Radiation safety

1. RADIATION
SAFETY

2.  Ionizing radiation used in diagnosis and therapy lead
to irradiation of patients , doctors, technicians and
other staff of department

3.  Protection of people and the environment from
harmful effects of ionizing radiation include
protection from both particle radiation and high
energy electromagnetic radiation

4. STOCHASTIC EFFECT
 Is one in which the probability of occurrence increases
with increasing absorbed dose but the severity in
affected individuals does not depend on magnitude of
absorbed dose.
 It is all or none phenomenon
 Seen when the cells are modified
 Malignancies, mutations, teratogenic effect

5. NON STOCHASTIC EFFECT
 It is increase in severity with increasing absorbed dose
in affected individuals owing to damage to increasing
no. of cells and tissues
 Seen when the cells are killed or loose capability to
divide.
 Examples – Radiation induced degenerative changes
such as fibrosis, lens opacification, blood changes and
decrease in sperm count.

6. EXPOSURE SITUATIONS
 Planned exposure situations- which are involving
the planned introduction and operation of sources.
 Emergency exposure situations- which are
unexpected situations such as those that may occur
during the operation of a planned situation, or from a
malicious act, requiring urgent attention.
 Existing exposure situations - which are exposure
situations that already exist when a decision on control
has to be taken, such as those caused by natural
background radiation

7. OBJECTIVES OF RADIATION
PROTECTION
 To prevent clinically significant radiation induced
deterministic effects by adhering to dose limit
 To limit the risk of stochastic effect (cancer and
hereditary effects to a reasonable level in relation to
societal needs, values and benefits gained).

8. DOSE EQUIVALENT
 The dosimetric quantity relevant to radiation
protection is dose equivalent (H)
 H= D*Q
 D is absorbed dose
 Q is quality factor for radiation
 SI unit is Sievert (Sv)
 1Sv= 1J/kg
 Older unit is rem =10 *-2 Sv

9. MAXIMUM PERMISSIBLE DOSE
 Maximum Permissible dose (MPD) is defined as that
dose which in the light of present knowledge is not
expected to cause appreciable bodily injury to the
person at any point during his lifetime

11. Rules of radiation protection
 Time
 Distance
 Shielding

12. Time
 Exposure should be kept as short as possible because
exposure is directly proprtional to time

13. Distance
 Distance from radiation source should be kept large as
possible
 Principle - Inverse Square Law

14. GENERAL DESIGN GUIDELINES
 Usually located at periphery of hospital complex
avoids the problem of therapy room in high occupancy
area
 Ground level is preferred as the problem of shielding
floor is less
 Whenever possible the areas around therapy machine
should be designated as controlled area
 Mazes should be designed wherever possible as they
reduce the need for heavy shielded door

15.  Doors should be provided at the maze entrance to
avoid casual entrance of public

16. Door shielding
 Door must provide shielding equivalent to the wall
surrounding the door
 Maze arrangement reduces shielding requirement for
the door
 With proper maze design, door is exposed mainly to
multiple scattered radiation of significant intensity
and energy

17.  Function of maze is to prevent direct incidence of
radiation at the door

18. Barriers of radiation protection
 Barriers to provide protection to primary beam are
called Primary Barriers
 Must be incorporated in any part of floor, walls and
ceiling of X ray room at which primary beam can be
fired
 Secondary Barriers – Any surface at which the primary
beam cannot be fired but which may receive scattered
radiation or leakage radiation need secondary barriers

19.  Lead is most commonly used protective material
 Have double advantage of high density and high
atomic number
 Means it has higher attenuation coefficient at all
radiation energies than any other commonly available
material.

20. Personnel Monitoring Service
 The term Personnel monitoring means,
monitoring of the radiation workers with respect
to absorbed dose in the body while working in the
radiation field

21. WHY IT IS REQUIRED
 To obtain an assessment of the effective dose and
where appropriate, the equivalent dose in significantly
exposed tissues, so as to demonstrate compliance with
managerial regulatory requirements
 To contribute to the control of operation & design of
facilities
 In case of accidental over exposure, to provide valuable
information for the support of appropriate health
treatment.

22. Personal Dosimeters
 Characteristics-
Lightweight, durable, reliable
Should be inexpensive
 Types
Film badge
Thermo luminescent dosimeters

23. Film badge
 Most commonly used and most economical
 Consists of 3 parts
a) Plastic film holder
b) Metal filters
c) Film packet

24.  The Film has 2 emulsions of (fast ) and (slow)
sensitivities extending the dose response from 100 msv
to 10 Sv.
 The Fast film is responsive to high dose rates
 The Slow film is responsive to low dose rates

26. TLD
 Thermoluminesecence Dosi Meter is the primary form
of personal radiation monitoring dosometer.
 Thermoluminesecence is the emission of light by heat.

27.  TLD measure ionizing radiation exposure by
measuring amount of visible light emitted from
crystal in the detector when the crystal is heated.
 When a strong energy source (such as ionizing
radiation) hits a TL material, electrons are freed
from some atoms and moved to other parts of the
material, leaving behind "holes" of positive charge.

28.  When the TL material is heated, the electrons and the
"holes" re-combine, and release the extra energy in the
form of light.
 The light intensity can be measured, and related to the
amount of energy initially absorbed through exposure to
the energy source

29. HOW IT WORKS
 TLDs work by storing the energy they receive from the
ionizing radiation
 Until they are heated to a high temperature (around
250°C).
 On heating, the absorbed energy is released in the
from of visible light.
 A plot of light intensity emitted against temperature is
know as a glow curve.

31. TLD READER
 Heat up the TLD using
nitrogen gas (250 C).
 Detect the resulting light
emission.
 Calculate the radiation
exposure.
 Restores the TLD to the
original condition.

33. How to wear the TLD Badges?
 The TLD badge should be worn on the body trunk with the
name label facing towards outwards
 The side with sliding window should face towards yourself
for properly measuring the radiation dose absorbed by you.
 TLD Badge should be worn under the lead apron for
estimating the dose of the major part of your body.

36. Where to store the TLD badges
after daily use?
 The user should store
their TLD badges away
from the RADIATION
AREA after work.
 It is recommended to
keep their own TLD
badges in a secure place
under lock and key away
from RADIATION
AREA

37. Can one use the same TLD badge for two or
more different Radiation Installations?
 No, you have to apply for different TLD badge for two
or more different Installations.

38. What should b e done if TLD is lost
?
 The users should report in writing by mail or email
immediately mentioning the service period for
which the TLD badges is lost.
 Also it should be clearly mention whether the card
or holder or both the card and holder has been
lost.

39.  The most commonly used TL phosphors are-
1. Lithium fluoride
2. Calcium fluoride
3. Lithium borate
4. Calcium sulphate
In India CaSo4:Dy embedded teflon TLD disk are used
They are usually manufactured in form of chips

41. BODY TLD
 Used for X ray gamma
rays and beta radiation.
 Measure dose to
a. Whole body
b. Skin
 Comprises of
a. TLD card
b. Wrapper
c. Holder

42. CONTAINS
 2 Pellets
 Thicker elements- Strongly
penetrating
 Thinner elements- weakly
penetrating
 Covered (front and back)
with thin retaining layer
(PTFE)
Polytetrafluoroethylene.
 Cards- Bar coded
 Wrapper (Aluminized
polyster)- Protect dosimeter
from contamination
(chemical and dirt)

43.  HOLDER
 Thicker filter:- Cover thicker element
 Circular open window :- covered thin element
 Rectangular open window: viewing the wearer
information text

44.  WEARER INFORMATION INCLUDE
 Serial #
 Worker #
 Change Date

45. WHOLE BODY TLD
 Material- LiF
 Dose range- 0.02 mSv to 10 Sv
 Change interval- Standard period of 3 months
 TLD gives measurement of dose in mGy with accuracy
of about 10%

46. Extremity TLD
 Used to measure
radiation to the skin of
extremeties
 Worn on fingers or taped
to the ankles to measure
the external equivalent
dose to the extremeties.
 Used to measure
radiation at depth
equivalent to that of
basal layer of skin.

47.  The minimum detectable dose for TLD ring dosimeter
30 milirem for Xrays and gamma rays
40 milirem for energetic beta radiation

48. Extremity TLD
 Material – LiF
 Dose Range- 0.15 mSv to
10 Sv
 Changing Interval –
Standard protocols of 3
months
 Mainly used in Nuclear
Medicine

49. FINGER STALL DOSIMETER
 Finger stall dosemeters
are available in two sizes,
to suit maximum finger
diameters up to 20 mm
(small size) and 24 mm
(large size).

50. THANK YOU