Radiation Hazards

and
Radiation Protection
Prepared by:
Lecturer of Oral & Maxillofacial
Radiology
• Radiation Biology
• Radiation Terminology
• Radiation Chemistry
• Radiation Protection
What Should the Dentist
Do?

1. Careful Selection of dental

radiograph
2. Routine radiograph is
unaccepted (a detailed
evaluation of the patient's need
for radiographs)
3. Experienced clinician with
sufficient knowledge.
 Radiation Hazards

Radiation Biology
 Radiation Biology

Types of Radiation
Natural Artificial

For example; For example;

❖Cosmic rays ❖Nuclear power
❖Radioactive elements ❖Atomic bombs
❖Medical x-rays
Types of Radiation

Tiny particles Waves of pure energy

Electrons, Protons, photons
Neutrons, Beta and Combination of electric
Alpha particles and magnetic fields
• Mass
• Charge except • Ionizing: cosmic rays,
neutrons X-rays, gamma rays
• Very high velocity
• Not used in dentistry • Non-ionizing:
ultraviolet, visible
light…
Types of Radiation

• Ionizing: cosmic
rays, X-rays, • Non-ionizing:
gamma rays ultraviolet,
visible light
Alpha Particles
• Atomic nuclei consisting of 2 protons and 2
neutrons
• Positive charged
• Emitted from naturally occurring heavy metals
(e.g uranium) or man-made elements
• Large in size
• Slow velocity
 Beta Particles
• Electrons ejected from nuclei of radioactive
atoms
• Fast moving
• Smaller than alpha particles
Cathode Rays
• Electrons originate in an x-ray tube
• Fast moving
 Neutrons

• Result from splitting of certain atoms inside a

nuclear reactor
 Cosmic Radiation
• Energetic particles (esp. protons) which
bombard the earth from outer space
• Intense at higher altitudes than at sea level
Electromagnetic Spectrum
X-rays and Gamma rays
• High energy ionizing electromagnetic radiation
• Pure energy photons with no mass and no charge
• Transmit in waves
• Great penetrating power

Generally produced Emitted from the nuclei

artificially of radioactive atoms
Power of Penetration
Radiation Hazards

Radiation Terminology
Exposure

Measurement of ionization in air produced by

x-rays

Dose
Amount of energy absorbed by a tissue
Dose Equivalent
• Measurement of the biologic effects of different types of
radiation
• Equal absorbed dose of different types of radiation produce
different amount of biologic damage

Dose Equivalent = Dose x Radiation Weighting Factor

Effective Dose Equivalent

• Assess the biological risks of radiation to a particular

part of the body
• As some parts of the body are more sensitive than
the others (Radiosensitivity)

Effective Dose Equivalent = Dose Equivalent x Tissue

Weighting Factor
Units of Radiation Measurements
Traditional System Systeme International (SI)

Old New
▪ Roentgen (R) Coulomb/Kg ▪
▪ Rad Gray (Gy) ▪
▪ Rem Sievert (Sv) ▪
Radiation Hazards

Radiation Chemistry
Tissue Damage

Direct Indirect

➢ Radiation
➢ Ionization ➢ Radiation
➢ Unstable Free Radicles ➢ Radiolysis of Water
➢ Dissociation or Cross- ➢ Unstable Free
linking Radicals
➢ Biologic Change ➢ Biologic Damage
 Indirect

Direct
 Radiation Chemistry

Classification of the Biological Damaging

Effects
According to

A. Type of cells affected

B. Time of appearance of the damage
C. Dose absorbed
A. Depending on Type of Cells affected

Somatic effects Genetic effects

Somatic cells affected Germ cells of reproductive
system (sperms and ova)
Seen in irradiated person Not

Not Transmitted to future

generations
 Radiosensitive

high medium low

Bone marrow Skin Muscles

Spleen Mesoderm Bones
Thymus organs Nervous system
Lymphatic
Gonads
Eye lens
B. Depending on Time of appearance of the
Damage
Short term effects (acute) Long term effects
(chronic)
Seen within minutes/days/weeks Seen after years or generations

Associated with large amounts of Associated with small amounts of

radiation in a short time (nuclear radiation over a long time
bomb)

Eg: acute radiation syndrome Eg: induction of cancer, birth

abnormalities
→ Not applicable in dentistry
C. Depending on Dose Absorbed
Deterministic Stochastic
(Non stochastic)
Has a dose threshold: Has no dose threshold (any dose)
Below it: no effect seen
Occurs with large doses All or none
(has the condition or not)

Severity proportionate to dose Severity does not depend on dose

Eg: oral changes, erythema, hair Eg: induction of cancer, genetic

loss.. mutation
Sequence of Radiation Injury

Latent • Time between exposure & visible signs

• Length of time depends on Dose & Dose rate
Period
Period of • Cell death, change in cellular function,
Injury abnormal mitotic activity….

Recovery • Cells repair damage

• Unrepaired damage → accumulates →
Period Cummulative effect of radiation → cancer,
birth defects..
End Results of Radiation Damage
• Ionization alters the structure of the
Reversible cells but has no overall damage
and the cells return to normal

• Cells are affected so that another

Conditional similar or smaller dose will cause
damage

Irreversible • A permanent damage has occured

Factors determining the Magnitude
of Damage
Radiation Factors Host Factors
• Type of radiation • Variation in species
• Total dose • Intrinsic resistance
• Dose rate of the organism
• The volume of tissue • Oxygen effect
irradiated • Tissue sensitivity
• Age
 Immature

Not Specialized

Rapidly Dividing

The exception to this are LYMPHOCYTES which are highly

specialized and do not divide, yet they are considered the most
sensitive to radiation. (Thyroid)
Radiation Protection
 The most important requirement for maintaining
satisfactory standards of radiation protection is to
ensure that the x-ray apparatus in a good order:

- All x-ray apparatus should be

served at least every 3y
- More than 20y old apparatus
need special attention
- Discourage the use of apparatus
operating below 60 KVp
Aims of Radiation Protection
• No practice is adopted unless it is beneficial
• ALARA principle
Radiation Protection
I. Protection of the Patient

II. Protection of the Operator

III. Protection of the Environment

 Radiation Protection

Protection of the patient

Protection of the Patient
Before Exposure After Exposure
1) Patient Selection 1) Processing of the Film
2) Choice of Equipment 2) Interpretation of the
3) Choice of the Technique Image
4) Adjusting Exposure
parameters
5) Quality Assurance
Measures
6) Continuing Education
Patient Selection
• Whether the patient needs it or not

• Careful choice of the technique of the

radiograph
Choice of the Equipment
a) Receptor Selection
b) PID
c) Collimation
d) Filtration
e) Timer
f) Lead Apron & Thyroid Collar
g) Film Holders
 Equipment
Receptor Selection
• Film Speed
• Analogue or Digital
• Intensifying Screen
 Equipment

Position Indicating Device

Shape Length
• Conical • Short
• Round • Long
• Rectangular
 Equipment

Collimation
• Circular
• Rectangular
• Slit (Panoramic)
 Equipment

Filtration
• Remove the low energy x-ray photons which
results in decreased patient exposure
• Machines operating below 70 kVp need 1.5mm Al
while those at or over 70 kVp need 2.5mm Al
 Equipment

Timers
Electronic timers are preferred than mechanical
one as they provide very short time adjustments
(fractions of a second)
 Equipment
Lead Apron & Thyroid Collar
• Although scatter radiation to the patient's abdomen is extremely
low, leaded aprons should be used to minimize patient's exposure
to radiation
• Leaded thyroid collars are strongly recommended
• Leaded aprons are useful because they attenuate as much as 98%
of the scatter radiation to the gonads . Similarly, thyroid shields
reduce the exposure of this gland by as much as %92
• They are made of 0.5 - 1 mm
 Equipment

Film Holder
• Direct protection
• Indirect protection (decrease the need for
retakes)
Choice of the Intraoral Technique
• Bisecting Angle
• Paralleling
Adjusting the Exposure Parameters
A) Kilovoltage A kVp best suited to the diagnostic
purpose should be used. The range of 70 to 90
kilovolt peak is suitable for most purposes

B) Milliampere-second Exposure should be

established for optimal image quality. Patient
exposure is directly proportional to mAs which
effects image quality (density)
Quality Assurance
• For the x-ray Machine

• For the Films

• For the Dental Office

Continuing Education
Practitioners should stay informed of new
information on radiation safety issue, as
well as developments in equipment,
materials and techniques
After Exposure
Processing the Films Interpretation of the Image

• Darkroom • Semi-darkened room

• Safe light • Viewers
• Automatic processor • Magnifying lens
 Radiation Protection

Protection of the Operator

Protection of the Operator
Guidelines Monitoring

1) The primary beam a) Equipment monitoring

2) The scattered radiation b) Personal monitoring
from the patient
3) The leakage radiation
from the tube housing
 The Primary Beam
• Never stand in the path of the useful beam

• Never hold the film in the patient’s mouth

The Scattered Radiation from the Patient
• Minimum distance of 6 feet (1.8 m) away
from patient behind the x-ray tube at an angle
90- 135 degree to the central rays
The Scattered Radiation from the Patient

• If he should stand closer than 6 feet form the patient

or machine he should stand behind a wall shielding
(drywalls are sufficient for the average dental
office) or lead barriers with glass: leaded windows
should be used with a 2m cable timer
 The Leakage Radiation from the Tube
Housing

• This problem is limited in recent machines

• The operator must never hold the tube head

during exposure to avoid exposing himself to
this leaking radiation
Equipment Monitoring

Radiation leakage of the machine can be

examined by using a film device that can
be obtained from the manufacturers
Personal Monitoring
• Film Badges
• Thermoluminescent Dosimeters (TLD)
• Ionization Chambers (Pocket Dosimeters)
❖ Self Reading
❖ Non Self Reading
 Radiation Protection

Protection of the Environment

 Protection of the Environment
1. The 1ry beam must never be directed to anyone
other than the patient

2. The patient should be seated so that the x ray

beam is aimed at the shielded wall not to a door
or any other opening
Protection of the Environment
3. Workers in the areas adjacent to the operating room should
wear monitoring devices
4. Radiation survey:
➢ Walls must be made of 3 “ solid concrete, ¾ “ steel or 1
m lead
➢ Geiger Muller detector can detect any radiation leakage
(survey instruments)
Protection of the Environment
5. Radiation signs and warning lights
What Should the Dentist
Do?

1. Careful Selection of dental

radiograph
2. Routine radiograph is
unaccepted (a detailed
evaluation of the patient's need
for radiographs)
3. Experienced clinician with
sufficient knowledge.