Radioprotection

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Radioprotection - basics
of radiobiology -
3 LF UK Praha Dept. of
Radiology
2011
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X rays - electromagnetic ionizing radiation
Photons of X-rays are ionizing the irradiated
matter By physical and chemical mechanisms they
induce biological effects. Radiobiology There
are two basic kinds of biological effects
Stochastic ( or random ) effects on the
cellular level
target
theory Deterministic ( or nonstochastic )
effects on the tissue

level
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Stochastic effect Deterministic effect
Ef
Ef
D
D

• without threshold with threshold
• linear
  non-linear
• genetic effects -
  damage of tissues
• - carcinogenesis -
  radiation sickness

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Example skin reaction on irradiation by ionizing
radiation - gradaion of
deterministic effects
B Ef
First threshold erytema dose
hyperaemia reddness - a Second threshold
epilation dose pigmentation and epilation -
b Third threshold necrotic dose damage
of skin with necrosis - c
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Units of dose
Physics absorbed dose
Gray ( Gy ) J/kg 100 rad Radiobiology
and radiation protection effective dose
Sievert ( Sv ) Dabs . QF 100 rem
Note Dose equivalent or effective dose enables
to compare biological effects of different kinds
of ionizing radiations. QF (quality factor)
equals 1 for X-rays and gamma rays. Therefore
by X-rays 1 Gy 1 Sv. Doses in radioprotection
are expressed in Sieverts Doses delivered in
radiotherapy are expressed in Grays
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Irradiation of a man on earth surface
CR
Natural sources radon, natural radionuclides,
cosmic rays 83,6 Arteficial sources medical
exposures, nuclear plants, radioactive fallout,

professional exposures 16,4
Medical exposures Dg and Th RDG NM 9
1 CR yearly 1 mSv CR average year
exposure of inhabitant 3,3 mSv


(2000)
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Radiation protection in radiodiagnostics
In radiodiagnostics we protect against external
sources of irradiation only, unlike in nuclear
medicine

• Basic rule of radioprotection
• Eliminate entirely the deteministic effests
• Minimize the stochastic effects

Note In radiotherapy we use the deteministic
effects to kill the malignant cells, but the
damage to the neighbouring tissues should be as
small as possible.
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Radioprotection in radiological departments
is concerning
patients and medical personnel
Each country has it own legislation on radiation
protection, implemented from EURATOM
regulations and control organs State
Office of Nuclear Safety EU EC Dir.
97/43/EURATOM ( Medical Exposure Directive )
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LEGISLATIVA NA POLI RADIACNÍ OCHRANY
EU EC Dir. 97/43/EURATOM ( Medical Exposure
Directive ) CR zákon c.
18/1997 Sb., novela c. 13/2002 Sb.
" atomic law"
vyhláška SÚJB o radiacní ochrane c. 184/1997 Sb.
novela c. 307/2002 Sb.
Directive on radiation protection

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• DIAGNOSTIC and INTERVENTIONAL
• RADIOLOGY
• basic approach - ALARA
• exposure should be As Low As Reasonably
  Achieveble
• diagnostic benefit gtgt radiation risk
• Principles - justification
• - optimalisation

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Principle of justification Diagnostic
gain from radiological examination must be
greater then possible risk or radiation
All examinations utilizing X-rays conventional
radiodiagnostics and CT
must be correctly indicated
Responsible is an indicating physician, but
radiologist shares responsibility as well
EU Referral guidelines for imaging
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Vestník MZd 2003
Czech referral guidelines

• The indication to X-ray examination should
  consider also the age and gender of a patient and
  radiosensitivity of irradiated tissues

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Czech referral guidelines
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Referral guidelines
Appraisal of indicated method recommendation
1. Indicated 2. Indicated as specialised
examination 3. Non indicated as first
examination 4. Non indicated in routine 5. Non
indicated at all
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Classification of effective doses
for different radiological examinations
Class 0 IV.
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Examples of effective doses in common RDG exams
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Equivalent doses Rx of thorax 1
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• Principle of optimalisation
• Medical irradiation exposure must be as low
  as
• technically feasible to obtain the optimal
  image

Exposure values should be set correctly in order
to minimize the irradiation of the patient and of
the personnel.
Regular controls of all X-ray sources by the
radiographers and by licensed technicians to
ensure their stability and reproducibility
Technical standards of different examinations
Proper use of shielding and protective
devices Clinical audit
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X-ray examination
Dose is dependent of exposition kV, mA,
s filtration of a primary beam primary diaphragm
delimitation of the field sensitivity of the
film and of the intensifying screen distance
between the focus of the tube and the skin
Proper development of a film is important as
well !
Defective film must be repeated the dose is
doubled !
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Czech standard protocols of CT examinations
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(No Transcript)
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X-ray examination room must be shielded in order
to eliminate irradiation of persons in the
neighbouring rooms and labeled with warning
signs
lead or barium plaster - Pb equivalent

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Personal protectors - patient and personnel
aprons
Protectors are shielding against secondary rays
only ! Radiologists and radiographers should
never enter in a primary beam !
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Dose limits
Defined only for personnel Wholebody
irradiation 20 mSv/year This limit is
derived from stochastic effects of the secondary
radiations. Controle personal film dosimeters
centrally registered Eye lens
- 150 mSv/year Skin - 500
mSv/year These limits are derived from
deterministic effects.
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Protective dosimetry - personnel
film dosimeter
ring dosimeter
obligatory
interventional radiology
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Risk assessment in X-ray exposure

• In small doses risk of stochastic effects
• - on cellular level -
• expressed by effective dose (mSv)
• In greater doses risk of deterministic effects
• - on tissue level -
• expressed by organ dose (mGy)

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Risk assessment in radiation exposure depends on
many factors

• Absorbed dose
• External or internal irradiation
• Wholebody or localised irradiation
• Kind of radiation - nonionizing
• - ionizing (
  directly or indirectly)
• RBE of the respective radiation ( QF )
• Radiosenzitivity of the respective tissue
• Other age, gender (women in productive age)

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Risks in small doses exposure
radiodiagnostics stochastic effects
Effective dose
Risk lower than 0,1 mSv
negligible 0,1 1 mSv
minimal 1 10 mSv
very low 10 100 mSv
low
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X-ray examination should bring
MAXIMUM CLINICALLY RELEVANT INFORMATION FOR
THERAPEUTIC DELIBERATION WITH MINIMAL IRRADIATION
AND FOR AN ACCEPTABLE PRICE
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Approximative shortening of a lifetime from
different causes ( in days )

smoking
2400 30 excess of
weight
1560 trafic accidents
700 home
accidents
290 accidents at work

55 radon in buildings
50 natural
radioactivity
9 medical exposures

6 nuclear reactors accidents
0,02
( WHO 2003 )
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Thank you for attention !