The document outlines the principles and practices of radiation protection, emphasizing the need to minimize risks from ionizing radiation through justification, optimization, and dose limits. It covers the biological effects of radiation, the categorization of ionizing radiation, and the importance of using protective measures in medical settings. Various dose metrics, including rad, rem, and tissue weighting factors, are explained alongside guidelines for occupational and public exposure limits.

1. Radiation protection
Pradeep Kumar
Radiology resident
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2. • Cardinal principles of radiation protection?
• Fundamentals of Radiobiology?
• Basic principles of Radiation Protection( ICRP)?
• Biological Effects of Radiation?
• Radiation and tissue weighting factors?
• Effective dose, Rad, Rem?
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3. Radiation
• Radiation is naturally present everywhere in the
world
• All life on earth has evolved in the presence of this
radiation.
• The basis of diagnosis and treatment in Radio-
diagnosis, Radiotherapy and Nuclear Medicine is
Ionizing Radiation mostly in the form of x-rays
and gamma-rays.
• Ionizing radiation is very harmful to human health
so these radiations should be used very carefully.
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4. Medical applications of radiation
 Among the leading diagnostic tools, more than 5
billion Medical Imaging studies are done each year
(2/3 involving ionizing radiation)
 About 40 million Nuclear Medicine procedures
involving medical radioisotopes are carried out.
 More than 5 million patients requiring cancer
treatment receive radiotherapy.
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5. Radiation Fundamentals
• Sources of Radiation Exposures
• Occupational
• Radiology/Radiotherapy professionals
• Nuclear facility professionals
• Non-occupational
• Naturally occurring sources
• Radon
• Sources in the human body
• Sources in earth’s crust (terrestrial)
• Cosmic radiation
• Manmade sources
• Medical radiation
• Industrial sources
• Atmospheric testing of nuclear weapons.
• Consumer products
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6. Radiation Fundamentals
Two general categories of
ionizing radiation:
PARTICLES
alpha
neutron
beta
PHOTONS
X-ray
gamma ray
102-5
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7. • Rad (Radiation absorbed dose)
• The absorbed dose D, is the energy absorbed per unit mass.
This quantity is defined for all ionizing radiation for any
material.
• Rad is used for any type of ionizing radiation.
• SI Unit of absorbed dose is Gray (J/Kg)
• 1 Gray = 100 rads
• 1 rad = 1 c Gy
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8. Radiation Fundamentals
• Rem (Roentgen equivalent man)
• Unit of equivalent dose, previously known as quality factor.
• Most commonly used unit – for person dose.
• Pertains to the human body.
• Takes into account the energy absorbed (dose) and the
biological effect on the body due to the different types of
radiation.
• Absorbed dose multiplied by radiation weighting factor WR
• SI unit of dose equivalent is Sievert
• 1 Sievert = 100 Rem
• 1 rem = 10 msv
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9. Radiation Weighting factor - WR:
 It is a value assigned to various forms of radiation
relative to X or Gamma radiation according to the
biological damage they can cause
 alpha = 20
 beta = 1
 gamma/x-ray = 1
 neutron = 10
 (rad x WR = rem, Gray x WR = Sv).
 Alpha particle has WR 20 implies that we need 20 rad
of x-rays to produce the same damage that is caused
by 1 rad of alpha radiation.
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10. Dose Limitation
Equivalent Dose ( HT )
• Absorbed dose x Radiation weighting factor. J/KG
Effective Dose (E)
• Sum of Dose equivalent for each tissue x appropriate
Tissue weighting factors J / KG
• Tissue weighting factor is the risk of stochastic effects
being induced in the organ when singly irradiated
compared to the total risk of inducing stochastic effects
if the same dose of radiation is received by the whole
body, accounts for radiosensitivity of tissue.
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11. Tissue weighting factor
• Gonads 0.20 ( latest icrp put it as 0.08)
• Bone marrow 0.12
• Thyroid 0.05
• Breast 0.05
• Lung 0.12
• Esophagus 0.05
• Stomach 0.12
• Liver 0.05
• Colon 0.12
• Urinary bladder 0.05
• Bone surface 0.01
• Skin 0.01
• Remainder 0.05
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12. Fundamentals of Radiobiology
(Law of Bergonie & Tribondeau)
• Stem cells are more radiosensitive than mature cells
• Younger tissues and organs are more radiosensitive
• When the level of metabolic activity is high, radio-
sensitivity is also high
• Radio-sensitivity increases as the proliferation rate of
cells and the growth rate of tissues increases.
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13. Biological Effects of Radiation
Biological effects are generally categorized into:
• Somatic effects
• Genetic effects
Radiation protection point of view they are
categorized into:
• Deterministic effect
• Stochastic effect(random probability)
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14. • Somatic effects
Appear in the exposed individual during life time
• Prompt effects – appear shortly after exposure
• Hair loss after exposure to scalp
• Delayed effects – appear years after exposure
• Cancer, cataracts
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Dose
(Rad)
Effect
0 -25 No detectable symptoms or blood
changes
25 -100 Changes in blood
100 - 300 Nausea, Anorexia
300 - 600 Diarrhea, hemorrhage, possible
death

15. LD50/60 for various species after whole body
radiation exposure (rads): dose of radiation
expected to cause death within 6o days to 50
percent of those exposed.
• Dog 250
• Human 350
• Guinea pig 425
• Mouse 620
• Rabbit 725
• Turtle 1500
• Cockroach 10000
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16. Biological Effects of Radiation
• Delayed Effects
• Result from continuing low-level chronic exposures or
from a single acute exposure
• Some result are from damage to the cell’s DNA
• Examples include:
• Cancer
• Cataracts
• Life shortening
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17. Biological Effects of Radiation
• Genetic Effects
• Abnormalities that may occur in the future generations
of exposed individuals. Hence , genetic effect may affect
subsequent unexposed generations.( vs somatic for
exposed only)
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18. Concepts and aims of Radiation Protection
• Radiation Protection is the science whose aim is to
minimize the risks (for people and environment)
generated by the use of ionizing radiation.
• Radiation Protection aims to reduce Stochastic
effects and eliminate Deterministic effects (Tissue
reactions) of radiation.
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19. Stochastic effects:
• Stochastic effects are random events. There is no
threshold point and risk increases in a linear- quadratic
fashion with dose. This is known as linear quadratic no
threshold theory. Although the risk increases with dose,
the severity of the effect does not, the patient will either
develop cancer or they will not. Current recommendation
of ICRP is based on assumption that there is no safe level
of exposure. Even smallest exposure has some probability
of causing stochastic effect.
• Radiation induced cancers (somatic) and hereditary effects
(genetic) are stochastic effect
• The principle health risk from low dose radiation.
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20. Deterministic effects:
Radiation effects which has a specific threshold and
appears only when the radiation dose exceeds
threshold value.
• Severity of effect increases with increasing dose
• Requires much higher dose to produce an effect
(Cataract 50-200rads, permanent sterility 350-
600rads)
• Lethal mutations affecting large number of cells
• Only observed in some lengthy fluoroscopically
guided interventional procedures in Diagnostic
radiology
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21. Framework of Radiation Protection
(System of Radiation Protection)
• “System of Radiation Protection” is the name
given by the International Commission on
Radiological Protection (ICRP) to the application
of the 3 basic principles of Radiation Protection
• Justification of practice
• Optimization of protection
• Application of individual Dose Limits
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22. Justification of Practice:
• No practice involving exposure to radiation should
be adopted unless it produces at least sufficient
benefit to the exposed individuals or to society to
offset the radiation detriment it causes.
• If the exposure has no justification then it should
be avoided regardless of how small the dose
might be.
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23. Optimization of Protection:
• If the exposure is justified, what can be done to
limit exposure to the smallest possible dose??
• Optimization means that minimum risk and
maximum benefit should be achieved.
• Optimization means that doses should be ‘as low as
reasonably achievable’ (ALARA).
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24. ALARA
• ALARA concept
• ALARA stands for As Low As Reasonably Achievable
• Refers to the continual application of the optimization
principle in the day-to-day practice
• Because of some risk, however small, exists from any
radiation dose, all doses should be kept ALARA.
• Includes reducing both internal and external radiation
dose.
• ALARA is the responsibility of all employees.
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25. ALARA
(Cardinal principles of radiation protection)
• Basic protective actions taken to minimize external
dose include:
• Minimizing time in radiation areas
• Maximizing the distance from a source of radiation
• Using shielding whenever possible
• Reducing the amount of radioactive material (source
reduction)
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26. ALARA
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100 200 300
100 µSv/hr 1 hour 2 hours 3 hours
An ALARA principle is to
reduce the time in a radiation field
µSv/hr

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

28. ALARA
 Shielding (Diagnostic Radiology)
 Gonadal shielding
 Personnel shielding
 Lead rubber apron ,thyroid shield 0.25-0.5mm LE), lead
rubber glove, lead glass goggles etc.
 X-ray tube shielding
 Room shielding (Structural shielding)
 Primary protective barrier (1.6 mm lead)
 Secondary protective barrier (0.8 mm lead)
 Viewing window – Lead glass (1.5 mm LE)
 Lead equivalent is thickness of lead required to achieve the
same shielding effect against radiation, under specified
conditions as provided by a given material.
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29. 2
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30. Application of Individual Dose
limits:
• A limit should be applied to the radiation dose
(other than from medical exposure and background
radiation) received by an individual as the result of
all practices to which he is exposed.
• Doses should not exceed specific values called
“individual dose limits”. These dose limits are
established in order to keep away from the
“maximum risk level” so that no individual is
exposed to a radiation that is judged to be
unacceptable in any normal circumstance.
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31. Dose Limit
The dose limit is determined by the law, based on
protection standards recommended by the ICRP.
 This is not the boundary between safety and danger.
 It does not apply to radiation exposure from natural
radiation and medical radiation
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32. Individual Dose limits
(occupational exposure)
• The occupational exposure of any worker should be
controlled so that the following limits be not exceeded.(ICRP
APRIL 2017 , FRANCE)
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Application Occupational dose limit
Whole body Effective Dose 20 mSv per year, averaged over
defined periods of 5 years
(50 mSv in any single year)
The lens of the eye 20 mSv a year averaged over
defined period of 5 years with no single year >50, previously was 150 msv
The skin 500 mSv
The hands and feet 500 mSv

33. Dose limits (public)
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Effective Dose 1 mSv in a year
Annual equivalent dose in:
The lens of the eye 15 mSv
The skin 50 mSv

34. How do we protect?
(Diagnostic radiology)
Patient Protection
• Maintain low current and therefore a higher kv.
• Tight collimation to area of interest.
• Do not use grid for smaller patients, when a substantial
gap is between the patient and detector remove the grid
as this utilises the air gap technique.
• patient positioning: protecting gonads
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35. How do we protect?
• Professional Protection
• Cardinal principles
• Use protective apparels
• Minimum fluoroscopy time
• Personnel monitoring
• ALARA
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36. How do we protect?
• Public protection
• Information boards
• Restricted entry inside radiation area
• Regular radiation survey
• X-ray room design
• Radiation warning lamps and signs
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37. Personnel Monitoring
• Personnel Monitoring is the monitoring of
individuals who are exposed to radiation during the
course of their work
• radiologists, medical physicists, radiographers and nurses
• Other frequent users of X Ray systems such as
endoscopists, anaesthetists, cardiologists, surgeons etc., as
well as ancillary workers who frequently work in controlled
areas, shall also be monitored.
• Monitoring is necessary when there is a chance
that an individual may receive about 1/10 of the
equivalent dose (Dose limit)
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38. Classification of working area
• Areas in a radiology department are generally
classified as controlled or supervised
• Controlled areas should include all x-ray rooms
(likely to receive ED more than 6mSv/yr)
• Supervised areas should include parts of the
facility where mobile x-ray units are used, and all
other parts other than public areas (likely to
receive ED of 1mSv/yr)
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39. Personnel Monitoring Devices
• Film badge (100 µSv)
• TL Dosimeter(10 µ Sv)
• OSL Dosimeter (10 µ Sv)
• Pocket dosimeters (1µSv)
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Passive Dosimeters
Active Dosimeter

40. Wearing the Personnel Dosimeter
• For general radiography a dosimeter should be worn at
the level of waist or collar
• When a lead apron is used:
• One dosimeter worn under the apron will yield a reasonable
estimate of effective dose for most instances
• The other body areas not protected by the apron will receive
higher dose so a dosimeter above the apron may overestimate
the dose received
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41. Wearing the Personnel Dosimeter
• In case of high workload (interventional radiology) an additional
dosimeter outside the apron should be considered by the RSO
• 1 under the apron at waist level
• 1 over the apron at collar level
• The effective dose E is given by:
E = 0.5 Hw + 0.025 Hn
where:
• Hw :dose at waist level under the apron
• Hn :dose at neck level over the apron
• The dosimeter worn over the apron at collar level gives also an
estimation of thyroid and eye lens doses
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42. Pregnancy and Medical Radiation
• Thousands of pregnant women are exposed to
ionising radiation each year
• Lack of knowledge is responsible for great anxiety
and probably unnecessary termination of
pregnancies
• For most patients, radiation exposure is medically
appropriate and the radiation risk to the fetus is
minimal
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43. Pregnancy and Medical Radiation
• Planned Exposures:
• patients needing radiological/nuclear medicine examinations
or even therapy while pregnant
• Assessment of valve functions or implants screening or
situations requiring cardiac catheterization
• Accidental exposure in pregnancy
• Occupational exposures in pregnancy
• Exposure of female of reproductive capacity
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44. Fetal Radiation Risk
• There are radiation-related risks throughout pregnancy which are
related to the stage of pregnancy and absorbed dose
• Irradiation is considered least hazardous during the first 2 weeks
of pregnancy
• Radiation risks are most significant during organogenesis and in
the early fetal period, somewhat less in the 2nd trimester and
least in the third trimester
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Less Least
Most
risk

45. Effects of Irradiation in-utero
• Up to 14 days
• Spontaneous abortion: 25% natural incidence, 0.1%
increase per 10rad (100mGy)
• 2-10 weeks
• Congenital abnormalities: 5% natural incidence, 1%
increase/10rad
• 2nd & 3rd trimester
• Cell depletion: no effect at less than 50rad
• Latent malignancy: 4:10,000 natural, 6:10,000/rad.
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46. Radiation-induced malformations
• Malformations have a threshold of 100-200 mGy or
higher and are typically associated with central
nervous system problems
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47. Termination of pregnancy
• Termination of pregnancy at fetal doses of less than 100 mGy is
NOT justified based upon radiation risk
• A fetal dose of 100 mGy has a small individual risk of radiation-
induced cancer. There is over a 99% chance that the exposed
fetus will NOT develop childhood cancer or leukaemia
• At fetal doses in excess of 100 mGy, there can be fetal damage,
the magnitude and type of which is a function of dose and
stage of pregnancy
• High fetal doses (100-1000 mGy) during late pregnancy are not
likely to result in malformations or birth defects since all the
organs have been formed
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48. • The threshhold radiation dose for temporary
sterility for man is 150 mGy and female is 650
mGy. For permanent its 3500 and 2500 mGy
respectively.
• 10th day rule: abdominal and pelvic examination
done during 10th day of menses. Since
organogenesis starts 3 to 5 weeks post
conception.
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54. Thank you
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