RADIATION PROTECTION - important for radiation workers .pdf

RADIATION PROTECTION
MODERATOR – DR ROHIT SHARMA
PRESENTER- DR AKANKSHA

BIOLOGICAL EFFECTS OF RADIATION
•Ionizing radiation which have high energy to ionize the medium with which they interact and thus brings
structural changes to the atom.
•It can directly hit the DNA and ionize it or water molecules absorb the radiation and dissociate into H+ and
OH- free radicals which will further react with DNA.
•Various types of DNA damage can occur : single/ double strand breaks , sugar damage , base damage,
DNA-DNA cross links, DNA-protein crosslinks which can lead to delay in repair mechanism , delay in
cell proliferation , cell transformation or cell lysis.
•Cells are most sensitive to radiation during M phase and G2 phase of cell cycle.
Loading…
DETERMINISTIC EFFECTS STOCHASTIC EFFECTS
Have threshold below which no effect
occurs
No threshold and may occur at even low
doses
Severity increases with dose Probability increases with dose
All people exposed above threshold will
be affected
Only portion of exposed population will
develop effects
Effects within days of exposure May happen years after
Ex : Skin erythema, epilation
Desquamation
Secondary ulceration
Cataract
Sterility

Ex: Cancer and hereditary effects which
can also pass on to the offspring of the
exposed individual
Loading…
Background Natural Radiation
•Natural background radiation sources are cosmic rays and terrestrial sources, natural radioactive material such as radon from
ground, building walls and floors, and traces of naturally occurring radioactive material in food and drinks.
•Artificial or man-made origin includes radioactive fallout from nuclear weapons test and major nuclear accidents, medical
diagnostic and therapeutic use of ionizing radiation, X-ray machines, particle accelerators, consumer products and transport of
radioactive materials.
•Worldwide average of effective dose from background natural radiation is about 2.4 mSv/year. (1.5-3.5 mSv/ year)
•The reported national average of outdoor natural radiation in India is 0.734 mSv per year.

RADIATION UNITS
• Exposure- charge created by X-rays per unit mass of air.
• Absorbed dose - energy deposited per unit mass of matter.
• Equivalent dose –measures potential of type of radiation to cause biological effect ( Absorbed dose x quality
factor)
• Effective dose- measures effect on specific tissue. (Equivalent dose x Tissue weighing factor)

REGULATORY BODIES FOR RADIATION PROTECTION
•AERB – Atomic Energy Regulatory Board- India
•NCRP – National Commission for Radiation Protection- USA
•ICRP – International Commission on Radiological Protection – International level
The ICRP was setup in 1928 and consists of a chairman, a secretary and 12 members from across the world. The AERB was set up on
November 15 1983 by President of India under section 27 of the Atomic Energy Act 1962. The purpose was to carry out certain safety
and regulatory functions under the act. The board has a full time chairman , a secretary , 3 part time members and an ex
officio member.

Loading…
PRINCIPLES OF RADAIATION PROTECTION
•JUSTIFICATION: Practices adopted should produce a net positive benefit.

•OPTIMIZATION: All exposures should be kept as low as possible.

•DOSE LIMITATION: Dose should not exceed the limits that have been recommended for a
particular practice.
JUSTIFICATION
•Every diagnostic practice should provide adequate benefit to the exposed individuals or to the society and outweigh the
radiation risk involved , i.e. the benefit to risk ratio should be high.
•Ex : the benefit to risk ratio is low for screening mammography below 35 years if age.
•3 levels of justification:
• At first and most general level , proper use of radiation in medicine is accepted as doing more good than harm to the
society.
• At second level is the justification of the procedure in improving the diagnosis or treatment and providing necessary
information about the exposed individual.
• At third level , the application of the procedure to an individual should be justified.
OPTIMIZATION
•The concept of ALARA states As Low As Reasonably Achievable.
•In United Kingdom , this has been modified as ALARP- As Low As Reasonably Practicable , economic
and societal factors being taken into account.
•2 levels of optimization
1. Optimization in selection , design and construction of X-Ray equipment .
2. Optimization in day to day methods of working to maximize net benefit and keep radiation doses as low
as practicable.

DOSE LIMITATION
•No radiation dose , however low its value , can be considered safe. Very low doses of radiation , for example , can
produce radiation induced cancer and serious hereditary effects if the cells irradiated are germ cells in the gonad.
•Maximum permissible dose (MPD): It may be defined as the dose of ionizing radiation which an individual may
accumulate over a long period of time with a negligible risk of significant body or genetic damage.
•MPD = 5 (N-1) R {where N is age in years and R is the exposures in Roentgens}. The unit of MPD is rem.
•The newer recommendation is MPD = age in years x 1 rem, i.e. the individual effective dose for a lifetime should
not exceed the value of his/her age.

ICRP recommends that occupational exposure of pregnant woman should fall into limits similar to that of the public.
DOSE LIMITS RECOMMENDED BY AERB
TYPES OF RADIATION GENERATING EQUIPMENT:
(RGE)• Computed Tomography
• Interventional Radiology
• Radiography (Fixed/Mobile)
• C-Arm/ O-Arm
• Mammography
• BMD (Bone Mineral Testing)
• Dental (Intraoral/OPG/Cone Beam CT)
• MRI and Sonography (Ultrasound) or non- ionising RGE do not come under purview of AERB
CARDINAL PRINCIPLES OF RADIATION PROTECTION
•1. Time
•2. Distance
•3. Shielding

1. Time: The time of exposure should be kept as short as possible.
Exposure = Exposure rate x Time

2. Distance: The distance between the radiation and the exposed person should be kept as large as possible.
The intensity (I) of radiation varies inversely with the square of the distance (d). This is known as the
inverse square law.
I α 1/d2

3. Shielding: Shielding means the attenuation of X-ray beam by certain materials like concrete, lead, etc.
when placed between the source of radiation and the exposed individual. The shielding can be in the form
of shielding of the X-ray tube, shielding of the room, personnel shielding or patient shielding.
The three types of radiation in radiation protection are:
1. Useful beam: It is also called the primary beam. The
useful or the primary beam is the radiation passing through
the tube aperture.
2. Leakage radiation: This includes all radiation passing
through the tube housing other than the useful radiation.
3. Scattered radiation: This includes all the radiation that
has undergone a change in direction.
SOURCE SHIELDING/SHIELDING OF THE X-RAY TUBE
•The X-ray tube is lined with thin sheets of lead to prevent the X-rays produced in the tube from scattering
in all directions.
•Shielding of the source protects both patients and radiation workers from leakage radiation.
•The leakage radiation exposure has to be limited to < 0.1 R per hour at 1 meter from the tube anode and
hence the X-ray tube housing needs to be shielded.
•AERB recommends a maximum allowable leakage radiation from the tube housing of not greater than 1
mGy/hour/1m .
ROOM SHIELDING
Ensures that the individuals outside these rooms are not exposed to unnecessary unwanted radiation. There are two
types of protective barriers.
1. Primary barrier: This is the one which is directly exposed to the useful beam. The atomic number and the
thickness of the primary barrier should be such that it reduces the exposure rate of the useful beam to the
permissible dose.
2. Secondary barrier: It is the one which is struck by radiation either by leakage from X-ray tube or by scattered
radiation from the patient.
The X-ray room shielding is influenced by the nature of occupancy of the adjoining area. Based on this
various types of areas are identified:
A. Control area: It is defined as the area routinely occupied by radiation workers and exposed to an
occupational dose. Recommended weekly shielding design goal (P) at control area is 40 mR/week (20mSv in a
year)
B. Uncontrolled area: These areas are occupied by individuals such as visitors to the facility and employees
who don’t work routinely around radiation sources. Areas adjacent to but not a part of xray facility is called
uncontrolled area. Recommended weekly shielding design goal (P) at uncontrol area is 2 mR/week (1 mSv in a year)
EXPOSURE CALCULATION
1. Workload : Quantity of xray generated per week
W=mAs/week

2. Exposure : converts workload into Roentgens

ex: at max energy of 100kVp with workload of 1000 mA.min.week,
weekly exposure =0.9R/mA.min X 1000 mA.min.week
=900R/week

•3. Use factor(U) : Time fraction for which the beam is directed at a particular barrier

•4. Occupancy factor(T) : This pertains to the time period for
which the area will be occupied.( used only for
areas occupied by non occupationally exposed
individual)

•5.Distance: Distance from source of radiation.
T=1
Full
occupancy
Labs , nurse stations
T=1/4
Partial
occupancy
Corridors, restrooms ,elevators using
operators
T=1/16
Occasional
occupancy
Waiting rooms, stairways, janitor closet,
outside areas used for pedestrian
Effective weekly exposure at any particular point is calculated as:

RADIATION PROTECTION
MODERATOR – DR ROHIT SHARMA
PRESENTER- DR AKANKSHA

BIOLOGICAL EFFECTS OF RADIATION
•Ionizing radiation which have high energy to ionize the medium with which they interact and thus brings
structural changes to the atom.
•It can directly hit the DNA and ionize it or water molecules absorb the radiation and dissociate into H+ and
OH- free radicals which will further react with DNA.
•Various types of DNA damage can occur : single/ double strand breaks , sugar damage , base damage,
DNA-DNA cross links, DNA-protein crosslinks which can lead to delay in repair mechanism , delay in
cell proliferation , cell transformation or cell lysis.
•Cells are most sensitive to radiation during M phase and G2 phase of cell cycle.
Loading…
DETERMINISTIC EFFECTS STOCHASTIC EFFECTS
Have threshold below which no effect
occurs
No threshold and may occur at even low
doses
Severity increases with dose Probability increases with dose
All people exposed above threshold will
be affected
Only portion of exposed population will
develop effects
Effects within days of exposure May happen years after
Ex : Skin erythema, epilation
Desquamation
Secondary ulceration
Cataract
Sterility

Ex: Cancer and hereditary effects which
can also pass on to the offspring of the
exposed individual
Loading…
Background Natural Radiation
•Natural background radiation sources are cosmic rays and terrestrial sources, natural radioactive material such as radon from
ground, building walls and floors, and traces of naturally occurring radioactive material in food and drinks.
•Artificial or man-made origin includes radioactive fallout from nuclear weapons test and major nuclear accidents, medical
diagnostic and therapeutic use of ionizing radiation, X-ray machines, particle accelerators, consumer products and transport of
radioactive materials.
•Worldwide average of effective dose from background natural radiation is about 2.4 mSv/year. (1.5-3.5 mSv/ year)
•The reported national average of outdoor natural radiation in India is 0.734 mSv per year.

RADIATION UNITS
• Exposure- charge created by X-rays per unit mass of air.
• Absorbed dose - energy deposited per unit mass of matter.
• Equivalent dose –measures potential of type of radiation to cause biological effect ( Absorbed dose x quality
factor)
• Effective dose- measures effect on specific tissue. (Equivalent dose x Tissue weighing factor)

REGULATORY BODIES FOR RADIATION PROTECTION
•AERB – Atomic Energy Regulatory Board- India
•NCRP – National Commission for Radiation Protection- USA
•ICRP – International Commission on Radiological Protection – International level
The ICRP was setup in 1928 and consists of a chairman, a secretary and 12 members from across the world. The AERB was set up on
November 15 1983 by President of India under section 27 of the Atomic Energy Act 1962. The purpose was to carry out certain safety
and regulatory functions under the act. The board has a full time chairman , a secretary , 3 part time members and an ex
officio member.

Loading…
PRINCIPLES OF RADAIATION PROTECTION
•JUSTIFICATION: Practices adopted should produce a net positive benefit.

•OPTIMIZATION: All exposures should be kept as low as possible.

•DOSE LIMITATION: Dose should not exceed the limits that have been recommended for a
particular practice.
JUSTIFICATION
•Every diagnostic practice should provide adequate benefit to the exposed individuals or to the society and outweigh the
radiation risk involved , i.e. the benefit to risk ratio should be high.
•Ex : the benefit to risk ratio is low for screening mammography below 35 years if age.
•3 levels of justification:
• At first and most general level , proper use of radiation in medicine is accepted as doing more good than harm to the
society.
• At second level is the justification of the procedure in improving the diagnosis or treatment and providing necessary
information about the exposed individual.
• At third level , the application of the procedure to an individual should be justified.
OPTIMIZATION
•The concept of ALARA states As Low As Reasonably Achievable.
•In United Kingdom , this has been modified as ALARP- As Low As Reasonably Practicable , economic
and societal factors being taken into account.
•2 levels of optimization
1. Optimization in selection , design and construction of X-Ray equipment .
2. Optimization in day to day methods of working to maximize net benefit and keep radiation doses as low
as practicable.

DOSE LIMITATION
•No radiation dose , however low its value , can be considered safe. Very low doses of radiation , for example , can
produce radiation induced cancer and serious hereditary effects if the cells irradiated are germ cells in the gonad.
•Maximum permissible dose (MPD): It may be defined as the dose of ionizing radiation which an individual may
accumulate over a long period of time with a negligible risk of significant body or genetic damage.
•MPD = 5 (N-1) R {where N is age in years and R is the exposures in Roentgens}. The unit of MPD is rem.
•The newer recommendation is MPD = age in years x 1 rem, i.e. the individual effective dose for a lifetime should
not exceed the value of his/her age.

ICRP recommends that occupational exposure of pregnant woman should fall into limits similar to that of the public.
DOSE LIMITS RECOMMENDED BY AERB
TYPES OF RADIATION GENERATING EQUIPMENT:
(RGE)• Computed Tomography
• Interventional Radiology
• Radiography (Fixed/Mobile)
• C-Arm/ O-Arm
• Mammography
• BMD (Bone Mineral Testing)
• Dental (Intraoral/OPG/Cone Beam CT)
• MRI and Sonography (Ultrasound) or non- ionising RGE do not come under purview of AERB
CARDINAL PRINCIPLES OF RADIATION PROTECTION
•1. Time
•2. Distance
•3. Shielding

1. Time: The time of exposure should be kept as short as possible.
Exposure = Exposure rate x Time

2. Distance: The distance between the radiation and the exposed person should be kept as large as possible.
The intensity (I) of radiation varies inversely with the square of the distance (d). This is known as the
inverse square law.
I α 1/d2

3. Shielding: Shielding means the attenuation of X-ray beam by certain materials like concrete, lead, etc.
when placed between the source of radiation and the exposed individual. The shielding can be in the form
of shielding of the X-ray tube, shielding of the room, personnel shielding or patient shielding.
The three types of radiation in radiation protection are:
1. Useful beam: It is also called the primary beam. The
useful or the primary beam is the radiation passing through
the tube aperture.
2. Leakage radiation: This includes all radiation passing
through the tube housing other than the useful radiation.
3. Scattered radiation: This includes all the radiation that
has undergone a change in direction.
SOURCE SHIELDING/SHIELDING OF THE X-RAY TUBE
•The X-ray tube is lined with thin sheets of lead to prevent the X-rays produced in the tube from scattering
in all directions.
•Shielding of the source protects both patients and radiation workers from leakage radiation.
•The leakage radiation exposure has to be limited to < 0.1 R per hour at 1 meter from the tube anode and
hence the X-ray tube housing needs to be shielded.
•AERB recommends a maximum allowable leakage radiation from the tube housing of not greater than 1
mGy/hour/1m .
ROOM SHIELDING
Ensures that the individuals outside these rooms are not exposed to unnecessary unwanted radiation. There are two
types of protective barriers.
1. Primary barrier: This is the one which is directly exposed to the useful beam. The atomic number and the
thickness of the primary barrier should be such that it reduces the exposure rate of the useful beam to the
permissible dose.
2. Secondary barrier: It is the one which is struck by radiation either by leakage from X-ray tube or by scattered
radiation from the patient.
The X-ray room shielding is influenced by the nature of occupancy of the adjoining area. Based on this
various types of areas are identified:
A. Control area: It is defined as the area routinely occupied by radiation workers and exposed to an
occupational dose. Recommended weekly shielding design goal (P) at control area is 40 mR/week (20mSv in a
year)
B. Uncontrolled area: These areas are occupied by individuals such as visitors to the facility and employees
who don’t work routinely around radiation sources. Areas adjacent to but not a part of xray facility is called
uncontrolled area. Recommended weekly shielding design goal (P) at uncontrol area is 2 mR/week (1 mSv in a year)
EXPOSURE CALCULATION
1. Workload : Quantity of xray generated per week
W=mAs/week

2. Exposure : converts workload into Roentgens

ex: at max energy of 100kVp with workload of 1000 mA.min.week,
weekly exposure =0.9R/mA.min X 1000 mA.min.week
=900R/week

•3. Use factor(U) : Time fraction for which the beam is directed at a particular barrier

•4. Occupancy factor(T) : This pertains to the time period for
which the area will be occupied.( used only for
areas occupied by non occupationally exposed
individual)

•5.Distance: Distance from source of radiation.
T=1
Full
occupancy
Labs , nurse stations
T=1/4
Partial
occupancy
Corridors, restrooms ,elevators using
operators
T=1/16
Occasional
occupancy
Waiting rooms, stairways, janitor closet,
outside areas used for pedestrian
Effective weekly exposure at any particular point is calculated as:

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-
- --
- -
-
- -
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RADIATION PROTECTION
MODERATOR – DR ROHIT SHARMA
PRESENTER- DR AKANKSHA

BIOLOGICAL EFFECTS OF RADIATION
•Ionizing radiation which have high energy to ionize the medium with which they interact and thus brings
structural changes to the atom.
•It can directly hit the DNA and ionize it or water molecules absorb the radiation and dissociate into H+ and
OH- free radicals which will further react with DNA.
•Various types of DNA damage can occur : single/ double strand breaks , sugar damage , base damage,
DNA-DNA cross links, DNA-protein crosslinks which can lead to delay in repair mechanism , delay in
cell proliferation , cell transformation or cell lysis.
•Cells are most sensitive to radiation during M phase and G2 phase of cell cycle.
Loading…
DETERMINISTIC EFFECTS STOCHASTIC EFFECTS
Have threshold below which no effect
occurs
No threshold and may occur at even low
doses
Severity increases with dose Probability increases with dose
All people exposed above threshold will
be affected
Only portion of exposed population will
develop effects
Effects within days of exposure May happen years after
Ex : Skin erythema, epilation
Desquamation
Secondary ulceration
Cataract
Sterility

Ex: Cancer and hereditary effects which
can also pass on to the offspring of the
exposed individual
Loading…
Background Natural Radiation
•Natural background radiation sources are cosmic rays and terrestrial sources, natural radioactive material such as radon from
ground, building walls and floors, and traces of naturally occurring radioactive material in food and drinks.
•Artificial or man-made origin includes radioactive fallout from nuclear weapons test and major nuclear accidents, medical
diagnostic and therapeutic use of ionizing radiation, X-ray machines, particle accelerators, consumer products and transport of
radioactive materials.
•Worldwide average of effective dose from background natural radiation is about 2.4 mSv/year. (1.5-3.5 mSv/ year)
•The reported national average of outdoor natural radiation in India is 0.734 mSv per year.

RADIATION UNITS
• Exposure- charge created by X-rays per unit mass of air.
• Absorbed dose - energy deposited per unit mass of matter.
• Equivalent dose –measures potential of type of radiation to cause biological effect ( Absorbed dose x quality
factor)
• Effective dose- measures effect on specific tissue. (Equivalent dose x Tissue weighing factor)

REGULATORY BODIES FOR RADIATION PROTECTION
•AERB – Atomic Energy Regulatory Board- India
•NCRP – National Commission for Radiation Protection- USA
•ICRP – International Commission on Radiological Protection – International level
The ICRP was setup in 1928 and consists of a chairman, a secretary and 12 members from across the world. The AERB was set up on
November 15 1983 by President of India under section 27 of the Atomic Energy Act 1962. The purpose was to carry out certain safety
and regulatory functions under the act. The board has a full time chairman , a secretary , 3 part time members and an ex
officio member.

Loading…
PRINCIPLES OF RADAIATION PROTECTION
•JUSTIFICATION: Practices adopted should produce a net positive benefit.

•OPTIMIZATION: All exposures should be kept as low as possible.

•DOSE LIMITATION: Dose should not exceed the limits that have been recommended for a
particular practice.
JUSTIFICATION
•Every diagnostic practice should provide adequate benefit to the exposed individuals or to the society and outweigh the
radiation risk involved , i.e. the benefit to risk ratio should be high.
•Ex : the benefit to risk ratio is low for screening mammography below 35 years if age.
•3 levels of justification:
• At first and most general level , proper use of radiation in medicine is accepted as doing more good than harm to the
society.
• At second level is the justification of the procedure in improving the diagnosis or treatment and providing necessary
information about the exposed individual.
• At third level , the application of the procedure to an individual should be justified.
OPTIMIZATION
•The concept of ALARA states As Low As Reasonably Achievable.
•In United Kingdom , this has been modified as ALARP- As Low As Reasonably Practicable , economic
and societal factors being taken into account.
•2 levels of optimization
1. Optimization in selection , design and construction of X-Ray equipment .
2. Optimization in day to day methods of working to maximize net benefit and keep radiation doses as low
as practicable.

DOSE LIMITATION
•No radiation dose , however low its value , can be considered safe. Very low doses of radiation , for example , can
produce radiation induced cancer and serious hereditary effects if the cells irradiated are germ cells in the gonad.
•Maximum permissible dose (MPD): It may be defined as the dose of ionizing radiation which an individual may
accumulate over a long period of time with a negligible risk of significant body or genetic damage.
•MPD = 5 (N-1) R {where N is age in years and R is the exposures in Roentgens}. The unit of MPD is rem.
•The newer recommendation is MPD = age in years x 1 rem, i.e. the individual effective dose for a lifetime should
not exceed the value of his/her age.

ICRP recommends that occupational exposure of pregnant woman should fall into limits similar to that of the public.
DOSE LIMITS RECOMMENDED BY AERB
TYPES OF RADIATION GENERATING EQUIPMENT:
(RGE)• Computed Tomography
• Interventional Radiology
• Radiography (Fixed/Mobile)
• C-Arm/ O-Arm
• Mammography
• BMD (Bone Mineral Testing)
• Dental (Intraoral/OPG/Cone Beam CT)
• MRI and Sonography (Ultrasound) or non- ionising RGE do not come under purview of AERB
CARDINAL PRINCIPLES OF RADIATION PROTECTION
•1. Time
•2. Distance
•3. Shielding

1. Time: The time of exposure should be kept as short as possible.
Exposure = Exposure rate x Time

2. Distance: The distance between the radiation and the exposed person should be kept as large as possible.
The intensity (I) of radiation varies inversely with the square of the distance (d). This is known as the
inverse square law.
I α 1/d2

3. Shielding: Shielding means the attenuation of X-ray beam by certain materials like concrete, lead, etc.
when placed between the source of radiation and the exposed individual. The shielding can be in the form
of shielding of the X-ray tube, shielding of the room, personnel shielding or patient shielding.
The three types of radiation in radiation protection are:
1. Useful beam: It is also called the primary beam. The
useful or the primary beam is the radiation passing through
the tube aperture.
2. Leakage radiation: This includes all radiation passing
through the tube housing other than the useful radiation.
3. Scattered radiation: This includes all the radiation that
has undergone a change in direction.
SOURCE SHIELDING/SHIELDING OF THE X-RAY TUBE
•The X-ray tube is lined with thin sheets of lead to prevent the X-rays produced in the tube from scattering
in all directions.
•Shielding of the source protects both patients and radiation workers from leakage radiation.
•The leakage radiation exposure has to be limited to < 0.1 R per hour at 1 meter from the tube anode and
hence the X-ray tube housing needs to be shielded.
•AERB recommends a maximum allowable leakage radiation from the tube housing of not greater than 1
mGy/hour/1m .
ROOM SHIELDING
Ensures that the individuals outside these rooms are not exposed to unnecessary unwanted radiation. There are two
types of protective barriers.
1. Primary barrier: This is the one which is directly exposed to the useful beam. The atomic number and the
thickness of the primary barrier should be such that it reduces the exposure rate of the useful beam to the
permissible dose.
2. Secondary barrier: It is the one which is struck by radiation either by leakage from X-ray tube or by scattered
radiation from the patient.
The X-ray room shielding is influenced by the nature of occupancy of the adjoining area. Based on this
various types of areas are identified:
A. Control area: It is defined as the area routinely occupied by radiation workers and exposed to an
occupational dose. Recommended weekly shielding design goal (P) at control area is 40 mR/week (20mSv in a
year)
B. Uncontrolled area: These areas are occupied by individuals such as visitors to the facility and employees
who don’t work routinely around radiation sources. Areas adjacent to but not a part of xray facility is called
uncontrolled area. Recommended weekly shielding design goal (P) at uncontrol area is 2 mR/week (1 mSv in a year)
EXPOSURE CALCULATION
1. Workload : Quantity of xray generated per week
W=mAs/week

2. Exposure : converts workload into Roentgens

ex: at max energy of 100kVp with workload of 1000 mA.min.week,
weekly exposure =0.9R/mA.min X 1000 mA.min.week
=900R/week

•3. Use factor(U) : Time fraction for which the beam is directed at a particular barrier

•4. Occupancy factor(T) : This pertains to the time period for
which the area will be occupied.( used only for
areas occupied by non occupationally exposed
individual)

•5.Distance: Distance from source of radiation.
T=1
Full
occupancy
Labs , nurse stations
T=1/4
Partial
occupancy
Corridors, restrooms ,elevators using
operators
T=1/16
Occasional
occupancy
Waiting rooms, stairways, janitor closet,
outside areas used for pedestrian
Effective weekly exposure at any particular point is calculated as:

RADIATION PROTECTION
MODERATOR – DR ROHIT SHARMA
PRESENTER- DR AKANKSHA

BIOLOGICAL EFFECTS OF RADIATION
•Ionizing radiation which have high energy to ionize the medium with which they interact and thus brings
structural changes to the atom.
•It can directly hit the DNA and ionize it or water molecules absorb the radiation and dissociate into H+ and
OH- free radicals which will further react with DNA.
•Various types of DNA damage can occur : single/ double strand breaks , sugar damage , base damage,
DNA-DNA cross links, DNA-protein crosslinks which can lead to delay in repair mechanism , delay in
cell proliferation , cell transformation or cell lysis.
•Cells are most sensitive to radiation during M phase and G2 phase of cell cycle.
Loading…
DETERMINISTIC EFFECTS STOCHASTIC EFFECTS
Have threshold below which no effect
occurs
No threshold and may occur at even low
doses
Severity increases with dose Probability increases with dose
All people exposed above threshold will
be affected
Only portion of exposed population will
develop effects
Effects within days of exposure May happen years after
Ex : Skin erythema, epilation
Desquamation
Secondary ulceration
Cataract
Sterility

Ex: Cancer and hereditary effects which
can also pass on to the offspring of the
exposed individual
Loading…
Background Natural Radiation
•Natural background radiation sources are cosmic rays and terrestrial sources, natural radioactive material such as radon from
ground, building walls and floors, and traces of naturally occurring radioactive material in food and drinks.
•Artificial or man-made origin includes radioactive fallout from nuclear weapons test and major nuclear accidents, medical
diagnostic and therapeutic use of ionizing radiation, X-ray machines, particle accelerators, consumer products and transport of
radioactive materials.
•Worldwide average of effective dose from background natural radiation is about 2.4 mSv/year. (1.5-3.5 mSv/ year)
•The reported national average of outdoor natural radiation in India is 0.734 mSv per year.

RADIATION UNITS
• Exposure- charge created by X-rays per unit mass of air.
• Absorbed dose - energy deposited per unit mass of matter.
• Equivalent dose –measures potential of type of radiation to cause biological effect ( Absorbed dose x quality
factor)
• Effective dose- measures effect on specific tissue. (Equivalent dose x Tissue weighing factor)

REGULATORY BODIES FOR RADIATION PROTECTION
•AERB – Atomic Energy Regulatory Board- India
•NCRP – National Commission for Radiation Protection- USA
•ICRP – International Commission on Radiological Protection – International level
The ICRP was setup in 1928 and consists of a chairman, a secretary and 12 members from across the world. The AERB was set up on
November 15 1983 by President of India under section 27 of the Atomic Energy Act 1962. The purpose was to carry out certain safety
and regulatory functions under the act. The board has a full time chairman , a secretary , 3 part time members and an ex
officio member.

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PRINCIPLES OF RADAIATION PROTECTION
•JUSTIFICATION: Practices adopted should produce a net positive benefit.

•OPTIMIZATION: All exposures should be kept as low as possible.

•DOSE LIMITATION: Dose should not exceed the limits that have been recommended for a
particular practice.
JUSTIFICATION
•Every diagnostic practice should provide adequate benefit to the exposed individuals or to the society and outweigh the
radiation risk involved , i.e. the benefit to risk ratio should be high.
•Ex : the benefit to risk ratio is low for screening mammography below 35 years if age.
•3 levels of justification:
• At first and most general level , proper use of radiation in medicine is accepted as doing more good than harm to the
society.
• At second level is the justification of the procedure in improving the diagnosis or treatment and providing necessary
information about the exposed individual.
• At third level , the application of the procedure to an individual should be justified.
OPTIMIZATION
•The concept of ALARA states As Low As Reasonably Achievable.
•In United Kingdom , this has been modified as ALARP- As Low As Reasonably Practicable , economic
and societal factors being taken into account.
•2 levels of optimization
1. Optimization in selection , design and construction of X-Ray equipment .
2. Optimization in day to day methods of working to maximize net benefit and keep radiation doses as low
as practicable.

DOSE LIMITATION
•No radiation dose , however low its value , can be considered safe. Very low doses of radiation , for example , can
produce radiation induced cancer and serious hereditary effects if the cells irradiated are germ cells in the gonad.
•Maximum permissible dose (MPD): It may be defined as the dose of ionizing radiation which an individual may
accumulate over a long period of time with a negligible risk of significant body or genetic damage.
•MPD = 5 (N-1) R {where N is age in years and R is the exposures in Roentgens}. The unit of MPD is rem.
•The newer recommendation is MPD = age in years x 1 rem, i.e. the individual effective dose for a lifetime should
not exceed the value of his/her age.

ICRP recommends that occupational exposure of pregnant woman should fall into limits similar to that of the public.
DOSE LIMITS RECOMMENDED BY AERB
TYPES OF RADIATION GENERATING EQUIPMENT:
(RGE)• Computed Tomography
• Interventional Radiology
• Radiography (Fixed/Mobile)
• C-Arm/ O-Arm
• Mammography
• BMD (Bone Mineral Testing)
• Dental (Intraoral/OPG/Cone Beam CT)
• MRI and Sonography (Ultrasound) or non- ionising RGE do not come under purview of AERB
CARDINAL PRINCIPLES OF RADIATION PROTECTION
•1. Time
•2. Distance
•3. Shielding

1. Time: The time of exposure should be kept as short as possible.
Exposure = Exposure rate x Time

2. Distance: The distance between the radiation and the exposed person should be kept as large as possible.
The intensity (I) of radiation varies inversely with the square of the distance (d). This is known as the
inverse square law.
I α 1/d2

3. Shielding: Shielding means the attenuation of X-ray beam by certain materials like concrete, lead, etc.
when placed between the source of radiation and the exposed individual. The shielding can be in the form
of shielding of the X-ray tube, shielding of the room, personnel shielding or patient shielding.
The three types of radiation in radiation protection are:
1. Useful beam: It is also called the primary beam. The
useful or the primary beam is the radiation passing through
the tube aperture.
2. Leakage radiation: This includes all radiation passing
through the tube housing other than the useful radiation.
3. Scattered radiation: This includes all the radiation that
has undergone a change in direction.
SOURCE SHIELDING/SHIELDING OF THE X-RAY TUBE
•The X-ray tube is lined with thin sheets of lead to prevent the X-rays produced in the tube from scattering
in all directions.
•Shielding of the source protects both patients and radiation workers from leakage radiation.
•The leakage radiation exposure has to be limited to < 0.1 R per hour at 1 meter from the tube anode and
hence the X-ray tube housing needs to be shielded.
•AERB recommends a maximum allowable leakage radiation from the tube housing of not greater than 1
mGy/hour/1m .
ROOM SHIELDING
Ensures that the individuals outside these rooms are not exposed to unnecessary unwanted radiation. There are two
types of protective barriers.
1. Primary barrier: This is the one which is directly exposed to the useful beam. The atomic number and the
thickness of the primary barrier should be such that it reduces the exposure rate of the useful beam to the
permissible dose.
2. Secondary barrier: It is the one which is struck by radiation either by leakage from X-ray tube or by scattered
radiation from the patient.
The X-ray room shielding is influenced by the nature of occupancy of the adjoining area. Based on this
various types of areas are identified:
A. Control area: It is defined as the area routinely occupied by radiation workers and exposed to an
occupational dose. Recommended weekly shielding design goal (P) at control area is 40 mR/week (20mSv in a
year)
B. Uncontrolled area: These areas are occupied by individuals such as visitors to the facility and employees
who don’t work routinely around radiation sources. Areas adjacent to but not a part of xray facility is called
uncontrolled area. Recommended weekly shielding design goal (P) at uncontrol area is 2 mR/week (1 mSv in a year)
EXPOSURE CALCULATION
1. Workload : Quantity of xray generated per week
W=mAs/week

2. Exposure : converts workload into Roentgens

ex: at max energy of 100kVp with workload of 1000 mA.min.week,
weekly exposure =0.9R/mA.min X 1000 mA.min.week
=900R/week

•3. Use factor(U) : Time fraction for which the beam is directed at a particular barrier

•4. Occupancy factor(T) : This pertains to the time period for
which the area will be occupied.( used only for
areas occupied by non occupationally exposed
individual)

•5.Distance: Distance from source of radiation.
T=1
Full
occupancy
Labs , nurse stations
T=1/4
Partial
occupancy
Corridors, restrooms ,elevators using
operators
T=1/16
Occasional
occupancy
Waiting rooms, stairways, janitor closet,
outside areas used for pedestrian
Effective weekly exposure at any particular point is calculated as:

Shielding of the X-ray Control Room
•The control room of an X-ray equipment is a secondary protective barrier. It should never be located where the primary
beam falls directly. The location of the control room should be such that the radiation should scatter twice before entering
it. A lead equivalence of 1.5 mm is essential for the walls and the viewing window of the control booth.
•For equipment operating at <125 kVp the control panel can be in the X-ray room while for equipments operating above
125 kVp the control panel should be in a separate room located outside the X-ray room. When located within the X-ray
room, a distance of not less than 3 meters is recommended by the AERB between the control panel and the X-ray unit.
•When there is no fixed control booth as in mobile radiography it is recommended by the AERB that the technologist
should remain at least 2 meters away from the X-ray tube and the primary beam.
•The AERB also recommends that the size of the gantry room in the CT scanner should not be less than 25 m2.
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Half Value Layer (HVL)
It is defined as the thickness of a specific substance which when introduced into the path of a
beam of radiation, reduces the exposure rate by 50%.
In general, the primary protective barrier should consist of 1/16 inch lead extending 7
feet from the floor when the X-ray tube is 5–7 feet from the wall.
A secondary protective barrier should consist of 1/32 inch lead extending from the top
of the primary barrier to the ceiling. The secondary barrier should overlap the primary
barrier at least 0.5 inches at the seam.
Shielding of the Personnel
Also follows the time-distance shielding principle.
• The workers should step behind the control booth or leave the room when possible, that is, should
remain in the radiation area for as less time as possible.
• The distance between the radiation workers and the source of radiation, i.e. the X-ray tube should be
maximized as the intensity of the radiation varies inversely as the square of the distance.
• Lead aprons, lead gloves, thyroid shields and eye glasses with side shields should be used to protect
the personnel.
PERSONAL PROTECTIVE
EQUIPMENTS
•PROTECTION LEAD EQUIVALENCE
•Lead Aprons 0.25 mm for 100kV
0.35 mm for 150kV
•Thyroid shields 0.5 mm
•Lead glasses 0.25 X 1mm
•Lead gloves 0.25 mm
Modern gloves have 0.5 or 1.0 mm
LEAD APRONS
•classified as secondary barriers as they provide protection only from scattered
radiation and not the primary beam.
•Lead apron provides protection to the radiation workers and it is recommended that
the minimum thickness of lead equivalence should be 0.25 mm by AERB.
•The thickness of lead in the apron determines the protection it provides as 0.25 mm
lead attenuates 66% of the beam at 75 kVp and thickness of 1 mm lead attenuates
99% of the beam at the same kVp.
•For women radiation workers a customized lead apron that reaches
below mid-thigh level and wraps completely around the pelvis is
recommended to avoid any accidental exposure to a conceptus.
•They should not be dropped on the floor, piled in a heap or draped
over the back of a chair. When the apron is not being used, it should
be hung on properly designed racks as improper care may lead to
internal fracturing of the lead compromising its protective ability.
•The apron should be radiographed for defects such as internal tears
and cracks at least once a year.
Zero lead aprons: New aprons known as zero lead aprons or lead free aprons are
available in the market which have a weight 20–40% less than the conventional lead
aprons. Lead is toxic and hence disposal needs proper care. The lead free aprons are
made of tungsten, antimony and bismuth, tin, aluminium or barium. These are
recyclable and hence disposal is not a problem.

○ Gonad shield, hand gloves and thyroid shields - These should have a minimum
lead equivalence of 0.5 mm.
Protective Devices – Quality Control
• All lead equivalent vinyl material (aprons, gloves, etc) should comply with relevant international standards.
They should be tested at purchase and regularly thereafter, at least every 2 years.
• Incorrect storage may lead to cracks in the shielding but this may not be detectable by visual
inspection alone.
• A simple test is to examine the devices using ﬂuoroscopy (at about 60 kVp). The use of automatic dose
rate or automatic brightness controls should be avoided.
• This test will only detect ﬂaws in the shielding. Faulty devices should be discarded immediately.
Shielding of the Patient
1. Beam filtration: The function of the filters is to absorb low energy photons thereby increasing the mean energy
penetrating power of the X-ray beam and hence reducing the patient dose. These beam filters absorb all rays below 10 kev.
These low energy photons contribute to the patient dose without contributing to the image.
The AERB has recommended the minimum total filtration for X-rays which depends on the kVp of the equipment. Total
beam filtration should always be indicated on the tube housing and should not be less than 1.5 mm. For screen film
mammography the total filtration in the useful beam should be at least 0.03 mm of molybdenum as per the AERB
guidelines.
2. Beam collimation: Collimators are used to reduce the area of exposure and limit it to the area of clinical interest.
Tissues exposed directly to the primary beam receive much higher radiation dose then the tissues outside the primary
beam. The use of collimators also reduces the amount of scattered radiation reaching the image receptor with the
resulting images having better contrast.
3. Image receptors: Intensifying screens convert the absorbed X-ray energy into visible light acting as an image amplifiers
and significantly reducing the patient absorbed dose. A fast screen (high speed) requires less exposure than a slow screen
(low speed) to provide a given image density. Rare earth screen film combinations reduce patient dose without loss of
diagnostic quality. Image intensifier tubes have efficient input phosphor that play a role in reducing dose to the patient.
4. Source to image receptor distance (SID): An equipment with a large SID will result in a lower patient dose.
5. Anti-scatter grids: These reduce the scatter radiation reaching the film improving the quality of the resulting radiograph
and hence reducing the chance of repeat exposure. However it increase radiation dose to the patient and hence where
required use the grid . For pediatric patients do not use the grids.
6. Tube screen alignment: The X-ray tube and fluoroscopic screen should be aligned and coupled in such a way that they
move together in synchrony. Also, in all positions of the tube and screen the axis of the X-ray beam should pass through the
centre of the screen.
7. Fluoroscopy tube housing and filtration: Every housing for medical X-ray equipment shall be so constructed
that leakage radiation through the tube housing shall not exceed 1 mGy in one hour at a distance of 1.0 m from the
X-ray target.
8. Lead rubber flaps: Protective flaps of lead equivalence 0.5 mm are suspended from the edge of the screen such
that these flaps extend down to the table top.
9. Field limiting diaphragm: Tube housing should be provided with a field limiting diaphragm even when the
diaphragm is fully opened and the screen is at the maximum distance from the table, there is an unilluminated
margin of at least 1 cm along the edges of the screen. The control knobs should be provided with local shielding of
at least 0.25 mm lead equivalence.
10. Fluoroscopy timer: There should be an audible signal after the preset site and the maximum range of the
cumulative timer should not exceed 5 minutes. The built-in cumulative timer device and an audible warning
system should ring after a preset fluoroscopy time to prevent excessive radiation exposure. If the screening time
exceeds the preset time it can be reset but the radiologist must be aware of the dose implications of doing so. The
fluoroscopy timer is a means for monitoring the passage of exposure time.
11. Footswitch and visual indicator: When the beam is on there is a visual indication on the control panel. For
conducting the fluoroscopy examinations a foot operated pressure switch is provided.
12.. Control panel: This should indicate all exposure parameters like tube potential, exposure time and tube
current. An indicator is provided on the control panel to show whether the X-ray beam is "ON or OFF"
Technique:
1. Optimum film processing: This helps to avoid repeat examinations.
2. Tube voltage and tube current: A higher kVp leads to a lesser radiation dose because of the better
penetration of the beam that leads to reduced scatter within the body. An attempt should be made to use the
highest kVp possible without reducing the image contrast to an unacceptable level in order to reduce radiation
dose to the patient. It is recommended by the NCRP that the kVp and mA should be visible to the person
performing the fluoroscopy procedure at all times.
3. Screening time and exposure factor: Intermittent fluoroscopy rather than continuous fluoroscopy should be
followed. The magnification mode should be avoided is it leads to an increase in the dose. The beam should be
collimated to the smallest possible and the mA should be kept as low as possible.
RADIATION PROTECTION IN INTERVENTIONAL RADIOLOGY

1. Pulsed Fluoroscopy
In this, the image is acquired only during a brief pulse of the X-ray beam, say 10 millisecond. Dose is reduced in pulsed
fluoroscopy by simply reducing the fraction of time the X-ray beam is on. Also, by using the lowest pulse rate possible,
patient dose and fluoroscopy times can be reduced. At pulsed fluoroscopy with 15, 10 and 7.5 pulses/second, dose savings
of 22%, 38% and 49% respectively, are achieved.

2. Last Image Hold (LIH)
This enables the user to spend time interpreting the image without use of radiation. Last image hold combined with pulsed
fluoroscopy reduces dose upto 75%.
3. Road Mapping A reference static image is displayed on a second monitor and is used as a mask for subtraction from
the real time fluoroscopy display. The only objects left in the image are the vessel of interest and the catheter moving through it.
Peak opacification is seen as maximum pixel values from a small bolus of contrast as it travels through the vessel of interest.
Fluoroscopy is terminated by the operator when the whole vessel appears to be filled. Use of this technique shortens the
procedure time thus decreasing patient and operator dose.

4. Dose Spreading Techniques An alteration in the direction of the X-ray beam can reduce the maximum dose
delivered to any one point on the patient’s skin. This can be achieved by simply rotating the C-arm a few degrees. This is
specially useful in prolonged procedures where entrance skin doses are high with a static X-ray beam. In these cases, the beam
can be moved by rotating the C-arm preventing erythema and epilation of the skin.

5. Ultra Low Dose Fluoroscopy (ULD) The system parameters are computer controlled and use the lowest
optimal dose over a broad range of examinations and patient types while still producing quality images.
PERSONNEL DOSIMETRY
Types of Dosimeter:
• Immediate read
○ Pocket Ionization Chambers
○ Ionization detectors with dose accumulation function

• Delayed read/Personnel monitors
○ Film Badges
○ TLD
○ Optically Stimulated Light-emitting Dosimeters- Al2O3:C
Pocket Dosimeter
• The pocket dosimeter consists of an ionization chamber and a movable
quartz fibre. When X-rays enter the dosimeter, ionization causes the
fibres to lose their charges giving a measure of the radiation dose.
• The pocket dosimeter however has several disadvantages in the form of
low accuracy and being subject to human reading errors as reading is
manual.
• Other disadvantages are its susceptibility to moisture and a limited range.
The range of the pocket dosimeter is limited by the charge on the
electrode which once gone, the device stops recording exposure.
Film Badge
A film badge uses a small double coated X-ray film sandwiched between several
filters to help detect
radiation. At least 6 pairs of filters are used to identify various components of incident
radiation. The six types of windows are:
1. Open window: Alpha rays
2. Plastic (1mm) : Gray—beta rays
3. Cadmium (1 mm): Yellow—slow neutrons
4. Thin copper (0.15 mm): Green-diagnostic X-rays
5. Thick copper (1 mm): Pink-gamma and therapeutic rays
6. Lead (1 mm): Black-fast neutrons and gamma rays
•A different degree of blackening will be produced by the same quantity of radiation
incident on the badge under each filter as various types of absorbers attenuate radiation
of a given energy to a different extent.
•After every 3-4 months, optical density of the film is read by densitometer.
•There are 2 types of film badge- Chest badge and Extremity badge.
•Disadvantages are they are not accurate to exposures less than 20 mrem ,must be
developed and read by processor which is time consuming , film fogging occurs with
time.

Thermoluminescent Dosimeter (TLD)
Certain materials known as phosphors have the tendency to emit light when heated. This property is known as
thermoluminescence. Examples of such material include lithium fluoride (LiF), calcium fluoride (CaF2), calcium
sulphate (CaSO4), lithium borate (Li2B4O7) show thermoluminescence.
Principle
➢ When a LiF crystal is exposed to radiation, few of the electrons get trapped at higher energy levels. When the crystal is
heated, these electrons return to their stable energy levels. The energy differences between the two orbital levels is
emitted as light which is then measured by a photomultiplier tube. The amount of light emitted gives an estimate of
the radiation dose as the two are proportional.
➢ The measurement of radiation from TLD is a two step procedure. First, the TLD is exposed to radiation. Then, the LiF
crystal is heated in a TLD analyzer. On heating, light is emitted. A glow curve can be obtained by plotting the intensity
of light as a function of the temperature. The highest peak and the area under the curve are proportional to the energy of
the radiation and can be used to measure radiation dose. After the reading is obtained, the TLD can be annealed at a

Shielding of the X-ray Control Room
•The control room of an X-ray equipment is a secondary protective barrier. It should never be located where the primary
beam falls directly. The location of the control room should be such that the radiation should scatter twice before entering
it. A lead equivalence of 1.5 mm is essential for the walls and the viewing window of the control booth.
•For equipment operating at <125 kVp the control panel can be in the X-ray room while for equipments operating above
125 kVp the control panel should be in a separate room located outside the X-ray room. When located within the X-ray
room, a distance of not less than 3 meters is recommended by the AERB between the control panel and the X-ray unit.
•When there is no fixed control booth as in mobile radiography it is recommended by the AERB that the technologist
should remain at least 2 meters away from the X-ray tube and the primary beam.
•The AERB also recommends that the size of the gantry room in the CT scanner should not be less than 25 m2.
Loading…
Half Value Layer (HVL)
It is defined as the thickness of a specific substance which when introduced into the path of a
beam of radiation, reduces the exposure rate by 50%.
In general, the primary protective barrier should consist of 1/16 inch lead extending 7
feet from the floor when the X-ray tube is 5–7 feet from the wall.
A secondary protective barrier should consist of 1/32 inch lead extending from the top
of the primary barrier to the ceiling. The secondary barrier should overlap the primary
barrier at least 0.5 inches at the seam.
Shielding of the Personnel
Also follows the time-distance shielding principle.
• The workers should step behind the control booth or leave the room when possible, that is, should
remain in the radiation area for as less time as possible.
• The distance between the radiation workers and the source of radiation, i.e. the X-ray tube should be
maximized as the intensity of the radiation varies inversely as the square of the distance.
• Lead aprons, lead gloves, thyroid shields and eye glasses with side shields should be used to protect
the personnel.
PERSONAL PROTECTIVE
EQUIPMENTS
•PROTECTION LEAD EQUIVALENCE
•Lead Aprons 0.25 mm for 100kV
0.35 mm for 150kV
•Thyroid shields 0.5 mm
•Lead glasses 0.25 X 1mm
•Lead gloves 0.25 mm
Modern gloves have 0.5 or 1.0 mm
LEAD APRONS
•classified as secondary barriers as they provide protection only from scattered
radiation and not the primary beam.
•Lead apron provides protection to the radiation workers and it is recommended that
the minimum thickness of lead equivalence should be 0.25 mm by AERB.
•The thickness of lead in the apron determines the protection it provides as 0.25 mm
lead attenuates 66% of the beam at 75 kVp and thickness of 1 mm lead attenuates
99% of the beam at the same kVp.
•For women radiation workers a customized lead apron that reaches
below mid-thigh level and wraps completely around the pelvis is
recommended to avoid any accidental exposure to a conceptus.
•They should not be dropped on the floor, piled in a heap or draped
over the back of a chair. When the apron is not being used, it should
be hung on properly designed racks as improper care may lead to
internal fracturing of the lead compromising its protective ability.
•The apron should be radiographed for defects such as internal tears
and cracks at least once a year.
Zero lead aprons: New aprons known as zero lead aprons or lead free aprons are
available in the market which have a weight 20–40% less than the conventional lead
aprons. Lead is toxic and hence disposal needs proper care. The lead free aprons are
made of tungsten, antimony and bismuth, tin, aluminium or barium. These are
recyclable and hence disposal is not a problem.

○ Gonad shield, hand gloves and thyroid shields - These should have a minimum
lead equivalence of 0.5 mm.
Protective Devices – Quality Control
• All lead equivalent vinyl material (aprons, gloves, etc) should comply with relevant international standards.
They should be tested at purchase and regularly thereafter, at least every 2 years.
• Incorrect storage may lead to cracks in the shielding but this may not be detectable by visual
inspection alone.
• A simple test is to examine the devices using ﬂuoroscopy (at about 60 kVp). The use of automatic dose
rate or automatic brightness controls should be avoided.
• This test will only detect ﬂaws in the shielding. Faulty devices should be discarded immediately.
Shielding of the Patient
1. Beam filtration: The function of the filters is to absorb low energy photons thereby increasing the mean energy
penetrating power of the X-ray beam and hence reducing the patient dose. These beam filters absorb all rays below 10 kev.
These low energy photons contribute to the patient dose without contributing to the image.
The AERB has recommended the minimum total filtration for X-rays which depends on the kVp of the equipment. Total
beam filtration should always be indicated on the tube housing and should not be less than 1.5 mm. For screen film
mammography the total filtration in the useful beam should be at least 0.03 mm of molybdenum as per the AERB
guidelines.
2. Beam collimation: Collimators are used to reduce the area of exposure and limit it to the area of clinical interest.
Tissues exposed directly to the primary beam receive much higher radiation dose then the tissues outside the primary
beam. The use of collimators also reduces the amount of scattered radiation reaching the image receptor with the
resulting images having better contrast.
3. Image receptors: Intensifying screens convert the absorbed X-ray energy into visible light acting as an image amplifiers
and significantly reducing the patient absorbed dose. A fast screen (high speed) requires less exposure than a slow screen
(low speed) to provide a given image density. Rare earth screen film combinations reduce patient dose without loss of
diagnostic quality. Image intensifier tubes have efficient input phosphor that play a role in reducing dose to the patient.
4. Source to image receptor distance (SID): An equipment with a large SID will result in a lower patient dose.
5. Anti-scatter grids: These reduce the scatter radiation reaching the film improving the quality of the resulting radiograph
and hence reducing the chance of repeat exposure. However it increase radiation dose to the patient and hence where
required use the grid . For pediatric patients do not use the grids.
6. Tube screen alignment: The X-ray tube and fluoroscopic screen should be aligned and coupled in such a way that they
move together in synchrony. Also, in all positions of the tube and screen the axis of the X-ray beam should pass through the
centre of the screen.
7. Fluoroscopy tube housing and filtration: Every housing for medical X-ray equipment shall be so constructed
that leakage radiation through the tube housing shall not exceed 1 mGy in one hour at a distance of 1.0 m from the
X-ray target.
8. Lead rubber flaps: Protective flaps of lead equivalence 0.5 mm are suspended from the edge of the screen such
that these flaps extend down to the table top.
9. Field limiting diaphragm: Tube housing should be provided with a field limiting diaphragm even when the
diaphragm is fully opened and the screen is at the maximum distance from the table, there is an unilluminated
margin of at least 1 cm along the edges of the screen. The control knobs should be provided with local shielding of
at least 0.25 mm lead equivalence.
10. Fluoroscopy timer: There should be an audible signal after the preset site and the maximum range of the
cumulative timer should not exceed 5 minutes. The built-in cumulative timer device and an audible warning
system should ring after a preset fluoroscopy time to prevent excessive radiation exposure. If the screening time
exceeds the preset time it can be reset but the radiologist must be aware of the dose implications of doing so. The
fluoroscopy timer is a means for monitoring the passage of exposure time.
11. Footswitch and visual indicator: When the beam is on there is a visual indication on the control panel. For
conducting the fluoroscopy examinations a foot operated pressure switch is provided.
12.. Control panel: This should indicate all exposure parameters like tube potential, exposure time and tube
current. An indicator is provided on the control panel to show whether the X-ray beam is "ON or OFF"
Technique:
1. Optimum film processing: This helps to avoid repeat examinations.
2. Tube voltage and tube current: A higher kVp leads to a lesser radiation dose because of the better
penetration of the beam that leads to reduced scatter within the body. An attempt should be made to use the
highest kVp possible without reducing the image contrast to an unacceptable level in order to reduce radiation
dose to the patient. It is recommended by the NCRP that the kVp and mA should be visible to the person
performing the fluoroscopy procedure at all times.
3. Screening time and exposure factor: Intermittent fluoroscopy rather than continuous fluoroscopy should be
followed. The magnification mode should be avoided is it leads to an increase in the dose. The beam should be
collimated to the smallest possible and the mA should be kept as low as possible.
RADIATION PROTECTION IN INTERVENTIONAL RADIOLOGY

1. Pulsed Fluoroscopy
In this, the image is acquired only during a brief pulse of the X-ray beam, say 10 millisecond. Dose is reduced in pulsed
fluoroscopy by simply reducing the fraction of time the X-ray beam is on. Also, by using the lowest pulse rate possible,
patient dose and fluoroscopy times can be reduced. At pulsed fluoroscopy with 15, 10 and 7.5 pulses/second, dose savings
of 22%, 38% and 49% respectively, are achieved.

2. Last Image Hold (LIH)
This enables the user to spend time interpreting the image without use of radiation. Last image hold combined with pulsed
fluoroscopy reduces dose upto 75%.
3. Road Mapping A reference static image is displayed on a second monitor and is used as a mask for subtraction from
the real time fluoroscopy display. The only objects left in the image are the vessel of interest and the catheter moving through it.
Peak opacification is seen as maximum pixel values from a small bolus of contrast as it travels through the vessel of interest.
Fluoroscopy is terminated by the operator when the whole vessel appears to be filled. Use of this technique shortens the
procedure time thus decreasing patient and operator dose.

4. Dose Spreading Techniques An alteration in the direction of the X-ray beam can reduce the maximum dose
delivered to any one point on the patient’s skin. This can be achieved by simply rotating the C-arm a few degrees. This is
specially useful in prolonged procedures where entrance skin doses are high with a static X-ray beam. In these cases, the beam
can be moved by rotating the C-arm preventing erythema and epilation of the skin.

5. Ultra Low Dose Fluoroscopy (ULD) The system parameters are computer controlled and use the lowest
optimal dose over a broad range of examinations and patient types while still producing quality images.
PERSONNEL DOSIMETRY
Types of Dosimeter:
• Immediate read
○ Pocket Ionization Chambers
○ Ionization detectors with dose accumulation function

• Delayed read/Personnel monitors
○ Film Badges
○ TLD
○ Optically Stimulated Light-emitting Dosimeters- Al2O3:C
Pocket Dosimeter
• The pocket dosimeter consists of an ionization chamber and a movable
quartz fibre. When X-rays enter the dosimeter, ionization causes the
fibres to lose their charges giving a measure of the radiation dose.
• The pocket dosimeter however has several disadvantages in the form of
low accuracy and being subject to human reading errors as reading is
manual.
• Other disadvantages are its susceptibility to moisture and a limited range.
The range of the pocket dosimeter is limited by the charge on the
electrode which once gone, the device stops recording exposure.
Film Badge
A film badge uses a small double coated X-ray film sandwiched between several
filters to help detect
radiation. At least 6 pairs of filters are used to identify various components of incident
radiation. The six types of windows are:
1. Open window: Alpha rays
2. Plastic (1mm) : Gray—beta rays
3. Cadmium (1 mm): Yellow—slow neutrons
4. Thin copper (0.15 mm): Green-diagnostic X-rays
5. Thick copper (1 mm): Pink-gamma and therapeutic rays
6. Lead (1 mm): Black-fast neutrons and gamma rays
•A different degree of blackening will be produced by the same quantity of radiation
incident on the badge under each filter as various types of absorbers attenuate radiation
of a given energy to a different extent.
•After every 3-4 months, optical density of the film is read by densitometer.
•There are 2 types of film badge- Chest badge and Extremity badge.
•Disadvantages are they are not accurate to exposures less than 20 mrem ,must be
developed and read by processor which is time consuming , film fogging occurs with
time.

Thermoluminescent Dosimeter (TLD)
Certain materials known as phosphors have the tendency to emit light when heated. This property is known as
thermoluminescence. Examples of such material include lithium fluoride (LiF), calcium fluoride (CaF2), calcium
sulphate (CaSO4), lithium borate (Li2B4O7) show thermoluminescence.
Principle
➢ When a LiF crystal is exposed to radiation, few of the electrons get trapped at higher energy levels. When the crystal is
heated, these electrons return to their stable energy levels. The energy differences between the two orbital levels is
emitted as light which is then measured by a photomultiplier tube. The amount of light emitted gives an estimate of
the radiation dose as the two are proportional.
➢ The measurement of radiation from TLD is a two step procedure. First, the TLD is exposed to radiation. Then, the LiF
crystal is heated in a TLD analyzer. On heating, light is emitted. A glow curve can be obtained by plotting the intensity
of light as a function of the temperature. The highest peak and the area under the curve are proportional to the energy of
the radiation and can be used to measure radiation dose. After the reading is obtained, the TLD can be annealed at a

Shielding of the X-ray Control Room
•The control room of an X-ray equipment is a secondary protective barrier. It should never be located where the primary
beam falls directly. The location of the control room should be such that the radiation should scatter twice before entering
it. A lead equivalence of 1.5 mm is essential for the walls and the viewing window of the control booth.
•For equipment operating at <125 kVp the control panel can be in the X-ray room while for equipments operating above
125 kVp the control panel should be in a separate room located outside the X-ray room. When located within the X-ray
room, a distance of not less than 3 meters is recommended by the AERB between the control panel and the X-ray unit.
•When there is no fixed control booth as in mobile radiography it is recommended by the AERB that the technologist
should remain at least 2 meters away from the X-ray tube and the primary beam.
•The AERB also recommends that the size of the gantry room in the CT scanner should not be less than 25 m2.
Loading…
Half Value Layer (HVL)
It is defined as the thickness of a specific substance which when introduced into the path of a
beam of radiation, reduces the exposure rate by 50%.
In general, the primary protective barrier should consist of 1/16 inch lead extending 7
feet from the floor when the X-ray tube is 5–7 feet from the wall.
A secondary protective barrier should consist of 1/32 inch lead extending from the top
of the primary barrier to the ceiling. The secondary barrier should overlap the primary
barrier at least 0.5 inches at the seam.
Shielding of the Personnel
Also follows the time-distance shielding principle.
• The workers should step behind the control booth or leave the room when possible, that is, should
remain in the radiation area for as less time as possible.
• The distance between the radiation workers and the source of radiation, i.e. the X-ray tube should be
maximized as the intensity of the radiation varies inversely as the square of the distance.
• Lead aprons, lead gloves, thyroid shields and eye glasses with side shields should be used to protect
the personnel.
PERSONAL PROTECTIVE
EQUIPMENTS
•PROTECTION LEAD EQUIVALENCE
•Lead Aprons 0.25 mm for 100kV
0.35 mm for 150kV
•Thyroid shields 0.5 mm
•Lead glasses 0.25 X 1mm
•Lead gloves 0.25 mm
Modern gloves have 0.5 or 1.0 mm
LEAD APRONS
•classified as secondary barriers as they provide protection only from scattered
radiation and not the primary beam.
•Lead apron provides protection to the radiation workers and it is recommended that
the minimum thickness of lead equivalence should be 0.25 mm by AERB.
•The thickness of lead in the apron determines the protection it provides as 0.25 mm
lead attenuates 66% of the beam at 75 kVp and thickness of 1 mm lead attenuates
99% of the beam at the same kVp.
•For women radiation workers a customized lead apron that reaches
below mid-thigh level and wraps completely around the pelvis is
recommended to avoid any accidental exposure to a conceptus.
•They should not be dropped on the floor, piled in a heap or draped
over the back of a chair. When the apron is not being used, it should
be hung on properly designed racks as improper care may lead to
internal fracturing of the lead compromising its protective ability.
•The apron should be radiographed for defects such as internal tears
and cracks at least once a year.
Zero lead aprons: New aprons known as zero lead aprons or lead free aprons are
available in the market which have a weight 20–40% less than the conventional lead
aprons. Lead is toxic and hence disposal needs proper care. The lead free aprons are
made of tungsten, antimony and bismuth, tin, aluminium or barium. These are
recyclable and hence disposal is not a problem.

○ Gonad shield, hand gloves and thyroid shields - These should have a minimum
lead equivalence of 0.5 mm.
Protective Devices – Quality Control
• All lead equivalent vinyl material (aprons, gloves, etc) should comply with relevant international standards.
They should be tested at purchase and regularly thereafter, at least every 2 years.
• Incorrect storage may lead to cracks in the shielding but this may not be detectable by visual
inspection alone.
• A simple test is to examine the devices using ﬂuoroscopy (at about 60 kVp). The use of automatic dose
rate or automatic brightness controls should be avoided.
• This test will only detect ﬂaws in the shielding. Faulty devices should be discarded immediately.
Shielding of the Patient
1. Beam filtration: The function of the filters is to absorb low energy photons thereby increasing the mean energy
penetrating power of the X-ray beam and hence reducing the patient dose. These beam filters absorb all rays below 10 kev.
These low energy photons contribute to the patient dose without contributing to the image.
The AERB has recommended the minimum total filtration for X-rays which depends on the kVp of the equipment. Total
beam filtration should always be indicated on the tube housing and should not be less than 1.5 mm. For screen film
mammography the total filtration in the useful beam should be at least 0.03 mm of molybdenum as per the AERB
guidelines.
2. Beam collimation: Collimators are used to reduce the area of exposure and limit it to the area of clinical interest.
Tissues exposed directly to the primary beam receive much higher radiation dose then the tissues outside the primary
beam. The use of collimators also reduces the amount of scattered radiation reaching the image receptor with the
resulting images having better contrast.
3. Image receptors: Intensifying screens convert the absorbed X-ray energy into visible light acting as an image amplifiers
and significantly reducing the patient absorbed dose. A fast screen (high speed) requires less exposure than a slow screen
(low speed) to provide a given image density. Rare earth screen film combinations reduce patient dose without loss of
diagnostic quality. Image intensifier tubes have efficient input phosphor that play a role in reducing dose to the patient.
4. Source to image receptor distance (SID): An equipment with a large SID will result in a lower patient dose.
5. Anti-scatter grids: These reduce the scatter radiation reaching the film improving the quality of the resulting radiograph
and hence reducing the chance of repeat exposure. However it increase radiation dose to the patient and hence where
required use the grid . For pediatric patients do not use the grids.
6. Tube screen alignment: The X-ray tube and fluoroscopic screen should be aligned and coupled in such a way that they
move together in synchrony. Also, in all positions of the tube and screen the axis of the X-ray beam should pass through the
centre of the screen.
7. Fluoroscopy tube housing and filtration: Every housing for medical X-ray equipment shall be so constructed
that leakage radiation through the tube housing shall not exceed 1 mGy in one hour at a distance of 1.0 m from the
X-ray target.
8. Lead rubber flaps: Protective flaps of lead equivalence 0.5 mm are suspended from the edge of the screen such
that these flaps extend down to the table top.
9. Field limiting diaphragm: Tube housing should be provided with a field limiting diaphragm even when the
diaphragm is fully opened and the screen is at the maximum distance from the table, there is an unilluminated
margin of at least 1 cm along the edges of the screen. The control knobs should be provided with local shielding of
at least 0.25 mm lead equivalence.
10. Fluoroscopy timer: There should be an audible signal after the preset site and the maximum range of the
cumulative timer should not exceed 5 minutes. The built-in cumulative timer device and an audible warning
system should ring after a preset fluoroscopy time to prevent excessive radiation exposure. If the screening time
exceeds the preset time it can be reset but the radiologist must be aware of the dose implications of doing so. The
fluoroscopy timer is a means for monitoring the passage of exposure time.
11. Footswitch and visual indicator: When the beam is on there is a visual indication on the control panel. For
conducting the fluoroscopy examinations a foot operated pressure switch is provided.
12.. Control panel: This should indicate all exposure parameters like tube potential, exposure time and tube
current. An indicator is provided on the control panel to show whether the X-ray beam is "ON or OFF"
Technique:
1. Optimum film processing: This helps to avoid repeat examinations.
2. Tube voltage and tube current: A higher kVp leads to a lesser radiation dose because of the better
penetration of the beam that leads to reduced scatter within the body. An attempt should be made to use the
highest kVp possible without reducing the image contrast to an unacceptable level in order to reduce radiation
dose to the patient. It is recommended by the NCRP that the kVp and mA should be visible to the person
performing the fluoroscopy procedure at all times.
3. Screening time and exposure factor: Intermittent fluoroscopy rather than continuous fluoroscopy should be
followed. The magnification mode should be avoided is it leads to an increase in the dose. The beam should be
collimated to the smallest possible and the mA should be kept as low as possible.
RADIATION PROTECTION IN INTERVENTIONAL RADIOLOGY

1. Pulsed Fluoroscopy
In this, the image is acquired only during a brief pulse of the X-ray beam, say 10 millisecond. Dose is reduced in pulsed
fluoroscopy by simply reducing the fraction of time the X-ray beam is on. Also, by using the lowest pulse rate possible,
patient dose and fluoroscopy times can be reduced. At pulsed fluoroscopy with 15, 10 and 7.5 pulses/second, dose savings
of 22%, 38% and 49% respectively, are achieved.

2. Last Image Hold (LIH)
This enables the user to spend time interpreting the image without use of radiation. Last image hold combined with pulsed
fluoroscopy reduces dose upto 75%.
3. Road Mapping A reference static image is displayed on a second monitor and is used as a mask for subtraction from
the real time fluoroscopy display. The only objects left in the image are the vessel of interest and the catheter moving through it.
Peak opacification is seen as maximum pixel values from a small bolus of contrast as it travels through the vessel of interest.
Fluoroscopy is terminated by the operator when the whole vessel appears to be filled. Use of this technique shortens the
procedure time thus decreasing patient and operator dose.

4. Dose Spreading Techniques An alteration in the direction of the X-ray beam can reduce the maximum dose
delivered to any one point on the patient’s skin. This can be achieved by simply rotating the C-arm a few degrees. This is
specially useful in prolonged procedures where entrance skin doses are high with a static X-ray beam. In these cases, the beam
can be moved by rotating the C-arm preventing erythema and epilation of the skin.

5. Ultra Low Dose Fluoroscopy (ULD) The system parameters are computer controlled and use the lowest
optimal dose over a broad range of examinations and patient types while still producing quality images.
PERSONNEL DOSIMETRY
Types of Dosimeter:
• Immediate read
○ Pocket Ionization Chambers
○ Ionization detectors with dose accumulation function

• Delayed read/Personnel monitors
○ Film Badges
○ TLD
○ Optically Stimulated Light-emitting Dosimeters- Al2O3:C
Pocket Dosimeter
• The pocket dosimeter consists of an ionization chamber and a movable
quartz fibre. When X-rays enter the dosimeter, ionization causes the
fibres to lose their charges giving a measure of the radiation dose.
• The pocket dosimeter however has several disadvantages in the form of
low accuracy and being subject to human reading errors as reading is
manual.
• Other disadvantages are its susceptibility to moisture and a limited range.
The range of the pocket dosimeter is limited by the charge on the
electrode which once gone, the device stops recording exposure.
Film Badge
A film badge uses a small double coated X-ray film sandwiched between several
filters to help detect
radiation. At least 6 pairs of filters are used to identify various components of incident
radiation. The six types of windows are:
1. Open window: Alpha rays
2. Plastic (1mm) : Gray—beta rays
3. Cadmium (1 mm): Yellow—slow neutrons
4. Thin copper (0.15 mm): Green-diagnostic X-rays
5. Thick copper (1 mm): Pink-gamma and therapeutic rays
6. Lead (1 mm): Black-fast neutrons and gamma rays
•A different degree of blackening will be produced by the same quantity of radiation
incident on the badge under each filter as various types of absorbers attenuate radiation
of a given energy to a different extent.
•After every 3-4 months, optical density of the film is read by densitometer.
•There are 2 types of film badge- Chest badge and Extremity badge.
•Disadvantages are they are not accurate to exposures less than 20 mrem ,must be
developed and read by processor which is time consuming , film fogging occurs with
time.

Thermoluminescent Dosimeter (TLD)
Certain materials known as phosphors have the tendency to emit light when heated. This property is known as
thermoluminescence. Examples of such material include lithium fluoride (LiF), calcium fluoride (CaF2), calcium
sulphate (CaSO4), lithium borate (Li2B4O7) show thermoluminescence.
Principle
➢ When a LiF crystal is exposed to radiation, few of the electrons get trapped at higher energy levels. When the crystal is
heated, these electrons return to their stable energy levels. The energy differences between the two orbital levels is
emitted as light which is then measured by a photomultiplier tube. The amount of light emitted gives an estimate of
the radiation dose as the two are proportional.
➢ The measurement of radiation from TLD is a two step procedure. First, the TLD is exposed to radiation. Then, the LiF
crystal is heated in a TLD analyzer. On heating, light is emitted. A glow curve can be obtained by plotting the intensity
of light as a function of the temperature. The highest peak and the area under the curve are proportional to the energy of
the radiation and can be used to measure radiation dose. After the reading is obtained, the TLD can be annealed at athe radiation and can be used to measure radiation dose. After the reading is obtained, the TLD can be annealed at a
higher temperature which zeroes the TLD reading dose and is read for reuse.
0.8 mm
thick
1.35 cm
diameter
52.5 x 29.9 x 1 mm
CaSO4 doped with
dysprosium
Al +Cu
perspex
Method to use TLD
•The TLD card should be loaded in the cassette and should not be removed till the end of the service period.
•A TLD badge should always be worn by all persons working in the radiation and should not be shared by any
other person.
•The TLD badge should always be stored in a radiation free place when not in use.
•While leaving the premises of the institution the badges should be submitted and not carried in a metro train
where again these would be screened through the X-ray machine leading to erroneous readings.
• The badge should also not be left in radiation field or near ovens, hot plates, furnaces, burners, etc.
Where to Wear the TLD Badge
•TLD badge can be worn at two places : Chest badge & Wrist badge. (Source: AERB website)
•When there is only one TLD badge it should be worn compulsorily at the chest level.
•In fluoroscopy a protective lead apron is worn by the radiologist while performing the various fluoroscopic procedures. In
such situations two TLD badges are to be worn ideally. One badge should be worn underneath the lead apron at the
chest level and the other needs to be worn at the level of the neck/collar region outside the lead apron. If it is not
feasible to wear two and only one is to be worn, it should be worn in the neck region outside the lead apron as the
neck receives about 10–20 times more exposure than the trunk which is protected by the lead apron.
•In special cases (Persons handling radioisotopes from close distances and radiologists/doctors doing the interventional
procedures), if the doses to the hands and forearms are expected to be significantly higher than at the chest level, additional
wrist badges may be procured and used.
How to Return the used TLD Cards
•All the cards whether used or unused should be returned once the service period is over (every 3 months). This should be done
along with the TLD/5 form. The TLD card should be arranged in the same order as listed in the TLD/5 forms and the nature of
the radiation sources handled against the respective names in the TLD/5 form should be written.
•Sending of TLD by an air courier should be avoided to prevent screening of the package under X-ray machine at the airport.
Plastic boxes should be used for returning the cards.
•If there is any damage to its filters (metallic pieces) or cassette holder, it should be immediately reported and a replacement be
asked for.
•Personal numbers are allotted by Bhabha Atomic Research Centre, Mumbai to the radiation workers. These numbers are
permanent and should not be changed. In case of any loss, a declaration stating the same duly signed by the RSO/Physicist
should be immediately sent.
Overexposure
•A dose exceeding 10 mSv in a quarter at chest level , 250 mSv at wrist level in a quarter is treated as
overexposure and should be reported immediately to the institution and the concerned individual.
•The institution should arrange to investigate the cause of overexposure and report the findings to the appropriate
authorities at BARC.
•A hematological examination including differential blood counts and chromosomal aberration test has to be carried
out on the person receiving more than 10 mSv.
•All overexposure cases are reviewed by BARC and advice on necessary follow-up is given to the concerned
institution.
Electronic Dosimeters
•The sensitivity of the electronic dosimeters is 50–200 times that of TLD
badges.
•These are based on single silicon diodes or Geiger Muller tubes.
•Electronic dosimeters provide the dose readings immediately and give out
effective alarms when dose limits are exceeded.
TECHNIQUES FOR CONTROLLING RADIATION DOSE AT CT
Using Automated Exposure Control (AEC)
•In automatic exposure control, the tube current is modulated according to the size of the patient. For larger patients, the
tube current in automatically increased while for the smaller patients, i.e. pediatric patients the tube current is automatically
decreased.

•The tube current gets modulated according to the regional X-ray attenuation measured from scout radiographs. There can be a
transverse (x-y), longitudinal (z) or a combined (x-y-z) modulation. A combined modulation is usually preferred when
available.

•A variation of the tube current during different portions of the cardiac cycle at ECG gated cardiac CT examination is also
possible and is known as temporal resolution.

•With the use of AEC techniques, a close attention should be paid to the gantry isocentre. If there is off-centering, it can
increase the doses as the scanners use the patient width from the scout image to determine tube current for AEC.
Automated Exposure Control
• Dose increases if one does not select factors properly e.g. Noise index or image quality parameter.
• If one selects:
High noise index- poor image quality, low dose
Low noise index- good quality, high dose
• Example: Kidney for stones: unlikely to be missed even in low dose scan, but for appendicitis-higher dose scan
is needed.
• Heavy patient- upper value may reach.
Modifying the Acquisition Parameters
•A reduction in radiation dosage can be achieved by altering the number of scanning phases and the scanning thickness.
• In CT angiography rather than using four phases (precontrast, postcontrast arterial, post-contrast venous and postcontrast
delayed scanning) if two phases are used (arterial and venous phases) a reduction in the dosage upto 50% can be achieved.
•The section thickness can also be altered to reduce radiation doses. If the noise index is kept constant at 15.3, the relative
dose with 2.5 mm thick section would be around 2.3 times that with 5 mm thick sections.

Optimum Tube Potential
•Automatic voltage selection techniques have been developed by some vendors, e.g. Care kV by Siemens Healthcare, kV
assist by GE Healthcare, etc.
•Lower voltages are selected for contrast enhanced examinations and angiography as compared to the nonenhanced scans.
•A substantial reduction in chest and abdominal CT examination doses can be achieved by the use of automatic voltage
selection techniques.
Iterative Reconstruction (IR)
•Iterative reconstruction is an image reconstruction technique that reduces image noise. Lower
levels of image noise result in lower levels of radiation dose.
•In this a primary image is produced using the same filtered back projection, artificial raw data
is created using a forward projection to the primary image and an updated image is generated
by correlating the simulated data to the measured raw data. A final back projected image is
produced as the output.
•IR also results in effective reduction of various artifacts such as metal or streak artifacts.
RADIATION IN PREGNANCY

28 Day Rule
•Any radiological examination , if
justified can be carried out
throughout the cycle unless period is
RECOMMENDED DOSE LIMITS IN PREGNANCY
•IRCP : Recommends dose limit of 2 mSv applied to lower abdomen of female for remainder of
pregnancy once pregnancy is established.
•NCRP: Recommends dose limit of 0.5 mSv per month for fetus/ embryo for occupational pregnant
worker.
•AERB: Recommends once pregnancy is established the equivalent dose to surface of pregnant woman’s
abdomen should not exceed 2 mSv for remainder of pregnancy and it should not exceed 1 mSv on the
embryo/fetus.
•According to ICRP, termination of pregnancy at fetal dose less than 100mGy is not justified based
on radiation risk. At fetal dose between 100 -500mGy , the decision should be based on individual
circumstances. At fetal dose in excess of 500mGy , there will be significant fetal damage , the
magnitude and type of which is a function of dose and stage of pregnancy.

THANKYOU

the radiation and can be used to measure radiation dose. After the reading is obtained, the TLD can be annealed at a
higher temperature which zeroes the TLD reading dose and is read for reuse.
0.8 mm
thick
1.35 cm
diameter
52.5 x 29.9 x 1 mm
CaSO4 doped with
dysprosium
Al +Cu
perspex
Method to use TLD
•The TLD card should be loaded in the cassette and should not be removed till the end of the service period.
•A TLD badge should always be worn by all persons working in the radiation and should not be shared by any
other person.
•The TLD badge should always be stored in a radiation free place when not in use.
•While leaving the premises of the institution the badges should be submitted and not carried in a metro train
where again these would be screened through the X-ray machine leading to erroneous readings.
• The badge should also not be left in radiation field or near ovens, hot plates, furnaces, burners, etc.
Where to Wear the TLD Badge
•TLD badge can be worn at two places : Chest badge & Wrist badge. (Source: AERB website)
•When there is only one TLD badge it should be worn compulsorily at the chest level.
•In fluoroscopy a protective lead apron is worn by the radiologist while performing the various fluoroscopic procedures. In
such situations two TLD badges are to be worn ideally. One badge should be worn underneath the lead apron at the
chest level and the other needs to be worn at the level of the neck/collar region outside the lead apron. If it is not
feasible to wear two and only one is to be worn, it should be worn in the neck region outside the lead apron as the
neck receives about 10–20 times more exposure than the trunk which is protected by the lead apron.
•In special cases (Persons handling radioisotopes from close distances and radiologists/doctors doing the interventional
procedures), if the doses to the hands and forearms are expected to be significantly higher than at the chest level, additional
wrist badges may be procured and used.
How to Return the used TLD Cards
•All the cards whether used or unused should be returned once the service period is over (every 3 months). This should be done
along with the TLD/5 form. The TLD card should be arranged in the same order as listed in the TLD/5 forms and the nature of
the radiation sources handled against the respective names in the TLD/5 form should be written.
•Sending of TLD by an air courier should be avoided to prevent screening of the package under X-ray machine at the airport.
Plastic boxes should be used for returning the cards.
•If there is any damage to its filters (metallic pieces) or cassette holder, it should be immediately reported and a replacement be
asked for.
•Personal numbers are allotted by Bhabha Atomic Research Centre, Mumbai to the radiation workers. These numbers are
permanent and should not be changed. In case of any loss, a declaration stating the same duly signed by the RSO/Physicist
should be immediately sent.
Overexposure
•A dose exceeding 10 mSv in a quarter at chest level , 250 mSv at wrist level in a quarter is treated as
overexposure and should be reported immediately to the institution and the concerned individual.
•The institution should arrange to investigate the cause of overexposure and report the findings to the appropriate
authorities at BARC.
•A hematological examination including differential blood counts and chromosomal aberration test has to be carried
out on the person receiving more than 10 mSv.
•All overexposure cases are reviewed by BARC and advice on necessary follow-up is given to the concerned
institution.
Electronic Dosimeters
•The sensitivity of the electronic dosimeters is 50–200 times that of TLD
badges.
•These are based on single silicon diodes or Geiger Muller tubes.
•Electronic dosimeters provide the dose readings immediately and give out
effective alarms when dose limits are exceeded.
TECHNIQUES FOR CONTROLLING RADIATION DOSE AT CT
Using Automated Exposure Control (AEC)
•In automatic exposure control, the tube current is modulated according to the size of the patient. For larger patients, the
tube current in automatically increased while for the smaller patients, i.e. pediatric patients the tube current is automatically
decreased.

•The tube current gets modulated according to the regional X-ray attenuation measured from scout radiographs. There can be a
transverse (x-y), longitudinal (z) or a combined (x-y-z) modulation. A combined modulation is usually preferred when
available.

•A variation of the tube current during different portions of the cardiac cycle at ECG gated cardiac CT examination is also
possible and is known as temporal resolution.

•With the use of AEC techniques, a close attention should be paid to the gantry isocentre. If there is off-centering, it can
increase the doses as the scanners use the patient width from the scout image to determine tube current for AEC.
Automated Exposure Control
• Dose increases if one does not select factors properly e.g. Noise index or image quality parameter.
• If one selects:
High noise index- poor image quality, low dose
Low noise index- good quality, high dose
• Example: Kidney for stones: unlikely to be missed even in low dose scan, but for appendicitis-higher dose scan
is needed.
• Heavy patient- upper value may reach.
Modifying the Acquisition Parameters
•A reduction in radiation dosage can be achieved by altering the number of scanning phases and the scanning thickness.
• In CT angiography rather than using four phases (precontrast, postcontrast arterial, post-contrast venous and postcontrast
delayed scanning) if two phases are used (arterial and venous phases) a reduction in the dosage upto 50% can be achieved.
•The section thickness can also be altered to reduce radiation doses. If the noise index is kept constant at 15.3, the relative
dose with 2.5 mm thick section would be around 2.3 times that with 5 mm thick sections.

Optimum Tube Potential
•Automatic voltage selection techniques have been developed by some vendors, e.g. Care kV by Siemens Healthcare, kV
assist by GE Healthcare, etc.
•Lower voltages are selected for contrast enhanced examinations and angiography as compared to the nonenhanced scans.
•A substantial reduction in chest and abdominal CT examination doses can be achieved by the use of automatic voltage
selection techniques.
Iterative Reconstruction (IR)
•Iterative reconstruction is an image reconstruction technique that reduces image noise. Lower
levels of image noise result in lower levels of radiation dose.
•In this a primary image is produced using the same filtered back projection, artificial raw data
is created using a forward projection to the primary image and an updated image is generated
by correlating the simulated data to the measured raw data. A final back projected image is
produced as the output.
•IR also results in effective reduction of various artifacts such as metal or streak artifacts.
RADIATION IN PREGNANCY

28 Day Rule
•Any radiological examination , if
justified can be carried out
throughout the cycle unless period is
RECOMMENDED DOSE LIMITS IN PREGNANCY
•IRCP : Recommends dose limit of 2 mSv applied to lower abdomen of female for remainder of
pregnancy once pregnancy is established.
•NCRP: Recommends dose limit of 0.5 mSv per month for fetus/ embryo for occupational pregnant
worker.
•AERB: Recommends once pregnancy is established the equivalent dose to surface of pregnant woman’s
abdomen should not exceed 2 mSv for remainder of pregnancy and it should not exceed 1 mSv on the
embryo/fetus.
•According to ICRP, termination of pregnancy at fetal dose less than 100mGy is not justified based
on radiation risk. At fetal dose between 100 -500mGy , the decision should be based on individual
circumstances. At fetal dose in excess of 500mGy , there will be significant fetal damage , the
magnitude and type of which is a function of dose and stage of pregnancy.

THANKYOU

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