PRACTICAL RADIATION PHYSICS FOR EMERGENCY MEDICAL PERSONNEL

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PRACTICAL RADIATION PHYSICS FOR EMERGENCY
MEDICAL PERSONNEL
Module III
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What is radiation?
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Ionizing radiation
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Electromagnetic radiation
IONIZING RADIATON
VISIBLE
X-RAYS
COSMIC
MICROVAVES
GAMMA
INFRARED
ULTRAVIOLET
TV, RADIO
Decreasing wave length
Increasing frequency
Increasing photon energy
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Forms of ionizing radiation
Directly ionizing
Particulate radiation
consisting of atomic or subatomic particles
(electrons, protons, etc.) which carry energy in
the form of kinetic energy of mass in motion
Indirectly ionizing
Electromagnetic radiation
in which energy is carried by oscillating
electrical and magnetic fields travelling through
space at speed of light
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Origin of radiation

• What is the relationship between atom structure
  and radiation production?

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Atom anatomy
Proton
Neutron
Electron
Nucleons
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Isotopes
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Why are some nuclides radioactive?Neutron to
proton ratio
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Half-life

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Activity

The number of decaying nuclei per unit of time
The Systéme International (SI) unit of
radioactivity is the Becquerel (Bq) One Bq 1
disintegration per second Non-SI unit of
radioactivity is the Curie (Ci) One Ci 3,7 x
1010 transformations per second One milicurie
(mCi) 3,7 x 107 s-1 One microcurie (µCi) 3.7
x 104 s-1 1 Bq 2.7 x 10-11 Ci
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Atomic symbols
MASS NUMBER (the number of protons and
neutrons)
A
XN
SYMBOL OF ELEMENT
Z
The number of neutrons
ATOMIC NUMBER (the number of protons)
Example
131
53I78
131I or I-131
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Mass-energy relationship
Measured Mass
Calculated Mass
E mc2
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Fission
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Nuclear reaction and energy production
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Mechanisms of radioactive decay
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Alpha (a) decay
AZX A-4Z-2Y 42He e.g. 23892U
23490Th 42He
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Beta (?-) decay

• n p e- ?
• AZX?AZ1 Y e- ? e.g. 13153 I ? 13154
  Xee-?

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Positron (?) decay
p n e ? AZX?AZ-1 Ye ?
e.g. 189 F? 188Oe?
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Electron capture
p e- ?n ? AZX? AZ-1 Y ? 12553 I ?
12552 Te?
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Gamma (?) emission
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Nuclear energy levelsgamma radiation
SIMPLIFIED NUCLEAR MODEL
Gamma ray
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How does radiation interact with matter?
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Excitation
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Ionization
Electron removal by ionization
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Alpha particle interaction
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Interaction of alpha radiation with living
matter external deposition

• Alpha radiation is not external hazard.
• The maximum range in tissue is lt0.1 mm
• All alpha radiation is absorbed in stratum
  corneum

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Interaction of alpha radiation with living
matter internal deposition
Prime danger is inhalation and ingestion of alpha
emitter
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Beta interaction with matter
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Interaction of beta radiation with living matter
Cell nucleus
Cell diameter
100 cell diameter
alpha
1.7 MeV beta
0.15 MeV beta
beta
5.3 MeV alpha
Auger
I I I I
I i
0.001 0.01 0.1 1
10 100
mm
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Positron interactionannihilation reaction
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Neutron interaction
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Neutron activation
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Interaction of gamma radiation with matter

• In terms of ionization, gamma radiation interacts
  with matter in three main ways
• 1. Photoelectric effect
• 2. Compton scattering
• 3. Pair production

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Gamma interaction by photoelectric effect
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Gamma interaction by Compton scattering
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Pair production
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Extranuclear energy release

• Bremsstrahlung radiation
• Characteristic X rays
• Auger electrons

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Bremsstrahlung radiation
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Importance of bremsstrahlung X rays in
radiation safety practice
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Characteristic X rays
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Difference between X rays and gamma rays
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Internal conversionAuger electrons
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Specific ionization andlinear energy transfer
(LET)
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Penetrating power of radiation
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Review points

• Characteristics of representative types of
  ionizing radiation
• particulate, charged, and directly ionizing
  radiation of alpha and beta particles
• particulate, uncharged, and indirectly ionizing
  radiation of neutrons
• electromagnetic, uncharged, and indirectly
  ionizing radiation of gamma rays and X rays.
• Radiation interacts with matter via two main
  processes ionization and excitation
• Energy, which comes in many forms, can be
  converted from one form to another
• Nuclear potential energy is converted into
  kinetic energy through nuclear fission
• Conversion of mass to energy was predicted by
  Albert Einstein in his mass-energy equation, E
  mc2
• Penetrating power of ionizing radiation is
  relative to radiation type and energy