Title: PRACTICAL RADIATION PHYSICS FOR EMERGENCY MEDICAL PERSONNEL
1PRACTICAL RADIATION PHYSICS FOR EMERGENCY
MEDICAL PERSONNEL
Module III
2What is radiation?
3Ionizing radiation
4Electromagnetic radiation
IONIZING RADIATON
VISIBLE
X-RAYS
COSMIC
MICROVAVES
GAMMA
INFRARED
ULTRAVIOLET
TV, RADIO
Decreasing wave length
Increasing frequency
Increasing photon energy
5Forms 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
6Origin of radiation
- What is the relationship between atom structure
and radiation production?
7Atom anatomy
Proton
Neutron
Electron
Nucleons
8Isotopes
9Why are some nuclides radioactive?Neutron to
proton ratio
10Half-life
11Activity
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
12Atomic 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
13Mass-energy relationship
Measured Mass
Calculated Mass
E mc2
14Fission
15Nuclear reaction and energy production
16Mechanisms of radioactive decay
17Alpha (a) decay
AZX A-4Z-2Y 42He e.g. 23892U
23490Th 42He
18Beta (?-) decay
- n p e- ?
- AZX?AZ1 Y e- ? e.g. 13153 I ? 13154
Xee-?
19Positron (?) decay
p n e ? AZX?AZ-1 Ye ?
e.g. 189 F? 188Oe?
20Electron capture
p e- ?n ? AZX? AZ-1 Y ? 12553 I ?
12552 Te?
21Gamma (?) emission
22Nuclear energy levelsgamma radiation
SIMPLIFIED NUCLEAR MODEL
Gamma ray
23How does radiation interact with matter?
24Excitation
25Ionization
Electron removal by ionization
26Alpha particle interaction
27Interaction 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
28Interaction of alpha radiation with living
matter internal deposition
Prime danger is inhalation and ingestion of alpha
emitter
29Beta interaction with matter
30Interaction 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
31Positron interactionannihilation reaction
32Neutron interaction
33Neutron activation
34Interaction 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
35Gamma interaction by photoelectric effect
36Gamma interaction by Compton scattering
37Pair production
38Extranuclear energy release
- Bremsstrahlung radiation
- Characteristic X rays
- Auger electrons
39Bremsstrahlung radiation
40Importance of bremsstrahlung X rays in
radiation safety practice
41Characteristic X rays
42Difference between X rays and gamma rays
43Internal conversionAuger electrons
44Specific ionization andlinear energy transfer
(LET)
45Penetrating power of radiation
46Review 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