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BDS3 - radiology > digital and film radiography 2 > Flashcards

digital and film radiography 2 Flashcards

1
Q

what is one of the most important parts of film radiography

A

Intra-oral film packet

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2
Q

where does the film packet go

A

This packet goes in the patient’s mouth when taking a radiograph

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3
Q

what is in the middle of a film packet

A

radiographic film

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4
Q

what surrounds the radiographic film

A

Protective (black) paper ~ protects film form light exposure, damaged by fingers and saliva

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5
Q

what is found behind the protective paper

A

lead foil

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6
Q

what is the purpose of the lead foil

A

Purpose of this is to absorb some excess x-ray photons
Ie the photons that have passed through the radiographic film and the protective paper as well as photons that have passed around the side of the packet and bounced off tissues within the mouth due to scatter that then are travelling back the way (want these absorbed before it hits the radiographic film as these photons can affect the image)

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7
Q

what surrounds the entire film packet

A

Outer wrapper is around all of this and usually made of plastic

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8
Q

what is the purpose of the outer wrapper

A

Prevents ingress of saliva

Indicates which side of the packet is the front

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9
Q

what is the radiographic film

A

Material in which the actual image is formed

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10
Q

what is the radiographic film sensitive too

A

Sensitive to both x-ray photons and visible light photons

Which is why it is important to make sure these are not accidentally exposed to day light

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11
Q

how is an image produced on the radiographic film

A

Photons interact with emulsion on film to produce latent image which only becomes visible after chemical processing

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12
Q

name the different components of the radiographic film

A
  • Transparent plastic base
  • Adhesive
  • Emulsion
  • Protect coating of clear gelatin
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13
Q

what is the purpose of the transparent plastic base

A

Supports the emulsion

Ie gives the whole thing support

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14
Q

what is the purpose of the adhesive

A

Attaches the emulsion to the plastic base

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15
Q

what is the emulsion

A

Layered on both sides of the plastic base

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16
Q

what is the function of the protective coating of clear gelatin

A

Shields the emulsion from mechanical damage

Protects it from finger prints and scrapes and scratches

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17
Q

what is the radiographic emulsion

A

Silver halide crystals embedded in a gelatin binder

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18
Q

what do the crystals do in the radiographic emulsion

A

• Crystals microscopic and are what effectively become the “pixels” of the final image
= film generally higher resolution than digital

• Ie the crystals = pixels
But the crystals are far smaller giving a higher resolution than digital

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19
Q

what do the silver halide crystals do

A
  • Usually silver bromide
  • Become sensitised upon interaction with x-ray (& visible light) photons

• During processing;
○ Sensitised crystals converted to particles of black metallic silver = dark parts of final image
○ Non-sensitised crystals removed = light parts of final image

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20
Q

why is the lead foil have an embossed pattern

A

• Embossed pattern to highlight (on image) if receptor was placed the wrong way around

○ Sort of a textured appearance

○ If you accidentally place the film packet back to front in the patient’s mouth and the x-ray photons have had to pass through the lead before reaching the radiographic emulsion then there is this embossed pattern that is very obvious

○ The whole point of this is that the final image will be very pale because not many x-ray photons were able to reach the radiographic emulsion (as they had to pass through the lead first) you will know the reason is because it is back to front and not because there is another problem with the x-ray process

21
Q

what excess x-ray photons does the lead foil absorb

A

Those in the primary beam continuing past the film

Those scattered by patient’s tissues and returning back to the film

22
Q

what is the film speed

A

Relates to the amount of x-ray exposure required to produce an adequate image Ie one that is not too dark and not too light
Increase speed = decrease radiation required to achieve an image

23
Q

what is film speed affected by

A

• Affected by number and size of the silver halide crystals
○ Large crystals = faster film but poorer image quality
○ Remember crystals act as the pixels so if they are larger there will be poorer resolution

24
Q

what are the film speeds with regards to using Kodak for example

A

• E is twice as fast as D
○ Therefore required 1/2 exposure time = 1/2 radiation dose

• F is 20% faster than E
○ 20% reduction in exposure time (& dose)

• So changing to a faster speed can be beneficial

25
Q

if changing to a different film speed what must be done

A

• If changing to different film speed, you must either:

○ Convert settings on x-ray unit (by qualified technician) ~ To make sure it is using the correct settings

○ Install a filter to absorb part of the primary x-ray beam ~ So that you are not over exposing the film

26
Q

when are intensifying screens used for

A

Used alongside special “indirect action” film for extra-oral radiographs (eg panoramic radiographs, cephalograms)

Too bulky for intra-oral use so not suitable for putting in a patient’s mouth

27
Q

what is the purpose of the intensifying screen

A

Reduce radiation dose

But also reduce detail in the final image

28
Q

what happens if the x-ray photon interacts with the intensifying screen before the radiographic film

A

If an x-ray photon interacts with the intensifying screen first
○ Then you have excitation within the intensifying screen along with the emission of visible light
○ The visible light spreads out in all directions so then by the time it actually reaches the x-ray film it is hitting quite a large area
○ Therefore you get excitation of all of the crystals in a larger area

29
Q

what happens if the x-ray photon doesn’t interact with the intensifying screen before the radiographic film

A

You will then have excitation of the crystals in one very small area

30
Q

what is film processing

A

Sequence of steps which converts the invisible latent image (in the radiographic emulsion) to a visible permanent image

• Start with the intra-oral packet
○ Have it exposed

• Then take out the radiographic film
○ Goes through processing

• Results in standard radiograph

31
Q

how can you ensure consistent image quality in film processing

A

it Must be carried out under controlled, standardised conditions to ensure consistent image quality and not variations from radiograph to radiograph

32
Q

what are the different methods of film processing

A

○ Manual
○ Automated
○ (self-developing films) ~ less commonly

33
Q

what are the common steps in film processing

A
  1. Developing
    ○ Converts sensitised crystals to black metallic silver particles
    ○ Resulting in darker areas on the image
  2. Washing
    ○ Removes residual developer solution
  3. Fixing
    ○ Removes non-sensitised crystals ~ so there is a lighter area created on the image
    ○ Hardens emulsion (which contains the black metallic silver) ~ Makes it more hard wearing and long lasting
  4. Washing
    ○ Removes residual fixer solution
  5. Drying
    ○ Removes water so that film is ready to be handled / stored
34
Q

what is the manual / wet cycle

A

• Person dips film into different tanks of chemicals
○ At precise concentrations / temperatures
○ For specific periods of time
§ Otherwise it will affect the quality of the image
○ Washes film after each tank

• Must be carried out in a dark room with absolute light-tightness and adequate ventilation
○ There are some lights in a dark room but these lights are always red
○ This is a special type of light that will not interact with the image

35
Q

what is the automated cycle

A

• All necessary steps carried out within a machine

• Exposed film goes in one end
○ = processed film comes out the other end
○ Comes out as an image ready to use

• Faster and more controlled than manual processing and avoids need for a dark room
○ But more expensive (need to buy the machine)

36
Q

how is developer solution squeezed out of the film in the automated cycle

A

in the automated cycle, sponge rollers squeeze developer solution out of film (instead of washing with water)

37
Q

what do you need to be careful about when opening a film packet for automated processing

A

Need to be careful not to expose the radiographic film to the visible light within the room as this may impair your image

38
Q

what are the steps for opening a film packet

A
  1. Disinfect the surface of the packet (& wipe off)
    ○ Will be covered in saliva
  2. Hold the packet under the hood of processor unit
    ○ The area with holes so you can put your hands into them
    ○ Means the area within is completely covered by darkness
  3. Peel back flap of outer wrapper
  4. Fold back lead foil
  5. Pull back paper flap
  6. Hold film by edges (NB: not surfaces) & slide out
  7. Insert film into processor slot / shelf
    ○ Which is found within the box / machine
    ○ Usually takes several minutes for the film to pass through the machine
39
Q

are self developing films recommended

A

no

40
Q

what are the advantages of self developing films

A

No dark room or processing facilities required

Faster eg 1 minute

41
Q

what are the disadvantages of self developing films

A

○ Poorer image quality

○ Image deteriorates more rapidly over time
§ May start to fade

○ No lead foil
§ Nothing to absorb excess photons

○ Easily bent

○ Difficult to use in positioning holders

○ Relatively expensive

42
Q

what are some processing issues with developing

A

• Developing involves a chemical reaction
○ Sensitised silver halide crystals are converted into black silver

• Reaction affected by time, temperature and solution concentration
○ Must be carefully monitored and kept consistent

• Developer solution oxidises in air
○ Becomes less effective over time
○ Needs to be replaced regularly
Irrespective to how many films have been developed (ie regardless of how many times you have used it)

43
Q

what are potenteial causes of pale image

A

• Exposure issue
○ Radiation exposure factors too low

• Developing issue
○ Film removed from solution too early
○ Solution too cold
○ Solution too dilute / old

• Note: opposite will result in dark image

44
Q

what are processing issues with fixing

A

• Fixing involves a chemical reaction which removes non-sensitised crystals and hardens the remaining emulsion

• Inadequate fixing means non-sensitised crystals are left behind
○ Image greenish-yellow or milky
○ Image becomes brown over time
○ All of which makes the image more difficult to see and of less diagnostic value / use

45
Q

what are processing issues with washing

A
  • Developer and fixer solution will continue to act if not washed off
  • Developer solution will continue to develop parts of the film
  • Fixer left in contact with film has impaired the image
46
Q

what is the problem with film storage

A
  • Takes up room
  • Need to be easily accessible and safe from damage
  • Require a reliable organisation system to allow images to be found easily and to reduce risk of images being lost / mixed up
47
Q

what are the advantages of digital radiography over film radiography

A

○ no need for chemical processing
§ Don’t need to worry about buying solutions or keeping certain temperatures or concentrations during processing

○ Easy storage and archiving of images

○ Easy back up of images
§ Can just copy a file

○ Images can be integrated into patient records (if digital)

○ Easy transfer / sharing of images

○ Images can be manipulated

48
Q

what are disadvantages of digital radiography compared with film radiography

A

○ Worse resolution = risk of pixelation
§ Can only have a limited number of pixels making up an image in contrast to the possibility of millions of crystals within the radiographic emulsion of film radiography

○ Requires diagnostic level computer monitors for optimal viewing

○ Risk of data corruption / loss (solved by backing up)
§ As with any digital files

○ Hard copy print outs generally have lower image quality
§ Compared to a radiograph film which is already a hard copy

○ Image enhancement can create misleading images

BDS3 - radiology (19 decks)

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