Radiation Safety and Protection

8/13/2019 Radiation Safety and Protection

1/30

GUIDED BY DR.SONIA SODHI

DR.LATA KALE


2/30

The application of radiation protection principles,collectively known as health physics

The goal of health physics is to prevent the occurrence ofdeterministic effects and reduce the likelihood of stochasticeffects by minimizing the exposure of office personnel and

patients during radiographic Examinations


3/30

They are categorized as being derived from twosources: natural and artificial

Natural radiation source1.Cosmic radiationA. Primary cosmic radiation

B. Secondory cosmic radiation2. Terrestrial radiation3.Internal sources

Artificial sources1.Medical diagnosis and treatment,2.Consumer and industrial products and sources,

3.Other minor source


4/30

Natural or background radiation is the largest contributor(83%) to the radiation exposure of people

Background radiation from external and internal sourcesyields an average annual E of about 3 msv.

External Sources:External exposure results from cosmic and terrestrialradiation, both of which originate from theenvironment.(16%)

COSMIC RADIATION1. primary cosmic radiation: Cosmic radiation includesenergetic subatomic particles, photons of extraterrestrial

origin that reach the earth


5/30

2. Secondary cosmic radiation-the particles and photons generated by the interactionsof primary cosmic radiation with atoms and moleculesof the earth's atmosphere.at sea level the exposure from cosmic radiation is about 0.24mSv per year;at an elevation of 1600m (approximately 1 mile it is about 0.50mSv per year)at an elevation of 3200 m (approximately 2 miles, or the it is about 1.25mSv per year)

Cosmic radiation is also greater at higher latitudesCosmic radiation also includes exposure resulting from airline travel


6/30

TERRESTRIAL RADIATION.

Elements such as thorium, uranium, radium, RN-222, and K-40 are naturallyoccurring radioactive elements that can be found in our everyday lives.These elements can be found in:

rocks, soil and building materials food and water

Some sources are a result of ground nuclear testing,which is not naturallyoccurring.

Most of the gamma radiation from these sources

comes from the top 20cm of soil


7/30

SOURCES OF INTERNAL RADIATION:Radionuclides that are taken up from the externalenvironment by inhalation and ingestion.Radon, a decay product in the uranium series,is estimatedto be responsible for approximately 56% of the radiationexposure,

The ubiquitous noble gas radon (radon-222)is transportedin the water and air ,Radon decay products become attached to dust particlesthat can be deposited in the respiratory tract,Exposure tothis quantity lung cancer


8/30

ARTIFICIAL RADIATION

These may be categorized into three major groups-

1.medical diagnosis and treatment

2. consumer and industrial products and sources3.Other minor sources-

(which, in total contribute an average annual E of aboutO.6mSv)


9/30

Patient dose from dental radiography is usuallyreported as the amount of radiation received by atarget organ.The surface exposure, obtained by directmeasurement, is the simplest way to record a

patient's exposure to x raysRadiosensitive target organs commonly reported

include bone marrow, thyroid gland, and gonads.Patient dose has also been reported as the effectivedose E


10/30


11/30

PATIENT SELECTION:

Diagnostic radiography should be usedonly after clinical examination,

consideration of the patient's history andconsideration of both the dental and the general healthneeds of the patient.

Radiographic selection criteria, also known as high yield orreferral criteria, are clinical or historical findings thatidentify patients for whom a high probability exists that aradiographic examination will provide informationaffecting their treatment or prognosis .


12/30

The conduct of the examination may be divided into choice of equipment, choice of technique, operation of equipment, and processing and interpretation of the radiographic

image.


13/30

selection of the image receptor,focal spot-to-film distance,

x-ray beam collimation, filtrationthe type of leaded apron and collar.


14/30

INTRAORAL IMAGE RECEPTORS:Beginning with the letter designation "A," film speed hasalmost doubled with the introduction of each new speed groupCurrently, intraoral dental x-ray film is available in threespeed groups-D, E, and F.Clinically, film of speed group E is almost twice as fast(sensitive) as film of group D and about 50 times as fast asregular dental x-ray filmF-speed film requires about 75% the exposure of E-speed filmand only about 40% that of D-speed means that the 9-secondexposure required for regular film in 1920 has been reduced toabout 0.2 second with the use of E-speed film and 0.15second with F-speed film.


15/30

INTENSIFYING SCREENS:

use the rare earth elements gadolinium and lanthanumrare earth screens decrease patient exposure by asmuch as 55% in panoramic and cephalometricradiographyUnlike digital intraoral imaging, there is no significantdose reduction to be gained by replacing extraoralscreen-film systems with digital imaging.

Image resolution with digital systems appears toapproach that obtained with rare earth regular-speedscreens matched with T-Mat film


16/30

The combination of proper collimation and extended

source-patient distance (focal spot-to-film distance) willreduce the amount of radiation to the patient.Two standard focal spot-to-film distances (FSFDs)

have evolved over the years for use in intraoralradiography,one 20cm (8 inches) and the other 41 cm (16 inches).

Use of an FSFD longer distance results in a 32%reduction in exposed tissue volume. This is because atthe greater distance, the x-ray beam is less divergent


17/30


18/30

The use of a longer FSFD also results in a smallerapparent focal spot size and thereby theoreticallyincreases the resolution of the radiograph,

Collimation:

The tissue area (and volume) exposed to the primaryxray beam should not exceed the minimum coverageconsistent with meeting diagnostic requirements and

clinical feasibility.


19/30

limiting the size of the x-ray beam even more thanrequired by law may significantly reduce patientexposure. This results in not only decreased patientexposure but also increased image quality,

First, a rectangular position-indicating device(PID) may be attached to the radiographic tube housing,

Use rectangular rectangular PID having an exitopening of 3.5 x 4.4cm (1.38 x 1.34 inches) reducesthe area of the patient's skin surface exposed by 60%over that of a round (7 cm) PID


20/30


21/30

Low-energy photons,less penetrating power, areabsorbed mainly by the patient and contribute nothingto the information on the film.The purpose of filtration is to remove these low-energy

x-ray photons selectively from the x-ray beam. Thisresults in decreased patient exposure with no loss ofradiologic information,

When an x-ray beam is filtered with 3 mm ofaluminum,the surface exposure is reduced to about20% of that with no filtration.


22/30

The philosophy of radiation protection currently in practice,however, is based on the principles of ALARA(as low asresonably achievable). This philosophy recognizes, the

possibility that, no matter how small the dose, some adverseeffect may result.

Any type of ionizing radiation poses some risk. As exposureincreases, so does risk.Limit your exposure whenever possible. Try to:

Minimize the time exposed Maximize the distance from exposure

Use proper shielding

Leaded aprons are useful because they attenuate as much as98% of the scatter radiation to the gonads,Thyroid shields reduce the exposure of this gland by as much as92%


23/30

the decision of whether to use x rays when the patientis pregnant is an individual one.The patient should be made aware of both the need forradiographs and the relative magnitude of exposure

before any films are made.


24/30

A significant reduction in the number of unacceptable periapical films was found when film holders were usedinstead of patient manual support.

KILOVOLTOGE

The kilovoltage is decreased, the effective energy of the x-ray beam is decreased and radiographic image contrast

increases,The introduction of constant-potential (fully rectified),high-frequency or direct current (DC) dental x-ray units has made

possible the production of diagnostic-quality radiographs with lowerkilovoltage and at reduced levels of radiation.


25/30

MILLIAMPERE-SECONDS:Of the three technical conditions

(tube voltage, filtration, and exposure time), exposuretime has been shown to be the most crucial factor ininfluencing diagnostic quality.Optimal image density can be obtained by using valueslisted, after considering the age and physical stature ofthe patient


26/30

Every effort should be made so that the operator can

leave the room or take a position behind a suitable barrier or wall during exposure of the film.Brick walls must be of sufficient density or thickness

that the exposure to non occupationally exposedindividuals is no greater than 100 microGy per week.The operator should stand at least 6 feet from the

patient, at an angle of 90 to 135 degrees to the centralray of the x-ray beam


27/30

N i h h i h ld h ld h


28/30

Neither the operator nor patient should hold theradiographic tube housing during the exposureThe best way to ensure that personnel are followingoffice safety rules is with personnel-monitoringdevices.Commonly referred to as film bandges these devices

provide a useful record of occupational exposure


29/30


30/30

1) White and pharoh 5 th edition2) White and pharoh 6 th edition3) Hall EJ: Radiobiology for the Radiologist, ed 5, Baltimore,

2000, Lippincott Williams and Wilkins.

4) National Council on Radiation Protection and Measurements:Control of radon in houses, NCRP Report 103,Bethesda, Md,1989.

5) National Council on Radiation Protection and Measurements:Dental x-ray protection, NCRP Report 35, Bethesda, Md,

1970.6) National Council on Radiation Protecti9n and Measurements:

Exposure of the population in the U.S. and Canada fromnatural background radiation, NCRP Report 94, Bethesda, Md,1987.

Radiation Safety and Protection

Documents

Transcript of Radiation Safety and Protection