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Module 4 - radiology > Image Receptors > Flashcards

Image Receptors Flashcards

1
Q

What type of x-rays use direct film image production?

A

intra oral

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2
Q

what is direct film image production?

A

x-rays act directly on silver halide crystals in film emulsion

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3
Q

what type of x-rays use indirect film image production?

A

extra-oral

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4
Q

what is indirect film?

A

light from intensifying screens act on silver halide crystals in film emulsion

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5
Q

what are the 2 types of digital image production?

A

solid state
PSP

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6
Q

What type of sensors produce solid state digital images?

A

CCD or CMOS

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7
Q

What type of digital image production is tolerated better?

A

PSP

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8
Q

What is a phosphor plate?

A

storage plate that converts existing film based imaging system to a digital format that can be integrated into a computer or network system

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9
Q

what part of the phosphor plate is exposed to x-ray photons and scanned by the red laser?

A

phosphor layer

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10
Q

what produces a latent image?

A

x-ray energy stored in the electrons of the phosphor crystals (trapped signal)

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11
Q

in PSP, what is released as blue light?

A

stored energy

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12
Q

in PSP, what converts light to a digital signal?

A

ACD

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13
Q

In PSP, what represents the shades of grey which form the image on the monitor?

A

numerical value assigned to each pixel according to the intensity of detected light

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14
Q

how is the image on the phosphor plate erased?

A

exposing the phosphor to bright light - releases any remaining trapped energy in the phosphor electrons

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15
Q

what is the phosphor coating on the phosphor plate?

A

barium fluoride

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16
Q

What is CCD?

A

Charged-coupled device

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17
Q

what is CCD used for?

A

digital radiography for the indirect conversion of x-ray photons into an electric charge

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18
Q

what gives off light in CCD?

A

X-rays hit the scintillator layer within the sensor

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19
Q

what makes up pixels of an CCD image?

A

light hits the photosensitive cells within a very thin piece of silicon

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20
Q

in CCD what is converted into an electrical signal?

A

the charge electrons within each pixel being released

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21
Q

what is converted to produce an image in CCD?

A

ELECTRICAL SIGNAL

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22
Q

What differs CCD to CMOS?

A

CCD - pixels connected to form lines of pixels
CMOS - individual pixels

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23
Q

what is exposure?

A

the amount of x-rays to produce an image

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24
Q

what is PACS?

A

picture archiving and communication system

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25
what are 0, 1, 2 PSP sizes used for?
periapical and bitewings
26
what are 0, 1 PSP sizes used for?
periapical anterior mouth of adult and all regions for children
27
what is 2 PSP size used for?
posterior mouth of adults
28
what is size 4 PSP used for?
occlusal
29
what size of solid state receptor would you normally use?
2
30
what is the lead foil in film packet?
composed of lead and aluminium - readily absorbs x-rays - prevents black scatter
31
what are the 4 layers of dental film?
- super coat - base - adhesive layer - emulsion
32
what is the emulsion layer of a dental film made of?
silver halide crystals (silver bromide and silver iodide) suspended in gelatine
33
what is the super coat of dental film made of?
gelatine
34
what does the adhesive layer in the dental film do?
sticks emulsion to the base
35
explain the image formation - direct action (intra oral)
- x-ray photons hit silver halide crystals within the emulsion of the film - silver halide crystals become sensitised - latent image is produced - silver bromide crystals are reduced to black metabolic silver
36
what is a latent image?
the pattern produced within the emulsion by the sensitising of silver bromide/ iodide crystals by light/ x-rays
37
what effects film speed?
- sensitivity of film to x-rays - exposure required to produce a given amount of blackening on an image - larger the crystals the faster the film speed
38
how does crystal size affect detail?
larger crystals = reduced detail
39
how is light produced in extra oral/ indirect film?
intensifying screens inside cassette
40
what is a positive and negative of intensifying screens?
reduce the dose required reduce detail
41
what are the layers of an intensifying screen?
reflective layer phosphor layer supercoat
42
explain extra oral image formation?
- x-ray photons hits the phosphor crystals in the intensifying screen and give off light - light hits silver halide crystals within the film emulsion - silver halide crystals become sensitised - latent image produced
43
how should films be stored?
cool dry away from radiation - x-ray, heat stock rotation
44
what are the 3 types of film processing?
automatic, manual and instant
45
what are the 5 stages of film processing?
- develop (make latent image visible) - wash (stop development and remove from film) - fix (make image permanent) - wash (stop fix and remove residual fixer) - dry (easier handled, prevent damage)
46
what does developing do?
making the image visible
47
how is an image made visible?
- sensitised silver halide crystals are acted on by developing agents (phenidone and hydroquinone) - silver bromide reduced to silver plus bromide - silver is in the form of black metallic silver thus giving the blackening on the film
48
what are developing agents?
phenidone and hydroquinone
49
what is the activator and development and what does it do?
calcium carbonate - controls the activity of the developing agents
50
what is the restrainer in development and what does it do?
potassium bromide - stops developer working on unexposed crystals
51
what is the preservative in development and what does it do?
sodium sulphite - slows down oxidation
52
what is the solvent in development?
water
53
what is the action of developing agents dependant on?
time temperature concentration
54
how is the image made permanent?
fixing agents change unexposed silver halide to soluble compound do they can be washed away
55
what is the clearing agent in fixing?
ammonium thiosulphate
56
what is the acidifier in fixing?
acetic acid (maintains pH)
57
What is the hardener in fixing?
aluminium chloride
58
what is the preservative in fixing?
sodium sulphite
59
what is the solvent in fixing?
water
60
what is the action of fixing agents dependant on?
time temperature concentration
61
what happens if an image is over fixed?
fixed image will be removed from film
62
what happens if an image is under fixed?
appear to have a green tinge and will not archive well
63
what are the 3 types of washing?
manual automatic instant
64
when does manual washing take place?
between dev. and fix between fix and dry
65
what does manual washing do?
stops action of developer and reduces carryover - removed unexposed silver halide crystals once made soluble by fixer
66
when does automatic washing take place?
between fix and dry
67
what does automatic washing do?
Remove unexposed silver halide crystals once made soluble by fixer.
68
what happens if film not washed properly?
feel tacky, and may have a green or silvered appearance. Will not archive well so will deteriorate.
69
what does drying ensure?
film is dry before it is handled and reduces the possibility of damage to emulsion
70
what is the health and safety act?
health and safety at work act 1974
71
what are the major components of the health and safety at work act 1974?
control of substances hazardous to health regulations (COSHH) Risk assessment adequate ventilation (10 or more room volumes per hour)

Module 4 - radiology (14 decks)

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