, one of the first radiobiologist.

The absorbed dose is a measure of the energy imparted per unit mass of tissue.

One Gray (Gy) is equivalent to an absorbed radiation energy of 1 joule per kilogram of tissue

In the US the unit rad is still in use. 100 rads being equivalent to 1 Gy

Training Module 2 – Version 1.1

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One Gray (Gy) is equivalent to an absorbed radiation energy of 1 joule per kilogram of tissue

Nature of Radiation

Measurement of absorbed dose

The unit of absorbed radiation dose is the gray (Gy) named after L.H.Gray, one of the first radiobiologist.

The absorbed dose is a measure of the energy imparted per unit mass of tissue.

Describes the intensity of the TREATMENT

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Nature of Radiation

Measurement of dose equivalent

The dose equivalent is the unit of absorbed energy that takes into account the estimated biologic effect of the type of radiation that imparts the energy to the tissue. The SI unit is Sievert (Sv).

The relative damage for each type of radiation is referred to as its quality factor (QF)

dose in Sievert = dose in Gray x QF

QF (alpha)=10-20, QF (protons, neutrons)=10, QF (beta, gamma)=1

Training Module 2 – Version 1.1

For Internal Use Only

®

Nature of Radiation

Measurement of dose equivalent

The dose equivalent is the unit of absorbed energy that takes into account the estimated biologic effect of the type of radiation that imparts the energy to the tissue. The SI unit is Sievert (Sv).

The relative damage for each type of radiation is referred to as its quality factor (QF)

dose in Sievert = dose in Gray x QF

Describes the amount of personal EXPOSURE

Training Module 2 – Version 1.1

For Internal Use Only

®

Radiation

Origin of Radiation and History

Nature of Radiation

Radiation and Life

Radiation Detection and Safety

Training Module 2 – Version 1.1

For Internal Use Only

®

Radiation and Life

The biological effects of radiation depend upon

Type of radiation (α,β,γ)

Amount of radiation (dose)

Time of exposure

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Radiation and Life

α-radiation: 0.04mm 5Mevβ-radiation: 7mm 1MeVγ-radiation: 65cm 1MeV

skin

muscle

Radiation penetration

Radiation Distance Energy

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Radiation and Life

Radiation effect after short time exposure

Less than 0.5 Sv temporary blood effects

0.8-1.2 Sv 10% Nausea and vomiting

4-5 Sv 50% lethal

5.5-7.5Sv 100% lethal

50 Sv Death within 1 week

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Radiation and Life

The sequence of events resulting in radiation damage

Initial InteractionIonization and excitation

10-17 to 10-15 seconds

Chemical DamageFree radical production

10-14 to 10-3 seconds

Biomolecular DamageProteins and nucleic acid damage

Seconds to hours

Biological DamageCell mutation, cell death and animal death

Hours to decades

Training Module 2 – Version 1.1

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Radiation and Life

Cellular effects

All radiation injury results primarily from radiation induced chemical changes in one or more of the complex molecules

(mainly DNA) which are present in living cells

Training Module 2 – Version 1.1

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Radiation and Life

Radiosensitivity and cell cycle

The greatest amount of damage occurs during the period of mitosis where one cell divides into two individual cells

Training Module 2 – Version 1.1

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Radiation and Life

Tissue sensitivity

Different organs of the body vary in their sensitivity to absorbed doses of radiation

The most sensitive organs are generally those with the highest rate of cellular replication

These are bone marrow, lung, thyroid, bone, gonads and female breast

Training Module 2 – Version 1.1

For Internal Use Only

®

Radiation

Origin of Radiation and History

Nature of Radiation

Radiation and Life

Radiation Detection and Safety

Training Module 2 – Version 1.1

For Internal Use Only

®

Radiation Detection and Safety

Monitors used for detection of radioactivity

pancake probe (α-, β- and γ-radiation)

scintillation probe (β- and γ-radiation)high sensitivity

monitor

reading

multiplier

Training Module 2 – Version 1.1

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Radiation Detection and Safety

Personal dosimetry

electronic dosimeter

thermo luminescent dose meter (TLD)

film badge

finger ring (TLD)

Dose limits recommended by the ICRP (1991):

Occupational: 100mSv in 5 years, 50mSv maximum in any year

Public: 5mSv in any 5 consecutive years

Training Module 2 – Version 1.1

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Radiation Detection and Safety

Dose calibrator

ionization chamber

electrometer

The exact amount of radioactivity can be assayed in a dose calibrator. A factor appropriate for the energy of the radionuclide is

entered and the amount of radioactivity can be read directly.

Training Module 2 – Version 1.1

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Radiation Detection and Safety

Radiation protection

The 3 methods of reducing external exposure relate to:

Time of exposure (the less the better)

Distance to the source (the more the better)

Appropriate Shielding (the more the better)

Training Module 2 – Version 1.1

For Internal Use Only

®

Radiation

Origin of Radiation and History

Nature of Radiation

Radiation and Life

Radiation Detection and Safety

Training Module 2 – Version 1.1

For Internal Use Only

®

Radiation

α-,β-,γ-radiation and Bremsstrahlung

radioactive decay and half-life time

absorbed dose and dose equivalent

biological effects of radiation

principles of radiation protection

What is most important to remember?