Radiotherapy, Cancer, Radiation Protection , FRCR

1. QUANTITIES AND UNITS USED
IN RADIATION PROTECTION
H.LANILRANJITH
HEAD, DIVISION OFRADIATION PROTECTION
ATOMIC ENERGYAUTHORITY

2. QUANTITIES:
ARE MEASURABLE CHARACTETISTICS
Eg LENGTH, DOSE ETC.
UNITS
ARE USED TO DESCRIBE THE QUANTITY
Eg METERS, GRAYS ETC.

3. RADIATION UNITS
• TO MEASURE RADIOACTIVITY
• TO EXPRESS ENERGY OF
RADIATION EMITED
• TO EXPRESS AMOUNT OF
ENERGY DEPOSITED IN THE
BODY
• TO QUANTIFY BIOLOGICAL
DAMAGES TO IRIDIATED
TISSUES

4. ACTIVITY
• NO.OF
DESINTEGRATIONS
PRE SECOND
• 1Bq = 1 dis/s
• ORDER OF
MAGNITUDE

5. THE CURIE
1 Curie (Ci) = Activity of 1g of 226
Ra
1g of 226
Ra disintegrate 3.7x1010
atoms per second
∴ 1 Ci = 3.7 x 1010
dis/s
∴ 1 Ci = 3.7 x 1010
Bq
1 Ci = 37 GBq

6. ENERGY OF RADIATION
ELECTRON VOLTS
1eV = 1.6 X 10 –19
J
COBALT- 60 RADIOACTIVE MATERIAL
EMITS TWO GAMMA RADIATIONS OF
ENERGIES 1.17 MeV AND 1.32 MeV.

7. DOSE
USES AS A GENERIC TERM THAT CAN
APPLY TO ANY OF THE RELEVANT
DOSIMETRIC QUANTIES
EXPOSURE
IN A GENERIC SENSE TO MEAN THE
PROCESS OF BEING EXPOSED TO
RADIATION

8. Exposure Unit
•Is a measure of ionization produced in air
•Is used only for X and γ radiation
•Is valid for quantum energy less than 3 MeV

9. X Unit
1 X unit = 1 C/kg air
One exposure unit is defined as that quantity
of x or gamma radiation that produces in air,
ions carrying 1 coulomb of change( of either
sign) per kg air.

10. Exposure
Exposure is measured under conditions of electronic
equilibrium
For photon energies above about 3 MeV, the ranges of
secondary electrons become a significant fraction of
the photon attenuation lengths and the departure from
equilibrium may be significant
Thus, exposure is not defined above photon energies
of 3 MeV

11. Roentgens (2/3)
• Is symbolized by R
• was used as the exposure unit before
SI system was adopted
• is still being used.

12. Roentgen
Is defined as the quantity of x or
gamma radiation that produces ions
carrying one statcoulomb of charge of
either sign per cubic centimeter of air
at STP.
Charge of the electron=1.6x10-19
C =4.8x10-10sC
1C =3x109
sC

13. 13
KERMA
KERMA (Kinetic Energy Released in a Material):
– Is the sum of the initial kinetic energies of all charged
ionizing particles liberated by uncharged ionizing
particles in a material of unit mass
– For medical imaging use, KERMA is usually expressed
in air
SI unit = joule per kilogram (J/kg)
or gray (Gy)
1 J/kg = 1 Gy

14. 14
Mean absorbed dose in a tissue or
organ
The mean absorbed dose in a tissue or organ DT is the
energy deposited in the organ divided by the mass of
that organ.

15. ABSORBED DOSE(1/2)
• MEASURES THE ENERGY
DELIVERED TO ANY MATERIAL
• IN RADIATION PROTECTION
THE MATERIAL CONCERNED IS
THE TISSUE OR ORGAN OF THE
HUMAN BODY

16. ABSORBED DOSE(2/2)
• DEFINED AS THE
“ENERGY ABSORBED
PER UNIT MASS OF
ANY MATERIAL”
• UNIT USED
“GRAY” OR
“RADS”

17. 1GRAY (Gy) = 1J/kg
1RADS = 100 ergs/g
100 RADS = 1 Gy

18. EQUIVALENT DOSE(1/2)
QUANTIFY THE BIOLOGICAL
DAMAGE TO THE ORGAN OR
TISSUE IRRIDIATED
The same dose levels of different radiations
(ie photons and neutrons) do not have the
same level of biological effect
Radiation weighting factor, wR
(related to radiation quality)

19. EQUIVALENT DOSE(2/2)
• BIOLOGICAL
EFFECTS OF AN
EXPOSURE ON A
ORGAN OR TISSUE
DEPEND ON:
• ENERGY TRANSMITTED
TO THE ORGAN OR
TISSUE BY RADIATION
• HAMFULNESS OF THE
TYPE OF RADIATION
INVOLVED (DEGREE OF
POWER OF IONIZATION)

20. Radiation weighting factors,
wR
1
Type and energy ranges
Radiation
weighting
factor, wR
1
1
5
10
20
10
5
5
Photons, all energies
Electrons and muons, all energies
Neutrons, energy < 10 keV
10 keV to 100 keV
100 keV to 2 MeV
> 2 MeV to 20 MeV
> 20 MeV
Protons, other than recoil protons, energy > 2 MeV
Alpha particles, fission fragments, heavy nuclei 20
1) All values relate to the radiation incident on the body, or,
for internal sources, emitted from the source.

21. Neutron radiation weighting
factors30
25
20
15
10
5
0
wR
Neutron energy - MeV
10-8
10-7
10-6
10-5
10-4
10-3
10-2
10-1
1 10 102
ICRP Recommendation
ICRP Approximation

22. EFFECTIVE DOSE
Different body tissues have different
biological sensitivities to the same
radiation type and dose
Tissue weighting factor, wT

23. EFFECTIVE DOSE
• MEASURES THE RISK OF
BIOLOGICAL DAMAGE TO
WHOLE BODY TAKING THE
RADIOSENSITIVITIES OF
TISSUE IRRIDIATED IN TO
ACCOUNT
• MEASURES THE RISK
REGARDLESS OF EXPOSURE
INVOLVED.( INTERNAL,
EXTERNAL, PARTIAL OR
TOTAL)
• MEASURES IN THE UNIT OF.
“SIEVERT”( Sv )

24. Roentgen (3/3)
1R = 0.0087 J/kg of air
IR = 0.0087 Gy = .87 Rad
IR = 0.0096 J/kg in Tissue
IR = 0.0096 Gy in Tissue
IR = .96 Rad in Tissue
1 R = 1 Rad
for x and γ rays
IR = 1 rem = .01 Sv

25. Multipliers of the equivalent dose to an organ or tissue to
account for the different sensitivities to the induction of
stochastic effects of radiation.
Tissue or organ wT Tissue or organ wT
Gonads 0.20 Bone marrow (red) 0.12
Colon 0.12 Lung 0.12
Stomach 0.12 Bladder 0.05
Breast 0.05 Liver 0.05
Oesophagus 0.05 Thyroid 0.05
Skin 0.01 Bone surface 0.01
Remainder 0.05 TOTAL 1.00
Tissue weighting factors

26. Committed Dose
Is a useful subsidiary dosimetric quality
to express dose to body during certain
time following an intake of radioactive
material to the body.
Note : The dose delivery to the body
during the above period is at
varying rates.

27. Committed Equivalent Dose
Defined as the time integral of the equivalent dose
rate and denoted by HT( τ )
τ = integration time in years following
the intake.
If t is not specified
Integration time is taken as
50 years for adults
70 years for children

28. Committed equivalent dose:
The quantity H(τ), defined as;
where to
is the time of intake, HT
(t) is the equivalent dose
rate at time t in an organ or tissue T and τ is the time elapsed
after an intake of radioactive substances.When τ is not
specified it will be taken to be 50 years for adults and to age
70 years for intakes by children.
( ) ( )H H t dtT
t
t
o
o
τ
τ
=
+
∫
.

29. Committed effective dose:
The quantity E(τ), defined as ;
where HT
(τ) is the committed equivalent dose to tissue T
over the integration time τ and WT
is the tissue weighting
factor for tissue T.
When τ is not specified it will be taken to be 50 years for
adults and to age 70 years for intakes by children.
( ) ( )E W HT T
T
τ τ= ∑ .

30. Collective Dose(1/2)
Is used to express dose to a
group or a population.
Takes account of the no of
people exposed to a source and
the average dose to the
individual.

31. COLLECTIVE DOSE(2/2)
DEFINED AS,
THE PRODUCT OF THE NUMBER OF
INDIVIDUAL EXPOSED TO A SOURCE AND
THEIR AVERAGE DOSE
UNIT: MAN SIEVERT (man Sv)

32. Is there
RADIATION
in this room?

33. Background Radiation
•Natural Background Radiation
•Background Radiation Due to
Man Made Sources.

34. NATURAL BACKGROUND
RADIATION
• TERRESTRIAL SOURCES
• EXTRA TERRESTRIAL SOURCES
( COSMIC RADIATION )

35. Natural sources of radiation…
(2.4 mSv.
y-1
)
Cosmic…
(0.4 mSv.
y-1
)
…from earth’s crust
(0.4 mSv.
y-1
)
…via ingestion
(0.3 mSv.
y-1
)
…via inhalation
(1.3 mSv.
y-1
)
C. Torudd ; Swedish Radiation Protection Institute
...internal

36. External terrestrial irradiation
0.4 mSv y-
Varies considerably with soil and rock type
Unusually high background in a few places
in e.g.
•Esperito Santos, Brazil
•Kerala, India
•Guandong province, China
Up to 50 µGy h-1
compared to 0.1 µGy h-1

37. External extra
terrestrial radiation
(Cosmic radiation)
Estimated spectrum
of secondary
particles in the
atmosphere from
cosmic radiation
Heinrich et al 1999 (0.4 mSv.
y-1
)

38. Cosmic radiation
Dose and ambient dose equivalent during a
flight from Bangkok to Copenhagen

39. External irradiation: Natural background
dose rates from external sources (mSv.
y-1
)

40. Internal irradiation
via inhalation, 1.2 mSv.
y-1
(mainly indoor radon)

41. Reasons for elevated levels of
indoor radon
•elevated levels of 238
U and 232
Th series in
the ground
•building material with elevated levels of
238
U and 232
Th series
•tight houses (cold climate…)

42. Internal irradiation
via ingestion
40
K
•abundance 0.0188% in potassium (K)
(0.15 mSv.
y-1
)
Also
•uranium and thorium series
(0.15 mSv.
y-1
)

43. Man-made Radiation
• Cigarette smoke
• Consumer products
– Building materials
– Smoke detectors
• Industrial use
• Medical use
• Nuclear power
• Nuclear fall out

44. …and artificial sources of
radiation
Medical examinations…
(0.4 mSv.
y-1
)
C. Torudd ; Swedish Radiation Protection Institute

45. …and more artificial sources of radiation
...and nuclear
weapons
(0.005 mSv.
y-1
atmospherical
tests)
Nuclear fuel
cycle…
(0.0002 mSv.
y-1
)
C. Torudd ; Swedish Radiation Protection Institute

46. Nuclear power

47. Nuclear weapons

48. © Chernobylinterninform 1996
Chernobyl accident, April, 1986

49. Practical concequencies of Chernobyl
accident
Effects of radiation and accident situation
•600,000-800,000 persons in cleaning up work
•Approximately 200,000 persons evacuated
•Large areas of land abandoned (30 km zone etc.)
Other effects:
•Cost estimated to 100 billion USD

50. Health concequencies of Chernobyl accident
Effects of radiation and accident situation
Seen:
•Immediate death of 30 persons
•1800 children diagnosed with thyroid cancer (1998)
Statistically:
•15,000 deaths in cancer (global)
Other factors influencing health:
•Poor food supply, social concequencies, anxiety

51. Source Mean effective dose (mSv)
Natural background 2,4
Medical examinations 0,4
Nuclear tests in the atmosphere 0,005
Chernobyl accident 0,002
Nuclear fuel cycle 0,0002
Individual exposure of the world’s population
due to ionising radiation, year 2000
UNSCEAR

52. DO WE NEED
RADIATION PROTECTION ?

53. Drinking Hot Coffee
Excess Temperature = 60º - 37 = 23º
1 sip= 3ml
3x 23= 69 calories

54. Lethal Dose= 4Gy
LD 50/60 = 4 Gy
For man of 70 kg
Energy absorbed = 4 x 70 = 280 Joules
= 280/418= 67 calories
= 1 sip
X-ray

58. We live with
1-3 mSv
Can kill
4000 mSv
Radiation
Where to stop, where is the safe point?
What are the effects of radiation?

59. What can radiation do?
Death
Cancer
Skin Burns
Cataract
Infertility
Genetic effects