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4 Radiology > Image receptors 2 > Flashcards

Image receptors 2 Flashcards

1
Q

what are the two types of film?

A

direct action film
indirect action film

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2
Q

what is direct action film used for?

A

intra-oral radiographs
peri-apical, bitewing, occlusal

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3
Q

what is direct action film sensitive to?

A

x-rays

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4
Q

what is indirect action film used for?

A

Extra-oral radiography e.g. DPTs, lateral ceph

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5
Q

why is direct action film placed in a sealed plastic barrier when used?

A

infection control

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6
Q

what are the 4 layers of a direct action film packet from outer to innermost?

A

outer layer
black paper
lead foil
direct action film

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7
Q

what is the purpose of the outer layer in direct action film packet? 3

A

Sealed to protect from saliva -> keep dry

Keep film light tight to prevent fogging as photosensitive

Indicates correct orientation: one side is white which goes next to x ray machine, the bump goes at the crown of the tooth

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8
Q

what is the purpose of the black paper in direct action film packet? 2

A

Protects from light leakage

Supports the film to prevent crimp/pressure marks

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9
Q

what does this image show?

A

fogging due to light exposure

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10
Q

the lead foil in a direct action film packet is composed of what?

A

mix of aluminium and lead

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11
Q

what is the purpose of lead foil in direct action film packet?

A

Absorbs back scatter -> x-rays may hit other structures then bounce back

Has a pattern in the lead which will show if film placed wrong way

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12
Q

what are the layers of direct action film from innermost to outer? 4

A

base layer of polyester plastic

adhesive layer containing anti-glare tint

emulsion layer -> silver halide (bromide) crystals in gelatine

gelatine layer

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13
Q

what is the function of the adhesive layer in direct action film?

A

Stick emulsion layer to base layer

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14
Q

what is the function of the emulsion layer in direct action film?

A

Reacts with the x-rays to form the image

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15
Q

what is the function of the gelatine layer in direct action film?

A

protection from physical damage (super coat)

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16
Q

How is the image formed in direct action film

when x-ray photons hit ??? they become sensitised and produce a ??

Not visible to naked eye but can be made visible during ?

A

silver halide crystals
latent image

processing

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17
Q

what are the 2 speeds of direct action film?

A

slow = less sensitive to x-ray photons
fast = more sensitive to x-ray photons

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18
Q

direct action film

The larger the crystals in the ? the ? the film speed and the ? the amount of x-rays required to produce an image

However larger crystals = ? detail = ? resolution

A

emulsion
faster
lower

less
lower

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19
Q

what are the sizes for direct action film?

20
Q

what is size 0 direct action film used for?

A

anteriors and children

21
Q

what is size 1 direct action film used for?

22
Q

what is size 2 direct action film used for?

A

adult posterior and bitewings and children over 10

23
Q

what is size 4 direct action film used for?

24
Q

what is indirect action film sensitive to?

A

light
(not x-rays so differs from direct action film)
X-rays react with intensifying screen which produces light and exposes the film

25
Q

where is the intensifying screen located in indirect film?

A

On either side of the film forming a cassette

26
Q

what are the 4 layers of an intensifying screen

A

base layer - plastic/polyester
reflective layer
phosphor layer
super coat

27
Q

what is the function of the reflective layer in intensifying screens?

A

reflect light to film

28
Q

what is the function of the phosphor layer in intensifying screens?

A

reacts with x-rays to produce light

29
Q

what is the function of the super coat in intensifying screens?

A

protects phosphor layer from damage

30
Q

indirect action film
How it works

X-ray photons hit ?? in ?? and produces ?

? reflected back towards ? and reacts with ?? in ??

Crystals sensitised producing a ??

A

phosphor layer
intensifying screen
light

light
film
silver halide
film emulsion

latent image

31
Q

indirect action film

Intensifying screen is very efficient so allows a reduction in ?? however has reduction in ? as 1 x-ray photon will produce ? light photons.

A

radiation exposure
resolution
multiple

32
Q

Film handling
It is very sensitive to ? and ?

A

pressure
bending

33
Q

what is the mark on the film caused by?

A

Film handling
It is very sensitive to pressure and bending

34
Q

how is the latent image made visible?

A

through processing using chemicals
Reduction of the exposed silver bromide crystals to black metallic silver

35
Q

what are the 5 stages in film processing?

A

develop
wash
fix
wash
dry

36
Q

what does developing stage do in film processing?

A

make the latent image visible

37
Q

film processing -> developing

Developing agents phenidone and hydroquinone act on the crystals reducing them to ??? causing the visible blackening

Calcium carbonate - ? - controls the activity of the developing agents

Potassium bromide - ? - stops developer working on unexposed crystals

Sodium sulphite - ? - slows down oxidation

Water - ? - dilutes the chemicals

Action of developer is determined by: ?, ? and ? (higher = darker)

A

black metallic silver

activator

restrainer

preservative

solvent

time
temperature
concentration

38
Q

what does the first wash stage do in film processing?

A

stop development and remove excess developer (only in manual processors)

39
Q

what does the fix do in film processing?

A

make the image permanent

40
Q

film processing -> fix

Fixing agents change ??? to ?? so they can be washed away

Clearing agent - ammonium thiosulphate

Acidifier - acetic acid - maintains the pH and neutralises the developer

Hardener - aluminium chloride

Preservative - sodium sulphite

Solvent - water

End left with only ?, ? and ? silver halide crystals
Action of fixing agents are determined by ?, ? and ?

A

unexposed silver halide
soluble compound

exposed
developed
fixed

time
temperature
concentration

41
Q

film processing
what does an underfixed image look like?

A

has a green/brown tinge

42
Q

what does the second wash in film processing do?

A

stop the fix and remove the residual fixer
Remove unexposed silver halide crystals once they have been made soluble by the fixer

43
Q

what is the function of drying in film processing?

A

easier handled (not sticky) and prevent damage

44
Q

name 3 methods of film processing

A

automatic
manual
instant

45
Q

Health and safety

COSHH - control of substances hazardous to health

All manufacturers must supply Material Safety Data Sheets for potentially hazardous substances

Protection: ventilation, PPE, change chemicals every 2 weeks

4 Radiology (19 decks)

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