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BDS3 RADIOLOGY > 5 - Digital and film radiography > Flashcards

5 - Digital and film radiography Flashcards

1
Q

What are the different types of intra-oral digital receptor?

A
  • phosphor plate
  • solid-state sensor
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2
Q

What are the different types of film receptor?

A
  • direct action film
  • indirect action film
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3
Q

What are the typical sizes of film/plates used?

A

Size 0 = anterior PA
Size 2 = BWs, posterior PA
Size 4 = occlusals

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4
Q

What is an x-ray shadow?

A
  • when x-ray photons are attenuated by the subject, they create an x-ray shadow
  • the receptor picks up the shadow and creates an image
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5
Q

How do digital plates display an image?

A
  • 1000s of pixels that can only display one colour at a time
  • colour determined by the number of photons that interact with it
  • ranges from 0-255
  • black = 0
  • white = 255
  • grey shades = 1-254
  • the more pixels there are the moral detailed the image
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6
Q

What format are digital images stored in?

A
  • DICOM
  • digital imaging and communications in medicine
  • international standard for handling digital medical images, which allows compatibility with all HC software
  • also stores patient ID, exposure settings and date
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7
Q

How are digital images managed?

A
  • PACS
  • picture archiving and communication system
  • stores multiple imaging modalities
  • secure network for transmission of patent information
  • allows for reviewing images
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8
Q

How should you review digital radiographs?

A
  • subdued lighting
  • avoid glare
  • clean monitor with adequate resolution, suitable brightness and contrast
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9
Q

How can you test if your screen is suitable to assess radiographs?

A
  • SMPTE test
  • society of motion picture and television engineers
  • assess resolution, contrast and brightness
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10
Q

How do phosphor plates function?

A
  • not connected to computer
  • must be scanned to read “final” image
  • phosphor crystals are excited by x-ray energy to create latent image
  • receptor is scanned by a laser cause the excited crystals to emit visible light
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11
Q

What are the different types of solid-state sensors?

A
  • CCD (charged-coupled device)
  • CMOS (complimentary metal oxide semiconductor)
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12
Q

How do solid-state sensors function?

A
  • connected to computer
  • latent image created and immediately read within sensor
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13
Q

What is the identification dot?

A

Located in corner of receptor to aid orientation

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14
Q

How is cross-infection controlled in intra-oral digital radiology?

A
  • single use covers
  • receptor also disinfected between uses
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15
Q

How can you reduce damage to digital receptors?

A

Handle by the edges

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16
Q

How do phosphor plates compare to solid-state sensors physically?

A
  • phosphor plates are thinner, lighter and more flexible
  • solid-state sensors are more rigid and bulkier
  • phosphor plates are wireless and therefore more comfortable and stable that solid-state sensors
17
Q

How do phosphor plates compare to solid-state sensors regarding storage?

A
  • phosphor plates are light sensitivity so should be stored in a dark box
  • solid-state sensors are not light sensitive
18
Q

Describe the composition of a dental film packet.

A
  • outer package
  • lead foil packaging
  • inner paper wrap
  • dental film
19
Q

What is the function of the lead foil in an intra-oral film packet?

A

Absorb excess x-ray photons

20
Q

What is the function of the outer wrapper in an intra-oral film packet?

A
  • prevent ingress of saliva
  • indicate which side of the packet is the front
21
Q

What is the function of the protective paper wrap in an intra-oral film packet?

A

Protect film from light exposure, damage by fingers and saliva

22
Q

How does radiographic film function?

A

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

23
Q

Describe the structure of radiographic film.

A
  • protective coating of gelatin (shields emulsion from mechanical damage)
  • emulsion (layered on both side of plastic base)
  • adhesive (attached emulsion to plastic base)
  • transparent plastic base (supports emulsion)
24
Q

What is the radiographic emulsion?

A
  • silver halide (often silver bromide) crystals embedded in gelatin binder
  • crystals are microscopic and are the “pixels”
25
Q

How does the emulsion capture a radiographic image?

A
  • silver bromide crystals become sensitised upon interaction with x-ray photons (and visible light - bad)
  • when processed, sensitised crystals converted to black metallic silver = dark parts of image and non-sensitised crystals are removed = light parts of image
26
Q

Define film speed.

A
  • the amount of x-ray exposure required to produce an image
  • high speed = less radiation required
  • speed is affected by number and size of silver halide crystals
  • larger crystals = faster film = poorer image quality
27
Q

What is an intensifying screen?

A
  • screen release visible light upon exposure to x-ray which creates latent image on film
  • bulky so used in extra-oral radiographs
  • reduced image quality but do reduce dose
28
Q

What are the stages of developing film?

A
  1. Developing
  2. Washing
  3. Fixing
  4. Washing
  5. Drying
29
Q

Describe developing film.

A

Converts sensitised crystals to black metallic silver particles

30
Q

Describe washing (1).

A

Removes residual developer solution

31
Q

Describe washing (2).

A

Removes residual fixer solution

32
Q

Describe fixing film.

A
  • removes non-sensitised crystals
  • hardens emulsion which still contains black metallic silver
33
Q

Describe drying film.

A

Removes water so that film is ready to be stored

34
Q

What are the advantages and disadvantages of self-developing films?

A

ADVANTAGES
- no dark room required or procession facilities
- faster

DSISADVANTAGES
- poor image quality
- image deteriorates after time
- no lead foil
- easily bent
- difficult to use

35
Q

What can cause a pale image?

A
  • radiation exposure factors too low
  • film removed from solution too early
  • solution too cold
  • solution too dilute
36
Q

What can cause a darker image?

A
  • radiation exposure factors too high
  • film removed from solution too late
  • solution too warm
  • solution too strong
37
Q

What causes a milky/greenish-yellow image?

A
  • inadequate fixing meaning non-sensitised crystals are left behind
  • image browns over time

BDS3 RADIOLOGY (9 decks)

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