3. Radiation protection can be classified into:-
1) General protection
2) Protection of patients
3) Protection of operator
General protection:-
Principle of ALARA should be followed. Radiation exposure should
be “AS LOW AS REASONABLY ACHIEVABLE”
1. Restrict the number of radiographs choosing the most appropriate
views required for a particular case.
2. The chosen technique should be properly executed and repetitions
must be avoided long cone technique helps to reduce patients
exposure.
3. Adequate filtration must be used which cuts off the long wave
photons that are not diagnostically useful.
4. Adequate combination must be used to restrict the size and the
shape of the x-ray beam.
5. Use optimum kvp.
6. Reduce the exposure time by using fast speed films and incensifying
screens.
7. Periodic maintenance of the x-ray machine to check for leakage is
recommended.
8. Good processing techniques must be used to obtain good quality
4. PROTECTION OF THE PATIENT:-
a) Before exposure:-
• Prescribing dental radiographs.
• The dentist uses professional judgment to make decisions
about the number of type of dental radiograph.
• A radiographic examination should never include a
predetermined number of radiographs, nor should radiographs
be taken at predetermined time intervals.
b) Proper equipments
c) Filtration:-
The x-ray beam united from the radiographic tube consists of not
only high energy x-ray photons but also may photons with relatively
cover energy how energy photons which have little penetrating
power, are absorbed mainly by the patient & contribute nothing to
the information of the image.
Purpose of filtration :- to remove these low energy x-ray photons
selectively from the x-ray beam which results in decreased patient
exposure with no loss of radiographic information.
5. Collimation:-
•Collimation is used to restrict the size and shape of the x-ray beam and to reduce
patient exposure.
• A rectangular collimator restricts the size of x-ray beam to an area slightly larger than
a size 2 intraoral film & significantly reduces patient exposure.
•Use of intensifying screens reduces patient exposure.
•Lead aprrons (2mm thick lead) can be use to drap the patient during exposure special
care must be taken in case of pregnant women.
A film holding device
•Helps to stabilize the film position in the mouth and reduce the chance of the
movement
• Its eliminates the need for patient to hold the film in place and therefore , the patients
figure is not exposed to unnecessary radiation
Lead goggles and lead couars can be used to protect the thyroid gland
and the cymphnodes
After exposure:- proper film handling.
6. • from the time films are exposed until they are processed; care full
handling is crucial .
•Proper film processing limit patient exposure to radiation.
Protection of the operator:-
1. Dentist are instructed not to hold the film in the patients mouth
Repeated exposure of dentist wet figures to radiation can lead to
hazardous consequences.
2. Include recommendation on distances, position and shielding
Distance recommendations :-
• Maintain adequate distance during exposure.
• The dental radiographer must stand at least 6 feet away from the x-ray
tube head during exposure
• Should not stand in the direction of the central ray ie aways stand behind
the x-ray tube .
Position recommendation:-
• To avoid the primary beam, which travels in a straight line , the dentist
must be position perpendicular to the primary beam or at 90 degree to
135 degree to the primary beam
7. •Use of lead barrier or partition between the dentist and the x-ray
machine is desirable while making the exposure.
•While screening ,a lead apron must be worn
•Filtration , collimation and suitable KVp must be used during
every exposure
•Dentist must work in well ventilated room
•Monitoring:-
it is periodic and the continuous determination of radiation dose in an
area or received by a person.
Personal monitors are of 3 types:-
•Pocket Dosimeter
•Film badge
•Thermo luminescent dosimeter(TLD)
Pocket Dosimeter:-
It has a quartz fiber mounted ion a house – shoe shaped bar and the
complete assembly is mounted in the sensitive chamber of the dosimeter
when it is exposed to x-rays; the quartz fiber loses its positive charge &
starts moving away from the zero position hence direct reading can be
taken.
8. Film badge:-
A dental film is placed in a film badge having a number of windows.
These windows have a different metallic filters . At the end of two
months the film is sent to a radiation protection services where it is
developed and depending upon the density; the radiation exposure is
calculated.
Advantage:
Different types of radiations energies can be recorded using a film
Badge
Disadvantage:
Accuracy is only 10-50%
THERMO LUMINESCENT DOSIMETER(TLD)
In this dosimeter crystalline substance like lithium fluoride or calcium
sulphate diphosphur is used. This crystals undergo ironic changes
when exposed to x-ray and subsequently when the crystals are heated
in a special containers they give out visual light after heating. They are
called as thermoluminescent crystals. The amount of light is measured
which is proportional to radiation exposure received.
9. Advantages:-
1) A wide range of exposures are detected.
2) Accuracy is upto 30%
3) Response is almost similar to human tissues.
4) Direct reading available at any time.
5) Response is independent of radiation energy.
6) It can be incorporated in jewelry.
7) Lithium fluoride crystals can be reused.
