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Main components of the tube head. The glass X-ray tube The step-up transformer The step-down transformer A surrounding lead shield Surrounding oil Aluminium filtration The Collimator The spacer cone or beam-indicating device (BID). Focal spot size and the principle of line focus.

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main components of the tube head
Main components of the tube head

The glass X-ray tubeThe step-up transformerThe step-down transformerA surrounding lead shieldSurrounding oilAluminium filtration

The Collimator

The spacer cone or beam-indicating device (BID)

x ray equipment films and processing
X-ray equipment, films and processing

X-ray generating equipmentImage receptorsProcessing facilities

main components of the control panel
Main components of the control panel

The main on/of switch and warning lights

The timer

An exposure time selectors

Warning lights and audible signals

circuitry and tube voltage
Circuitry and tube voltage

To generate the high potential difference (kV) to accelerate the electrons across the X-ray tube via the step-up transformer

To provide the low –voltage current to heat the tube filament via the step-down transformer

rectified circuits
Rectified circuits

Definition-electrical device which converts alternating current to direct current

Half-wave rectified

Single-phase, full-wave rectified

Three-phase, full-wave rectified

Constant potential

advantages of constant potential circuitry
Advantages of constant potential circuitry

X-ray production per unit time is more efficient

More high-energy, diagnostically useful photons are produced per exposure

Fewer low energy, harmful photons are produced

Shorter exposure times are possible

image receptors
Image receptors

Direct –action

Indirect- action

direct action non screen films
Direct-action (non-screen) films

Uses

Sizes

31/41 mm for periapicals

22/35 mm for bitewings

57/76 mm for occlusals

the film packet contents
The film packet contents

Outer packet

Black paper

Lead foil

the radiographic film
The radiographic film

A plastic base

A thin layer of adhesive

The emulsion on both sides of the base

A protective layer of clear gelatine

indirect action film
Indirect-action film

Uses- extraoral views and intraoral vertex occlusal radiograph

Construction- different emulsions are sensitive to blue, ultraviolet ,green or red light

It is essential that the correct combination of film and intensifying screens is used

For identification metal letters L or R are placed on the outside of the cassette

slide15

Film speed –depends on size and number of crystals

  • Film sensitivity- this is the reciprocal of the exposure required to produce an optical density of 1.0 above background fog
slide16

Film latitude-this is a measure of the range of exposure that produces distinguishable differences in optical density

  • Film contrast –the difference in optical density between two points on a film that have received different exposures
slide17

Resolution- a measure of the radiograph’s

ability to differentiate between the different structures that are close together

  • Factors affecting resolution

- image sharpness

- size of crystals

- contrast

intensifying screens
Intensifying screens
  • Action
  • Cassettes
  • Film storage
  • Screen maintenance
processing
Processing

Definition of processing

Processing theory

Diagram

practical processing methods
Practical processing methods

Manual

Automatic

Self-developing films

requirements for manual processing
Requirements for manual processing

Absolute light-tightness

Adequate working space

Adequate ventilation

Adequate film storage facilities

slide22

Safelights

  • Processing equipments-tanks,
  • thermometers immersion, heater,
  • timer, film hangers
  • Adequate washing facilities
manual processing cycle
Manual processing cycle

The exposed film packet is unwrapped and the film clipped on to a hanger

The film is immersed in developer (at 20 degrees for 5 minutes) and agitated several times

Rinse the residual developer for 10 seconds

slide24

Immerse the film in the fixer for 8- 10 minutes

  • Wash the film under running water for 10- 20 min. to remove the residual fixer
  • The film is dried in a dust – free atmosphere
constituents of developer solutions and their functions
Constituents of developer solutions and their functions

Phenidone- bring out the image

Hydroquinone- builds contrast

Sodium sulphite- reduces oxidation

Potassium carbonate- activates developing agents

slide26

Benzotriazol- prevents fog

  • Glutaraldehyde- hardens the emulsion
  • Fungicide- prevents bacterial growth
  • Buffer- maintains pH ( 7+)
  • Water- solvent
important points regarding development
Important points regarding development

The alkaline developer should be made up according to manufacturer’s instruction

Solutions should be changed every 10-14 days, irrespective of the number of films processed during that time

The recommended time is 5 minutes at 20 degrees

fixer s constituents and their functions
Fixer’s constituents and their functions

Ammonium thiosulphate- removes unsensitized crystals

Sodium sulphite- preservative

Aluminium chloride- hardener

Acidic acid- maintains pH

Water- solvent

important notes regarding fixing
Important notes regarding fixing

Avoid contamination with developer and prepare according to manufacturer’s recommendations

Films should be fixed for double the clearing time (the time it takes to remove the unsensitized silver halide crystals)

slide30

Films may be removed from the fixer after 2-4 minutes for wet reading but should be returned to the fixer to complete fixing

  • Inadequate fixed films may appear greenish, yellow or milky and later brown
automatic processing
Automatic processing

Processing cycle- it is the same as for manual processing except that the rollers

squeeze off any excess developing solution before passing the film on to the fixer

Infection control measures

advantages
Advantages
  • Time saving
  • No need for a darkroom
  • Standardized processing conditions
disadvantages
Disadvantages
  • Strict maintenance and regular cleaning are essential
  • Some models need to be plumbed in
  • Equipment is relatively expensive
  • Smaller machine cannot process large extraoral films
self developing films
Self-developing films

Advantages

- No darkroom or processing facilities are needed

- Time saving- the final radiograph is ready in about a minute

disadvantages1
Disadvantages
  • Poor overall image quality
  • The image deteriorates rapidly with time
  • There is no lead foil inside the film packet
  • The flexible film packet is difficult to use in positioning holders
  • Relatively expensive