3. Radon gas
42%
terrestrial Radiation
18%
cosmic Radiation
14%
Internal Radiation
11%
Man made Radiation
15%
Natural background Radiation
Worldwide average of effective dose from background natural
radiation is about 2.4 mSv/year
4. USA
0.40 (0.88)
Guarapari,Brazil
5.5 (35)
Kerala,India
3.8 (35)
Ramsar,Iran
10.2 (260)
Yangjiang,China
3.51 (5.4)
Japan
0.43 (1.26)
China
0.54(3.0)
India
0.48 (9.6)
Ireland
0.36 (1.58)
Italy
0.50 (4.38)France
0.6 (2.2)
Germany
0.48 (3.8)
Denmark
0.33 (0.45)
Norway
0.63 (10.5)
World Avg. : 0.50 mGy/year
* Avg.(Max.)
Units: mGy/year
5. Radon is a colorless, odorless, radioactive gas. It
forms naturally from the decay (breaking down) of
radioactive elements, such as uranium, which are
found in different amounts in soil and rock
throughout the world. Radon gas in the soil and
rock can move into the air and into underground
water and surface water
6.
7. Cosmic rays are a form of high-energy radiation,
mainly originating outside the Solar System and
even from distant galaxies. Upon impact with the
Earth's atmosphere
17. Radiation Protection in Radiotherapy Part 3, lecture 1: Radiation protection 17
Genetic Risks
Ionizing radiation is known to cause
heritable mutations in many plants and
animals
BUT
intensive studies of 70,000 offspring of the
atomic bomb survivors have failed to
identify an increase in congenital
anomalies, cancer, chromosome
aberrations in circulating lymphocytes or
mutational blood protein changes.
Neel et al. Am. J. Hum. Genet. 1990, 46:1053-1072
18.
19. Radiation Protection in Radiotherapy Part 3, lecture 1: Radiation protection 19
RADIATION EFFECT ON
CELLULAR LEVEL
Ionizing radiation
interacts at the
cellular level:
• ionization
• chemical changes
• biological effect
cell
nucleus
chromosomes
incident
radiation
20.
21. Stage Process
Duration
Physical Energy absorption, ionization
10-15 s
Physico-chemical Interaction of ions with molecules,
10-6 s formation of free radicals
Chemical Interaction of free radicals with
seconds molecules, cells and DNA
Biological Cell death, change in genetic data
tens of minutes in cell, mutations
to tens of years
22.
23.
24.
25.
26.
27.
28.
29. Dose to the tumor determines probability of cure (or
likelihood of palliation)
Dose to normal structures determines probability of
side effects and complications
Dose to patient, staff and visitors determines risk of
radiation detriment to these groups
Low dose:
Stochastic
effects
High dose:
Deterministic
effects
30. Three basic types:
1) Stochastic : probability of effect
related to dose, down to zero (?) dose
2) Deterministic : threshold for effect -
below, no effect; above, certainty,
and severity increases with dose
3) Hereditary: (genetic) - assumed
stochastic incidence, however,
manifests itself in future generations
31. Due to cell changes (DNA) and
proliferation towards a
malignant disease
Severity (example cancer)
independent of the dose
No dose threshold - applicable
also to very small doses
Probability of effect increases
with dose
dose
Probability
of effect
32. Due to cell killing
Have a dose
threshold - typically
severalGy
Specific to particular
tissues
Severity of harm is
dose dependentdose
Severity of
effect
threshold
33. Coal mining 1 in 7,000
Oil and gas extraction 1 in 8,000
Construction 1 in 16,000
Radiation work (1.5 mSv/y) 1 in 17,000
Metal manufacture 1 in 34,000
All manufacture 1 in 90,000
Chemical production 1 in 100,000
All services 1 in 220,000
STOCHASTIC EFFECT
37. Early Observations of the
Effects of Ionizing Radiation
1895 X Rays discovered by Roentgen
1896 First skin burns reported
1896 First use of X Rays in the treatment of cancer
1896 Becquerel: Discovery of radioactivity
1897 First cases of skin damage reported
1902 First report of X Ray induced cancer
1911 First report of leukaemia in humans and lung
cancer from occupational exposure
1911 94 cases of tumour reported in Germany
(50 being radiologists)