This document discusses radiation protection and safety criteria related to ionizing radiation. It begins by defining radiation hazards and outlining the biological effects of radiation exposure, which can be either deterministic or probabilistic. Key aspects of radiation protection covered include determining radiation hazards, evaluating radiation doses, and the principles and recommendations established by the International Commission on Radiological Protection. The document then provides examples of calculating radiation intensity and shielding requirements for various radiation sources and energies. It emphasizes protecting workers and the public through principles of time, distance and shielding, and highlights planning considerations for medical x-ray facilities to ensure safe and compliant operation.

1. Radiation Protection
DR. HARSH MOHAN
DEPARTMENT OF PHYSICS
M.L.N. COLLEGE
YAMUNA NAGAR
(HARYANA)

2. UNIT – II
Basic radiation safety criteria, Protection
from direct radiation, Energy
deposition, Effect of distance and
shielding, Protection from contamination,
Preparation of a safe radiation area,

3. A hazard is a situation that poses a
level of threat to life, health, property,
or environment.
Most hazards are dormant or potential,
with a theoretical risk of harm.
Once a hazard becomes active, it can
create an emergency situation.
What is hazard?

4. Nature of effect:
 Deterministic
effect
 Probabilistic
effectWho is affected:
 Exposed individual
 Progeny of exposed person
When effect appears:
 Immediate
 Delayed
Radiation Hazards

5. BIOLOGICAL EFFECTS OF
RADIATION
• Deterministic effects:
– Temporary Sterility
– NVD
– Epilation
– Skin burn
– Cataract
– Lethality

6. BIOLOGICAL EFFECTS OF
RADIATION (CONTD.)
• Probabilistic effects:
– Cancer
– Leukaemia
– Hereditary effect
No threshold dose
is defined !!

7.  Determination of the radiation hazard that
may result from exposure to radiation.
 Assessment of the dose received by the
exposed persons
Hazard Evaluation

8. Type of Radiation Hazard
External Hazards –
source of radiation outside the body
Internal Hazards –
source of radiation inside the body

9. Evaluation of Rad Hazard
Required to take control measures in radiation area
This is done at two stages - design stage
- user’s stage (normal
working conditions)
Rad. Levels at different locations can be estimated
provided
- nature and activity of the source
- energy of radiation emitted

10. International Commission on
Radiological Protection (ICRP)
• Established in 1928
• Modifies safety recommendations time to
time (at 4 occasions)
• Radiobiological investigations on human
exposed

11. ICRP
Recommendations on Radiation Protection in 1991
ICRP Publication No.60
Recommendations on Radiation Protection in 2007
ICRP Publication No.103
International Basic Safety
Standards for Protection against Ionizing Radiation and for the Safety
of Radiation Sources (BSS)
(WHO, ILO, IAEA, Etc.)

12. Objective of Protection from
Ionizing Radiation
To prevent following effects induced from
radiation by considering economic and social
factors
o deterministic effects
o minimize likelihood of stochastic effects

13. PRINCIPLES OF RADIOLOGICAL
PROTECTION
Basic the principles of radiological
protection are
 Justification of Practice,
 Optimisation of Practice, and
 Dose Limitations

14. Justification of Practice
It is judged from the total detriment from
a proposed practice involving exposure
from ionising radiation
Total detriment < The expected benefit

15. OPTIMIZATION OF PROTECTION
Greater the level of protection:
Higher the degree of safety
But :
Involves expenditure and
Reduces ultimate value of practice

16. Nucleonic Gauges
Amount of radioactivity
μCi to mCi
Radiations emitted
α, β, char. x-rays
Well shielded to achieve prescribed
degree of safety

17. Other nucleonic gauges
Where :
Large activities (mCi or Ci)
Energetic radiation (penetrating)
( Gamma & Neutrons)
Need adequate structural and local radiation shields.

18. Huge shielding and extreme protections
Provides great safety
But would achieve a small increase in
degree of safety
Increase in the expenditure.
Thus - recommended that protective measures
should be optimized
As Low As Reasonably Achievable (ALARA)
This consideration should be followed in optimizing the level
of protection.

19. Radiation workers in India receive an
average eff. Dose = 1.49 mSv/y
(1.49 mSv is 1/30 of MPL)
Follows the principle of (ALARA)
This corresponds : 0.6 excess fatal cancers
per year among 40,000
radiation workers
Number is quit small to distinguish from total number of
annual fatalities which is only 0.02

20. Hazard Evaluation from Ionizing
Radiation
Distance (Intensity)
Time
Shielding

22. Inversely proportional to distance
S1 r1
I1S2 r2
I2
I1 = S1/4π
(r1)2
I2 = S2/4π
(r2)2

23. I1 /I2 = S1 x r2
2
/S2 x r1
2
If S1 = S2 = 1 cm2
I1 /I2 = r2
2
/ r1
2
I1 /I2 = d2
2
/ d1
2
Larger the distance from the source lesser will
be the dose

24. I1 /I2 = S1 x r2
2
/S2 x r1
2
If S1 = S2 = 1 cm2
I1 /I2 = r2
2
/ r1
2
I1 /I2 = d2
2
/ d1
2
Larger the distance from the source lesser will
be the dose

25. Effect of Time
Cumulated exposure = Exposure rate x time
Dose received αtime spent near source
Lesser the time spent near the source of radiation,
lesser will be the radiation dose received

26. Shielding for different radiation
For α particle - do not pose problem
For β particle - perspex (low Z material)
followed by lead
For γ photon - high Z material like lead
For neutrons - hydrogeneous material

27. Shielding for Alpha particle
• Alpha particles are nuclei of helium atoms
• Large mass and double positive charge
• Intense ionisation resulting in rapid loss of energy
• Range of 5 MeV α particle is ≈ 5 cm in air or
50 microns in tissue
• No such external hazard
• Very high internal hazard

28. Shielding for Alpha particle
• Alpha particles are nuclei of helium atoms
• Large mass and double positive charge
• Intense ionisation resulting in rapid loss of energy
• Range of 5 MeV α particle is ≈ 5 cm in air or
50 microns in tissue
• No such external hazard
• Very high internal hazard

29. Shielding for Beta particle
• Beta particles are similar to electron & positron
• Mass and charge same as that of e-
& e+
• Range of 1MeV β particle is ≈ 1-2 cm in tissue
• Range (gm/cm2
) = E avg(MeV)/2
• For practical purposes, E avg = E max/3
• Breammstrahlung production
• Shielding should be of low Z followed by high Z
• High internal hazard

30. Shielding for X-rays & gamma
• Photons are electromagetic in nature
• No mass and no charge
• Range of photons is very high
• Interacts with matter by PE, CE, PP etc
• Shielding should be of high Z material
• High external hazard

31. Shielding for Neutrons
• Neutrons are uncharged particle
• Do not cause ionisation directly
• Type of interation depends on neutron energy
• Slowing down of fast and absorbing slow neutn.
• Hydrogeneous material is best for shielding
• Shielding should be of low Z followed by Lead
• High external hazard

32. Relation between transmitted
intensity and shield
Io
I
x

33. Relation between transmitted intensity
and shield
I =B. Io. e-µx
Where
I & Io – transmitted and initial intensity
µ - linear Attenuation coefficient (cm-1
)
X - thickness of the shielding material (cm)
B - build-up factor

34. • µ depends on radiation energy and Z of the
medium
• Value of µ increases with increasing Z of the
medium and decrease in energy
• µ = 0.693/HVT
• B = (Intensity of primary + scattered Rad.)
Intensity of only primary radiation

35. Half value thickness (HVT)
HVT- It is that thickness of the shielding material
which will reduce the radiation intensity to half of
the original intensity
Io/I = ½ = e μ.HVT
HVT = ln 2/ μ = 0.693/ μ
HVT will be more for low Z material

36. Tenth value thickness (TVT)
TVT- It is that thickness of the shielding material
which will reduce the radiation intensity to one
tenth of the original intensity
Io/I = 1/10 = e μ.TVT
TVT = ln 10/ μ = 2.302/ μ
TVT = 3.3 x HVT

37. HVT & TVT in Lead
Source HVT(cm) TVT(cm)
Ir – 192 0.48 1.6
Cs- 137 0.7 2.2
Co- 60 1.2 4.0
(HVTZ1 x DensityZ1) ≈ (HVTZ2 x DensityZ2)

38. Gamma Ray Constant
k-Factor
How to find out intensity at a
particular point?
B

39. Evaluation of Intensity (exposure) at a
point without shield
31 2 4
1 – Source strength 2 –
Gamma Ray constant
3 – distance from the source 4 – Time
spent at the point

40. Exposure level at 10 cm from 10 MBq of 57
Co ?
Exposure rate constant for 57
Co
= 0.2 mGy/h from 1 MBq at 1 cm
=0.2 x 10 x (1/10)2
mGy/h
=0.02 mGy/h

41. Evaluation of Intensity (exposure) at
a point with shielding
1 2 4
1 – Source strength 2 – Gamma Ray constant
3 – distance from the source 4 – Time spent at the pt.
5 – Shielding thickness 6 – μ of shielding mat.
3
5&
6

42. Intensity with TVT
I = Io/10 = 0.1 x Io
If x = 1 TVT
If I = 100 mR/h
1 TVT will reduce I to
10.0 mR/h
Additional 1 TVT will reduce I to
1.0 mR/h

43. Decay factor
Physical decay of activity
A = Ao e-λt
λ = decay constant = 0.693/T½
t = time elasped
T½ = physical half life
Modify the previous equation
Exposure R = Ro . e-λt

44. Control of external hazards
External
Time (First effort)
Distance (Second effort)
Shield (where above fail)
Selection of lower activity

45. Control of external hazards
Two monitoring devices are used :
a) Personnel monitoring
TLD (routing monitoring)
Film Badge
Pocket dosimeter
b) Area monitoring
Ionisation chamber type
GM type survey meter

46. What would be the radiation level at a distance of
10 meters from a 400 MBq Ir- 192 source ?
What is the distance in meters required to reduce
the radiation level from a 5 Ci Co-60 soure to 2.5
mR/h ?
What would be the radiation level at 10 cm
distance from a 100

47. • Regulatory requirements for diagnostic
installations
• Planning of X-ray facilities
- Area requirement
- Model layout
- Workload
- Shielding calculations
• Radiological Protection Survey
• Instruments to be used
• Assessment of doses
• Protective accessories
Protection from contamination, Preparation of
a safe radiation area,

48. MAMMOGRAPHY
DIAGNOSTIC RADIOLOGY
COMPUTED
TOMOGRAPHY
RADIOGRAPHY &
FLUOROSCOPY
OPG INTERVENTIONAL
RADIOLOGY

49. Radiation safety can be divided as
Design safety (built in safety)
 Equipment (QA)
 Facility (proper planning)
Operational safety
 Time-Distance-Shielding
 Proper work practice

50. REGULATORY DOCUMENTS CONCERNING REQUIREMENTS
FOR SAFE OPERATION OF MEDICAL X-RAY MACHINES ARE:
• AERB SAFETY CODE NO. AERB/SC/MED-2 (REV-1)2001 and
Amendment 2012
• ATOMIC ENERGY (RADIATION PROTECTION ) RULES, 2004
• ATOMIC ENERGY ACT, 1962

51. Some Of The Statutory Requirements
• Plan approval
• Protective devices
• Type Approved X-ray units
• Qualified man power
• Registration/Licensing of X-ray
installations
• Personnel Monitoring Badges

52. Planning of X-ray installation involves:
Site selection
Room specifications
Shielding calculations
Availability of protective accessories
Planning of interior (relative positions of control
panel, chest stand, MPB, door, window etc.)

53. Site Selection
Rooms housing the diagnostic x-ray units and
related equipment should be located as far away
as feasible from areas of high occupancy and
general traffic, such as maternity and pediatric
wards and other departments of the hospital that
are not directly related to radiation and its use.

54. Room Specifications
AREA REQUIREMENT
X-RAY R / F : 18 SQ.MT. (4 m)
CT-SCAN/CATH LAB : 25 SQ.MT. (4 m)
MAMMOGRAPHY : 10 SQ.MT. (3 m)
OPG : 15 SQ.MT. (3.5 m)
MOBILE/C-ARM : NA

55. Purpose of shielding
To protect :
the x-ray department staff
the patients (when not being x-rayed)
visitors and the public
persons working adjacent to or near the x-ray facility

56. Shielding is designed against three
sources of radiation
In decreasing importance, these are :
primary radiation (the x-ray beam)
scattered radiation (from the patient)
leakage radiation (from the x-ray tube)

57. Radiation Shielding design concept
Data required include consideration of
Type of X-ray equipment
Usage (work load)
Positioning
Whether multiple tubes /receptors are used
Primary beam direction
Operator location
Surrounding areas

58. SHIELDING REQUIREMENTS
STRUCTURAL SHIELDING
WALL THICKNESS : 9” BRICK
CEILING/FLOOR : 6” CONCRETE
DOORS : 1.7MM Pb (equivalent)
LINING

59. SHIELDING REQUIREMENTS
PROTECTIVE ACCESSORIES
 Mobile Protective Barrier : 1.5 MM Pb EQUV.
 LEAD GLASS(V.W.) : 1.5 MM Pb EQUV.
 LEAD APRONS : 0.25 MM Pb EQUV.
 LEAD GLOVES : 0.25 MM Pb EQUV.
 PB RUBBER FLAPS : 0.5 MM Pb EQUV.

60. The type of equipment is very important for the
following reasons
Primary beam direction
The No. and type of procedures to be performed
Location of radiographer
Energy of X-rays (kVp)

62. Typical room layout
(for shielding calculation purpose)

63. Calculation points
For walls 1,3 and 4
Radiation due to scatter + radiation leakage from tube
For wall 2
--Primary + Scatter + leakage
Maximum total work load of the machine
= 300 mAmin/week
(Assumed)

64. Data required
Out of which for (100 kV) – 300 mA min/week
Output of the machine for 100 kVp = 10-12 mR/mAs
Output of the machine for 70 kVp = 3-4 mR/mAs
Scattered radiation at 1 m = 0.1 % of primary
As per AERB/SC/MED-2 code Tolerance for maximum
leakage from tube is 115 mR in one hour (work load 180
mA min in one hour)

65. Dpri = 12 mR/mAs X 300 mA min/week X 60 s/min
= 2.16 X 105
mR/week
Dsc = 2.16 X 105
X 10-3
= 216 mR /week at 1 m.
For leakage (300 mA min)
Dlek = (300 X 115 )/180
= 191.67 mR/week ~ 200 mR/week
Total dose at 1m = 200 + 216
= 416 mR/week

66. HVT/TVT values for shielding materials
Shielding material HVT (cm) TVT (cm) Density(gm/cc)
Lead
(1oo kVp)
0.025 0.084 11.3
(150 kVp) 0.029 0.096
Concrete
(100 kVp)
1.6 5.5 2.35
(150 kVp) 2.2 7.0
Brick
(100 kVp)
2.5 8.61 1.5
(150 kVp) 3.44 10.96

67. Reduction factor (RF) = W U T / P d2
Where
W – work load
U – use factor
T – Occupancy factor
P – Weekly permissible dose
(2 mR/week – for general public)
d - distance

68. Work load
Different X-ray equipment have different work load
Eg. A dental unit uses low mAs and low kVp (~70)
and takes relatively few X-rays per week.
A CT scanner uses high (~140 kVp), high mAs, and
takes many scans per week

69. W - WorkloadW - Workload
A measure of the radiation output in one weekA measure of the radiation output in one week
Measured in mA-minutesMeasured in mA-minutes
Varies greatly with assumed maximum kVp ofVaries greatly with assumed maximum kVp of
x-ray unitx-ray unit
Usually a gross overestimationUsually a gross overestimation
Actual dose/mAs can be estimatedActual dose/mAs can be estimated

70. For example:For example: a general radiography rooma general radiography room
The kVp used will be in the range 60-120 kVpThe kVp used will be in the range 60-120 kVp
The exposure for each film will be between 5 mAsThe exposure for each film will be between 5 mAs
and 100 mAsand 100 mAs
There may be 50 patients per day, and the roomThere may be 50 patients per day, and the room
may be used 7 days a weekmay be used 7 days a week
Each patient may have between 1 and 5 filmsEach patient may have between 1 and 5 films
SO HOW DO WE ESTIMATE W ?SO HOW DO WE ESTIMATE W ?

71. Assume an average of 40 mAs per film, 2Assume an average of 40 mAs per film, 2
films per patientfilms per patient
Thus W = 40 mAs x 2 films x 50Thus W = 40 mAs x 2 films x 50
patients x 6 dayspatients x 6 days
= 24,000 mAs per week= 24,000 mAs per week
= 400 mA-min per week= 400 mA-min per week
We could also assume that all this work isWe could also assume that all this work is
performed at 100 kVpperformed at 100 kVp

72. Workload - CT
• CT workloads are best calculated from local
knowledge
• Remember that new spiral CT units, or
multi-slice CT, could have higher workloads
• A typical CT workload is about 28,000 mA-
min per week

73. U - use factorU - use factor
fraction of time thefraction of time the primaryprimary beam is in abeam is in a
particular direction i.e.: the chosenparticular direction i.e.: the chosen
calculation pointcalculation point

74. For some x-ray equipment, the x-ray beamFor some x-ray equipment, the x-ray beam
isis alwaysalways stopped by the image receptor,stopped by the image receptor,
thus the use factor is 0thus the use factor is 0 in other directionsin other directions
e.g.: CT, fluoroscopy, mammographye.g.: CT, fluoroscopy, mammography
This reduces shielding requirementsThis reduces shielding requirements

75. For radiography, there will be certain directionsFor radiography, there will be certain directions
where the x-ray beam will be pointedwhere the x-ray beam will be pointed
towards the floortowards the floor
across the patient, usually only in one directionacross the patient, usually only in one direction
toward the chest Bucky standtoward the chest Bucky stand
The type of tube suspension will be important,The type of tube suspension will be important,
e.g.: ceiling mounted, floor mounted, C-arm etc.e.g.: ceiling mounted, floor mounted, C-arm etc.

76. T - OccupancyT - Occupancy
T = fraction of time a particular place isT = fraction of time a particular place is
occupied by staff, patients or publicoccupied by staff, patients or public
Has to be conservativeHas to be conservative
Ranges from 1 for all work areas to 0.06 forRanges from 1 for all work areas to 0.06 for
toilets and car parkstoilets and car parks

77. Occupancy (NCRP49)
Area Occupancy
Work areas
(offices, staff
rooms)
1
Corridors 0.25
Toilets, waiting
rooms,car parks
0.06

78. (RF) = W U T / P d2
= (400 X1 X1)/(2 X 22
[distance from X-ray source])
= 50
= 2n
or 10n
= 5.64 HVT or 1.69 TVT
Shielding thickness for concrete
= 1.69 X 5.5 = 9.29 cm of concrete
OR = 9.29 X 2.35/1.5 = 14.55 cm of brick

79. For Primary wall (Chest Stand wall)
Work load ∼ 200 mA min/week
Output for 70 kV ∼ 3-4 mR/mAs
dose at primary wall 2
= (4mR/mAs X 200 mAmin/wk X60)/22
= 12,000 mR/wk
Dleakage= (500 X 115)/(180 X 22
)
= 79.86 mR/wk ∼ 80 mR/wk
Total dose at wall 2 = 12080
RF = 12080/2 = 6040 = 3.78 TVT

80. CT room design
• General criteria:
– Large room with enough space for:
• CT scanner-gantry
• Auxiliary devices (contrast media injector, emergency bed
and equipment, disposable material containers, etc)
– Other spaces required:
• Console room with large window large enough to see the
patient all the time
• Patient preparation room
• Patient waiting area
• Report room
• Film printer or laser film printer area

81. Room shielding
• Workload
• Protective barriers
• Protective clothing
2.5 µGy/1000 mAs-scan
Typical scatter dose distribution around
a CT scanner

82. • Workload (W): The weekly workload is usually expressed in
milliampere minutes.
– The workload for a CT is usually very high
– Example:
6 working day/week, 40 patients/day, 40 slices/patient,
200 mAs/slice, 120 kV
• Primary beam is fully intercepted by the detector assembly.
Barriers are required only for scattered radiation
mAmin/week32000W 60
200.40.40.6
==

83. Radiological Protection Survey:
The assessment of radiation levels at different
locations in the vicinity of radiation sources
or any radiation practice is known as
Radiological Protection Survey.
On the basis of measurements taken one
would be able to find out the adequacy of the
existing radiation protection facilities.

84. Radiological Protection Survey
X-Ray tube
Filter
Table top
SDD
Phantom (PEP)

85. In radiological protection survey radiation levels
are measured at different locations such as control
panel, patient waiting area, outside
doors/windows etc. using properly calibrated
survey meter and with dummy patient/ water
phantom as it simulates the human body.
Using measured values of dose rates and weekly
workload, the weekly doses can be estimated.
Survey meter to be used : ionisation chamber
based survey meter

86. If the dose rate at operators position =
4 mR/hour for 20 mA
Dose received by the operator is =
203 mAmin/wk X 4 mR/hour
60 X 20 mA
= 0.67 mR/week
The allowable weekly dose for radiation
worker is 40 mR/week.

88. Some of the important points to be
considered while planning the X-Ray
installation are
1. Ideal location – away from the crowded area
2. Room size - 18 Sq. Meters
3. Wall thickness - 23cm (9”) brick
4. Number of entry doors – preferably one.
5. Lead lining of the door –1.7 mm lead

89. 66. Windows /ventilators -2m above the finished. Windows /ventilators -2m above the finished
floor level from outside the X-ray room.floor level from outside the X-ray room.
77. The unit shall be so located that it shall not. The unit shall be so located that it shall not
be possible to direct the primary X-ray beambe possible to direct the primary X-ray beam
towards the dark room, door, windows, andtowards the dark room, door, windows, and
control panel, or areas of high occupancy.control panel, or areas of high occupancy.
88. Warning signal provided at the entrance door. Warning signal provided at the entrance door