RADIATION PROTECTION, ITS HAZARDS & AERB GUIDELINES

PRESENTED BY DR BHASKAR JYOTI

SAIKIA

MODERATORS: PROF DR R.K.GOGOIPROF & HOD DR

M.H.BHUYAN

Introduction Scientists were quick to realize the benefits of X-rays, but

slower to comprehend the harmful effects of radiation. The first recorded biologic effect of radiation was seen by

Becquerel, who developed erythema and subsequently ulceration when radium container was left accidentally in his left pocket.

Elihu Thomson demonstrated that x ray causes erythema and blisters in 1897

Thomas Edison’s assistant, Clarence Dally, who had worked extensively with X-rays, died of skin cancer in 1904, it was the first death attributed to radiation effect

William Herbert Rollins developed leaded tube housings, collimators , and other techniques to limit patient dose during 1896-1904.

- Also demonstrated that exposure of a pregnant guinea pig resulted in killing of the fetus

- He was a true pioneer of x-ray protection

Rome Vernon Wagner, an x-ray tube manufacturer, had begun to carry a photographic plate in his pocket and to develop the plate each evening to determine if he had been exposed (1907)

Pioneer for personal monitoring Died of cancer in 1908 Film badge came into effect from 1920

The first tolerance dose or permissible exposure limit was equivalent to about 0.2 rem per day.

Rolf Sievert also put forth a tolerance dose- 10% of the skin erythema dose

Hermann Muller demonstrated the genetic effects of radiation(1926)

2nd International congress of radiation in 1928 set up the International X-ray and radium protection committee

EARLY CHRONOLGY OF RADIATION PROTECTION

Pioneer Era (1895-1905)- in which recognition of the gross somatic hazard occurred, and relatively simple means were devised to cope.

Dormant Era (1905-1925)- little overt progress was made, but in which great gains were made in technical and biological knowledge which were later applied to protection.

Era of Progress (1925-1945), which saw the development of radiation protection as a science

Atomic Age International X-ray and radium protection committee

was remodeled into The International Commission on Radio logical Protection (ICRP) and The International Commission on Radiation Units and Measurements (ICRU)

The International Commission on Radiological Protection (ICRP) was the primary body created to advance for the public benefit, the science of radiological protection

It is a registered charity, independent non-governmental organization

It provides recommendations and guidance on protection against the risks associated with ionizing radiation, from artificial sources widely used in medicine, general industry and nuclear enterprises, and from naturally occurring sources

The first report Publication 1 (ICRP, 1959)--->Publication 26(ICRP, 1977)--->Publication 60(ICRP, 1991b, international Basic Safety Standards)--->Latest is Publication 103(ICRP, 2007)

OTHER GOVERNING BODIES IAEA (International Atomic Energy Agency) establishes

standards of safety and provides for the application of the standards

National commission on radiation protection and measurement(NCRP) is recommendation body of USA

In India regulatory and recommendation authority is Atomic Energy Regulatory Board (AERB)

Atomic Energy Regulatory Board(AERB) Was constituted in 1983 by government of India Carries out certain regulatory and safety functions under the Atomic Energy Act,1962 and Environment Protection Act, 1986,

Radiation Protection Rules 2004 It is the recommendation, research and licensing body in India

TERMINOLOGIES OF RADIATION PROTECTION

Amount of radioactivity material expressed as the nuclear transformation rate

Conventional unit: curie

SI unit: Bequerel

1 curie = 3.7 x 1010 Bq

ACTIVITY

EXPOSUREAmount of ionization per mass of air due to x rays

and gamma raysThe ICRU defines exposure (x) as quotient of dQ by

dm where dQ is the absolute value of total charge of ions of one sign produced in air when all the electrons liberated by photons in air of mass, dm are completely stopped in air.

X= dQ/dmConventional units: Roentgen®SI unit: c/kg1R=2.58 x 10-4 c/kg

ROENTGENThe roentgen (R) is

defined as unit of exposure that will liberate a charge of 2.58 x 10-4 C/kg of air.

1R=1 electrostatic unit(esu)/cm3 air at standard temp and pressure(STP)

ABSORBED DOSEDeposition of energy in patient by

radiation exposure

Independent of composition of irradiated material and energy of beam

RAD: unit of absorbed dose

GRAY: SI unit of absorbed dose

Gray defined as the quantity of radiation that results in an energy deposition of 1 joule per kilogram.

I GRAY = 100 RAD1RAD = 1 cGY

DOSE EQUIVALENT

It is a measure of biological effectiveness of radiationREM: unit of absorbed dose equivalentSI unit : SIEVERT

1 sievert = 100 rems

H=D x Q (D is absorbed dose) (Q is quality factor for radiation ) (H is absorbed dose equivalent)

Rem = rads x quality factor

Quality factorIt is the parameter used to describe the quality of beam.Gives the amount of energy deposited per unit length

travel. Expressed in KEV per micron.

Type of radiation Q factorX rays 1 Gamma rays 1Beta particle 1Electrons 1Thermal neutrons 5Other neutrons 20Protons 20 Alpha particle 20

EFFECTIVE DOSE EQUIVALENT

Purpose – to relate exposure to riskIt is calculated by multiplying the dose

equivalent received by each individual organ or tissue (DT) by an appropriate tissue weighting factor (WT) and summing for all the tissues involved.

o b ta in th eE F F E C TIV E D O S E

to th e p t in m s v

sum o f a ll th e o rg a n s an d tissues irrad ia ted

m ultip ly b y th eTIS S U E W E IG H IN G F AC TO R W t

fo r th e tissue o r o rg an c o n ce rn ed

E Q U IV AL E N T D O S Eto th e o rg an in m sv

m ultip ly b y th eR AD IATIO N W E IG H IN G F AC TO R W r

O R Q U AL ITY F AC TO Rfo r th e rad ia tio n used

fo r eac h o rg an an d tiss ue e s tim ate th eAB S O R B ED D O S E

in m g y

EFFECTIVE DOSE EQUIVALENT LIMITS

NRCP recommendation on exposure limits of radiation workers are based on following criteria.

a) At low radiation levels the nonstochastic effects are esentially avoided.

b) The predicted risk factor for stochastic effects should not be greater than the average risk of accidental death among workers in safe industries.

c) Safe industries are defined as those having an associated annual fatality accident rate of 1 or less per 10,000 workers.

d) The ALARA principle should be followed for which the risks are kept as low as reasonable achievable.

RADIATION SOURSES

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NATURAL BACKGROUND RADIATION- cosmic rays External - gamma rays from rocks & soil - ingested radioisotopes in certain foods Internal - inhaled radon decay products (granite )

ARTIFICIAL BACKGROUND RADIATION- fallout from nuclear explosions - radioactive waste

MEDICAL AND DENTAL DIAGNOSTIC RADIATION OCCUPATIONAL EXPOSURE

May 2, 2023 Dr Saad Wahby Al Bayatti 22

RADIATION HAZARDS

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N u clera r b o m sn ueclea r rea c to rs lea ks

W h o le b o d yra d ia tio n

M ed ica l(d ia g n o s tic & thera p u tic)

D en ta lX - ra ys

S pec ific a reara d ia tio n

R a d ia tion exp o su re

SPECIFIC VERSUS WHOLE-BODY RADIATION

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Ind irec t D irec t

Som aticA ffec ts ind iv idua l

N o e f fec t on o f fspr ing

G ene ticD o no t a f fec t ind iv idu ia l

O ffspr ing is a f fec ted

R ad ia tion da m age

Radiation

DNA /RNA molecule nuclear acid

breakdown

Nuclear acid breakdown Somatic cells radiation induced malignancy Genetic cells radiation induced congenital

abnormality

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DIRECT DAMAGE

H 2 O H + + OH -

H + + H + H 2

OH - + OH - H 2 O 2

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Radiation

INDIRECT DAMAGEWATER HYDROLYSIS

H2O2 + DNA Molecular breakdownH2O2 + Proteins

Molecular breakdown Cell damage

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D irec tD N A /R N A h it

R a d ia tio n in d u ced m a lig n a n cy

In d irec tH 2 O 2 fo rm a tio n

T O X ICb rea k d o w n o f la rg e m o lecu les(p ro tien s /D N A )

S o m a tic

R a d ia tio n d a m a g e

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D ir e c tD N A /R N A h it

R a d ia tio n in d u c e d c o n g e n ita la b n o r m a lity

I n d ir e c tH 2 O 2 fo r m a tio n

T O X I Cb r e a k d o w n la r g e m o le c u le s ( p r o te in s / D N A )

G e n e tic

R a d ia tio n d a m a g e

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Radiation health effects

CELL DEATH BOTH

TYPEOF

EFFECTS

CELL TRANSFORMATION

Radiation health effects

DETERMINISTICSomaticClinically attributable in the exposed individual

CELL DEATH

STOCHASTICsomatic & hereditaryepidemiologically attributable in large populations

ANTENATALsomatic and hereditary expressed in the foetus, in the live born or descendants

BOTH

TYPEOF

EFFECTS

CELL TRANSFORMATION

The Biological Effects Of Radiation

Prompt personal effects

Delayed personal effects

Racial effects

PROMPT PERSONAL EFFECTS

On receiving very large doses

Occurs within few hours or days

Symptoms associated are erythema,vomiting.diarrhoea

A single dose of 500 rad could result in death

DELAYED PERSONAL EFFECTS

Chronic low dose irradiation over a considerable period of time or few exposures giving a high dose

Clinical Features Scaling ,warty growth on hands Skin cancer Thyroid cancer Cataract formation Bone marrow compromise leading to fatal anaemia and

leukaemia Premature ageing Growth and development of fetus and young children

• Deterministic(Threshold/non-stochastic)

• Existence of a dose threshold value (below this dose, the effect is not observable)

• Severity of the effect increases with dose

• A large number of cells are involved

Radiation injury from an industrial source

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

dose

Severity ofeffect

threshold

Threshold Doses for Deterministic Effects

Stochastic EffectsStochastic(Non-Threshold)

No threshold Probability of the effect increases with doseGenerally occurs with a single celle.g. Cancer, genetic effects

RADIATION EFFECTS

DETERMINISTIC EFFECTMechanism is cell killingHas a threshold doseDeterministic in natureSeverity increases with

doseOccurs only at high dosesCan be completely

avoided Causal relationship

between radiation exposure and the effect

Sure to occur at an adequate dose

STOCHASTIC EFFECTMechanism is cell modificationHas no thresholdProbabilistic in natureProbability increases with doseOccurs at even at low dosesCannot be completely avoidedCausal relationship cannot be established at low dosesOccurs only among a small percentage of those exposed

RADIATION EFFECTS DETERMINISTIC EFFECTRadiation SicknessRadiation syndromes

Haematopoietic syndromeGI syndromeCNS syndrome

Damage to individual organs

DeathLate damage

STOCHASTIC EFFECT

Chromosomal damage

Cancer Induction (Several years after exposure to radiation)

Genetic Effects (Hereditary in future generations only)

Somatic Mutations

C H A IN O F EVEN TS FO LLO W IN G EXPO SU R E TO IO N IZIN GR A D IA TIO N

CELL DEATHDETERM INISTIC EFFECTS

CELLULAR TRANSFO RM ATIONM AY BE SOM E REPAIRSTO CHASTIC EFFECTS

CELLULAR LEVEL

SUBCELLULAR DAM AG E(M EM BRANES, NUCLEI, CHRO M O SO M ES)

m olecular changes(DNA,RNA, ENZYM ES)

free radicals(chem ical changes)

ionisation

exposure

Radiosensitivity [RS]

RS = Probability of a cell, tissue or organ of suffering an effect per unit of dose.

RS laws (Law of Bergonie & Tribondeau)

Radiosensitivity of living tissues varies with maturation & metabolism; Stem cells are radiosensitive. More mature

cells are more resistant Younger tissues are more radiosensitive Tissues with high metabolic activity are

highly radiosensitive High proliferation and growth rate, high

radiosensitivty

Radiosensitivity

MuscleBonesNervous system

SkinMesoderm organs (liver, heart, lungs…)

Bone MarrowSpleenThymusLymphatic nodesGonadsEye lensLymphocytes (exception to the RS laws)

Low RSMedium RSHigh RS

Factors Affecting RadiosensitvityDose: the amount of

radiation received. The higher the dose, the greater is the effect (consider the threshold)

Dose rate: the rate of exposure. e.g. a total dose of 5Gy can be given as- 5Gy/min (single dose) is more destructive - 5mGy/min(fractionized), less destructive, injured cells can recover

Oxygen: the higher the O2 level in irradiated cells, the greater is the damage. (H2O2 formation)

Linear Energy Transfer (LET): the rate of loss of energy from a particle as it moves in its track through matter (tissue)e.g. alpha particles vs. X-ray

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RADIATION PROTECTION

DEFINITIONInternational Atomic Energy Agency (IAEA) as "The

protection of people from harmful effects of exposure to ionizing radiation and the means for achieving this".

The IAEA also states "The accepted understanding of the term radiation protection is restricted to protection of people”

Three Principles Of Radiation Protection JUSTIFICATION: Any decision that alters the radiation

exposure situation should do more good than harm.

OPTIMISATION: The likelihood of incurring exposure, the number of people exposed, and the magnitude of their individual doses should all be kept as low as reasonably achievable, taking into account economic and societal factor.

DOSE LIMITATION: 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 specified by the Commission

JUSTIFICATION

A practice involving exposure to radiation should produce sufficient benefit to the exposed individual or to society In the case of patients, the diagnostic or therapeutic benefit

should outweigh the risk of detriment In the occupational exposure, the radiation risk must be

added and compared with other risks in the workplace In cases in which the individual receives no benefit, the

benefit to society must outweigh the risks

OPTIMISATION The principle of optimisation is to keep the likelihood

of incurring exposures, the number of people exposed, and the magnitude of individual doses as low as reasonably achievable

Optimisation is always aimed at achieving the best level of protection under the prevailing circumstances through an ongoing, iterative process that involves:

evaluation of the exposure situation, including any potential exposures (the framing of the process);

OPTIMISATION selection of an appropriate value for the constraint or

reference level; identification of the possible protection options; selection of the best option under the prevailing

circumstances; and implementation of the selected option.

ALARA As low as reasonable achievable In USA, ALARA has cash value of about 1,000$ per

10 mSv If the exposure of one person can be avoided by this

amount of money, it is considered reasonable At higher dose levels, additional exposure may

threatened worker's job by exceeding the lifetime dose limit, here reasonable cost is 10,000$

DOSE LIMITATIONS In the 1930s, the concept of a tolerance dose was

used, a dose to which workers could be exposed continuously without any evident deleterious acute effects such as erythema of skin

Early 1950s , emphasis shifted to late effects and maximum permissible dose was designed to ensure that probability of injury is so low that the risk would be easily acceptable to the average person

This was based on geneticist H.J Muller work who had indicated that the reproductive cells were vulnerable to even smallest doses of radiation

Permissible Dose The concept of tolerance dose indicated that there

was a level of radiation below which it was safe. The concept of stochastic effects of radiation

invalidated this dogma Most scientists rejected that there was a threshold

dose below which exposure to radiation was harmless The concept of permissible dose therefore introduced

Maximum Permissible Dose

“There is no safe level of exposure and there is no dose of radiation so low that the risk of a malignancy is zero” — Dr. Karl Z. Morgan, father of Health Physics

Maximum Permissible dose (MPD) is defined as that dose which in the light of present knowledge is not expected to cause appreciable bodily injury to the person at any point during his lifetime

Maximum Permissible Dose Advantages

- explicit acknowledgment that doses below MPD have a

risk of detrimental effects

- acknowledged danger due to stochastic effects of

radiation

- introduced the concept of acceptable risk- probability of

the radiation induced injury was to be kept low to be

easily acceptable to individual

Recommendations on exposure limits At low radiation levels non stochastic effects are

essentially avoided The predicted risk for stochastic effects should not be

greater than the average risk accidental death among workers in “safe industries”

As low as reasonably achievable principle should be followed( “safe” industries are defined as “those having an associated annual fatality accident rate of 1 or less per 10,000 workers i.e. Average annual risk is 10-4)

General recommendations on Dose Limitations

The first general Recommendations were issued in 1928 and concerned the protection of the medical profession through the restriction of working hours with medical sources

This corresponds to an individual dose of about 1000 millisievert (mSv) per year

1956 Recommendations limits on weekly and accumulated doses were set that corresponded to annual dose limits of 50 mSv for workers and 5 mSv for the public

All the standard dose limitations are made for “reference man”

Reference man is defined as being 20-30 yrs of age, weighing 73 kg, is 170 cm in height, lives in a climate with an average temperature of 10 to 20oC, he is Caucasian and is western European or north American in habitat and custom

Most countries have changed the concept of reference man – e.g Indian reference man

Enables base line calculations of organ doses

General guidelines on Dose limitations Individual doses due to combination of exposures from all

relevant practices should not exceed specified dose limits for occupational or public exposure

Different dose limits are specified for the radiation workers as the expected benefit from the work they do while they do while handling radiation will outweigh the small increase in risk

Pregnant radiation workers have to be protected so that the fetus/embryo is given the same radiation protection as given to public

Dose limits are not applicable for medical exposure as the benefits gained outweighs the harm

Does not include natural background or radiation for medical purposes

LIMITS FOR OCCUPATIONAL EXPOSURE

STOCHASTIC EFFECTS1. No occupational exposure should be permitted until the

age of 18 years2. The effective dose in any year should not exceed 50mSv(5

rem)3. The individual worker's lifetime effective dose should not

exceed age in years Х 10mSv

PROTECTION OF THE EMBRYO/ FETUS

1. NCRP recommends 0.5 mSv to the embryo/ fetus once the pregnancy is declared

2. ICRP recommends a limit of 2 mSv to the surface of woman's abdomen for the remainder of her pregnancy

3 There is a provision that a declared pregnancy can later be “undeclared” if the female worker so desires

EMERGENCY OCCUPATIONAL EXPOSURE

If possible, older workers with low life time accumulated effective doses should be chosen among the volunteers

If exposure do not involve saving life should be avoided If for lifesaving the exposure may approach 0.5 Sv to a large

portion of the body, the worker needs to understand potential for acute effects, but also substantial increase lifetime risk of cancer

EXPOSURE OF PUBLIC

For continuous or frequent exposure, the annual effective dose should not exceed 1 mSv

Maximum permissible annual equivalent dose is 5 mSv for infrequent dose

METHODS OF RADIATION PROTECTION

Exposure time distance Lead barriers

Exposure timeExposure is the amount of light per unit area (the image

plane luminance times the exposure time) reaching a photographic film or electronic image sensor, as determined by shutter speed, lens aperture and scene luminance

Exposure is measured in lux seconds, and can be computed from exposure value (EV) and scene luminance in a specified region

Total dose equivalent x time

DISTANCE- Inverse square law applies. - whenever possible , distance should be

2 meter from x-ray tube.

-Distance 1 m - 400 (exposure) -Distance 2 m - 100

LEAD BARRIERS

- efficient absorber of x rays. - great reduction of exposure by

placing it in between source and person

- thickness stated in HALF VALUE LAYER (HVL) for kilo voltage x rays.

(HVL – any material thickness which reduces exposure rate by one –half.)

HVL (HALF VALUE LAYER)Half-Value Layer . The thickness of any given material

where 50% of the incident energy has been attenuated is know as the half-value layer (HVL).

The HVL is expressed in units of distance (mm or cm). Like the attenuation coefficient, it is photon energy dependent. Increasing the penetrating energy of a stream of photons will result in an increase in a material's HVL.

Protective barriers in radiation and fluoroscopytube must enclosed in metal housing that reduces leakage

radiation ( is radiation which penetrates the protective housing )

Wall protection

• Useful beam ( radiation pass through aperture)

• Leakage radiation• Scattered radiation

(radiation undergoes change in direction through its path)

• Stray radiations (scattered + leakage radiation)

4 types of radiations

PROTECTIVE BARRIER

PRIMARY • In radiography up to 140 kV about 1/16 inch

lead extending 7 feet up from the floor when tube is 5-7 f.t from the wall.

• protects from useful beam(mainly).

SECONDARY• is about 1/32 inch lead.• - extends from the top of the 1ry barrier to ceiling.• - ordinary plaster often suffice as a 2ry barrier

without added lead.

Lead apron – worn in fluoroscopy room. - Pb equivalent 0.5 mm.

Check lead protective apron periodically for cracks by means of a radiography test.

DOSE REDUCTIONBEAM FILTRATION:- exposure greatly reduced by ALUMINIUM filter. - removes lower energy photons. - recommendations:-

operating kVp Minimum HVL Al (mm)

< 50 0.3

50-70 1.2

> 70 2.3

COLLIMATION (BEAM LIMITATION)

decrease in cross sectional area of the beam avoids unnecessary exposure of tissues outside the area of interest.

- also reduces amount of scattered radiation.

- modern equipment have automatic variable beam limiting device with manual override.

GONADAL’THYROID SHIELDINGbeam should be so restricted that direct exposure of gonads does not occur.

- thyroid ,testes shield must have lead equivalent 0.5

mm. - ovaries should be shielded whenever possible.

MODIFIED SHIELDINGIn radiography of girls for scoliosis should be use PA view.

- Reduces breast dose at least 98 % without loss of radiographic quality.

HIGH KILOVOLTAGE :- - high kVp with low mAs delivers smaller absorbed

dose to the patient.

CAREFUL TECHNIQUE :- - to minimize repeat examination.

Radiographic examination in fertile women preferably performed during 1st 10 days following onset of menstrual period.

Ovulation and pregnancy are much less apt during this time than later menstrual cycle

PROTECTION IN MAMOGRAPHY

Skillful technique minimizes breast dose.

Goal achieved by molybdenum targets and filters in mammographic tubes.

Low dose screens and films, with/ without grid having ratios of 3:1 or 4:1.

Efficient breast compression device :- reduces breast thickness and make more uniform.

ADVANTAGES1. decreases exposure factors with reduction of dose.

2. diminished amount of scattered radiation thereby improving contrast.

3. improved recorded details by bringing breast closer to the image receptor.

CT SCANNINGDose in CT scanning , by measuring absorbed dose at the

center of one “slice” with small dosimeter in water phantom.

Scanning this slice and 3 adjoining slices on both side.

Dosimeter record dose from direct beam through the center slice, as well as scattered radiation from adjoining slices.

Collimator should also be checked periodically to assure its proper function.

PATIENT PROTECTION IN FLUORORSCOPYIntermittent fluoroscopy – decreases exposure and prolong

tube life.

Restriction of field size – must be limited by suitably lead shutters placed between tube and patient.

Correct operating factors – exposure decreases as kVp increases and mA is lowered.

Recommended factors are 90-100 kVp, 2-3 mA and 2.0 mm aluminium filter

The source-skin distance must be at least 15 inch with stationary and 12 inch with mobile fluoroscopic equipment.

Filtration :- – increase in hardness of x ray beam by filter. – Filter removed relatively more soft than hard x-

rays.

PROTECTON IN NUCLEAR MEDICINEMedical compounds containing radionuclide's are called

radiopharmaceuticals.

Types of radiation – alpha particles – beta particles – gamma rays

radiopharmaceuticals emits beta and gamma rays

Gamma rays are electromagnetic wave and have much greater penetrability than beta particle.

Beta particles consist of high-speed electrons.

Beta particles are much less penetrating ,their effect limited to the skin (external source) immediate vicinity(internal source).

AERB GUIDELINES

Step- by-step guidelines for submission of layout plan in diagnostic radiology facility

1) Decide a suitable room for housing an X-ray unit to facilitate the easy movement of staff and patient positioning.

2) Room should have preferably one entrance door and window if present, should be above 2m from the finished floor level outside the x-ray room.

3) Door should have a hydraulic mechanism to ensure that door is closed during procedure and should be provided with overlapping at the joints to avoid streaming.

4) Identify the walls as Wall A, Wall B, Wall C & Wall D (in any sequence)

5) Position the location of the equipment for each modality as follows:

a) Radiography and Fluoroscopy equipment: Couch, Control console and chest stand placed in such a way

that chest stand is on the opposite wall of the entrance door and the control console.

Mobile protective barrier with lead equivalent glass viewing window should be positioned in such a manner that the operator is completely shielded during the exposure.

Control console should be positioned as far away as possible from the x-ray tube.

b) Computed Tomography and Interventional radiology equipment: Gantry / C-Arm, Couch, Separate control console room, viewing window, - Position the gantry and couch such that the patient is completely visible from the control console, during the scanning - The entrance door to the gantry room from the control console shall have similar requirements as the patient entrance door.

c) Mammography/ OPG/ CBCT: Control console, Equipment and Protective barrier Positioning of equipment should be as far as possible from the door and the control console.

6) Decide on the material and thickness of walls and door by referring to equipment specific table.

7) Measure the distances of all the walls, doors, windows from the centre of the couch

8) Note that the required shielding of any material shall be provided at least up to the height of 2m from external finished floor of x-ray room

Dose Limits by AERB

The limits on effective dose apply to the sum of effective doses from external as well as internal sources. The limits exclude the exposures due to natural background radiation and medical exposures.

Calendar year shall be used for all prescribed dose limits

Occupational exposures

1. An effective dose of 20 mSv/yr averaged over five consecutive years (calculated on a sliding scale of five years);

2. An effective dose of 30 mSv in any year; 3. An equivalent dose to the lens of the eye of 150 mSv in a year; 4. An equivalent dose to the extremities (hands and feet) of 500 mSv in a year

and 5. An equivalent dose to the skin of 500 mSv in a year; 6. Limits given above apply to female workers also. However, once pregnancy

is declared the equivalent dose limit to embryo/fetus shall be 1 mSv for the remainder of the pregnancy.

Apprentices and Trainees The occupational exposure of apprentices and trainees between 16 and 18

years of age shall be so controlled that the following limits are not exceeded:

1. An effective dose of 6 mSv in a year; 2. An equivalent dose to the lens of the eye of 50 mSv in a year; 3. An equivalent dose to the extremities (hands and feet) of 150 mSv

in a year and 4. An equivalent dose to the skin of 150 mSv in a year.

Dose Limits for Members of the Public

1. An effective dose of 1 mSv in a year; 2. An equivalent dose to the lens of the eye of 15 mSv in a year; and 3. An equivalent dose to the skin of 50 mSv in a year.

ConclusionThe dosimetric quantity relevant to radiation protection is the dose

equivalent.

Harmful effects of ionizing radiation are classified as stochastic and non stochastic.

Effective dose equivalent limits for occupational and general population has been recommended by the regulatory board of that country

The values quoted for radiation workers are such that the hazards that the doses represent to health is small compared with ordinary hazards of life

A radiation worker is far more likely to be involved in a motor car accident an to suffer from ill effects of radiation,even if receiving the MPD.

THANK YOU !!!