x ray film

SHREE BANKEY BIHARI DENTAL COLLEGE

DEPARTMENT OF ORAL MEDICINE,

DIAGNOSIS & RADIOLOGY

X-RAY FILMS

PRESENTED BY –ASHISH KUSHWAHA

FINAL YEAR8630016

• Introduction-

The X-Ray films, help us to record the information regarding the object (tissue) through which the x-rays passes & hence they greatly help in diagnosis, & treatment of the patient problem.

Karjodkar 2nd edition

Image recorded on film is caused by exposure to photons

X-RAY FILM

X-RAY FILM• HISTORY -

• The first x-rays were recorded on glass plates.

• These were coated with emulsion on one side only.

• The exposure dose was quite high.

• In 1839, the phenomenon of development was discovered by Louis Daguerre

• One year later, it was discovered that treating exposed silver chloride paper with sodium chloride would make the image permanent.

• Nitrocelluose based film was found to be a more feasible choice for recording x-rays.

• This film was single-emulsion.

• It was later discovered that double-emulsion responded to x-rays faster.

• In 1924, cellulose acetate replaced the nitrocellulose based film.

COMPOSITION

X- ray film

Adhesive Base

Polyester polyethylene terephthalate

Emulsion

Silver halide grains

Vehicles matrix

X-RAY FILM- CROSS SECTION

FILM BASE -

• It is a transparent supporting material.

• POLYESTER POLYETHYLENE TEREPHTHALATE RESIN are used.

• Thickness - 0.18 mm

FilmBase 0.18 mm

IDEAL PROPERTIES BASE MATERIAL

1. Structural support for fragile emulsion

2. Low light absorption

3. Flexible, thick, & strong

4. Dimensional stability

5. NON -FLAMMABLE

FUNCTIONS OF BASE

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Provide support for emulsion layer.

To transmit light.

ADHESIVE LAYER

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Also called subbing layer or Substratum layer.

Made of mixture of gelatin solution and solvent of film base.

It keeps emulsion layer and base adhered to each other during coating stage and processing.

Provides uniform surface over which the emulsion can be coated uniformly.

EMULSION LAYER

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Has 2 principle components – I. Silver halide grainsII. Vehicle matrix

It consists of a homogeneous mixture of gelatin and silver halide crystals.

In typical emulsion 90 to 99% is AgBr and about 1 to 10% AgI .

EmulsionLayers

The presence of AgI produce an emulsion of much sensitivity than a pure AgBr emulsion.

It also contains traces of sulfur (ALLYLTHIOUREA).

……CONTD

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Silver halide in a emulsion is in the form of small crystals.

Silver halide crystals may be tabular, globular, polyhedral, or irregular in shape.

Crystal size might vary from 1.0 –1.5 microns in diameter with about 6.3 x 1010 grains per centimeter of emulsion.

• Granular

• Tabular Scanning electron micrographs of emulsion comparing flat tabular silver bromide crystals of InSight film

Scanning electron micrographs of emulsion comparing with globular silver halide crystals of Ultra-Speed film .

• How silver halide crystals are made … ???

Dissolve Metallic silver in nitric acid.

to formSilver nitrate

by mixing

silver nitrate + KBr = Ag-Br + potassium nitrate

GRAIN SIZE AND DISTRIBUTION

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GRAIN SIZE and DISTRIBUTION affects the following:

SPEED: The bigger the average grain size, the higher the speed of the film.

CONTRAST: Affected by size distribution. The more available in the film, the lower the contrast.

GRAININESS: Graininess is the apparent clumping of the crystal as seen on the radiograph. The bigger the crystal, the higher the graininess o f the film.

GELATIN

Gelatin is used as the suspending medium and binding agent for the silver halide particles.

It comes collagen fiber in which primary source are the cartilage, skin and the protein matrix (ossein) of bone of animals.

WHY WE USE GELATIN AS BINDER…?

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It is a medium in which SILVER NITRATE and SODIUM BROMIDE can react and the resulting AgBr get finely and evenly dispersed and remain suspended.

In warm state it can be easily spread on the film base. On cooling, it sets firmly on the base as gel. It is flexible and does not crack easily on bending. It is optically transparent . Gelatin does not react chemically with the silver halide . It is porous so the processing chemicals can penetrate to the

silver halide crystals. Some of the constituents in gelatin enhances the activity of

Silver bromide and some act as antifoggant.

?

SUPERCOAT (OVERCOAT)

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Protective layer of gelatin Provides sturdiness to unexposed radiographic film. Antistatic Reduces damage from scratches, pressure, or

contamination during storage, handling and processing.

Supercoating

FEW ADDITIVES

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Preservative – Phenol as bacteriocide Silver iodide – To extend sensitivity towards blue

range. Some dyes may extend Colour sensitivity further Glycerin to make the emulsion pliable Saponin – To make the emulsion receptive to the

processing chemicals Alcohol – To prevent frothing during coating

characteristic Photographic film Radiographic film

Mode of image capture

By reflected light By penetrated/ transmitted light

Emulsion layer On one side Either On one side or both

Speed Slow Fast

Grain size Small Large

Resolving power 1000 lines/mm 6-10 lines/mm

Irradiation by Light only Light as well as x-ray

Difference In B/W Photographic Film And Radiographic Film

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TYPES OF X-RAY FILM -1. According to their USES –

• Intraoral filmsPeriapical films

No. 0 – childrenNo. 1 – anterior adultNo.2 – standard adult

Occlusal films

Bitewing films

• Extraoral films

• 2. According to SPEED –

• Slow film Speed A Speed B Speed C

• Fast film D – ultra speed E – ekta speed F – ultra ekta speed

• Hyper speed G

• 3. According to emulsion layer -

• Single coated

• Double coated

• 4. According to packaging –

• Single film packet

• Double film packet

• What is speed of X-RAY FILM …???

It is defined as the amount of the radiation required to produce the radiograph of adequate density.

Slow film – Require more exposure & vice versa.

• Factors affecting film speed –Size of crystalsShape of grainsThickness of emulsions

Difference b/w Single Coated And Double Coated X-ray Film

Characteristic Single coated Double coated

Emulsion layer One side Both side

Patient Radiation dose More Less

Radiographic detail More Less

Average gradient (G) Very less more

Parallax effect No yes

Contrast

Less more

INTRAORAL FILMS

• Periapical view –Used to record crown, root & surrounding bone.3 sizes-

0 - for children 22 X 35 mm1 - narrow, for anterior teeth 24 X 40 mm2 – standard size for adults 31 X 41 mm

Size ‘0’22 X 35 mm

Size ‘2’

31 X 41 mm

Size ‘1’24 X 40 mm

Standard adult

Anterior adultChild

Size of IntraOral Periapical

• Indications – to evaluate the -

Dental cariesPeriapical infectionsPeriodontal diseasesMixed dentition analysisCyst & tumor in the periapical regionPathology of bone in the periapical regionPulp calcification & pulp stoneDental anomaliesImpacted teethAssessment of working lengthAssessment of root morphology before extraction.

• Bitewing view – (Interproximal view) –• A paper wing present on the middle of film.

Uses -1.Crown of maxillary & mandibular teeth in one image.2.Interproximal caries 3.evaluation of height of alveolar bone

Size ‘0’22 X 35 mm

Size ‘2’

31 X 41 mm

Size ‘1’24 X 40 mm

Posterior adult

Anterior childPosterior Child

Size of Bitewing Film

Size ‘3’

27 X 54 mm

Anterior adult

• Occlusal view –• Size 57 X76 mm (3 times larger than size 2)• To show larger area.• Used to obtain right angle views to the usual

periapical view.• Film usually is held in position by having the patient

bite lightly on it to support it between the occlusal surface of the teeth.

Size ‘4’

57 X 76 mm

• Indications –

To evaluate the impacted canine, third molar & supernumerary tooth

To localize foreign body like sialolith in duct of salivary gland

To detect complete extension of large cyst an tumor.

Assessment of fracture of the anterior teeth and alveolar bone.

For determining the buccolingual relationship of pathological lesions.

EXTRAORAL FILMS

EXTRAORAL FILMS

• Panoramic, cephalometric, & other skull views are more frequently used extra oral projections in dentistry.

• Screen film is used with intensifying screens to reduce patient exposure.

• It is placed in between 2 intensifying screens when an exposure is made.

• intensifying screens absorb x-rays & emit visible light.

• Silver halide crystals are sensitive to U.V. & blue light and thus are sensitive to screens that emit U.V. & blue light.

• When film is used with screens that emit green light, the silver halide crystals are coated with sensitizing dyes to increase absorption.

• They do not have embossed dot.

• They are used in film holder or cassette.

• High contrast medium speed – panoramic, skull radiography.

• Less contrast & wider latitude – cephalometric radiography.

• 2 types – Screened Non screened

• Size – • Available in various size –

• Lateral Oblique film – 5” X 7”

• Panoramic film – 6” X 12” / 5” X 12”

• Cephalometric film – 8” X 12”

• Skull radiography – 10” X 12”

CHARACTERISTICS DIRECT EXPOSURE FILM INDIRECT EXPOSURE FILM

Exposed with Only by x-rays Mainly by visible light

Used Without Screen With screenEmulsion layer Thick Thin Image formation In deep superficialyProcessing time more lessResolution more lessExposure dose more lessUsed in Orbit and extremities

radiography. Also in Industrial Radiography

General radiography

Difference B/W Non Screen & Screen Film

CONTENT OF FILM PACKET• Intraoral x-ray film packet contain –

Outer plastic wrapper Lead foil Black paper X-ray film

• Wrapper –

• Made up of non absorbent paper or plastic.• Water proof• It is sealed to prevent the ingress of saliva & light.• It has 2 sides –• Tube side – (usually white, faces toward the x-ray

tube.)• Labelled side- reverse side. Usually of 2 color

• Black paper –• Protect the film from –• Light• Damaged by finger

• Lead foil –

• Placed behind the film• Prevent back scattering• Reduce exposure• If film is placed in wrong way then embossed pattern

present on the film.

• X-Ray film – it has

• Rounded corner• Raised dot

• One corner of each dental film has a small, raised dot that is used for –

• Orientation• Mounting• Side determination

• Film Holding Device –

• It is the device that is used to position an intraoral film in the mouth & maintain the film in position during exposure.

Film Storage

• Clean, dry location, light tight location• 40 – 60 % Humidity 70 º Fahrenheit• Away from chemical fumes• Safe from radiation exposure• Standing on edge• Expiration date clearly visible. Film can be

stored for about 45 days.

FILM BIN - STORAGE

Care And Protection Of Film

Films should be protected from Physical damage

Light

High temperature

High relative humidity

Harmful gases and fumes

X-rays and radioactive source

Fire

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Reference

Oral radiologyPrinciple & interpretation

6th editionBy- white And pharoah

Textbook ofDental and

maxillofacial radiology2nd edition

By- Freny R. Karjodkar

THANK

YOU

INTENSIFYING SCREENS

• An intensifying screen is a plastic sheet coated with fluorescent material called phosphors .

• Phosphors are materials which convert photon energy to light

INTENSIFYING SCREENS

composition

• Intensifying screens are made of -

Phosphor layer

Protective coat

Base

• Base – form of polyester plastic.Thickness about 0.25 mm.Provide mechanical support.

• Phosphor layer –• Is composed of phosphorescent crystals suspended

in a polymeric binder.• When crystals absorb x-ray photons they fluoresce.

• Protective layer –• Thickness 15 µm.• Placed over phosphor layer to protect the phosphor layer.• Provide a surface that can be cleaned.

• The speed & resolution of a screen depends on –

Phosphor type and phosphor conversion efficiency

Thickness of phosphor layerAmount of phosphor / unit volumePresence of reflective layerPhosphor grain size

• FUNCTIONS –

Create an image receptor system 10 to 60 times more sensitive than the film alone.

Substantial reduction of patient exposure to x-radiation.

The resolving power of screens is related to their speed.

Slower the speed – greater its resolving power.

Image characteristics• Depends on –

1. Radiographic density2. Radiographic contrast3. Radiographic speed4. Film latitude5. Radiographic blurring6. Image quality

1. Radiographic density –Influenced by exposure and thickness & density of

the subject.

A. Exposure• Overall film density depends on the no. of photons absorbed

by the film emulsion.

Exposure time

no. of photons

Density of

radiograph

B. Subject thickness

Thicker the subject, the more the beam is attenuated and lighter the resultant image.

C. Subject density

The greater the density of a structure , the greater the attenuation of the x-ray beam

2. Radiographic contrast –

It is the difference in densities between light and dark region on a radiograph.

High contrast – low gray scale Low contrast – high gray scale

It is result of the interrelation of subject contrast, film contrast & scattered radiation.

3. Radiographic speed –1. -

• It is refers to the amount of radiation required to produce an image of a standard density.

• A fast film requires relatively low exposure.

• A slow film requires relatively high exposure for same density.

• Film speed is controlled by the size of silver halide grains.

• Although film speed can be increased slightly by processing the film at higher temperature.

4. Film latitude –

5. Radiographic blurring -

• Sharpness – is the ability of a radiograph to define an edge precisely.

• Resolution – is the ability of a radiograph to record separate structures that are close together.

• Radiographic blurring is caused by – Image receptor blurringMotion blurringGeometric blurring

6. Image quality -

• It is describes the subjective judgment by the clinicians of the overall appearance of a radiograph.

• It combines the features of density, contrast, latitude, sharpness, resolution and other parameters.

GRIDS

• Functions – To reduce the amount of scattered radiation.

• Compositions –

A grid is composed of alternating strips of a radiopaque material (lead) & radiolucent material (plastic).