Radiation as relevant to Medcicne

1. RADIATION

2. Radiation is an energy in the form
of electro-magnetic waves or
particulate matter, traveling in the
air.”

3. HISTORY
• 1895 - Wilhem Conrad Roentgen discovered X-rays
and in 1901 he received the first Nobel Prize for
physics.
• 1903 - Marie Curie and Pierre Curie, along with
Henri Becquerel were awarded the Nobel Prize in
physics for their contributions to understanding
radioactivity, including the properties of uranium.
• 1942 - Enrico Fermi and others started the first
sustained nuclear chain reaction in a laboratory
beneath the University of Chicago football stadium.
• 1945 – Nuclear bombs dropped on Japan.

4. RADIATION SOURCES

5. Sources of radiation can be divided
into two categories:
Natural Background Radiation
Man-Made Radiation

6. NATURAL BACKGROUND RADIATION
Cosmic Radiation
Terrestrial Radiation
Internal Radiation

7. COSMIC RADIATION
 The earth, and all living things on it, are
constantly bombarded by radiation from
outer space
 Charged particles from the sun and stars interact with
the earth’s atmosphere and magnetic field to produce
a shower of radiation.
 The amount of cosmic radiation varies in different
parts of the world due to differences in elevation and
to the effects of the earth’s magnetic field.
 35 mrad / yr normal altitude
 Jet pilots – 300 mrad / yr

8. ATMOSPHERIC RADIATION
 Terrestrial
 Radioactive material is also found throughout
nature in soil, water, and vegetation.
 Important radioactive elements include uranium,
thorium, radium & isotopes of potassium(K40)
 Some radioactive material is ingested with food and
water.
 The amount of terrestrial radiation aprox. 50 mrad/yr
 Atmospheric
 Gases like Radon & thorum – 2 mrad/yr

9. INTERNAL RADIATION
 People are exposed to radiation from radioactive
material inside their bodies. Besides radon, the most
important internal radioactive element is naturally
occurring potassium-40. Others - uranium, thorium,
strontium & carbon.
 25 mrad / yr.
 May go up to 70 or 80.
Total natural radiation - 0.1 rad / yr.

10. MAN-MADE RADIATION SOURCES
 Examples of man-made sources of radiation to
members of the public:
 Lantern mantles
 Medical diagnosis
 Building materials
 Nuclear power plants
 Coal power plants
 Tobacco
 Phosphate fertilizers
 T V sets
 Radium watches

11. ANNUAL AVERAGE DOSE (MREM/YEAR)
MAN-MADE SOURCE
0.4 0.2 0.15
2
4
7
60
25
70
60
50
40
30
20
10
0
Smoking
(perWeek)
Medical
Building
Material
Phosphate
Fertilizer
Natural Gas
Nuclear Plant
Lantern
Mantles
Coal Plant

12. NUCLEAR FALL OUT
 Fallout is the residual radioactive material
propelled into the upper atmosphere following
a nuclear blast
 Carbon C14 , iodine I131, cescium Cs137 &
strontium Sc90
 The Chernobyl disaster was a nuclear reactor
accident in the Chernobyl Nuclear Power Plant in
the Soviet Union on 26 April 1986.

13. RADIATION
 Ionizing Radiation
 Higher energy electromagnetic waves (gamma) or heavy
particles (beta and alpha).
 High enough energy to pull electron from orbit.
 Non-ionizing Radiation
 Lower energy electromagnetic waves.
 Not enough energy to pull electron from orbit, but can
excite the electron.

14. ELECTROMAGNETIC SPECTRUM
Ionizing Radiation Nonionizing Radiation
Short wave
TV
Cosmic Rays Broadcast
Power
FM
Radar
Infrared
Visible
Near Far
Ultraviolet
X Rays
Gamma Rays
Transmission
10-14 10-12 10-10 10-8 10-6 10-4 10-2 1 102 104 106 108
Wavelength in Meters
1010 108 106 104 102 1 10-2 10-4 10-6 10-8 10-10 10-12 10-14
High Energy - Electron Volts Low

15. NON-IONIZING RADIATION

16. Definition:
“ They are electromagnetic waves incapable of
producing ions while passing through matter,
due to their lower energy.”
 Sources
• Ultraviolet light
• Visible light
• Infrared radiation
• Microwaves
• Radio & TV
• Power transmission

17. NONIONIZING EXAMPLES
• Ultraviolet – Black light – induce
fluorescence in some materials
• Vision – very small portion that animals
use to process visual information
• Heat – infrared – a little beyond the red
spectrum
• Radio waves – beyond infrared
• Micro waves
• Electrical power transmission – 60
cycles per second with a wave length of
1 to 2 million meters.

18. IONIZING RADIATION

19. IONIZING RADIATION
Definition
“ It is a type of radiation that is able to disrupt
atoms and molecules on which they pass
through, giving rise to ions and free radicals”.
Sources – x-rays, radioactive material
produce alpha, beta, and gamma
radiation, cosmic rays from the sun and
space.

20. IONIZING RADIATION
Paper Wood Concrete
Alpha
Beta
Gamma
Energy
Low
Medium
High

21. RADIOACTIVE MATERIAL
 Either natural or created in nuclear
reactor or accelerator
 Radioactive material is unstable and
emits energy in order to return to a more
stable state (particles or gamma-rays)
 Half-life – time for radioactive material to
decay by one-half

22. ALPHA PARTICLES
 Two neutrons and two protons
 Charge of +2
 Emitted from nucleus of radioactive atoms
 Transfer energy in very short distances (10
cm in air)
 Shielded by paper or layer of skin
 Primary hazard from internal exposure
 Alpha emitters can accumulate in tissue
(bone, kidney, liver, lung, spleen) causing
local damage

23. BETA PARTICLES
 Small electrically charged particles
similar to electrons
 Charge of -1
 Ejected from nuclei of radioactive atoms
 Emitted with various kinetic energies
 Shielded by wood, body penetration 0.2
to 1.3 cm depending on energy
 Can cause skin burns or be an internal
hazard of ingested

24. GAMMA-RAYS
 Electromagnetic photons or radiation
(identical to x-rays except for source)
 Emitted from nucleus of radioactive
atoms – spontaneous emission
 Emitted with kinetic energy related to
radioactive source
 Highly penetrating – extensive shielding
required
 Serious external radiation hazard

25. X-RAYS
 Overlap with gamma-rays
 Electromagnetic photons or radiation
 Produced when electrons strike a target
material inside and x-ray tube
 Emitted with various energies & wavelengths
 Highly penetrating – extensive shielding
required
 External radiation hazard

26. RADIATION UNITS
 Exposure: Roentgen 1 Roentgen (R) = amount of X or
gamma radiation that produces ionization resulting in 1
electrostatic unit of charge in 1 cm3 of dry air.
 Absorbed Dose: rad (Roentgen absorbed dose) =
absorption of 100 ergs of energy from any radiation in 1
gram of any material; 1 Gray (Gy) = 100 rads = 1
Joule/kg; Exposure to 1 Roentgen approximates 0.9 rad
in air.
 Biologically Equivalent Dose: Rem (Roentgen
equivalent man) = dose in rads x QF, where QF =
quality factor. 1 Sievert (Sv) = 100 rems.

27.  SI Unit for radiation exposure
 Coulombs/kilogram (C/Kg)
 1 Roentgen = 2.58 X 10^-4 C/Kg
 SI unit for absorbed dose
 Gray (Gy)
 1 Gy =100 Rad
 SI Unit for activity
 Becquerel (Bq) = 1 disintegration/ second
 Curie (Ci) = 3.7 X 10^10 disintegrations/ second

28. BIOLOGICAL EFFECTS

29. ACUTE EFFECTS
0-25 No observable effect.
25-50 Minor temporary blood changes.
50-100 Possible nausea and vomiting and
reduced WBC.
150-300 Increased severity of above and
diarrhea, malaise, loss of appetite.
300-500 Increased severity of above and
hemorrhaging, depilation. Death may
occur
> 500 Symptoms appear immediately, then
death has to occur.

30.  Delayed Somatic Effects: Delayed effects to
exposed person include: Cancer, leukemia,
cataracts, life shortening from organ failure,
and abortion. Probability of an effect is
proportional to dose (no threshold). Severity
is independent of dose. Doubling dose for
cancer is approximately 10-100 rems.
 Genetic Effects: Genetic effects to off-spring
of exposed persons are irreversible and nearly
always harmful. Doubling dose for mutation
rate is approximately 50-80 rems.
(Spontaneous mutation rate is approx. 10-
100 mutations per million population per
generation.)

31. DOSE RESPONSE TISSUE
Examples of tissue Sensitivity
Very High White blood cells (bone marrow)
Intestinal epithelium
Reproductive cells
High Optic lens epithelium
Esophageal epithelium
Mucous membranes
Medium Brain – Glial cells
Lung, kidney, liver, thyroid,
pancreatic epithelium
Low Mature red blood cells
Muscle cells
Mature bone and cartilage

32. ORGAN SPECIFIC
 Skin
 Erythema – desquamation (reversible)
 Hair loss
 Mucous Membranes
 Fibrin Plaquing
 Urinary and Bladder Changes
 Visceral Changes (secretory)
 Reproductive Organs
 Irreversible damage to gametes
 Sterility
 Bone
 Suppress osteoblast activity
 Decrease number of osteocytes

33. STANDARDS
• Permissible dose from man made < 5 rad/yr
• X- ray greatest hazard – 4 rad in one minute

34. RADIATION PROTECTION

35. REDUCING EXPOSURE
 Time
Reduce the spent near the source of radiation.
 Distance
Increase the distance from the source of radiation.
 Shielding
Place shielding material between you and the
source of radiation.

36. MONITORING
 Personal Dosimeters: Provide a record of
accumulated exposure for an individual worker
over extended periods of time and are small
enough for measuring localized exposures
 Common types: Film badges; pocket dosimeters, &
Thermoluminescence detectors (TLD);

37.  Direct Reading Survey Meters and Counters:
Useful in identifying source of exposures and in
evaluating potential sources, such as surface or
sample contamination, source leakage, inadequate
decontamination procedures, background radiation.
 Common types:
Alpha  Proportional or Scintillation counters
Beta, gamma  Geiger-Mueller or
Proportional counters
X-ray, Gamma  Ionization chambers
Neutrons  Proportional counters

38.  Continuous Monitors: Continuous direct reading
ionization detectors (same detectors as above) can
provide read-out and/or alarm to monitor
hazardous locations and alert workers to leakage,
thereby preventing exposures.
 Long-Term Samplers: Used to measure average
exposures over a longer time period. For example,
charcoal canisters or electrets are set out for days
to months to measure radon in basements (should
be <4 pCi/L).