RADIATION PROTECTION

-By Lavina Jagtiani

RADIATION PROTECTION

Sources of radiation Exposure.

1) Natural Rediation• External sources Cosmic

Terrestnal

• Internal sources Radon Ingestion of food & water containing

radio nuclides2) Artificial radiation.

• Medical- x-ray diagnosis• Consumer & industrial products & sources

Radiation protection can be classified into:-1) General protection2) Protection of patients3) 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

radiographs which will help to avoid repeating the exposure.

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 equipmentsc) 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.

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.

• 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

•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.

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.

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.