The document discusses radiation protection and its principles. It defines radiation protection as protecting people from harmful effects of ionizing radiation exposure. The objectives are to minimize health effects and avoid deterministic effects. The principles proposed by ICRP are justification, optimization, and individual dose limitation. Justification requires any new radiation source do more good than harm. Optimization means keeping doses as low as reasonably achievable. Dose limitation sets limits on individual accumulation of radiation doses.

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“Assignment”
Submitted by:
Zainab Maqsood
Subject:
Health and Medical Physics

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“Contents”
1) What is radiation protection?
2) Objectives of radiation protection.
3) Principles of radiation protection:
i. Justification.
ii. Optimization.
iii. Dose limitation.
4) Dose Reduction Techniques
5) Conclusion.
6) References.

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What is Radiation protection?
Radiation protection, sometimes known as radiological
protection, is the protection of people from harmful effects of
exposure to ionizing radiation. Exposure can be from a radiation
source external to the human body or due to an intake of
radioactive material into the body.
Radiation protection, sometimes known as radiological
protection, is the science and practice of protecting people and
the environment from the harmful effects of ionizing radiation.
Ionizing radiation is widely used in medicine and industry and
can present a significant health hazard. It causes microscopic
damage to living tissue, which can result in skin burns and
radiation sickness at high exposure, and statistically elevates risk
of cancer at low exposure.
Objectives of radiation protection:
The objectives of radiation protection are to minimize the health
effects due to ionizing radiation. Ionizing radiation can present a
significant health hazard to living tissue. This can result in skin
burns and radiation sickness at high exposures, known as
"deterministic effects” and statistically elevated risks
of cancer at low exposures, known as "stochastic effects”.
Based on the characteristics of the above effects, aims of
radiation protection are to:
1. Avoid the deterministic effects.
2. Lower the probability of stochastic effects to an acceptable
level.

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“Principles for radiation
protection:”
International Commission on Radiological Protection (ICRP)
proposed a system of radiation protection with its three
principles:
1. Justification.
2. Optimization.
3. Individual dose limitation.
“Radiation protection Principle”
Justification and optimization, these two principles are
source-related and apply in all exposure situations where the
principle of dose limitation is individual-related and applies in
planned exposure situations. The principle of radiation
• Any decision that alters the radiation
exposure situation should do more
good than harm.
Justification
• Doses should all be kept as low as
reasonably achievable.Optimisation
• The total dose to any individual
should not exceed the
appropriate limits
Dose
Limitation

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protection is interrelated with the exposure situations, the
categories of exposure, the dose criteria, and the
application of the system. Figure below illustrating these
interrelationships:
“Interrelationshipsbetween the principles of protection,
the exposure situations, the categories of exposure, the
dose criteria, and the application of the system.”
1. The principle of justification:
Any decision that alters the radiation exposure situation
should do more good than harm. , i.e. by introducing a new
radiation source, by reducing existing exposure, or by
reducing the risk of potential exposure, one should achieve
sufficient individual or societal benefit to offset the detriment
it causes.

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The principle of justification applies at three levels in
medicine (ICRP, 2007a) as described below:
 At the first level, the proper use of radiation in medicine is
accepted as doing more good than harm to society.
 At the second level, a specified procedure is justified for a
group of patients showing relevant symptoms, or for a group
of individuals at risk for a clinical condition that can be
detected and treated.
 At the third level, the application of a specified procedure to
an individual patient is justified if that particular application is
judged to do more good than harm to the individual patient.
2.The principle of Optimization:
Optimization of protection for patients is also unique. The
basic aim of this optimization of protection is to adjust the
protection measures for a source of radiation in such a way
that the net benefit is maximized. The optimization of
protection in medical exposures does not necessarily mean the
reduction of doses to the patient. The optimization of
radiological protection means keeping the doses ‘as low as
reasonably achievable (ALARA), economic and societal
factors being taken into account.
The ALARA radiation safety principle is based on the
minimization of radiation doses and limiting the release of
radioactive materials into the environment by employing all
“reasonable methods.” The ALARA concept is an integral
part of all activities that involve the use of radiation or
radioactive materials and can help prevent unnecessary
exposure as well as overexposure. The three major principles
to assist with maintaining doses “As Low as Reasonably
Achievable” are time, distance and shielding.

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Reduction of patient’s dose can be achieved by:
1) Reducing the number of images taken of patient.
2) Reducing the absorbed dose per image.
The optimization of radiological protection for patients in
medicine is usually applied at two levels:
 The design, appropriate selection, and construction of
equipment and installations.
 The day-to-day methods of working.
Principles for maintaining doses:
The three major principles to assist with maintaining doses are:
1. Time: Reducing the time of exposure can directly reduce
radiation dose.
2. Distance: Increasing the distance between you and the
radiation source you will reduce exposure by the square of the
distance.

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3. Shielding: Lead or lead equivalent shielding for X-rays and
gamma rays is an effective way to reduce radiation exposure.
“Principle for maintain doses illustrating Time,
distance, and shielding”
3.The principle of dose limitation:
Dose limit is used to apply controls on each individual’s
accumulation of dose. The total dose to any individual from
regulated sources in planned exposure situations other than
medical exposure of patients should not exceed the appropriate
limits recommended by the Commission. There are legal dose
limits for workers and members of the public, based on
ensuring that no deterministic effects are produced and that the
probability of stochastic effects is reasonably low and For
patients ‘reference values’ have been published to indicate
levels above which exposures should be reviewed. Dose limits
do not include medical exposures and natural background
radiation.
Annual Dose Limits (ADL):
There are different categories of dose limits for:
1. Radiation workers.
2. Members of the public.
3. Trainees of radiation.

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4. planned special exposures.
5. Female pregnant workers.
OCCUPATIONAL EXPOSURE:
For occupational exposure of workers over the age of 18 years,
the dose limits are:
(a) An effective dose of 20 mSv per year averaged over five
consecutive years64 (100 mSv in 5 years), and of 50 mSv in any
single year;
(b) An equivalent dose to the lens of the eye of 20 mSv per year
averaged over 5 consecutive years (100 mSv in 5 years) and of
50 mSv in any single year;
(c) An equivalent dose to the extremities (hands and feet) or the
skin65 of 500 mSv in a year. Additional restrictions apply to
occupational exposure for a female worker who has notified
pregnancy or is breast-feeding. For occupational exposure of
apprentices of 16 to 18 years of age who are being trained for
employment involving radiation and for exposure of students of
age 16 to 18 who use sources in the course of their studies, the
dose limits are:
I. An effective dose of 6 mSv in a year;
II. An equivalent dose to the lens of the eye of 20 mSv in a
year;
III. An equivalent dose to the extremities (hands and feet) or
the skin65 of 150 mSv in a year.
PUBLIC EXPOSURE:
For public exposure, the dose limits are:
(a) An effective dose of 1 mSv in a year;
(b) In special circumstances66, a higher value of effective dose
in a single year could apply, provided that the average effective

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dose over five consecutive years does not exceed 1 mSv per
year.
(c) An equivalent dose to the lens of the eye of 15 mSv in a
year.
(d) An equivalent dose to the skin of 50 mSv in a year. The
effective dose limits specified, apply to the sum of the relevant
doses from external exposure in the specified period and the
relevant committed doses from intakes in the same period; the
period for calculating the committed dose shall normally be 50
years for intakes by adults and up to age 70 years for intakes by
children.
“Dose Reduction Techniques”
1) Removal of Grid:
The presence of grids in x-ray systems primarily increases the
contrast and hence the image quality; however, they increase the
dose to the patient and staff by a factor of two or more. Removal
of the grid has resulted in dose reduction of up to
one-third to one-half with little or no degradations in contrast
and image quality. Use non-grid techniques when examining
children and small adults.
2) Last Image Hold and Electronic Collimation:
A useful feature on many modern fluoroscopy systems is last
image hold, whereby the last image is digitally “frozen” on the
monitor after x-ray exposure is terminated. Last image hold is a
dose saving feature, since it allows physicians to contemplate
the last image and plan the next move without additional
radiation exposure in an interventional procedure. In addition,
some modern systems have electronic collimation, which

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overlays a collimator blade on the last image hold so that one
can adjust field dimensions without exposing the patient.
3) Adjustment of Beam Quality:
Beam energy primarily depends on the peak kilovotage selected
and the amount of filtration in the beam. Selection of higher
kilovolt peaks increases the average beam energy of the x rays
(beam hardening) and therefore the fraction of the entrance
beam that passes through to the image receptor.
4) Intermittent Fluoroscopy:
Most radiologists are trained to control the fluoroscope
intermittently, that is, keeping the x rays on only a few seconds
at a time, long enough to view the current catheter position. This
simple technique is particularly effective when combined with
last image hold features.
5) Dose Spreading:
Some reduction of maximum skin dose can be achieved by
periodically rotating the fluoroscope about a center within the
anatomy of interest. This method tends to spread the maximum
dose over a broader area of the patient’s skin so that no single
region receives the entire dose.

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“Conclusion”
Physicians and radiologists must be aware of the radiation
risks and benefits associated with medical exposure, and
understand and implement the principles of radiation
protection for patients. The education of the referring
physician and radiologist are also important.

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“References”
 www.ncbi.nlm.nih.gov
 www.hko.gov.hk
 sites.google.com