Effects of radiation on health and how to prevent them

1. Radiation Hazard
We Know it.
But, we didn’t much concern about it.
Presented by:
Capt. Soe Moe Htoo
Radiologist
Radiology Dept. ,DSLH

2. OBJECTIVE
• To become familiar with the mechanisms &
biological effects following exposure to ionizing
radiation.
• To be aware of the risks of ionizing radiation .
• To know main safety issues of protection.

3. RADIATION
• Radiation is the energy that comes from a source
and travels through some material or space as
waves or photons.

4. Ionizing Radiation
• Radiation that can cause specific changes is called
ionizing radiation (>10ev)
• Has enough energy to break chemical bonds.
• Interaction with matter produce ions.
Non-Ionizing Radiation
• Radiation that does not have enough energy to
break chemical bonds but can vibrate atom.
• Low-energy radiation e.g. sound waves, visible
light, microwaves
• Cannot produce ions.

5. Radiation Sources

6. UNITS OF RADIATION
Roentgen (R)
• Radiaton exposure in a volume of air.
Rem
• It is the unit of effective dose.
• Used only in radiation protection.
• The SI unit is Sievert
• 1 Sv= 100 rem
• 1 mSv = 0.001 Sv = 0.1 rem

7. Linear Energy Transfer (LET)
• The average energy deposited per unit length of
track.
• Measured in kiloelectron volts per micron
• Low mass, increased travel distance (gamma rays, X
rays).
• Large mass, decreased travel distance (alpha
particles, protons, low energy neutrons).
• Causes dense ionization along its path with a high
probability of interacting directly with DNA

9. Radiation Effects

10. Outcomes after cell exposure
DAMAGE TO
DNA
DAMAGE
REPAIRED
CELL DEATH
(APOPTOSIS)
TRANSFORMED
CELL
Viable Cell
Non-Viable
Cell
Cancer?

11. Reactions Within Body
• Reactions produce
1. free electrons e-
2. ions H- and OH-
3. free radicals H* and OH*

12. Free Radicals
• A free radical is an atom or molecule that has an
unpaired electron in its valence shell.
• Pair with electrons from other atoms, including
those that make up the DNA molecule.

13. Direct Action
• Causes damage directly to DNA or other important
molecules in the cell.
• More likely when the beam of charged particles
consist of alpha particles, protons, or electrons

14. Indirect Action
• Causes damage by interacting with the cellular
medium producing free radicals which then
damage the DNA molecule.
• More likely when x-rays or gamma-rays compose
the beam.

16. Chromosome deletion
Chromosome translocation

17. Radiosensitivity
• Actively reproducing cells are more radiosensitive
than mature cells.
• During mitosis, the cell is in a stressed state and
shows an increase in damage caused by radiation.

18. Radiosensitivity
HIGH MEDIUM LOW
Bone marrow
Spleen
Thymus
Lymph nodes
Gonads
Eye lens
Lymphocytes
Skin
Mesodermal
origins (Liver,
heart, lungs, …)
Muscle
Bones
Nervous system

19. Dose-Response Relationships
• Two effects of radiation exposure:
• Deterministic (threshold)
• Stochastic: cancer

20. Non-Stochastic
(Deterministic)
Effects
• Occurs above threshold
dose
• Severity increases with
dose
• Alopecia (hair loss)
• Cataracts
• Erythema
• Radiation Sickness
• Temporary Sterility
Stochastic
(Probabilistic)
Effects
• Occurs by chance
• Probability increases
with dose
• Carcinogenesis
• Mutagenesis
• Teratogenesis

21. Effects in eye
• Eye lens is highly RS.
• Coagulation of proteins occur with doses greater
than 2 Gy.
• There are 2 basic effects:
Effect Sv single exposure Sv per years for
many years
Detectable
opacities
0.5 – 2.0 > 0.1
Visual impairment
(Catarct)
5.0 > 0.15

22. 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

23. Symptoms of Acute Radiation Sickness
• Hemopoietic: 3-8 Gy LD50/60 radiation damages
precursors to red/white blood cells & platelets:
eg. Chernobyl personnel (203 exhibited symptoms,
13 died)

24. Gastrointestinal : >10 Gy
• radiation depopulates GI epithelium (crypt cells)
• abdominal pain/fever, diarrhea, dehydration
• death 3 to 10 days (no record of human survivors
above 10 Gy) examples include Chernobyl
firefighters
Cerebrovascular : > 100 Gy
• death in minutes to hours

25. Radiation Protection

26. RADIATION PROTECTION
• Based on two components.
• A) JUSTIFICATION.
• B) OPTIMIZATION.

27. JUSTIFICATION
• Applications of ionising radiation are only justified
when they provide a net benefit with minimization
of risks of radiation for people.

28. GUIDELINES FOR REFERRING
PHYSICIANS:
1) Repeating investigations which have already been
done
2) Investigation when results are unlikely to affect
patient management
3) Investigating too often: i.e. before the disease
could have progressed or resolved
4) Doing the wrong investigation
5) Failing to provide appropriate clinical information
& questions that imaging Investigation should
answer.

29. 0.01 mSv
0.5 CXR
0.02mSv
1 CXR
0.07 mSv
3.5 CXR
1.3mSv
65 CXR
0.7mSv
35 CXR
1.0mSv
50 CXR
2.5mSv
125 CXR
3.0mSv
150 CXR
7.0mSv
350 CXR

30. 2.3mSv
115 CXR
8.0mSv
400 CXR
10mSv
500 CXR

31. 4 mSv
200 CXR
15 mSv
750 CXR

32. THYROID SCAN
1.0 mSv
50 CXR
RENAL SCAN
1.0 mSv
50 CXR
LUNG PERFUSION SCAN
1.0 mSv
50 CXR
BONE SCAN
4.0 mSv
200 CXR
FDG PET (HEAD)
5.0 mSv
250 CXR
CARDIAC GATED
6.0 mSv
300 CXR

33. ALARA PRINCIPLE
OPTIMIZATION
• Once a practice is justified, the exposure to ionising
radiation should be kept as low as reasonably
achievable (ALARA).

34. FUNDAMENTAL PRINCIPLES OF
RADIATION PROTECTION
1. Distance.
2. Exposure time.
3. Barriers & Shielding.

35. DISTANCE
INVERSE SQUARE LAW:
• Intensity of radiation is inversely proportional to
the square of the distance from the source of
radiation.
• For Example: If the dose is 9 R at 3 feet, stepping
back to a distance of 6 feet will cause the dose to
decrease to 2.25 R.

36. EXPOSURE TIME
• The amount of radiation received is proportional to
the length of the exposure time.
• Minimized by conducting procedures as quickly as
possible.
• For Example, using short bursts of fluoroscopy.
• Employing image intensifiers & Intensifying screens.
• Using high kVp , low mAs techniques.

37. BARRIERS & SHIELDING
• Most commonly used protective material  lead.
• High density and high atomic number
• Lead equivalent: thickness of lead which provide
the same degree of protection as the material.
ROOM SHIELDING:
• Should be located as far as away from areas of high
occupancy and general traffic.
• Wall on which primary beam falls should not be
less than 35 cm thick brick or equivalent.
• Shielding of 1.7mm lead (23 cm brick) in front of
doors & windows of x-ray room.

38. X-RAY CONTROL ROOM:
• Walls & viewing windows of
control booth should have lead
equivalent of 1.5 mm.
• Distance between control panel
& X-ray unit / chest stand should
be minimum 3 meters.

39. PATIENT WAITING ROOM:
• Provided outside X-ray room a
proper warning signal when unit
is in use.
• Warning devices may include
audible and visual signs.

40. LEAD APRON
• Typically thickness of 0.5 mm lead equivalent is
used.
• Weight ranges from 2.5 to 7 kg.
• Should cover much of red bone marrow & breast.

41. LEAD GLOVES
• Lead salts or metallic lead are added to rubber or
plastic.
• Lead equivalent of these is about ¼ mm.

42. LEAD GLASS
• Made by adding lead salts to silicates , in the
manufacturing of glass.
• It is acceptably transparent and a better protective
material.
• Contains 60% of lead by weight.

43. GONADAL SHIELDING
• Must be 0.5 mm of lead.
• Must be used when gonads will lie within 5 cm of
the collimated area.
• Separate male vs. female shielding available.
MALE GONADAL SHIELD
OVARIAN PROTECTION

44. THYROID COLLER

45. • Have standard projections for specific indications.
• Additional views - on a case-by-case basis
• Use PA projections, where practical, for chest and spine
radiographs.
• Avoid repeating exposures.
• Use safe exposure factors – high KVp and low mAs
technique.
• Never stand in the primary beam.
• Always wear protective apparel when not behind a
protective barrier.
• Always wear a radiation monitor and position it outside
the protective apron at collar level.
• The person holding the patient must wear protective
apron and if possible gloves.
• Always collimate to smallest field size appropriate to
examination.

46. Summary
• Ionizing radiation use should be only used
when benefit outweighs possible risks.
• Every examination should be Justified.
• Optimized protocols for lowering patient dose
without affecting accurate diagnosis should be
done.
• Use all kinds of radiation protection during
work...It's your life.!

48. THANK YOU…
HAVE A NICE DAY!