BY SAMAD

PG I YEAR DEPT. OF ORAL MEDICINE AND RADIOLOGY

RADIATION PROTECTION

Contents

• Introduction• Patient protection measures• Operator protection measures• Enviornment protection measures• Radiation exposure guidelines• Radiation protection and patient education• Conclusion• References

Introduction

• Many of the early pioneers in dental radiography suffered

from the adverse effects of radiation.

• Some pioneers lost fingers, limbs, and ultimately their lives to

excessive doses of radiation.

• Hazards of radiation are well documented, and radiation

protection measures can be used to minimize radiation

exposure to both the dental patient and the dental radiologist.

• X-radiation causes biologic changes in living cells and

adversely affects all living tissue.

• Use of proper patient protection techniques, the amount of x-

radiation received by a dental patient can be minimized.

• Patient protection techniques - Before,

During,

After x-ray exposure.

Patient protection measures

• Before Exposure

• Patient protection measures can be used before any x-

radiation exposure.

• Proper prescribing of dental radiographs and the use of

equipment can minimize the amount of x-radiation that a

dental patient receives.

• PRESCRIBING DENTAL RADIOGRAPHS

• First important step in limiting the amount of x-radiation

received by a dental patient - proper prescribing, or

ordering, of dental radiographs

• Dentists (should) exercise professional judgment when

prescribing diagnostic radiographs for dental patients.

• Diagnostic radiography should be used only after clinical

examination, consideration of the patient's history and

consideration of both the dental and the general health

needs of the patient.

• PROPER EQUIPMENT

• Another important step in limiting the amount of x-

radiation

• Dental x-ray tube head must be equipped with appropriate

aluminum filters, lead collimator, and position-indicating

device.

• FILTRATION

Purpose of filtration is to remove low-

energy x-ray photons resulting in

decreased patient exposure with no

loss of radiologic information

Two types of filtration

1.Inherent filtration and

2.Added filtration.

• Inherent Filtration : takes place when the primary beam

passes through the glass window of the x-ray tube, the

insulating oil, and the tube head seal.

• Approximately 0.5 to 1.0 millimeter (mm) of aluminum.

• Added Filtration : refers to the

placement of aluminum disks in the

path of x-ray beam between the

collimator and the tube head seal.

• Aluminum disks added to the tube head

in 0.5-mm increments.

• Total Filtration - Inherent Filtration + Added Filtration

• Dental X ray machines - at or below 70 (kVp) require a

minimum total of 1.5 mm aluminum filtration.

• Above 70 kVp require a minimum total of 2.5 mm

aluminum filtration

• Filtration of the x-ray beam results in higher energy and

more penetrating useful beam.

• Disadvantage of using filters - 1. Increase exposure time

2.Decrease in the contrast

• COLLIMATION

• Restrict the size and shape of the

x-ray beam and reduce patient

exposure.

• Collimator, or lead plate with a

hole in the middle, is fitted

directly over the opening of the

machine housing where the x-

ray beam exits the tube head .

• Collimator may have either a round or

rectangular opening .

• Rectangular collimator restricts the size of

the x ray beam to an area slightly larger than

size 2 intraoral film and significantly reduces

patient exposure.

• Circular collimator produces a cone-shaped

beam - 2.75 inches in diameter, considerably

larger than a size 2 intraoral film.

• when the x-ray tube is operated above 50kVp -

x-ray beam should be collimated so that the field of

radiation is"contained in a circle having a diameter of no

more than 7 cm (2 3/4 inches)”.

• Coliimation decreases

Risk of radiation,

Minimises scattered radiation and

Decreases the fog, with a sharper image and better contrast

• POSITION-INDICATING DEVICE OR CONE

• Extension of the x ray tube head used to direct the x-ray

beam.

• Help to minimize the volume of tissue irradiated

• Increase the target film distance by using longer position

indicating devices to direct the X ray beam.

• Three basic types of PIDs:

(1) Conical,

(2) Rectangular,

(3) Round.

• Conical PID appears as a closed,

pointed plastic cone.

• x-rays exit from the pointed cone,

penetrate the plastic and produce

scatter radiation- no longer used in

dentistry

• Open-ended and lead-lined rectangular

or round PIDs are used -do not produce

scatter radiation.

• Available in two lengths: short (8 inch)

long (16 inch).

• long PID is preferred

because less divergence of

the x-ray beam occurs .

• Rectangular type is most

effective in reducing patient

exposure.

• During Exposure

Thyroid collar,

Lead apron,

Fast film,

Film-holding devices

limit the amount of radiation received by the patient.

• Exposure factors and good technique - further protect the

patient from excess exposure to x-radiation.

• THYROID COLLAR

• Flexible lead shield placed securely around

the patient's neck to protect thyroid gland -

scatter radiation.

• Separate shield or part of lead apron -

thickness of 0.2 mm.

• Recommended for all intraoral films as thyroid gland is

exposed to x-radiation because of its location.

• Not recommended with extra oral films - obscures

information on the film resulting in non diagnostic

radiograph.

• Lead apron

• Flexible shield placed over the patient's

chest and lap to protect the reproductive

and blood-forming tissues from scatter

radiation

• Recommended for all intraoral and extra

oral films with protective equivalent of l/4th

mm of lead.

• Act as secondary measure to protect the patient

• Should not be substituted for use of fast films, lead

collimation and aluminum filtration which are primary

means of reducing exposure to the patient.

If holding a patient is required…

• Use shielding

Apron, gloves, thyroid shield, glasses

• Avoid exposing assisting person to the primary beam.

• Gloves, aprons ,eyewear

Protect from scatter or transmitted

radiation,

• Eye Protection

Glasses 0.75mm Pb (0.9% @ 90kV)

• Hand protection

• Gloves

• 0.5mm Pb (1.2% @ 90kV)

• 1.4 kg each

• Person assisting the patient must wear a lead apron and

lead gloves if their hands will be in the beam.

13/04/2023

• Solid 2mm Pb

10% @ 90kV

• Flexible 0.5mm Pb

2.5% @ 90 kV

Gonad protection (patient)

• Fast film

• Most effective method of reducing patients exposure to x-

radiation.

• Avaliable for both intraoral and extra oral radiography.

• Intraoral dental x-ray film - available in three speed

groups-D, E, and F.

• Clinically, film speed of group E is almost twice as fast

(sensitive) as film of group D , about 50 times as fast as

regular dental x-ray film.

• F-speed film requires about 75% exposure of E-speed film

and only about 40% that of D-speed.

• F-speed film has same density range, latitude, contrast,

image quality as D- and E-speed films without sacrifice of

diagnostic information.

• Current digital sensors offer equal or greater dose saving

than F speed film and comparable diagnostic utility.

Intensifying screens

• Used in extra oral radiography - use the rare earth elements

gadolinium and lanthanum.

• Emit green light on interaction with x rays.

• Decrease patient exposure by about 55% in panoramic and

cephalometric radiography compared with older calcium

tungstate screens.

• Focal spot film distance

• X-rays are less divergent at a longer

distace , leading decrease in the

volume of the patient exposed .

• Use of long source to skin distance of

40 cm, rather than short distance of 20

cm decreases exposure by 10 to 25 %

• Equipment operating below 50 kVp should have a

minimum distance af 10 cm (4") from the end of the PID

to the focal spot.

• Above 50 kVp should have a minimum distance of 18 cm

(7”) from the end of the PID to the focal spot.

• Film-holding devices

• Helps to stabilize the film position in

the mouth and reduces the chances of

movement .

• Eliminates the need for the patient to

hold the film in place.

• Patient's finger is not exposed to

unnecessary radiation.

• Possibility of misaligning the X-

ray tube and partially missing

the film (cone cut), is also

reduced.

• Exposure factors selection

• Dental radiologist can control the exposure factors by

adjusting the

Kilovoltage peak,

Milliamperage, and

Time settings

on the control panel of the dental x-ray machine.

• limiting the amount x ray radiation exposure to patient.

• Setting of 70 to 90 kVp keeps patient exposure to a

minimum.

• PROPER TECHNIQUE

• Ensure diagnostic quality of films and reduces the amount

of exposure patient receives.

• To produce diagnostic films, radiologist/ radiographer

must have thorough knowledge of the techniques most

often used in dental radiography.

 

• AFTER EXPOSURE

• After the films have been exposed, they must be handled

and processed.

• Meticulous film handling and proper film-processing

techniques are critical for the production of high-quality

diagnostic radiographs

• OPERATOR PROTECTION MEASURES

• Dental radiologist must use proper protection measures to

avoid occupational exposure to x-radiation (e.g., primary

radiation, leakage radiation, scatter radiation).

• Minimize the amount of radiation that a dental radiologist

receives.

• And includes 1. Protection guidelines

2. Radiation-monitoring devices.

• Protection guidelines

• Include recommendations on

Distance,

Position, and

Shielding.

• Distance and position -recommendations

• If no barrier is available, the operator

should stand at least 6 feet from the

patient,

• At an angle of 90 to 135 degrees to the

central ray of the x-ray beam when the

exposure is made.

• Proper operator position also includes the following:

• Never hold a film in place for a patient during x-ray

exposure.

• Never hold the tube head during x-ray exposure.

• Shielding recommendations

• Dental radiologist should stand behind a protective

barrier such as a wall during x-ray exposure

• Constructed of gypsum wall board.

• Radiation Monitoring

• Used to identify excess occupational exposure and to

protect the dental radiologist.

• Includes monitoring of both equipment and personnel.

• Equipment monitoring

• Dental x-ray machines must be monitored for leakage

radiation through the use of a film device.

• Obtained through the state health department or from

manufacturers of dental x-ray equipment.

• Personnel monitoring

• Amount of x-radiation that reaches the body of the dental

radiologist can be measured through the use of a personal-

monitoring device known as a film badge.

.

• Consists of a piece of radiographic film in a

plastic holder.

• Radiologist - have his or her own film badge

• Worn at waist level whenever exposing x-ray

films.

• Should never be worn when the radiologist is

undergoing x-ray exposure.

• Film badges not worn, stored in radiation-safe

area

• After the dental radiologist has worn the film badge for a

specified interval (eg., 1 week, 1 month), the badge is

returned to the service company.

• Company processes and evaluates the film for exposure

• Provides the dental office with an exposure report for each

radiologist.

• HARING & HOWERTON Dental Radiography 3rd edition

• Advantages• Inexpensive• Easy to handle and process• Reasonably accurate

• Disadvantages• Can not be reused• Sensitive to heat and humidity• Must be changed monthly

Film Badges

Thermoluminescent dosemeters

• Measurement range 0. 1 µSv

to 5 Sv

• TLD has several Advantages over film badges.

• Not sensitive to heat or humidity

• More sensitive and accurate.

• Can be changed quarterly instead of monthly

• Disadvantages

• Cost but changing badges less frequently than

monthly eliminates cost problem.

• ENVIORNMENT PROTECTION MEASURES

• Surrounding environment must be protected from radiation to

avoid exposure to persons in the environment

• Primary beam - never be directed at any one other than patient.

• Patient should be positioned such that the X-ray beam aimed at

the wall of the room and not through the door or other opening

where people may be located,

• Walls made of 3" of concrete, or 1 mm of lead will suffice

to protect adjacent rooms, even if the work load in the

radiology department is high.

• An alternative to lead is Barium due to it's

High atomic number,

High density and

High linear co efficient of attenuation.

• Used in the form of Barium Plaster or Barium Concrete.

• If it is not possible to incorporate

lead or barium into the walls, they

can be lined with lead plywood, 0.25

mm of lead sandwiched between

layers of wood.

• Primary barrier should be incorporated

in any part of the floor or ceiling of the

room at which the beam is fired.

• Secondary barrier in the walls, provide

protection against scattered or leakage

radiation and as exposure rates are

small they are 1/2 the thickness of the

primary wall.

• Windows:

• As the patient is being irradiated,

window is provided so that the

operator can see.

• Situated, where the primary beam is

not directed on it

• Lead glass should be used

• Doors - radiology room should

function as secondary barriers

having lead incorporated in them.

• Switches may be incorporated so that

the beam is cut off as soon as the

door is opened and not allow the

beam to be switched on till the door

is closed completely.

• Warning Light and Placard

• Warning signal (red light ) should be placed at an

conspicuous place outside the X-ray room which should go

on when the exposure button is pressed, or

• Placard should be placed to signal that the process of X-

ray taking is in progress.

• Quality assurance

• Defined as any planned activity to ensure that a dental

office will consistently produce high quality images with

minimum exposure to patients and personnel.

• Regular radiation surveys

• Should be performed at regular intervals as the amount of

exposure is dependent on many factors, such as :

• Machine's kilo voltage

• Work load of the X-ray machine

• X-ray absorbing ability of the walls

• Amount of time the adjacent areas are occupied by

people.

• RADIATION EXPOSURE GUIDELINES

• Protect the patient and operator from excess radiation

exposure,

• Guidelines include 1.Radiation safety legislation

2.Exposure limits

for the general public and for persons who are

occupationally exposed to radiation.

• Radiation Safety Legislation

• Established at both the state and the federal level to protect

the patient, operator, and general public from radiation

hazards.

• At federal level - Radiation Control for Health and Safety

Act was enacted in 1968 to standardize the performance of

x-ray equipment .

• Federal Consumer-Patient Radiation Health and Safety Act

was enacted in 1981 to address the issues of the education

and certification of persons using radiographic equipment.

• Radiation legislation varies greatly from state to state.

• Dental radiologist must be familiar with the laws that

apply to his or her workplace.

• Exposure limits• Maximum Permissible Dose:

• Defined by the NCRP as the maximum dose equivalent

that a body is permitted to receive in a specific period of

time.

• MPD - dose of radiation that the body can endure with

little or no injury.

•  Maximum Accumulated Dose

• When occupationally exposed workers must not exceed an

accumulated lifetime radiation dose.

• Determined by formula based on the worker's age.

• N refers to the person's age in years.

• 18 refers to the minimum required age of a person who

works with radiation.)

• ALAR A CONCEPT

• states that all exposure to radiation must be

kept to a minimum, or "as low as

reasonably achievable.''

• To provide protection for both patients and

operator.

• Every possible method of reducing

exposure to radiation should be employed

to minimize risk.

• RADIATION PROTECTION AND PATIENT EDUCATION

• Education and orientation of all radiation personnel to

the ill effects of radiation is mandatory.

• Continuing education programs keep them alert to the

possible risk and orient them to new equipment.

• Dental radiologist must be prepared to explain exactly how

patients are protected before, during, and after x-ray

exposure

• Printed handouts or pamphlets outlining the steps used to

protect patients from excess radiation can be provided to

the patient.

• Placed in reception area or room where dental radiographs

are taken.

• Recommendations of NCRP• Dentists Role in Radiation Protection

•  Establish a radiation protection program

• Prescribe all radiographic examinations

• Shall conduct a clinical history and physical exam and

determine health benefit to patient from the radiographic

procedure

• Shall obtain guidance from a qualified expert - facility

design & radiation protection

• Dentists Role in Patient Protection

• Shall make an effort to obtain recent radiographs from

patient's previous dentist

• Take radiographs only if indicated after an evaluation of

clinical history, physical exam or laboratory findings

• Shall limit radiographic examinations of symptomatic

patients to those required for diagnosis and treatment of

current disease

• Shall not expose radiographs for administrative purposes

Conclusion Basi

References

• Oral radiology Principles and Interpretation,

White and Pharoah – Fifth edition

• Textbook of Dental and maxillofacial Radiology,

Freny. R. Karjodkar – 2 edition

• Essentials of Dental Radiography and Radiology,

Eric Whaites – Fourth edition

• J. Anthony Seibert, “X-Ray Imaging Physics for Nuclear

Medicine Technologists. Part 1: Basic Principles of X-Ray

Production”

J Nucl Med Technol 2004; 32:139–147