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Image Prod & Eval > Week 5 - Chapter 13 > Flashcards

Week 5 - Chapter 13 Flashcards

1
Q

What makes it easier to identify objects in images?

A

A greater difference between the shade of the object and the background

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2
Q

What are intensity differences called?

A

Contrast

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3
Q

What does a greater difference in intensity produce?

A

Higher contrast

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4
Q

What is image noise?

A

Unwanted often grainy appearances in radiographs

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5
Q

What is one form of noise?

A

Scattered radiation

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6
Q

What are 2 other forms of noise in images?

A

Electronic and statistical

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7
Q

What is Electronic noise?

A

Mechanical noise from a machine (monitor)

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8
Q

What is Statistical noise?

A

Noise from an algorithm used to construct an image

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9
Q

What is quantum mottle?

A

Image noise that occurs from a lack of penetration due to low kVp or mAs

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10
Q

What is the predominant type of noise in digital images?

A

Quantum mottle

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11
Q

What does noise do to images?

A

Degrades the image and reduces contrast

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12
Q

When is scatter radiation generated?

A

When x-rays strike atoms in a patient, table or other objects

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13
Q

What direction does scatter travel?

A

In random directions

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14
Q

What contrast level is the goal of technologists?

A

Optimum contrast

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15
Q

How does noise affect contrast?

A

Noise reduces subject contrast

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16
Q

Can noise be entirely eliminated?

A

No

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17
Q

What are the three factors that make up the visibility of an image?

A
  • Intensity
  • Contrast
  • Noise
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18
Q

How should intensity and contrast be kept in an image?

A

At an optimal level

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19
Q

How should noise be kept?

A

At a minimum

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20
Q

What is gray scale?

A

The range of different brightness’s in an image

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21
Q

What is a long gray scale?

A

An image with many different grays with small differences between them

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22
Q

What is the contrast of long gray scale?

A

Low contrast

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23
Q

What is short gray scale?

A

An image with less gray and more differences between them

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24
Q

What is the contrast of short gray scale?

A

High contrast

25
Q

How can digital images that appear on monitors have their contrast adjusted?

A

Through windowing

26
Q

How does windowing work?

A

When the brightness levels are adjusted and the gray scale is changed from long to short and vise versa

27
Q

How should images be presented on a screen?

A

Not entirely white or black, should be in an intermediate level of gray scales

28
Q

What happens if an image is too long in contrast?

A

One gray may not be able to be distinguished from each other

29
Q

What does an image that is overly dark indicate?

A

That the part/object was over penetrated

30
Q

What does over penetration of an object mean in terms of attenuation?

A

Little attenuation

31
Q

How can optical density be measure in film radiographs?

A

Using a densitometer

32
Q

How is digital brightness indicated?

A

Numerically, usually known as level (c)

33
Q

How are most images viewed?

A

As Negatives

34
Q

What are the qualities of image negatives?

A

The tissues that attenuate the beam more are white and tissues that attenuate the beam less are black

35
Q

What process is used to change a negative image to a positive image?

A

Subtraction

36
Q

What are qualities of image positives?

A

The tissues that attenuate the beam more are black and the tissues that attenuate the beam less are white

37
Q

What is radiographic contrast?

A

The proportional difference between the brightness of two adjacent details

38
Q

What is image contrast independent of?

A

Brightness

39
Q

How is contrast measured?

A

As a ratio between the darker detail and lighter detail

40
Q

How can an image be darkened while retaining its contrast?

A

If the ratio between bright and dark shades stays the same

41
Q

What kV produces a longer wavelength photon?

A

Low kV

42
Q

What is the penetration of a longer wavelength photon?

A

Low penetration

43
Q

What type of gray scale does a longer wavelength photon (low kV) create?

A

Short scale

44
Q

How can the brightness of digital images be manipulated on a computer?

A

By leveling

45
Q

What is signal?

A

All the desirable information for an object based on its contrast

46
Q

How is signal calculated?

A

The total exposure minus the scatter

47
Q

What is the Signal to Noise Ratio (SNR) compare?

A

The relationship between information and noise in an image

48
Q

How can an image be made better regarding noise and signal?

A

By reducing noise or increasing signal

49
Q

How does an increased signal usually appear on an image?

A

As a brighter overall image

50
Q

What are artifacts?

A

Any objects that are not a part of the image

51
Q

What are some types of artifacts?

A
  • Snaps on a hospital gown
  • Leads to EKGs
  • Zippers, Jewelry
52
Q

How does a densitometer work?

A

Measures the darkness of a plastic film

53
Q

What are not examples of Artifacts?

A

Bullets or objects swallowed

54
Q

What is brightness?

A

The opposite of density and the degree of whiteness of an image

55
Q

What is brightness caused by?

A

A lack of radiation exposure

56
Q

What is density?

A

The opposite of brightness, and the degree of darkness in an image

57
Q

What is density caused by?

A

The presence of radiation exposure

58
Q

Diagnostic information can be lost if an image has these qualities?

A
  • Excessive contrast
  • Excessive grey scale
  • Excessive blur
59
Q

How does focal spot relate to sharpness of detail?

A

The smaller the focal spot, the better the sharpness

Image Prod & Eval (10 decks)

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