NAME: SAR BARI SAHA.

AIMS OF RADIATION PROTECTION

INTRODUCTION

There are various Regulatory Bodies at the international and National level, which lay down norms for radiation protection.

1. International Commission for Radiation Protection ( ICRP)

2. National Commission for Radiation Protection (NCRP ) in America

3. Atomic Energy Regulatory Board (AERB) in India.

HISTORY

ICRP was formed in 1928 on the

recommendation of the first International

Congress of Radiology .

It also initiated the birth of the ICRU or the

International Commission on Radiation Units

and measurements.

The AERB was constituted on November 15,

1983.

SOURCES OF RADIATION

Natural background radiation

• Terrestrial

• Radioactivity

• Cosmic radiation

• Radio nuclides

Man made radiation

• Medical

• Occupational exposure

• Radioactive Discharge

• Consumer products

AIM OF RADIATION

PROTECTION

PREVENT OCCURRENCE

OF DETERMINISTIC

EFFECTS

MINIMIZE STOCHASTIC

EFFECT

OBJECTIVE OF RADIATION

PROTECTION

“The goal of radiation protection is to prevent the occurrence of serious radiation induced conditions in exposed persons and to reduce stochastic effects in exposed persons to a degree that is acceptable in relation to the benefits to the individual and to society from the activities that generate such exposure” (NCRP).

“Current standards of protection are meant to prevent occurrence of deterministic effects by keeping doses below relevant thresholds and ensure that all reasonable steps are taken to reduce induction of stochastic effects” (ICRP).

“The overall objective of radiation protection is to provide an appropriate standard of protection for man without unduly limiting the beneficial practices giving rise to radiation exposure”(ICRP).

BIOLOGICAL EFFECTS

DETERMINISTIC EFFECT

One which increases in severity with increasing

absorbed dose in affected individuals.

Appear at high doses > 0.5 Gy

Result from cell death

Threshold dose

E g: skin erythema, dry skin, organ atrophy,

cataract induction…

STOCHASTIC EFFECT

One in which the probability of occurrence

increases with increasing absorbed dose.

Important at low doses <0.5 Gy.

Severity is independent of the radiation dose.

E g : carcinogenesis

Somatic effect

The radiation effects, produced in an exposed individual during his life time.

Genetic effects

The radiation effects, produced in the successive generation of the exposed individual.

FETAL RISK

10 days early intrauterine death

20-40 days congenital abnormalities

50-70 days microcephaly

70-150 days growth & mental retardation

After 150 days childhood malignancies

Depend on the gestation period of the pregnant woman.

PRINCIPLES OF RADIATION

PROTECTION

1) Justification of practice :No practice involving

radiation exposures shall be adopted unless it

produces a net positive benefit

2) Optimization : Every effort shall be taken to

reduce the dose as low as reasonably achievable

, considering the clinical , social and economic

factors

3) Dose limits : the effective doses to the individuals

shall not exceed the limits recommended by the

commission

This could be achieved by

• By setting limits well below threshold dose to

deterministic effects.

• The probability of stochastic effects could be

reduced by limiting exposures as low as reasonably

achievable (ALARA)

ALARA CONCEPTS

• Reasonably Achievable aspect implies a balancing of benefit (risk reduction) Vs cost( financial and social)

Approach:

1. Planning radiology dept.in advance of construction.

2. Promoting awareness in the department

PROTECTIVE MEASURES

Cardinal principles of radiation protection:

1. Minimize the Exposure Time

2. Maximize the Distance - Inverse Square Law

3. Maximize the shielding/Barriers - usually lead or concrete

CLASS OF EXPOSED INDIVIDUAL REMS mSv

Occupational exposure

Stochastic effects

Non stochastic effects

lens of eye

other areas

Lifetime cumulative exposure

5

15

50

1(×age in yrs)

50

150

500

10 ( ×age in yrs)

Public exposure

Effective dose eq. limit

Dose eq. limits for lens, skin &

extremities

0.5

5

5

50

Trainees under 18yrs of age

Effective dose eq. limit

Dose eq. limits for lens, skin &

extremities

0.1

5

1

0.5

Embryo-fetus exposure

Total dose eq. limit

Dose eq. limit in a month

0.5

0.05

5

0.5

NCRP Recommendations for Radiation Dose Limits

NEW RECOMMENDATION

Limit for Life

time exposure = age x 1 rem

An individual’s lifetime effective dose equivalent should not exceed the value of age in years

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