RADIATION HAZARDS AND PROTECTION

RADIATION
HAZARDS AND
PROTECTION
[Type the document subtitle]
SHIVA KUMAR SHRESTHA
1/1/2017

Preface
The purpose of this report is to provide the basic knowledge about radiobiology and principles of
radiation protection. Radiobiology is quite complex scope of science but it is compressed and
simplified in this report for easy understanding by radiographers. The first aim of this report is
to caution radiation worker as well as public by giving the required knowledge of radiation
effects. The report uses very simple language so people not concern with radiation can also get
easy knowledge about radiation hazards. After being cautions for radiation ; this report provide
how the radiation protection is supposed to achieve by following the simple principle e
established by ICRP (International commission for radiation protection and measurement ) . I
hope this report will encourage the radiation worker to promote and advertise the knowledge
about radiation worker because non-radiation workers because radiation safety is not in hand of
radiation worker only. On the last chapter, there is written about survey which gives information
of basic infrastructure necessary for radiation safety I n diagnostic radiology department. At last,
the summery of problems associated with radiation protection in Nepal is given which aim is to
get attention by concerned authority.
I think my teacher shailendra raj pandey sir for giving me massive inspiration and passion
toward radiography field and of course for giving me opportunity and appreciable support to
prepare this report. I would like to acknowledge mr.sada Shiva rao sir for giving me great time of
learning during CCP (comprehensive clinical practice) period .I am also thankful to all staffs of
hospitals for their co-operation during survey and sharing their knowledge during CCP. I am
very much thankful to my dear sister shreya chawal for her huge technical support by which
computerizing this report become possible.

Objectives of radiation protection
• The International commission of Radiation protection (ICRP) Stated that “the overall
objectives of radiation protection is to provide an appropriate standard of protection for
man without unduly limiting the beneficial practices giving rise to radiation exposure”.
• NCRP (1993)- “The goal of radiation protection is to prevent the occurrence of serious
radiation induced conditions in exposed persons & to reduce stochastic effects in exposed
persons to a degree that is acceptable in relation to the benefits to the individual & society
from activities that generate such exposure”.
RADIOGRAPHY
Radiography is study of image the internal structure of body by using electromagnetic radiation
specially x-rays. Radiographer is those professional personnel who are qualified to use x-ray for
imaging body structure to diagnose disease or injury. Since x-ray is being used medically in
many modality like fluoroscopy, mammography, ct scan etc the scope of radiography is being
broad. However in of Nepal, radiographer is those who are qualified to use electro –magnetic
radiation in diagnostic radiology.
The meaning of radiographer is different among countries. To become radiographer in
Nepal, one most pass diploma level in PCL radiography (proficiency certificated level) which is
divided in 3 years. These programme are conducted by CTEVT (council for technical education
and vocational training) through vocational health training institutes. 15 institutes are conducting
radiological technological education. Ensuring and developing quality of products, registering,
accrediting of health professional including radiographer is done by Nepal Health Professional
council (NHPC)

COUNCIL FOR TECHNICAL EDUCATION AND VOCATIONAL TRAINING (CTEVT)
CTEVT is constituted in 2045 B.s is national body of technical and
vocational education and training a (CTEVT) committed for production of technical and skillful
human resources required for the nation. It is mainly involved in policy formation, preparation
of competency based curriculum developing skill standard of various occupations and testing
the skill of people.
COMPREHENSIVE CLINICAL PRACTICE (CCP) IN RADIOGRAPHY
CCP is practice to gain the practical knowledge after gaining the theoretical
knowledge. CCP is done at hospital for 6 months on which theoretically prepared students are
allowed to face the working condition of their concern field.
The aim of CCP is to provide access to practical exercise through which knowledge and skill is
developed. The significance of CCP is given below in points.
It produces such qualified and skill manpower who will give reliable and quality health care
service.
The required skills in radiography (handling and positional of patient, use of equipments,
evaluation of image criteria, assisting the radio technologist during procedure, application of
emergency drugs etc) are provided to students t5hrough CCP.
CCP teaches us about discipline of hospital staff, right of a radiographer and system of hospitals.
It gives us vocational training to inform the patient about their rights and legal aspects.
Imamura College of health science (ICHS)
ICOHOS is health education institution affiliated to CTEVT which aim is to provide qualified
medical or paramedical personal for nation. Its location is in sallaghari, Bhaktapur. The
institutional programs includes lab Technician, Health Assistant, PCL nursing and radiography
as well. This collage is known for strict academic syllabus and excellent quality products.

INTRODUCTION TO RADIATION
The terms “radiation’’ means the emission of energy as form of wave or
particles from one medium to another or through space. If emitted energy is influenced by
electric as well as magnetic field then it is called electromagnetic radiation. EM radiation is
given wide range of names according to their wavelength and frequency.
EM radiation also includes the alpha particles, beta particles, neutron particles in which
subatomic practices are associated. It can be said that all kinds of the radiation is involved with
acceleration of subatomic practices [electron, proton and neutron].
The word “radiation” is associated with the ‘harmful’ or ‘hazardous’ which is not always
true. All radiation is not harmful but all ionizing radiation are harmful. So how the ionizing and
non-ionizing radiations can is differentiated?
IONIZING RADIATION
Ionizing radiation has sufficient energy to eject the electron from an atom or molecule
causing ionizing, breakage of chemical bond. Only the radiation having shorter wavelength can
interact at the electronic level. Radiation with energy more than 10eV can ionize an atom.
Radiation having shorter wavelength and sufficient energy falls in this category. It includes X-
rays, gamma
Rays, alpha particles, beta particles and neutron particles. Since the diagnostic radiology deals
with the ionizing radiation (especially X-ray)

As well as non-ionizing radiation (USG, MRI). We are only concern with first one in this report.
X-RAY
X- Radiation is the ionizing electromagnetic rays which wavelength ranges from 1-
0.1 A0 and frequency 9*1016-9*1019hertz.
X-ray is produced in radiology by hitting the electron into the target material which is
usually high atomic material tungsten alloy or molybdenum (in mammography). Free electrons
are produced by the thermo-ionic emission method.
General X-ray, computed tomography, mammography, orthopantomography, and fluoroscopy
uses X-ray for imaging of which CT delivers much of the radiation dose to the patient.
Radiation emitted by the X Ray tube
• Primary radiation: before interacting photons
• Scattered radiation: after at least one interaction;
• Leakage radiation: not absorbed by the X Ray tube housing shielding
• Transmitted radiation: emerging after passage through matter
SOURCE OF RADIATION
In general public there is a concept that radiation is produced artificially in medical sector which
results in radiation dose to population. It is important to know that every individual is exposed to
radiation primarily by natural radiation. Many genetics believes that the natural radiation which
can cause mutation and genetic effect is responsible for the evolution of life.
Natural radiation
It is further categorized into:
1. External source
2. Internal source

External source
Cosmic radiation:
 it is radiation results from the sun and stars. The intensity of this radiation depends upon
altitude and latitude
Terrestrial gamma radiation:
 it is result of deposition of radionuclide’s(uranium, thorium etc) on earth
Radon:
 it accounts the largest radiation dose to the population about 1.98 mSv. Decay of
radionuclide’s results in gas particles which emits alpha particles
Ingested or inhaled radionuclide (40K, 14C) results about 0.39mSv/annum
Man –made radiation
 Man made radiation mainly includes radiation used during diagnostic medical imaging (X-
radiation, gamma radiation) and nuclear medicine (alpha particle, beta particle)

HISTORY OF RADIATION EFFECTS
Since X-radiation was discovered in November 1895 by Roentgen he did not
described the radiation is biologically harmful. Due to lack of this knowledge many radiation
workers worked in hazardous condition. After few months, many somatic effects of radiation
induced malignancy reported.
After getting the result of ignorance to radiation, in 1924, American
roentgen ray society established the limit that radiation worker must not be exposed to dose more
than one-tenth of dose causing erythematic protection established recommended dose limit of 0.5
roentgen per day.
BASICS OF RADIOBIOLOGY
Radiobiology is the study of biological effects of ionizing radiation to analyze and
minimize its occurrence. When radiation interacts with the matter, it provides energy to electron
of atom and ejects it out causing ionization resulting deposition of energy in tissue.
Photo-electric effect is the main reason of radiation absorption in the tissue in which all
energy of radiation is impaired to the electron of an atom or molecule causing ionization. Ionized
atom or molecule either function abnormally and cause to function or it get combine with other
free electrons neutralizing the effect of radiation so there is always a chance of recovery of
radiation damage.
FACTORS AFFECTING RADIOSENSITIVITY
Radio sensitivity is degree of response to radiation by irradiated tissue. Law of
Bergonie and tribondeau states that stem cell, younger tissue and tissue with high metabolic rates
are more radiosensitive.
Physical factor
Linear energy transfer (LET) and relative biological effectiveness
(RBE)
LET is degree of energy transfer from radiation to per unit length of soft tissue. Its value is
3Kev/µm. RBE is ability to produce biological effect. RBE increases with LET.
Protraction and fractionation

If same dose quantity is given in two different time period, effect of dose is lessened in long time
period. In protraction, dose is delivered at lower dose rate to extend time. In fractionation, dose is
delivered at repeatedly between some time intervals. Irradiated tissue gets time for intracellular
repair and tissue recovery resulting the less effect.
Biological factor
Oxygen effect
Tissue show more radio sensitivity when it is oxygenated or in aerobic state. Diagnostic
radiology is performed under the condition of full oxygenated.
Age
Human are most sensitive before birth. After birth, sensitivity decreases with age but in old age
human again become more radiosensitive.
Recovery
When radiation interacts with biological tissue, the cell in it is damaged or killed. The damaged
cell or tissue is recovered by the intracellular repair and repopulation.
Chemical agent
Radio sensitizer enhances the radiation sensitivity of tissue. Eg:halogenated pyrimidine, vitamin
k etc.
Radioprotection reduces the radio sensitivity of tissue if it is present in it. Eg: cysteine,
cysteamine
Hormesis
This theory states that low dose of radiation exposure stimulates the hormonal and immune
response to other toxic environmental agent. This theory has not been justified clearly.
RADIATION DOSE RESPONSE RELATIONSHIP
The aim of the radiology is to determine the relationship between dose and its effects so that
radiation can be used optimally.

Radiation induced effects may be either linear or non-linear. In linear dose response, the severity
of effects increase proportionally with increased absorbed dose whereas in non-linear dose
response, severity is increase but in irregular manner. If the effect is shown at any dose, then it
has no threshold and if an effect is shown after delivering some amount of dose, then it has
threshold dose below which no response is expected to occur.
EFFECTS OF RADIATION
Mechanism of effects of radiation may be direct or indirect. In direct effects, the radiation energy
directs interacts with molecule causing initial ionization in it. Target molecule is such molecule
when gets irradiated, cell is severely affected because of its important role and insufficiency. In
direct effect, target molecule is not initially ionized. They only get damaged by the free radicals
or ionized atoms which is result of radiation of ionization of non critical molecule. DNA is target
molecule of human cell.
Radiation effects can be divided into 2 categories:
1-Deterministic effects
2-Non- deterministic effects
1-Deterministic effects
 The effects of radiation is said to be deterministic if it occur only after some limit of
exposure and severity of effects is increases with absorbed radiation dose.
 It has some threshold value below which lead to dysfunction of tissue or organ.
 Early effects of radiation can be called deterministic or non- deterministic effects.
 These effects are followed by high radiation dose more than .05 Gray which is very rare
in diagnostic radiology but threshold dose varies with individual.
 Acute death, skin burn, erythma, epilation (loss of body hair), organ atrophy and fibrosis,
genital dysfunction, hematological depression is example of it.
 Since diagnostic radiology follow partial body exposure, deterministic effects are very
rare to appear.

Threshold Doses for Deterministic Effects
• Cataracts of the lens of the eye 2-10 Gy
• Permanent sterility
• males 3.5-6 Gy
• females 2.5-6 Gy
• Temporary sterility
• males 0.15 Gy
• females 0.6 Gy
2-Non-deterministic effects
 Radiation induced effects is said to be stochastic if it can occur at any limit of exposure
(either low or high exposure) and probability of its occurrence increased absorbed dose
not severity.
 Since it does not have threshold dose, it is important low doses and depends upon sex
and age.
 Most of the stochastic effects are late effects which may e seen at later period.
 Stochastic effects are important in diagnostic radiology because to follows low dose of
exposure delivered intermittently over a long period.
Radiation induced malignancy, genetic effects, leukemia are example of it.

Radiation effects can be discussed in another way:
1. Somatic effects
2. Genetic effects
Fetal risk Somatic effects:
 The radiation effects induced in another generation of exposed individual then it is
known as genetic effects.
 Genetic effects are result of exposure of germ cell.
 There is no significant evident of genetic effects observed in human. The data of genetic
effects are based on experiment on mice and flies.
 Genetic effects are late effect of radiation with no threshold.
CHAIN OF EVENTS FOLLOWING EXPOSURE TO IONIZING
RADIATION
CELL DEATH
DETERMINISTIC EFFECTS
CELLULAR TRANSFORMATION
MAY BE SOME REPAIR
STOCHASTIC EFFECTS
CELLULAR LEVEL
SUBCELLULAR DAMAGE
(MEMBRANES, NUCLEI, CHROMOSOMES)
molecular changes
(DNA,RNA, ENZYMES)
free radicals
(chemical changes)
ionisation
exposure

Fetal risk:
 Fetus is most radiosensitive living biological specimen.
 Before fetus, it is concern with effects on fertility.
 Since the high radiation dose to the testis or ovary can cause sterility described as
deterministic effect, low dose chronic irradiation does not repair the fertility which is
good news for radiation worker.
 Result of fetus irradiation might be spontaneous abortion, congenital abnormality mental
retardation, childhood malignancy, impaired growth and development, genetic mutation
depends upon period of irradiation.
The first trimester during pregnancy is most radiosensitive period whereas
irradiation dose cause death of embryo which is onset from vagina in regular menstrual cycle or
embryo don’t get damaged.
Radiation dose unit and measurement
After knowing the biological effects of radiation, radiation measurements
become important part for radiation protection. Early technologist has to check the blood count
weekly to rule out biological effect. If blood counts decrease 25% than hematological depression
occurs in high dose.
Several units and dose have been described which we are discussing in brief in this report.
EXPOSURE (E)
It is dimensioning which quality the radiation output but do not relate with
biological effects of irradiated matter. Exposure is calculated by using ionization property of
radiation. The unit of exposure is Roentgen ®
The roentgen is defined as unit of radiation exposure which will liberate a charge of
2.58*10-4 per kg of air. Roentgen is independent of field size i.e., 1R exposure can irradiate
either finger only or whole hand. It is not unit of dose so it does not correspond biological effect.
ABSORBED DOSE (D)

Amount of energy absorbed per unit mass is called absorbed dose (D). There is
another dimension called KERMA which define the sum of initial kinetic energy of all charged
particle due to interaction of photon in matter of unit mass. KERMA and absorbed dose is related
because radiation is absorbed by transfer of its energy to irradiated matter. The unit of both is
joule per kilogram (J/kg). The SI unit of absorbed dose is Gray (G) and special unit is
rad(radiation absorbed dose)
1Gy = 100rad = 1J/kg
EQUIVALENT DOSE (H)
Since the biological effect increase with the increased absorbed dose but
absorbed dose is independent of type of radiation and composition of irradiated matter. Different
type of radiation has different biological effectiveness which is compared with the effect caused
by standard radiation (250Kvp X-ray). If effect of given radiation is greater than that of standard
radiation at same amount of absorbed dose then weighting factor or qualifying factor of given
radiation is more than 1and vice-versa. The weighting factor (WR) of diagnostic x-ray and
gamma ray is 1.
The unit of equivalent dose is rem used in radiation protection. The SI unit of
equivalent dose is Sievert (S) mathematically it can be defined as
H = D × WR where D = absorbed dose
WR = weighting factor
1Sv = 100 rem
The weighting factor of x-ray and gamma ray is 1 so

1 rad = 1 rem and 1Gy = 1 Sv
EFFECTIVE DOSE (E)
Previous dose do not relate the radio sensitivity of irradiated tissue whereas
different tissue have different response to radiation. So effective radiation dose describe the sum
of radiation effects of different tissue irradiated. Every tissue has different response so weighting
factor of tissue varies with its radio sensitivity. The sum of weighting factor of all tissue in
human is equal to 1. Mathematically,
E = ∑H ×WT
= ∑D × WR × WT
Where WT is tissue weighting factor, H is equivalent dose.
Effective dose equivalent

 Whole body exposures are rarely uniform.
 Tissues vary in sensitivity to radiation induced effects
 Effective dose is a measure of radiation and organ system specific damage in man
 The effective dose equivalent H E=Sum of WT*HT
 Wt=weighing factor of tissue t
 Ht= mean dose equivalent received by the tissue t
NRCP recommendation on exposure limits of radiation workers are based on following
criteria.
 At low radiation levels the nonstochastic effects are esentially avoided.
 The predicted risk factor for stochastic effects should not be greater than the
average risk of accidental death among workers in safe industries.
 Safe industries are defined as those having an associatedannual fatality accident
rate of 1 or less per 10,000 workers.
 The ALARA principle should be followed for which the risks are kept as low as
reasonable achievable.

Radiation detection and monitoring device
Radiation detection device are used to indicate presence of radiation in
interested area. It either cause beeping sound, ticking in presence of radiation or show range of
exposure. Radiation monitoring device are used to measure the intensity of the radiation also
called radiation dosimeters. Most of dosimeter is used personally by radiation worker hence
called personal monitoring device (PMD)
Few types of radiation detecting and monitoring device are discussed below.
Radiation detecting device Radiation monitoring device
1. Ionization chamber 1. Film badge
2. Thimble chamber 2. Thermoluminiscent dosimeter
3. Condenser chamber 3. Pocket dosimeter
4. Geiger counter
obtain the
EFFECTIVE DOSE
to the pt in msv
sum of all the organs and tissues irradiated
multiply by the
TISSUE WEIGHING FACTORWt
for the tissue or organ concerned
EQUIVALENT DOSE
to the organ in msv
multiply by the
RADIATION WEIGHING FACTOR Wr
OR QUALITY FACTOR
for the radiation used
for each organ and tissue estimate the
ABSORBED DOSE
in mgy

IONIZATION CHAMBER
 This is one of the radiation detecting devices which uses the ionizing property of radiation to
detect it.
 It consists of cylindrical chamber inner coated with graphite (cathode) to make it conduct
and central electrode (anode) insulated with chamber wall.
 When radiation interact with the air inside the chamber wall.
 When radiation interact with the air inside the chamber the ion pair are formed which are
collected by electrodes and conducted through circuit.
 The current produced in the circuit indicate the radiation intensity.
THIMBLE CHAMBER
 Working mechanism of thimble chamber is same as ionization chamber but difference is its
chamber wall is air equivalent i.e. attenuate radiation as air does.
 The central electrode is made up of aluminum. By knowing the volume of air (V), density of
air (p), radiation induced charge (Q). One can calculated exposure (X).
X = Q/(V×p)
CONDENSER CHAMBER
 Condenser chamber is modified thimble chamber in which the fully charged chamber
(condenser) is connected to thimble chamber by central electrode.
 When radiation induces the charge in thimble chamber the voltage in the electrode changes
(V1 – V2). The charge (Q) liberated can be calculated by
Q = C (V1- V2) where C is capacitance of system.
GEIGER COUNTER
 Geiger counter (GM counters) is special types of ionization chamber in which special type of
gas is filled at certain pressure.
 It is used to detect low amount of radiation and alpha [particle, beta particle etc.

FILM BADGE
 Film badge use special type of photographic film to measure the exposure to personnel.
 The badge is worn by radiation worker and gets exposed by radiation.
 The exposure of radiation form latent image in film. After certain period, the exposed film is
developed and optical density is accumulated is compared with standard calibration curve.
 Optical density is directly proportional to exposure.
 It consists of film similar to dental radiographic film sandwich between metal filters inside
the plastic holder.
 Different metal filter allow only specific types of radiation to expose different part of film.
 It normally consist two films i.e. slow and fast. Slow film record high exposure and fast film
record low exposure.
Film badge are cheap but it is affected by temperature and humidity,
cannot be reused and have short monitoring period. It cannot detect exposure less than 10mR.

THERMOLUMINISCENT DOSIMETER (TLD) BADGE
 TLD badge uses the principle of thermoluminiscence in which radiation energy is stored in
specific matter and released as light energy when it get stimulated by heat energy.
 The used specific material used in calcium sulphate (CaSO4) doped with dysprosium.
 It consists of aluminum coated card with 3 holes in which TLD disc is placed.
 The card is holded by the cassette in which three filters (Al+Cu, prefix, open) are
incorporated correspond to each TLD disc allowing only specific radiation to interact.
 When TLD disc is irradiated, the electron in crystal lattice get excited and store energy.
 The stored energy is released as light energy by heating the TLD disc.
 This process is called thermoluminiscence.
 The intensity of emitted light is further multiplied which indicate the indicate the intensity of
radiation.
It is more sensitive and accurate (as low as 5mR) than film badge but twice
more expensive. TLD can be reused for interval up to 1 year.
POCKET DOSIMETER
 Pocket dosimeter is used to for non – routine work I which radiation level may vary.
 It provides instant check of radiation dose received by personnel.
 The dosimeter should be fully charged prior to their use. Its capacity to monitor exposure
varies with each dosimeter.
Radiation protection
Diagnostic radiology is all about ionizing radiation i.e. X-ray. Although the
diagnostic radiology deals with the least amount, we must not forget the stochastic effects of
radiation which is possible to occur at low dose delivered over long period so all the radiation
protection guideline are based on linear non-threshold dose response relationship which include
risks like cancer, leukemia, genetic effects.
Radiation protection guidelines are simple and easy to understand. The guidelines are based on
linear hypothesis which state that, any dose, no matter how small, may inflict some degree of
detriment which can be latent and takes form of cancer and genetic effect in later period. The risk

of such effect exists even in absence of radiation but it is thought that exposure increase the
probability of risk.
The principle of radiation protection guidelines are drawn by international commission on
radiation protection (ICRP) which is described in this section of report.
 Justification
 Optimization
 ALARA principle
 Cardinal principle
 Limitation
Justification
Although the x-ray has numerous clinical applications, before every examination
which involves ionizing radiation, the validity of study should be evaluated or will it reflect the
real clinical condition. The disadvantages (radiation risk and cost effectiveness) and benefits of
examination must be evaluated before the examination. The examination must have sufficient
benefits to offset the risk. It always gives priority to alternative imaging modality like ultrasound,
MRI which doesn’t use ionizing radiation.
Optimization
It always defines that the number of individual exposed, magnitude of
individual dose and possibility of incurring exposure should be kept as low as reasonably
achievable keeping the individual dose below recommended limit. It inspires radiation worker to
use radiation wisely and optimally and remind them that have they done enough to reduce the
radiation dose? It is dependent on design and construction of equipment, radiological protocol or
practice of organization and medical or paramedical person who is associated with radiation
examination. Optimization is main part for the radiation protection in which radiographer or
radiation workers can be involved directly and in addition reliance on dose limit is not enough to
provide acceptable level of radiation protection. ALARA principle is identical to optimization
process and is acceptable worldwide. Its stands for “as low as reasonably achievable”. ALARA
is radiation safety principle as well as regulatory requirement for all radiation protection
programme. It is based on minimization of radiation doses ALARA includes all the methods
which helps in unnecessary exposure and overexposure.
While using ALARA principle in diagnostic radiology, minimum exposure technique must be
employed and all methods which results in low dose must be adopted. While using such

technique, it must be considered that image quality must be sufficient enough for diagnosis
otherwise repeated examination will be necessary which result in additional radiation dose.
The cardinal principles assist in maintaining ALARA principle which is discussed below.
Cardinal principle
Cardinal principle is also known as TDS principle which stands for time, distance and shielding.
Time
 The longer the person exposed to radiation, higher the dose and its effect so exposure time
must be kept minimum as possible.
 It reduce to patient as well as radio- technologist during fluoroscopy (pulsed fluoroscopy
technique)
Exposure time = Exposure
Exposure rate
Or
Exposure = Exposure rate x Time
The algebraic expressions simply imply that if the exposure time is kept short,
then the resulting dose to the individual is small
Distance
 X-ray also follows the inverse square law so its intensity of radiation decreases rapidly with
increasing distance in diagnostic radiology, the radiographer is protected behind the
protective barrier.
 The second radiation protection action relates to the distance between the source of radiation
and the exposed individual.
 The exposure to the individual decreases inversely as the square of the distance. This is
known as the inverse square law, which is stated mathematically as :
1
I ~ ———
d2
 This concept can be used in fluoroscopy procedure whereas in diagnostic radiology, the
source-image receptor (SID) must not be too low which results in high entrance skin
exposure (ESE) due to convergence of x-ray.

 Even if scatter radiation don’t emits from point source but radiation worker must assume
their exposure from scatter follow inverse square law which can be used in mobile
radiography.
Shielding
 Shielding implies that certain materials (concrete, lead) will attenuate radiation (reduce its
intensity) when they are placed between the source of radiation and the exposed individual.
 Lead is used as a radiation shielding material as it has a high atomic number (i.e. 82)
 Protective barrier and protective apparel are example of shielding. Protective apparel is
mainly made up of 0.5mm lead
 For the photoelectric process, the mass absorption coefficient increases with the cube of the
atomic number (z3)
• It is known that
• 0.25 mm lead thickness attenuates 66% of the beam at 75kVp
• and 1mm attenuates 99% of the beam at same kVp.
• It is recommended that for general purpose radiography the minimum thickness of
lead equivalent in the protective apparel should be 0.5mm.
Four aspects of shielding in diagnostic radiology
1. X-ray tube shielding

2. Room shielding
(a) X-ray equipment room shielding
(b) Patient waiting room shielding.
3. Personnel shielding
4. Patient shielding (of organs not under investigation)
1) X-ray tube shielding (Source Shielding)
• The x-ray tube housing is lined with thin sheets of lead because x-rays produced in
the tube are scattered in all directions.
• This shielding is intended to protect both patients and personnel from leakage
radiation.
• Leakage radiation is that created at the X-ray tube anode but not emitted through
the x-ray tube portal.
• Rather, leakage radiation is transmitted through tube housing.
• According to AERB recommendations
• manufacturers of x-ray devices are required to shield the tube housing so as to limit
the leakage radiation exposure rate to
• 0.1 R/ hr at a distance of 1 meter
• from the tube anode.
2) Room shielding (Structural Shielding)
The lead lined walls of Radiology department are referred to as protective barriers because
they are designed to protect individuals located outside the X-ray rooms from unwanted
radiation.
• There are two types of protective barriers.
(a) Primary Barrier:

is one which is directly struck by the primary or the useful beam.
(b) Secondary Barrier:
is one which is exposed to secondary radiation either by leakage from X-ray tube or by
scattered radiation from the patient.
The shielding of X-ray room is influenced by the nature of occupancy of the adjoining area.
In this respect two types of areas have been identified.
Control Area:
• Is defined as the area routinely occupied by radiation workers who are exposed to
an occupational dose.
• For control area, the shielding should be such that it reduces exposure in that area
to <26mSv/kg/week
Uncontrolled areas:
• Are those areas which are not occupied by occupational workers.
• For these areas, the shielding should reduce the exposure rate to <2.6mSv/kg/week
AERB has laid down GUIDELINES for shielding of X-ray examination room and
patient’s waiting room which are as follows.
The room housing an X-ray unit is not less than 18m2 for general purpose radiography and
conventional fluoroscopy equipment.
Shielding of the Xray control room :
• The control room of an X-ray equipment is a secondary protective barrier which
has two important aspects:
• (a) The walls and viewing window of the control booth, which should have lead
equivalents of 1.5mm.
(b) The location of control booth, which should not be located where the primary
beam falls directly, and the radiation should be scattered twice before entering the
booth

3) Personnel shielding
• Shielding of occupational workers can be achieved by following methods:
• Personnel should remain in the radiation environment only when necessary (step
behind the control booth, or leave the room when practical)
• Lead aprons are shielding apparel recommended for use by radiation workers.
These are classified as a secondary barrier to the effects of ionizing radiation.
• These aprons protect an individual only from secondary (scattered) radiation, not
the primary beam .
• The thickness of lead in the protective apparel determines the protection it provides.
Care of the lead apparel:
• It is imperative that lead aprons are not abused, such as by
– dropping them on the floor,
– piling them in a heap
– improperly draping them over the back of a chair.

• Because all of these actions can cause internal fracturing of the lead, they may
compromise the apron’s protective ability.
• When not in use,
• all protective apparel should be hung on properly designed racks.
• Protective apparel also should be radiographed for defects such as internal cracks
and tears at least once a year
• Other protective apparel include eye glasses with side shields, thyroid shields and
hand gloves.
• The minimum protective lead equivalents in hand gloves and thyroid shields should
be 0.5mm.

Posting, Warning sign
Limitation
Limitation is last guideline for radiation protection. If justification and optimization is applied in
well manner the limitation will not be that mandatory however effective dose to individual
should not exceed the dose recommended to avoid deterministic effect and reduce the probability
of stochastic effect. Its aim is to ensure no individual is exposed to that dose which will induce
effect to patient.
Recommended dose limit is established by several scientific group associated with radiation
safety. These group include national commission on radiation protection (NCRP), international

commission on radiation protection (ICRP), international atomic energy agency etc. these
organization can review and change the dose limit periodically but don’t enforce radiation safety
policy.
Radiation protection of uterus
The protection of uterus of reproductive aged female is one of the most important considerations
in radiation protection because it can cause many dangerous effects as we discussed above.
10 day rule or pregnancy rule is postulated by ICRP for woman of reproductive age. The day of
radiological examination of lower abdomen and pelvis of reproductive aged woman must be
within 10 days following the onset of menstruation. In fact, there is no chance of pregnancy
within 14 days but 10 days is considered because cycle of menstruation varies with individual.
The first two weeks after post-conception is not considered harmful because radiation exposure
in this period either causes undetectable death of embryo or nothing at all. In addition,
malformation is unlikely or very rare to occur where as abortion is likely to occur dose more than
100mGy. So based on this, 28 day rule is implemented. This rule intends that radiological
examination can be carried throughout the cycle until the period is missed. If period is missed,
pregnancy can be suspected. Following this rule is responsibility of every radiographer.
If radiation worker get pregnant, the dose must not exceed 5mSv during pregnancy and 0.5mSv
in each month. The radiographer must wear fetal shield and given 2dosimeter one for collar and
another inside fetal shield. The dose to fetus can be calculated by given formula.
Radiation protection of pediatric patient
Children are 10 times more radio sensitivity than adult even girl are more sensitive than boy.
They have long post-period to show any late effects induced by radiation. There is considerable
amount of bone marrow in their bone protected by less compact bone and have high mitosis rate
in their tissue. Because of these reasons, radiography of pediatric must be done with maximal
radiation protection.
Every pediatric examination must be justified whether there is alternative imaging modality like
USG, MRI which don’t use ionizing radiation. If examination is justified then optimization
process begun in which radiographer can be involved directly.

There are given some considerations for pediatric radiography which comprises optimization
process.
Use of high Kvp technique and lower mAs, increased filtration, tight collimation, shielding of
gonad thyroid and lens whenever possible, increased source to image-receptor distance(SID) and
use of PA projection ( in pelvis, skull, thorax result less dose to thyroid gonads eyes) can reduce
radiation dose to patient.
Grid are not necessarily used to gain image quality because patient thickness is usually lesser.
Small focus spot and short exposure time (to avoid motion blur and repeat examination) are used
to obtain good image quality.
Immobilizing device must be applied to if possible to avoid dose to parents or radiographer
himself.
Keep the no. of case of greenstick fracture don’t go for lateral projection.
Motion blur is most occurring reason for repeat examinations in diagnostic radiology which
requires kind approach if child is approachable. Approaching the child include greeting, gentle
smile, communication to child at his/her eye level, praising the children etc. before entering the
patient in x-ray room, all pre-work (exposure factor, tube position, cassette position) must be
completed so that patient stays in x-ray room for minimum time.
Radiation protection of patient
Radiation protection of patient is responsibility of every medical radiation worker. Since the
protection of patient is not only in the hand of radio-technologist or radiographer but by
following general principles of optimization, he/she can reduce considerable amount of radiation
dose to patient. In this section, we describe what an individual radiographer can do to reduce
patient radiation dose.
Elimination of unnecessary examination.
The choice of performing examination is not in the control of radiographer. Many of x-ray
examinations are performed which don’t give helpful information or have minimum significance.
Routine x-ray examinations screening for tuberculosis, chest x-ray examination can be
eliminated if there is no clear clinical information however on doing so, the clinician or
radiologist may get criticized. The radiographer must ask if any x-ray examination performed
previously to eliminate examination or for review. Radiology department can eliminate

unnecessary examinations by promoting the radiation protection guidelines to concern hospital
or individual to clinician associated with radiological examination.
Elimination of repeat examinations
The main reasons of repeat examination is inadequate patient preparation, inaccurate exposure
factor, improper collimation or patient positioning, lack of review of patient information etc. this
all reason can eliminated by radiographer. In busy department, the repeat examination should not
exceed the ratio of 1:20.
Appropriate radiographic technique
Following the ALARA principle, the exposure factor must be minimum as possible without
compromising image quality. In digital radiography, 15% rule can be used which state that 15%
increase in Kvp accompanied by half reduction in mAs results in same optical density. Reduction
in this mAs result in lesser patient dose but increase in Kvp may cause reduction in contrast
which can be acceptable.
While examining the structure having high subject contrast like chest, GI tract during barium
study significant increase in Kvp don’t result in loss of contrast so mAs in lowered in such case
which is compensated by high Kvp also known as high kVp technique which results in less
radiation dose.
Choice of receptor
in manual processing, the high speed screen film combination requires less amount of radiation
to obtain same optical density but result in noise so considering the image quality, high screen
(rare earth) film must be used whenever possible specially in pediatric radiography.
Patient positioning
Most of the postero-anterior projection of axial skeleton results in less dose to specific
radiosensitive organ. For example; the PA projection of skull results in less radiation dose to eye
and thyroid gland as well in c-spine PA projection, PA projection of chest in female result in less
radiation dose to breast due to its compression. During upper limb radiography, the useful beam
should never direct towards gonads.
Limiting the field size

Field size must be limited to area of interest. Increased field size increases the exposure area
resulting increased radiation dose. The field size is limited by collimator and positive beam
limiting device. Practice of applying tight collimation reduce considerable amount radiation
dose. Whenever collimator is not accurate, we can use lead divider to cover the uninterested area
limiting the field size. Limiting field size not only reduces exposure but also improve image
quality by eliminating scatter radiation.
Source to skin distance]
If the source i.e.; x-ray tube is placed near to the patient the entrance skin exposure is higher
because the x-ray beam is condensed to small area as described by inverse square law. This is
applied in fluoroscopy whereas in diagnostic radiology, SID is standardized to 100cm. when
source to skin distance (SSD) is high; there is less exposure of patient by leakage radiation too.
Shielding apparel
Every patient must be given protective lead apparel if it don’t obscure the region of interest
specially children. Gonad shield, thyroid shield, lead apron must be handled with care and
regularly checked for any leakage. Sometime the lead apparel is avoided by the patient or visitor
holding patient due to its heavy weight. In such cases, its responsibility of radiographer to aware
the patient party about radiation effects.
Suitable use of grid
Grid must be used in such condition when there is more scatter radiation i.e. thicker body parts,
large field size and high kVp factor. It may not be necessary to use grid in case of pediatric
patient and hyposthentic or sthenic patient due to lesser thickness however the acceptance of
image quality depends upon radiologist.
PERMISSIBLE DOSES
 Regulating Bodies

 One of the first bodies involved in regulating radiation hazards is the ICRP (international
commission on radiation protection)
 In U.S the regulatory board is the NCRP(National council on radiation protection and
measurements)
 In India the board is the AERB(Atomic energy regulatory board)
 Constituted in Nov 15,1983.
 Headquarters in Mumbai.
 ICRP has recommended a series of maximum permissible dose(MPD) for different body
tissues.
 The quoted values are maximum and every effort should be made to keep the doses to
absolute minimum.
 The dose for general public are set at1/10 th of maximum possible dose for corresponding
tissues
 ICRU has also recommended maximum values for amounts of different radioisotopes which
can be deposited in the body without constituting radiation hazards
Dose limits for pregnant women
 The total dose equivalent limited to fetus is 5 mSv(0.5 rem)
 Exposure not exceeding 0.5mSv(0.05 rem) in any 1 mths
For pregnant staff,
 a risk assessment must be performed,
 dose to fetus < 1 mSv for rest of pregnancy.

If the dose equivalenttothe embryo/fetusisdeterminedtohave alreadyexceeded
500 mremwhena workernotifiesheremployerof herpregnancy,the workershall notbe assigned
to taskswhere additional occupational radiationexposureislikelyduringthe remainderof the
pregnancy.
Radiation protection survey and programme
• The responsibility for establishing a radiation protection programme rests with the
hospital administration / owners of the X-ray facility
• The administration is expected to appoint a Radiation Safety Committee (RSC), and a
Radiation Safety Officer (RSO).
• It is recommended by NCRP that the RSC should comprise of a radiologist, a medical
physicist,, a senior nurse and an internist. It is the duty of RSC to perform a regular
radiation protection survey
This survey has 5 phases which are:
1. Investigation: To obtain information regarding layout of the department, workload,
personnel monitoring and records.
2. Inspection: Each diagnostic installation in the department is examined for its protection
status with respect to its operating factors, control booth and availability of protection
devices.
3. Measurement: Measurements are conducted on exposure factors. In addition scattered
radiation and patient dose measurements in radiography and fluoroscopy are performed.
4. Evaluation: The radiation protection status of the department is evaluated by
examination of records, equipment working, status of protective clothing and the
radiation doses obtained from phase-3.
5. Recommendations: A report is prepared on the protection status of the department and
the problem areas if any identified, for which recommendations are made regarding
corrective measures

SUMMARY
Being a radiographer, it is necessary to know the benefits as well as effects of harmful ionizing
radiation. The duty of radiation worker is to deliver the benefits of radiation to patient in safe
manner.
The effects of radiation are categorized into two. They are stochastic and deterministic.
Deterministic effects appear beyond the threshold dose and severity increases absorbed dose
which include acute death, hematological depression, skin burn, gonads dysfunction etc. in

diagnostic radiology, these effects are very rare because dose in diagnostic radiology do not
exceed the threshold dose normally. The main focus is given to stochastic effect because it can
occur at any dose limit and probability of its occurrence increase with increase absorbed dose
which include risk like cancer, leukemia and genetic effects. All the radiation protection
guidelines are based on stochastic effects or late effects of radiation which follow linear non-
threshold dose response. To assist in establishing radiation protection law, the organization like
NCRP, ICRP have established radiation units and dose limits.
Fundamental of radiation protection guidelines include justification, optimization and limitation.
Justification encourage us to have finite clinical reason to perform radiological examination and
also suggest to undergo investigation like USG,MRI which don’t involve ionizing radiation.
Optimization is another important guideline in which radiographer has more access. It promotes
the concept of using radiation minimally and wisely. The ALARA principle and cardinal principle
are simple rule which help in optimization of radiation use. The third guideline limitation ensures
that no individual get affected by negative aspect of radiation. These are ensured by
recommended dose limits. The radiographer must follow special considerations in case of
pediatric radiography and women of reproductive age (10 day rule or 28 day rule).
Radiation protection principles are easy to understand and imply. One must not necessarily have
deep knowledge of radiation effect or protection to reduce patient dose. By only following
ALARA principle and cardinal principle, radiation dose can be reduced significantly to patient
and himself as well. Radiation consciousness and promoting habit of radiation protection
guideline must be quality of radiographer. Since radiation effects are not seen instantly,
radiographer must always remember linear hypothesis and never ignore radiation.
Problems of radiation protection in Nepal
Development of field of diagnostic radiology is taking action slowly in Nepal however lot more
has to be done to improve status of radiation safety and quality assurance. The problems are
given in summarized form
Lack of qualified manpower is great issue in radiology field. The numbers of radio-technologists
are very low according to need. Due to this, advance modality is being operated by unqualified
manpower. However no. of radiographers are increasing per year but they are centralize to

valley. Decentralization of qualified manpower is necessary. Government does not have plan to
fulfill the requirement qualified staff for radiology. In rural area, the x-ray service is given
without the minimum requirements of protective measures. Old generation and conventional type
equipment is used without collimation. Due to lack of basics knowledge of protection, these
conditions are avoided and uses high dose of radiation energy increasing the risk of radiation
hazard.
In rural area, lack of radiographer if fulfilled by trained radiographer. It is also seen that post
technologist is being fulfilled by radiographer. The reasons behind this may be lack of radio
technologists over expenditure decreasing strategy of private hospital or both.
Another problem is shortage of bio-medical physicist or engineer. The maintenance facility for
x-ray equipment is poor.
Due to lack of public awareness toward radiation, the government is not seriously concerned
with radiation field. It can be said that half of the Nepal population is illiterate which means they
neither know the hazards of radiation nor the benefits of it. It is responsibility of radiation worker
to create awareness among people. It is seen in practice that the large no of CT examinations are
performed without justification. It may be due to lack of knowledge to choice imaging modality,
lack of knowledge of radiation protection principle or for some commission amount. Whatever
the reason, the patient pays high amount of money and receive unnecessary radiation dose in
bonus.
There is no quality assurance test or radiation safety test conducted to radiology department so
the status of equipment is unknown. In many cases, the equipment is being operated in hazardous
condition for patient so there must be assurance program conducted in every radiology to provide
safe, effective and quality radiology service.
Lack of radiation monitoring device is big problem. There is no research centre of institution in
Nepal which can provide personnel monitoring device to radiation worker, monitor it and
regulate the dose limit. There is monitoring device used in radiation therapy but in diagnostic
radiology it is just being started which is provided by Bhabha Atomic Energy Center, India.
It is quite obvious that, there is urgent need of radiation safety policy. Although Nepal has
become a member of IAEA (international atomic energy agency) in august 2008, no radiation
protection act has been established however the organization like Nepal radiological society,
Nepal radiologist association etc are enforcing the government for new radiation policy which is
on the way.
ICRP (International Commission on Radiation Protection)

ICRP is dependent, international, non- government organization which provides
recommendation and guidance on protection. It was founded in 1928 called international x-ray
and radium protection committee (IXRPC). In 1950, it was reconstructed to takes account of
radiation guidance outside the medical sector hence given the present name. Their scientific
departments is in Ottawa, Canada and have 200 volunteer from 30 countries on 6 continents who
represent world’s leading scientists and policy makers in the field of radiation field. The function
of ICRP is to issuing recommendation in the form of reports and publication. In collaboration
with ICRU, it assisted in defining many of the dose quantities.
NCRP (National Council on Radiation Protection and Measurement)
It is U.S organization that seeks to formulate and disseminate information guidance and
recommendation on radiation protection and measurement founded in 1964. Its objectives are to
collect, analyze, develop and disseminate information about protection against radiation. It co-
operate with other organization like ICRP to provide effective scientific guidance and
recommendations.
IAEA (International Atomic Energy Agency)
It is international organization that seeks to promote peaceful use of nuclear energy and inhibits
its use in military purpose formed in 1953. It has 168 member states including Nepal. Nepal got
membership in 2008. IAEA has urged the Nepal government to enact the nuclear law and
establish atomic energy commission. It also has recommended in its preliminary report submitted
to ministry of science and technology to enforce law and regulation as soon as possible in the
country.

RADIATION HAZARDS AND PROTECTION

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