RADIO

1. Dr. Pramod Kumar Gahwai

2.  The harmful effects of exposure to ionizing radiation
were largely unsuspected at the time of discovery of
xray.
 The acceptance by society of risks associated with
radiation is conditional on the benefits to be gained
from the use of radiation.

3. RADIATION HAZARDS
 RADIATION UNITS
 BIOLOGICAL EFFECTS OF RADIATION
 POPULATION EXPOSURES

4. DEFINITIONS
 ABSORBED DOSE- radiation necessary to deposit energy of 1
joule in 1 kg of tissue.(SI unit- Gray)
 ABSORBED DOSE EQUIVALENT- measure of biological
effectiveness of radiation.
ABSORBED DOSE EQUIVALENT = absorbed dose x quality
factor
 Quality factor – function of particle type and energy.
X rays, β particles,ϒ rays, electrons 1
thermal neutron 5

5.  The amount of energy deposited per unit length of travel
called LINEAR ENERGY TRANSFER.
Particle size α linear energy transfer α biological
damage
 EFFECTIVE DOSE equivalent (hε)- purpose is to relate
exposure to risk.
.

6. NATURAL RADIATION
External and internal sources
EXTERNAL SOURCES
 cosmic radiation, terrestrial gamma radiation.
 Exposure varies with latitude and altitude.
INTERNAL SOURCE
 Radionuclide's within the body.
 K40, Rb87, C14 and members of the thorium and uranium
series.
 Radon is largest contributor to avg annual effective dose
equivalent.

7. MEDICAL RADIATION
 Two category – 1. diagnostic medical x-rays, CT
2. nuclear medicine
 IN X RAY- 3 procedure provide > ½ of total dose (in mSv)
Barium enema - 4.0
Upper GI examination - 2.45
Lumber spine - 1.3
OTHERS-
 Thoracic Spine- 1.0
 Pelvis- 0.7
 Chest- 0.06

8.  In CT scan(mSv)-
- CT Head -2
- CT Chest- 7
- CT Abdomen/Pelvis -10
- Whole-Body CT Screening -10

9. EFFECTS
1. STOCHASTIC EFFECT
2. NONSTOCHASTIC EFFECT

10. STOCHASTIC EFFECT
 Defined as an effect in which the probability of occurrence
increases with increasing absorbed dose.
 severity does not depend on the magnitude of absorbed
dose.
 ALL OR NONE PHENOMENON, NO DOSE THRESHOLD.
 Example –cancers and genetic effects.

11.  Radium watch dial workers – bone ca.
 Uranium miners – lung ca
 Early medical radiation workers - leukemia
 Thymus gland treatment – thyroid ca
 Atomic bomb survivors – leukemia/breast, lung and
bone Ca

12. NONSTOCHASTIC EFFECTS
 Defined as somatic effect that increases in SEVERITY with
increasing absorbed dose.
 degenerative effects such as organ atrophy and fibrosis.
 Examples- lens opacification
blood changes
decreased sperm production

13. REGULATORY BODIES
ICRP – International Commission for radiation protection
is the international regulatory body.
AERB – Atomic Energy Regulatory board is Indian
regulatory body.
NCRP – National Commission for radiological protection
is the American counterpart .
.

14. FUNCTIONS
• Lay down norms for protection against radiation.
• Guidelines regarding the specification of medical x–
ray equipment, room layout of x– ray installation,
protective devices
• Responsibilities of the radiation personal, employer
and radiation safety officer
• Recommends the dose limits for radiation workers
and general public.
 Approval for new models of x– ray equipment.
• Registration, inspection and ISO certification

15. DOSE LIMITING RECOMMENDATIONS
 Atomic energy regulatory board (AERB) making
recommendations on limits of exposure to ionizing
radiation.
 There are 3 classes of individuals-
-occupationally exposed individuals
-the general public
-embryo-fetus

16. OCCUPATIONAL LIMITS
 For stochastic effects-
ANNUAL LIMIT- 50 mSv
 For lifetime dose equivalent limit(mSv) to the whole body
= 10 times of age (in yr) of individual
 For nonstochastic effect:-
- lens 150 mSv
- all other organ 500 mSv
 Worker exposed to x ray for their own medical diagnosis or
treatment does not count as an occupational exposure.

17. EMBRYO-FETUS
 Specific dose equivalent limit applies to the conceptus
(embryo + fetus), not to the mother.
 Recommended dose equivalent limit 5 mSv for entire
gestational period.
 Rate not exceeding 0.5 mSv in any one month.

18.  CNS – Exencephaly , microcephaly , skull
malformation & hydrocephalus.
 Ocular-absence of eyes, microphthalmia, absence of
lens, cataract.
 Skeletal malformation- stunting, cleft palate, spina
bifida

19. GENERAL PUBLIC
 When a member of general population eg. visitor enters a
radiation area , he becomes an occasionally exposed
individual.
 Annual dose limit-
- <1mSv - frequent exposure
- 5 mSv - infrequent exposure

20. ALARA CONCEPT
 ` As Low As Reasonably Achievable`
 For any given radiation source, magnitude of
individual doses, number of people exposed, and
likelihood of incurring exposures should be kept to
as low as reasonably achievable, taking economic
and social factors into considerations.

21. .
 Judicious use of investigation
 These include substituting non-ionizing
methods of examination in place of ionizing
radiation methods.
 Ex – Evaluation of LN status in the abdomen by
USG in place of repeated CT scan & use of colour
Doppler flow imaging in place of diagnostic
angiography.

22. PERSONNEL PROTECTION FROM EXPOSURE TO X
RAYS
RADIATION MONITORING
 Devices
- pocket dosimeter
- film badge
- TLD( thermo luminescent dosimeter)
TLD(principle):-depends on the ability of certain
crystalline materials to store energy on exposure to
ionizing radiation because of the trapping of valence
electron in crystal lattice defect.

23. Crystal (lithium fluoride) heated under controlled condition
↓
electrons return to normal state
↓
stored energy released in the form of light
↓
photomultiplier device
↓
initial radiation exposure

24. PROTECTIVE MEASURES
 Basic 3 principles:-
- exposure time
- distance
- lead barriers
 EXPOSURE TIME :- total dose equivalent α 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

25.  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.)
 Means if initial dose H 100 mSv and HVL is 1 mm Pb
for given kVp , then 1 mm Pb will reduces H to 50
mSv and second HVL of 1 mm Pb will reduce another
one- half(25 mSv).

26. PROTECTIVE BARRIERS IN RADIOGRAPHY AND
FLUOROSCOPY
 RADIATION SOURCES :-
- tube must enclosed in metal housing that
reduces leakage radiation ( is radiation which penetrates
the protective housing )
 WALL PROTECTION :- 4 type of radiation
- USEFUL BEAM – is radiation passing through tube
aperture (aka Iry radiation)
- LEAKAGE RADIATION

27.  SCATTERED RADIATION- undergone change in
direction during passage through matter.
 STRAY RADIATION – Scattered + leakage radiation
 There are 2 type of wall barriers-
Iry protective barrier - protects from useful
beam(mainly).
-In radiography upto 140 kV is about 1/16 inch
lead extending 7 feet up from the floor when tube is
5-7 ft from the wall.

28.  IIry protective barrier :- 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.
- leaded glass observation port in the control booth should
have same lead equivalent as the adjacent wall.
- leaded glass must 4 times as thick as lead sheet.

29.  Lead apron – worn in fluoroscopy room.
- Pb equivalent 0.5 mm.
 Check lead protective apron periodically for cracks by
means of a radiography test.

30. DOSE REDUCTION IN RADIOGRAPHY
 BEAM 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

31.  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.

32.  GONADAL ,THYROID SHIELDING :-
- beam 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.

33.  MODIFIED PROJECTION :-
- In radiography of girls for scoliosis should be use PA view.
- Reduces breast dose at least 98 % without loss of
radiographic quality.

34.  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.

35. PROTECTION IN MAMMOGRAPHY
 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.

36.  ADVANTAGE :-
1. decreases exposure factors with reduction of dose.
2. diminished amount of scattered thereby improving
contrast.
3. improved recorded details by bringing breast closer to the
image receptor.

37. CT SCANNING
 Dose in CT scanning , by measuring absorbed dose at
the centre 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
centre slice, as well as scattered radiation from adjoining
slices.
 Collimator should also checked periodically to assure its
proper function.

38. PATIENT PROTECTION IN FLUOROSCOPY
 Intermittent 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.
mm aluminium filter

39.  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
xrays.

40. PROTECTION IN NUCLEAR MEDICINE
 Medical compounds containing radionuclide's are called
radiopharmaceuticals.
 Types of radiation
– alpha particles
– beta particles
– gamma rays
 radiopharmaceuticals emits beta and gamma rays.

41.  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).

42.  PRINCIPLES:-
- Distance
- Shielding
- Time of exposure

43. DISTANCE: -
- In case of gamma rays inverse square law applies
for the purpose of protection in storage and handling.
- long forceps should be used.
- avoid spillage of liquids
- container should be as remote as possible.

44.  SHIELDING:-
- shield may be incorporated in the container itself
or it may be placed as a barrier around sources.
- γ emitting radiopharmaceuticals should be stored in their
container and surrounded with lead bricks (5 cm) on all
sides.
LEAD-SHIELDED SYRINGES – always be used for i.v.
injection.
- Disposable gloves should be worn to protect against
contamination by radionuclide's and by infection as well.

45.  Low energy β particles are absorbed by container ,
cornified layer of skin.
 Medical radionuclide P32 requires plastic such as
polystyrene.
 LENGTH OF EXPOSURE-
- faster procedure → less exposure

46. THANK YOU