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PRACTICAL RADIATION PHYSICS FOR EMERGENCY MEDICAL PERSONNEL

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PRACTICAL RADIATION PHYSICS FOR EMERGENCY MEDICAL PERSONNEL Module III What is radiation? Ionizing radiation Electromagnetic radiation Forms of ionizing radiation ... – PowerPoint PPT presentation

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Title: PRACTICAL RADIATION PHYSICS FOR EMERGENCY MEDICAL PERSONNEL


1
PRACTICAL RADIATION PHYSICS FOR EMERGENCY
MEDICAL PERSONNEL
Module III
2
What is radiation?
3
Ionizing radiation
4
Electromagnetic radiation
IONIZING RADIATON
VISIBLE
X-RAYS
COSMIC
MICROVAVES
GAMMA
INFRARED
ULTRAVIOLET
TV, RADIO
Decreasing wave length
Increasing frequency
Increasing photon energy
5
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
6
Origin of radiation
  • What is the relationship between atom structure
    and radiation production?

7
Atom anatomy
Proton
Neutron
Electron
Nucleons
8
Isotopes
9
Why are some nuclides radioactive?Neutron to
proton ratio
10
Half-life

11
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
12
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
13
Mass-energy relationship
Measured Mass
Calculated Mass
E mc2
14
Fission
15
Nuclear reaction and energy production
16
Mechanisms of radioactive decay
17
Alpha (a) decay
AZX A-4Z-2Y 42He e.g. 23892U
23490Th 42He
18
Beta (?-) decay
  • n p e- ?
  • AZX?AZ1 Y e- ? e.g. 13153 I ? 13154
    Xee-?

19
Positron (?) decay
p n e ? AZX?AZ-1 Ye ?
e.g. 189 F? 188Oe?
20
Electron capture
p e- ?n ? AZX? AZ-1 Y ? 12553 I ?
12552 Te?
21
Gamma (?) emission
22
Nuclear energy levelsgamma radiation
SIMPLIFIED NUCLEAR MODEL
Gamma ray
23
How does radiation interact with matter?
24
Excitation
25
Ionization
Electron removal by ionization
26
Alpha particle interaction
27
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

28
Interaction of alpha radiation with living
matter internal deposition
Prime danger is inhalation and ingestion of alpha
emitter
29
Beta interaction with matter
30
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
31
Positron interactionannihilation reaction
32
Neutron interaction
33
Neutron activation
34
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

35
Gamma interaction by photoelectric effect
36
Gamma interaction by Compton scattering
37
Pair production
38
Extranuclear energy release
  • Bremsstrahlung radiation
  • Characteristic X rays
  • Auger electrons

39
Bremsstrahlung radiation
40
Importance of bremsstrahlung X rays in
radiation safety practice
41
Characteristic X rays
42
Difference between X rays and gamma rays
43
Internal conversionAuger electrons
44
Specific ionization andlinear energy transfer
(LET)
45
Penetrating power of radiation
46
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
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