Image Receptors 2

Question 1

what are the two types of film available ?

Answer 1

• Direct
• Indirect

Question 2

Direct film is only used for?

Answer 2

Intra-oral radiographs

Question 3

When using a direct action film it can be placed in a sealed plastic barrier envelope, what does it do?

Answer 3

Protects the film from saliva and is torn open on complex of the x-ray and disposed of in the clinical waste leaving the clean film packet ready to handle

Question 4

When you open the packet and remove the outer layer, you will reveal black paper what does it do?

Answer 4

Helps protect the film from light leakage. it also helps to prevent crimp and pressure marks on the film by providing a bit of support

Question 5

Inside the black paper you will find the film sitting on shiny layer. the shiny layer is lead foil what does it do?

Answer 5

prevents degradation of image by absorbing the scatter.

Question 6

what does film emulsion mean?

Answer 6

the layer that reacts with the x-rays to form the image. it is comprised of silver halide crystals usually silver bromide, suspended in gelatin

Question 7

what are the two functions of gelatin?

Answer 7

• allows even distribution of the crystals
• absorbs liquid easily which helps during processing

Question 8

what is a latent image?

Answer 8

when an x-ray photon hits the silver halide crystal within the emulsion it becomes sensitised

Question 9

what are the two speeds in which x-rays are available ?

Answer 9

Slow and fast

Question 10

What does sensitivity of the film depend upon?

Answer 10

on the size of the crystals in the emulsion - the larger the crystals the faster the film speed and the lower the amount of x-rays required to produce an image

• the larger the crystals, the less detail you have on the film. it has a lower resolution

Question 11

Film size is just the same as digital receptor sizes, 0,1,2, and 4, what do they correspond to?

Answer 11

0 - anteriors and children
1 - canines
2 - adult posteriors and bitewings and children over 10
4 - for occlusals

Question 12

what is indirect action film used for?

Answer 12

extra-oral radiography

Question 13

when would u use indirect action films?

Answer 13

For DPT’s, lateral cephs and other head and neck radiography

Question 14

what is the difference between indirect and direct action films?

Answer 14

Indirect film is sensitive to light rather than x-rays, the x-rays react with the intensifying screens to produce light which then exposes the film. This system allows you to reduce the exposure required to produce an image and therefore the dose received by the patient

Question 15

what does the intensifying screen do?

Answer 15

allows a significant reduction in the radiation exposure

Question 16

How should you handle film?

Answer 16

• It is very easily damaged and must be handled with care
• Any damage will be obvious once the film is processed
• pressure sensitises the silver halide crystals so you must be careful not to bend it
• Never hold a film by one edge, the weight of it will make it bend
• hold it by opposite corners and be careful not to scratch it with your nails

Question 17

Where would you store film ?

Answer 17

• You do not want to store it in areas which are too hot or too cold
• If a box has been opened it must be kept in darkened conditions
• Most darkrooms have a big light tight drawer called a hopper to store film in
• You also do not want to use out of date film, the emulsion starts to degrade over time and can start to stick to the intensifying screens

Question 18

What happens in both direct and indirect film?

Answer 18

Silver halide crystals are sensitized to form the latent image
- the latent must then be processed with chemicals to produce an image that can be seen with the eye

Question 19

How do you process the latent image?

Answer 19

Film processing is the reduction of the exposed silver bromide crystals to black metallic silver, and then making this image permanent

Question 20

what are the three processing film methods, in intra-oral?

Answer 20

• automatic processer
• manual processor
• instant processing

Question 21

describe the 5 stages to developing an image

Answer 21

• develop - is where you make the latent image-visible
• wash - is where you stop development and remove the excess developer
  (this first wash only happens in manual processors)
• Fix - is where you make the image permanent
• Wash - is where you stop the fix and remove the residual fixer
• Dry - stops the image feeling sticky and prevents damage

Question 22

The action of the developing agents on the silver halide crystals is very dependant on?

Answer 22

1) Time - if the film stays in the developer too long it will be too dark. Not long enough and it will be too light
2) The developer temperature - too hot and the film will be dark, too cold and the film will be too light
3) the concentration - to save storage space chemicals tend to come in small bottles and have to be diluted with water. if you mix the developer wrong there will be consequences!

Question 23

What is fixing?

Answer 23

process by which the image is made permanent

Question 24

what are the components that make up a fixer?

Answer 24

• clearing agent - ammonium thiosulphate
• acidier, acetic acid, which maintains the pH
• hardner, usually aluminium chloride
• a preservative, usually sodium sulphite
• solvent, which is water

Question 25

if a film hasn’t been washed properly what happens?

Answer 25

feels sticky and has this cloudy appearance, it will not archive well and the image will deteriorate

Question 26

what is the main regulation u need to be aware of in terms of health and safety ?

Answer 26

COSHH - control of substances hazardous to health

Question 27

Answer 27

Question 28

Answer 28

Question 29

Answer 29

Question 30

Answer 30

Question 31

Answer 31