Radiation Protection Course For Orthopedic Specialists: Lecture 3 of 4: Basics Radiation Protection

1. Radiation Protection Course For
Orthopedic Specialists
Lecture 3 of 4
Basics Radiation Protection
Prof Amin E AAmin
Dean of the Higher Institute of Optics Technology
&
Prof of Medical Physics
Radiation Oncology Department
Faculty of Medicine, Ain Shams University

3. Dealing With Ionizing
Radiation
It should be emphasised that ionizing radiation
needs to be treated with CARErather
than FEAR.

4. Aspects of the Problem
• There are four main aspects of the problem to be
considered.
–Firstly, radiological procedures should be based on a
demonstrated medical need.
–Secondly, when radiological procedures are required, it
is essential that patients be protected from excessive
radiation during the exposure.

5. Aspects of the Problem
–Thirdly, it is necessary that personnel in radiology
departments be protected from excessive exposure
to radiation in the course of their work.
–Finally, personnel in the vicinity of radiology
facilities and the general public require adequate
protection.

6. Radiation
safety
Patients
Users
General
public

7. Specific Effects Of Radiation
Radiological protection aims at avoiding deterministic effects
by setting dose limits below their thresholds. Stochastic
effects are believed to occur, albeit with low frequency, even
at the lowest doses and therefore have been taken into account
at all doses.

8. Aims Of Radiation Protection
• Deterministic effects
❖RP aims to ELIMINATE them.
• Stochastic effects
❖RP aims to REDUCE them.

9. The Aim Of Radiological
Protection
The primary aim of radiological protection is to provide
an appropriate standard of protection for man without
unduly limiting the beneficial practices giving rise to
radiation exposure.

10. Sources Of Radiation
Background
❖Natural sources of radiation
❖Artificial sources of radiation

11. Natural Sources Of Radiation
Background
❖Cosmic rays
❖Terrestrial radiation
❖Radionuclides in the body
❖Radon gas and its decay products

12. Let’s Compare Backgrounds
• Sea level - 30 mrem/year
from cosmic radiation
• 10,000 ft. altitude - 140
mrem/year
from cosmic radiation

13. Terrestrial Radiation
❖ Terrestrial radiation comes from radioactivity emitting
from Primordial radio nuclides - these are radio
nuclides left over from when the earth was created.
❖ Common radionuclides created during formation of earth:
❖ Radioactive Potassium (K-40) found in bananas, throughout
the human body, in plant fertilizer and anywhere else stable
potassium exists.
❖ Radioactive Rubidium (Rb-87) is found in brazil nuts
among other things.

14. Terrestrial Radiation
• Greatest contributor is 226Ra (Radium) with significant
levels also from 238U, 232Th, and 40K.
–Igneous rock contains the highest concentration
followed by sedimentary, sandstone and limestone.
–Fly ash from coal burning plants contains more
radiation than that of nuclear or oil-fired plants.

 ++

15. Another Look at Sources

16. Artificial Sources Of Radiation
Background
Two artificial sources of radiation to which
every body is exposed;
❖Fall-out from nuclear explosions.
❖Radioactive waste, including discharges from
nuclear establishments.

17. Artificial Sources Of Radiation
Background
Two artificial sources of radiation to which not
all the population are exposed;
❖Radiation used for medical purposes.
❖Occupational exposure to radiation.

19. Relative Contribution Of Different
Sources Of Background Radiation
Radon
32%
Terestri
al
19%
Body
17%
Cosmic
Rays
14%
Medical
12%
Thoron
5%
Artificial
1%
Average radiation exposure from all sources: 2.8 mSv/year

20. Annual Dose To The General Population
From Natural And Man-made Sources
Radiation Source
Effective Dose
Equivalent
(mrem/year)
Percentage of Total
Natural
Cosmic
Cosmogenic
Terrestrial
Inhaled (due to radon)
In the Body
Subtotal
27
1
28
200
39
295
8%
-
8%
55%
11%
82%
Man-made
Medical X-rays
Nuclear Medicine
Consumer Products
Others
Subtotal
39
14
10
<1
64
11%
4%
3%
-
18%
Rounded Total 360 100%

21. System Of Radiation Protection
“System of RP” is the name given by the ICRP
to the application of the 3 basic principles of RP
(no part should be taken in isolation):
❖ Justification
❖ Optimization
❖ Limitation

22. The framework of radiation
protection (I)
• Justification of a practice
• Optimization of protection
• Application of individual limits

23. Principles of Protection in
Practices
❖Justification of a practise - no practice should be adopted
unless it produces sufficient benefit to the exposed individuals or
to society to offset the radiation detriment it causes.
❖Optimization of protection - the magnitude of individual doses,
the number of people exposed, and the likelihood of incurring
exposures should be kept as low as reasonably achievable,
economic and social factors being taken into account.
❖Individual dose limits - exposure should be restricted so, that
exposure of any individual from authorized source does not exceed
any relevant dose limit.

24. Practices Vs Intervention
Human activities which increases the overall exposure
to radiation are called practices. Other human activities
which can decrease the overall exposure by influencing
the existing causes of exposure are called intervention.

25. The Framework Of Radiation
Protection II
In diagnostic radiology the radiation sources (X-rays) are
deliberately used and are under control. Such situations are called
by the International Commission on radiation Protection (ICRP)
“practices”.
The basic components of the system of protection for “practices”
can be summarized as follows:
No practice involving exposures to radiation should be adopted
unless it produces at least sufficient benefit to the exposed
individuals or to society to offset the radiation detriment it
causes (this is called “justification of a practice”).

26. The Framework Of Radiation
Protection III
In relation to any particular source of radiation within a practice
(e.g. X-rays in radiodiagnostic), all reasonable steps should be
taken to adjust the protection so as to maximize the net benefit,
economic and social factors being taken into account (this is
called “optimization of protection”).
A limit should be applied to the dose (other than from medical
exposures) received by any individual as the result of all
practices to which he is exposed (this is called “application of
individual dose limits”).

27. Justification
Justification means that any dose
exposure MUST have a benefit to
exposed individuals or to society.
Thus, if the exposure has no
benefit it is not justified.

28. Justification
Benefit of the radiation exposure must outweigh
the risk of exposure
vs

29. Justification
• No practice involving exposures to radiation should be adopted
unless it produces sufficient benefit to the exposed individuals
or to society to offset the radiation detriment it causes.
• Justification of exposures is primarily the responsibility of the
medical professional i.e. the Radiologist.
• The expected clinical benefit associated with each type of
procedure should have been demonstrated to be sufficient to
offset the radiation detriment.

30. Optimization
❖ Optimization means that minimum
risk and maximum benefits should
be achieved, economic and social
factors being taken into account.
❖ Optimization includes the ALARA
criterion: doses should be “As Low
As Reasonably Achievable”,
economic and social factors being
taken into account.
BENEFIT
RISK

31. Optimisation
• For every exposure, operators must ensure
that doses arising from the exposure are kept
as low as reasonably practicable and
consistent with the intended diagnostic
purpose.
• THIS IS OPTIMISATION

32. ALARA
ALARA (As Low As Reasonably
Achievable) refers to the continual
application of the optimization principle
in the day-to-day practice.

33. Limitation
❖ Doses should not exceed specific
values, called “individual dose limits”.
❖ These dose limits are established in
order to keep away from the
“maximum risk level” so that no
individual is exposed to a radiation risk
that is judged to be unacceptable in any
normal circumstance.

34. Limitation
• Limits are set such that deterministic effects
never happen
• Limits are set such that chances of stochastic
effects are minimised

35. Types Of Exposure
There are three types of radiation exposure;
Occupational exposure; Which is the exposure incurred at work,
and principally as a result of work.
Medical exposure; Which is principally the exposure of persons
as part of their diagnosis or treatment.
Public exposure; Which includes all other exposures (i.e.
exposure incurred by members of the public from authorized
radiation sources, excluding any occupational and medical
exposure and exposure from natural background radiation). Their
justification (for those of non natural origin) is the general benefit
brought by the use of ionizing radiation in Medicine or Industry.

36. Legal Dose Limits - Patients
• For examinations directly
associated with illness – there are
no dose limits.

37. Legal Dose Limits – Radiation Workers
• Radiation workers are those exposed to radiation
as part of their occupation
• No benefit – only risk

38. Legal Dose Limits
• Receive high levels of radiation exposure
• Very unlikely for dental
• Require annual health check
• Compulsory dose monitoring
• For classified worker
– Whole body 20 mSv per year effective dose (18 years old and above)
– Lens of eye 150 mSv per year equivalent dose
– Skin 500 mSv per year equivalent dose
– Extremities (hands and feet etc) 500 mSv per year equivalent dose

39. Radiation Dose Limits
❖ Old Radiation Dose Limits
❖ 50 milliSieverts per year (mSv/y) for occupational
exposure
❖ 5 mSv/y for the general public
❖ New Radiation Dose Limits
❖ 20 mSv/y for occupational exposure (5 year average) with
a maximum of 50 mSv in any one year
❖ 1 mSv/y for the general public

40. Radiation Dose Limits
• 20 mSv/y for occupational exposure
• 1 mSv/y for the general public
• No limit for medical exposure

41. Dose limits (public)
(*) In special circumstances, an effective dose of
up to 5 mSv in a single year provided that the
average dose over five consecutive years does
not exceed 1 mSv per year.
Public dose limitApplication
1 mSv in a year (*)Effective dose
Annual equivalent dose in:
15 mSvThe lens of the eye
50 mSvThe skin

42. Dose Limits (Occupational
Exposure)
The occupational exposure of any worker should be
controlled so that the following limits be not exceeded:
Occupational dose limitApplication
20 mSv per year, averaged over defined
periods of 5 years 50 mSv in any single yearEffective dose
Annual equivalent dose in:
150 mSvThe lens of the eye
500 mSvThe skin
500 mSvThe hands and feet

43. Individual Dose Limits
Public exposure
• an effective dose limit for a member of the public (e.g. office
worker in room next door to x-ray) is 1 mSv in any single year
• an effective dose of 5 mSv in a single year in special
circumstances provided that the average dose over 5
consecutive years does not exceed 1 mSv per year;
• an equivalent dose to the lens of eye of 15 mSv in a year
• an equivalent dose to the extremities or the skin of 50 mSv in a
year

44. Individual Dose Limits
Occupational exposure
• an effective dose of 50mSv in any single year;
• an effective dose of 100 mSv in 5 consecutive years;
(an effective dose of 20 mSv per year averaged over 5
consecutive years);
• an equivalent dose to the lens of eye of 150 mSv in a year
• an equivalent dose to the extremities or the skin of 500 mSv in
a year

45. Recommended Dose Limits In
Planned Exposure Situations
(ICRP 103)
PublicOccupationalType of limit
1 mSv in a year20 mSv per yearEffective dose
15 mSv
50 mSv
150 mSv
500 mSv
500 mSv
Lens of the eye
Skin
Hands and feet

46. Optimisation – Staff Dose Investigation
Level (DIL)
❖ Dose Investigation Level
▪ 1.2 mSv per year
▪ Or 0.1 mSv per month
❖ This is a level of dose that should
trigger an investigation in conjunction
with your RPA, and ensures that you
do not receive anywhere close to the
legal limit.

47. Investigational Levels
Level 2Level 1
3.75 mSv1.25 mSvWhole body
55.00 mSv17.50 mSvDistal
Extremities

48. Pregnant Workers
A female worker should, in becoming aware that she is
pregnant, notify the employer in order that her working
conditions may be modified if necessary.

49. Pregnant workers
The notification of pregnancy should not be considered a
reason to exclude a female worker from work; however, the
employer of a female worker who has notified pregnancy
should adapt the working conditions in respect of
occupational exposure so as to ensure that the embryo or
fetus is afforded the same broad level of protection as
required for members of the public.

50. The Occupational Exposure Of
Women
❖ The basis for the control of the occupational exposure of
women who are not pregnant is the same as that for men
and the ICRP recommends no special occupational dose
limit for women in general.
❖ Once pregnancy has been declared, the conceptus should
be protected by applying a supplementary equivalent dose
limit at the surface of the woman’s abdomen (lower trunk)
of 2 mSv for the remainder of the pregnancy.

51. Medical Exposure
❖ Medical radiation is the largest radiation source
other than natural background
❖ Medical radiation dose accounts for about 95%
of doses from “man-made” sources
❖ There are about 2 billion diagnostic x-ray
examinations, 32 million nuclear medicine
procedures and 5.5 million radiation therapy
treatments annually

52. Medical Exposure
Exposure incurred by :
• patients as part of their own medical or dental
diagnosis or treatment;
• persons (other than occupationally exposed),
voluntarily helping in the support and comfort of
patients;
• volunteers in a program of biomedical research
involving their exposure.

53. Medical Exposure
• Medical exposure is different from most other uses of
radiation. Too little or too much dose are bad in both
diagnosis and therapy
• The task is to provide enough dose for the task but not
much more

54. Dose limitation for comforters
and visitors of patients (I)
The dose limits should not apply to comforters
of patients, i.e., to individuals exposed while
voluntarily helping (other than in their
employment or occupation) in the care, support
and comfort of patients undergoing medical
diagnosis or treatment, or to visitors of such
patients.

55. ➢ However, the dose of any such comforter or
visitor of patients should be constrained so
that it is unlikely that his or her dose will
exceed 5 mSv during the period of a patient's
diagnostic examination or treatment.
➢ The dose to children visiting patients who
have ingested radioactive materials should be
similarly constrained to less than 1 mSv.
Dose Limitation For Comforters
And Visitors Of Patients (II)

56. Some cases are not considered for dose limits, although
they may increase the effective dose:
❖Natural background radiation
❖Origin: cosmic radiation and natural radioactive
elements in the environment (2-3 mSv/year)
❖Radiation received as consequence of medical exposure
❖It may represent an increment of dose > than natural
radiation, but it is not taken into consideration for
dose limits.
Not Considered For Dose
Limits

57. Code of Practice
➢ Detailed procedures for patient, worker and
visitor safety.
➢ Identification of all "Controlled Areas",
displaying schematically the location of all
external radiation devices.

58. Code of Practice
➢ Radiation dose information to patients for all
routine diagnostic examinations, as
determinate by direct measurement.
➢ Establishment of a quality control program to
maintain optimum standards for quality and
safety.

59. Controlled Areas
• This is an area where it is
necessary to follow special
procedures to restrict exposure
to ionizing radiation, or
• An area where any person is
likely to receive 1/10th of the
dose limit or more.

60. Controlled Areas
• High radiation areas and each radiation area
where the possibility presents of approaching
10% of the occupational dose limit shall be
treated as controlled areas.

61. Controlled Areas
The specific requirements are:
1. The area must be secured when it is not occupied by responsible
personnel.
2. The area must be posted with proper signs indicating the radiation zone(s)
and the sources which is present.
3. Personnel monitoring must be provided where appropriate, as determined
by the Radiation Safety Office.
4. Surveys must be performed to maintain surveillance on the hazards which
might be present, and records kept.
5. Personnel must receive written instructions as to the hazards present in the
area.

62. Surveys & Monitoring

63. Dose monitoring
• Film badges
• Thermoluminescent dosemeters (TLD)
– Badge
– Extremities
• Ionisation chambers

64. Personnel Monitoring

65. Who Should Wear Radiation
Dosimeters Or Badges?
• Those “likely” to exceed 10% of their annual
limit are required
• Minors & Declared Pregnant Workers*

66. Monitoring is conducted at either monthly or quarterly
intervals depending upon the radiation level associated
with the work environment.
The radiation monitor shall be worn under the
protective garment in such a manner as to record the
maximum incident exposure.
Personnel Monitoring

67. Film Badges
Copper
Tin
Image filter
Open window
Al2O3 strip

68. Film Badge Advantages
➢ Inexpensive
➢ Easy to handle
➢ Reasonably accurate
➢ Provides a permanent dose record
➢ Measure type and energy of radiation
➢ Simple and robust

69. Film Badge Disadvantages
❖ No immediate indication of exposure
❖ Processing can lead to errors
❖ Prone to filter loss

70. TLD
• Similar use as for film badges
• They absorb radiation and release this
as light when heated
– Advantages:
• Re-usable
• Easy to read out
– Disadvantages:
• Read out is destructive
• Limited info on type of radiation

71. Personal Dose Monitoring
Extremity
TLD
“ring badge”
• Wear facing source
• Wear under gloves
• Exchange every 3 months

72. Area Survey
• Area Surveys are used to measure:
– radiation level
– contamination level

73. • Area Surveys should be conducted:
– Daily whenever radionuclides are used
– Monthly even if no experiments
• Keep record of all surveys conducted
Area Survey

74. Area Survey

75. • A complete radiation survey shall be performed for each X-ray
installation, at the time of acceptance and after any important
change or repair to confirm the adequacy of structural shielding
required, added shielding, or its accessories.
Area Survey

76. Procedures To Reduce Dose
To X-ray Personnel

77. X-ray Tube
Primary Beam
Scattered Radiation Staff
Patient
The Real Risk To Staff

78. Protection From External
Radiation
External hazards arise from
❖radioactive sources
❖machines producing radiation eg x-rays
Protection Methods
fall under three headings
1) Time limit the exposure time
2) Distance use inverse square law
3) Shielding attenuate the beam

79. Basic Principles of Dose
Reduction
•Time
•Distance
•Shielding

80. Reduction of External Dose
❖Minimize the time spent near the radiation source
❖Maximize the distance away from the source
❖Make use of available shielding

81. Time
An ALARA principle is to
reduce the time in a radiation field
100 200 300 mrem
100 mrem/hr 1 hour 2 hours 3 hours

82. 20
Time
Dose is proportional to
the time exposed
It is wise to spend no more time
than necessary near radiation sources

84. Methods For Minimizing
Time I
• Pre-plan and discuss the task thoroughly prior
to entering the area.
• Use only the number of workers actually
required to do the job.
• Have all necessary tools before entering the
area.
• Use mock ups and practice runs.
• Take the most direct route to the job site.

85. • Never loiter in an area controlled for
radiological purposes.
• Work efficiently but swiftly.
• Do the job right the first time.
• Perform as much work outside the area as
possible.
Methods For Minimizing
Time II

87. Inverse Square Law
For a point source, the
Radiation Dose
decreases as the square
of the distance from
the source.
Dose a 1/d2

88. In air, x-rays obey the
Inverse Square Law.
I∞1/d2
•Double distance = 1/4 dose
•Triple distance = 1/9
th dose.

89. Distance
Another ALARA principle is to
maximize the distance from source
0 1 2 3 4
ft. ft. ft. ft. ft.
100 25 11 6 mrem/hr
Inverse
square
1 1/4 1/9 1/16

90. Distance
•Double distance = 1/4 dose
•Triple distance = 1/9
th dose.

91. 22
Distance
•It is recommended that an individual remains as
far away as possible from the radiation source .
•Procedures and radiation areas should be designed
such that only minimum exposure takes place to
individuals doing the procedures or staying in or
near the radiation areas.

92. Methods For Maintaining Distance From
Sources Of Radiation I
• The worker should stay
as far away as possible
from the source of radiation.
• For point sources, the dose
rate follows the inverse
square law. If you double the
distance, the dose rate falls to
1/4. If you triple the distance,
the dose rate falls to 1/9.

93. • Be familiar with radiological
conditions in the area.
• During work delays, move to
lower dose rate areas.
• Use remote handling devices
when possible.
Methods For Maintaining Distance From
Sources Of Radiation II

94. Consequence
• Distance is very efficient for radiation protection as the
dose falls off in square
• Examples:
– long tweezers for handling of sources
– big rooms for imaging equipment

96. Shielding
• Materials “absorb” radiation
• Proper shielding = Less
Radiation Exposure
• Plexiglass vs. Lead

97. Shielding

98. Shielding

99. 26
Shielding
incident
radiation transmitted
radiation
Barrier thickness

101. Shielding For Various Types of
Radiation
Alpha

−−

 ++
Beta
Gamma and X-rays
Neutron
Paper Plastic Lead Concrete


n

 g

102. Shielding
•Various high atomic number (Z) materials that absorb radiations
can be used to provide radiation protection
•The ranges of alpha and b particles are short in matter the
containers themselves act as shields for these radiations
–Alpha can be stopped by a piece of paper
–Beta low molecular weight element Al or glass can stop its effect.
(Whay don’t we use lead for shielding of beta radiation?)
•Gama radiations are highly penetrating absorbing material must
be used for shielding of g-emitting sources
–Lead is most commonly used for this purpose.

103. Proper Uses Of Shielding
Shielding reduces the
amount of Radiation dose
to the worker. Different
materials shield a worker
from the different types of
radiation.

104. Proper Uses Of Shielding
It should be remembered
that the placement of
shielding may actually
increase the total dose
(e.g., man-hours involved
in placement,
Bremsstrahlung, etc.).

106. X-Ray Tube Shielding
• The shielding of the housing must be such that, at each rating
specified by the manufacturer for that tube, the leakage
radiation, measured at a distance of one metre in any direction
from the focal spot of the x-ray tube, does not exceed 0.1% of
the exposure rate at the same distance along the central axis of
the useful beam.

107. Protective Clothing
1. Protective body aprons
2. Gonad shields
3. Protective gloves

108. Protective Body Aprons
• Protective body aprons used
for radiographic or
fluoroscopic examinations
with peak x-ray tube
potentials of up to 150 kVp
must provide attenuation
equivalent to at least 0.5 mm
of lead.

109. Gonad Shields
• Contact-type gonad shields used for routine
diagnostic radiology must have a lead equivalent
thickness of at least 0.25 mm and should have a lead
equivalent thickness of 0.5 mm at 150 kVp. Contact-
type gonad shields must be of sufficient size and
shape to exclude the gonads completely from
primary beam irradiation.

110. Protective Gloves
• Protective gloves used in
fluoroscopy must provide
attenuation equivalent to at least
0.25 mm of lead at 150 kVp.

111. Eye Shielding
Wear safety glasses/goggles to
protect the eyes from beta
radiation, when applicable.