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23 Radiology > 3 - Digital Imaging > Flashcards

3 - Digital Imaging Flashcards

1
Q

is film or digital less expensive initially

A

film: less espensive initially
digital: expensive initially

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2
Q

does film or digital have quick acquisition

A

film: slow
digital: quick

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3
Q

how do process film vs. digital

A

film: chemical processing
digital: no darkroom and no chemicals

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4
Q

radiation dose of film vs digital

A

film: more radiation dose
digital: 80% less radiation dose

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5
Q

security of film vs. digital

A

film: physical security
digital: cyber security

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6
Q

what is smallest element of digital picture

A

pixel

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7
Q

what is spatial distribution of pixels in rows and columns with different shades of grey in each pixel

A

matrix

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8
Q

what is a digital image with an approximation of real scene

A

digitization

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9
Q

what is used for sensor construction

A
  1. scintillation screen
  2. fiber optic faceplate
  3. active semiconductor layer
  4. charge-coupled device (CCD)
  5. complementary metal oxide semiconductor (CMOS)
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10
Q

what protects semiconductor layer and provides a sharper image to reduce scatter

A

fiber optic faceplate

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11
Q

what is active semiconductor layer made of

A

silicon

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12
Q

what happens to active semiconductor layer when exposed to radiation

A
  • Electrons are released from valence band into the conduction band, generating an electron hole charge pair
  • Electrons are then attracted towards the most positive potential in the device where they create “charge packets”
  • Each packet corresponds to one pixel
  • Amount of electron hole pairs is proportional to the amount of exposure an area receives
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13
Q

what is this called:

each pixel is like a tiny battery with its charge equal to the number of electrons trapped inside; the computer records the charge in each pixel and converts it into a gray value

A

Simplified Sensor Concept

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14
Q

what move photogenerated charge from pixel to pixel and convert it to voltage at an output node

A

charge-coupled device (CCD)

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15
Q

what has each pixel individually read

A

complementary metal oxide semiconconductor (CMOS)

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16
Q

a small range of voltage values are grouped together as a single value

A

sampling (Analog to digital conversion)

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17
Q

poor representation of original image, less storage space

A

wide sampling

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18
Q

better representation of original image, more storage space

A

narrow sampling

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19
Q

every sampled signal is assigned a numeric value

A

quantization

20
Q

the emission by a substance of stored energy as light

A

luminescence

21
Q

main advantage of PSP

A

flexible (fits in patient’s mouth better)

22
Q

what consists of reusable imaging plate coated with phosphor instead of the sensory

A

PSP

23
Q

key characteristics of PSP

A

1) Made of europium-doped barium Fluoro halide
2) X-ray exposure - energy is stored (latent image)
3) Plate processing
4) Image is read with a scanning laser
5) Photomultiplier tube amplifies the signal
6) Light energy is converted to electrical energy
7) Analog to digital converter (ADC) - converts electrical energy to digital image
8) Plate is exposed to bright white light to erase any residual trapped energy to
reuse the PSP

24
Q

what is PSP made of

A

europium-doped barium Fluoro halide

25
Q

PSP workflow

A

Plate
exposure -> Plate processing -› Plate erasing Pack and reuse plate

26
Q

CCD/CMOS vs PSP:

direct vs indirect

A

CCD/CMOS: direct
PSP: indirect

27
Q

CCD/CMOS vs PSP:

sensor positioning difficulty

A

CCD/SMOS: difficult
PSP: easier

28
Q

CCD/CMOS vs PSP:

does it have cable

A

CCD/CMOS: yes cable
PSP: no cable

29
Q

CCD/CMOS vs PSP:

exposure latitude size

A

CCD/CMOS: small exposure lattitude
PSP: large exposure lattitude

30
Q

CCD/CMOS vs PSP:

cheap or expensive

A

CCD/CMOS: expensive
PSP: cheap

31
Q

CCD/CMOS vs PSP:

processing

A

CCD/CMOS: digital image automatically captured
PSP: plates require processing

32
Q

what is the degree of darkening of exposed film

A

density

33
Q

factors that affect radiographic density of image

A
  1. exposure
  2. subject thickness
  3. subject density
34
Q

what does exposure depend on

A

mA (most important), time, kVp, distance

35
Q

the [thicker or thinner] the subject, the more the beam is attenuated and the ligher the resultant image

A

THICKER

36
Q

if exposure factors intended for adults are used on children or edentulous patients, what happens to the resultant films? why?

A

films are DARK because smaller amount of absorbing tissue is in the path of the xray beam

37
Q

the [greater OR lesser] the density of a structure within the subject, the greater the attenuation of the xray beam directed thru the subject or area

A

greater

38
Q

what is difference in density between areas on the radiograph

A

contrast

39
Q

what does contrast depend on

A
  1. subject contrast
  2. film contrast
  3. fog and scatter
40
Q

when is difference in xray intensity transmitted thru various parts of subject

A

subject contrast

41
Q

what does subject contrast depend on

A
  1. thickness diff
  2. density diff
  3. atomic number diff
  4. radiation quality (kVp)
42
Q

what is LESS important for detecting dentoalveolar disease than contrast and density

A

resolution

43
Q

useful tools for digital image processing

A

Histogram: best means to alter contrast and brightness
Gamma adjustment, zoom, rulers

44
Q

sometimes useful tools for digital image processing

A

filters, digital subtraction

45
Q

what are considered “toys” for digital image processing

A

inversion, color conversion, embossing

23 Radiology (15 decks)

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