Radiation
®
Training Module 2 – Version 1.1
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Radiation
®
Training Module 2 – Version 1.1
Origin of Radiation and History
Nature of Radiation
Radiation and Life
Radiation Detection and Safety

Radiation
®
Training Module 2 – Version 1.1
Origin of Radiation and History
Nature of Radiation
Radiation and Life
Radiation Detection and Safety

Origin of Radiation and History
®
Training Module 2 – Version 1.1
Sources of radiation doses (UK)
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Origin of Radiation and History
®
Training Module 2 – Version 1.1
Radiation doses depending on where we are
Background radiation in Europe
Cosmic radiation
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Origin of Radiation and History
®
Training Module 2 – Version 1.1
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
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Radiation
®
Training Module 2 – Version 1.1
Origin of Radiation and History
Nature of Radiation
Radiation and Life
Radiation Detection and Safety

Nature of Radiation
®
Training Module 2 – Version 1.1
Composition of matter
 Matter is composed of molecules
 Molecules are composed of atoms
 Atoms are composed of subatomic particles
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Nature of Radiation
®
Training Module 2 – Version 1.1
Atom model
electron (-)
nucleus
neutron
proton (+)
atom
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Nature of Radiation
®
Training Module 2 – Version 1.1
Standard atomic notation
atomic mass (Z+N)
A
Z
atomic number
(number of protons)
X
N
(number of neutrons)
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Nature of Radiation
®
Training Module 2 – Version 1.1
Stability of atoms depending on the proton/neutron ratio
unstable
very unstable
Unstable atoms decay into stable atoms,
emitting α-,β-,γ-radiation
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Nature of Radiation
®
Training Module 2 – Version 1.1
Radioactive decay
Unstable atoms decay into stable atoms,
emitting either α-,β- or γ-radiation
radiation
unstable
stable
They are - what we call – radioactive!
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Nature of Radiation
®
Training Module 2 – Version 1.1
Alpha decay
nucleus
(helium atom nucleus)
Very large unstable atoms can transform themselves into smaller
atoms by emitting alpha radiation
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Nature of Radiation
®
Training Module 2 – Version 1.1
Beta decay
electron
Too many neutrons result in a
negatron decay
positron
Too many protons result in a
positron decay
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Nature of Radiation
®
Training Module 2 – Version 1.1
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.
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Nature of Radiation
®
Training Module 2 – Version 1.1
Gamma ray
Wavelength [m]
low
energy
high
energy
Gamma ray is a photon (energy) with a much higher energy than
visible light.
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Nature of Radiation
®
Training Module 2 – Version 1.1
Penetrating properties of radiation
α
β
γ
paper
copper /
perspex
lead /
concrete
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Nature of Radiation
®
Training Module 2 – Version 1.1
Bremsstrahlung (‘braking radiation’)
γ
β
lead / perspex
The intensity depends on the density of the material; the denser
the material the more Bremsstrahlung.
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Nature of Radiation
®
Training Module 2 – Version 1.1
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
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Nature of Radiation
®
Training Module 2 – Version 1.1
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)
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Nature of Radiation
®
Training Module 2 – Version 1.1
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
®
Training Module 2 – Version 1.1
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
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Nature of Radiation
®
Training Module 2 – Version 1.1
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
Describes the intensity of the
TREATMENT
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Nature of Radiation
®
Training Module 2 – Version 1.1
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
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Nature of Radiation
®
Training Module 2 – Version 1.1
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

Radiation
®
Training Module 2 – Version 1.1
Origin of Radiation and History
Nature of Radiation
Radiation and Life
Radiation Detection and Safety

Radiation and Life
®
Training Module 2 – Version 1.1
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
®
Training Module 2 – Version 1.1
Radiation penetration
skin
muscle
Radiation
α-radiation:
β-radiation:
γ-radiation:
Distance
0.04mm
7mm
65cm
Energy
5Mev
1MeV
1MeV
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Radiation and Life
®
Training Module 2 – Version 1.1
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
®
Training Module 2 – Version 1.1
The sequence of events resulting in radiation damage
Initial Interaction
Ionization and excitation
10-17 to 10-15 seconds
Chemical Damage
Free radical production
10-14 to 10-3 seconds
Biomolecular Damage
Proteins and nucleic acid damage
Seconds to hours
Biological Damage
Cell mutation, cell death and animal death
Hours to decades
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Radiation and Life
®
Training Module 2 – Version 1.1
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
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Radiation and Life
®
Training Module 2 – Version 1.1
Radiosensitivity and cell cycle
The greatest amount of damage occurs during the period of
mitosis where one cell divides into two individual cells
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Radiation and Life
®
Training Module 2 – Version 1.1
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
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Radiation
®
Training Module 2 – Version 1.1
Origin of Radiation and History
Nature of Radiation
Radiation and Life
Radiation Detection and Safety

Radiation Detection and Safety
®
Training Module 2 – Version 1.1
Monitors used for detection of radioactivity
reading
multiplier
scintillation probe
(β- and γ-radiation)
high sensitivity
monitor
pancake probe
(α-, β- and γ-radiation)
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Radiation Detection and Safety
®
Training Module 2 – Version 1.1
Personal dosimetry
electronic dosimeter
film badge
thermo luminescent
dose meter (TLD)
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
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Radiation Detection and Safety
®
Training Module 2 – Version 1.1
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.
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Radiation Detection and Safety
®
Training Module 2 – Version 1.1
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)

Radiation
®
Training Module 2 – Version 1.1
Origin of Radiation and History
Nature of Radiation
Radiation and Life
Radiation Detection and Safety

Radiation
®
Training Module 2 – Version 1.1
What is most important to remember?
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
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