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RAD1418 > Unit 4 > Flashcards

Unit 4 Flashcards

1
Q

Image Contrast

A

the degree of difference between the light and dark areas of a radiograph

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2
Q

What makes blacks, whites, and grays?

A

differential absorption

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3
Q

Subject Contrast

A

the component of image contrast determined by the size, shape, and x-ray attenuating characteristic of the subject who is being examined and the energy of the x-ray beam

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4
Q

What controls subject contrast?

A

kVp

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5
Q

What is the process that produces subject contrast?

A

Differential Absorption

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6
Q

Differential Absorption

A

the difference between the x-ray photons absorbed and those that penetrate the body

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7
Q

Attenuation

A

removal of any photons from the primary beam before striking the image receptor

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8
Q

Causes or attenuation

A

Patient absorption
Compton scatter

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9
Q

differential attenuation

A

a form of primary beam attenuation specific to patient absorption and compton scatter

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10
Q

Absorption

A

refers to x-ray photons that are attenuated by the body and do not reach the IR

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11
Q

Transmission

A

refers to x-ray photons that pass through the body and reach the IR

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12
Q

Primary Beam

A

the x-ray beam as it is upon exiting the collimator and exposing the patient

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13
Q

Remnant Beam

A

the x-ray beam that remains after interaction with the patient and that is exiting the patient to expose the IR

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14
Q

What is the remnant beam composed of?

A

transmitted photons and scattered photons

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15
Q

Radiopaque

A

body structures that readily absorb x-ray photons

(bones)

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16
Q

Radiolucent

A

less dense body structures that have much lower probability of absorption

(air-filled lungs)

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17
Q

Photoelectric Effect

A

absorption

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18
Q

How is absorption represented radiographically?

A

white

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19
Q

How is transmission represented radiographically?

A

black

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20
Q

What are the various shades of gray caused by?

A

tissues of the body where photons aren’t completely absorbed or transmitted

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21
Q

High contrast

A

large differences in brightness (B/W) on a radiograph

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22
Q

What is brightness?

A

exposure

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23
Q

What “scale” is high contrast?

A

Short Gray-Scale

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24
Q

Does short gray scale have more B/W or more Gray?

A

More B/W.

Only a few grays

25
Q

A decrease in kVp results in _____ contrast and _____ gray scale.

A

A decrease in kVp results in high contrast and short gray scale.

26
Q

An increase in kVp results in ______ contrast and _____ gray scale

A

An increase in kVp results in low contrast and long gray scale

27
Q

low contrast

A

small differences in brightness on a radiograph

28
Q

What “scale” is low contrast?

A

Long gray scale

29
Q

Does long gray scale have more b/w or more gray?

A

More gray

Some b/w

30
Q

What term describes the total number of differences in brightness levels that are visible on a radiograph?

A

Gray Scale

31
Q

Bit Depth

A

total brightness levels that an imaging monitor is capable of displaying

32
Q

8 factors affecting image contrast

A
  1. x-ray beam quality (kVp)
  2. differential absorption (subject contrast)
  3. Computer processing and display
  4. filtration
  5. compton scatter
  6. radiographic grids
  7. OID
  8. beam restriction
33
Q

high kvp = ___ contrast

A

high kvp = low contrast

34
Q

low contrast = _____ gray scale

A

long

35
Q

8 factors: kVp

increasing kvp _____ pentrability

A

increases

36
Q

8 factors: kVp

a greater percentage of the beam passing through the patient = a ____ percentage of differential absorption

A

decreased

37
Q

8 factors: kVp

a decreased percentage of differential absorption = ____ gray scale, and ___ image contrast

A

long gray scale
low image contrast

38
Q

8 factors: kVp

decreasing kvp = _____ penetrability

A

decreased

39
Q

8 factors: kVp

a decreased percentage of beam passing through the patient = ____ percentage of differential absorption

A

increased

40
Q

8 factors: kVp

an increased percentage of differential absorption = ____ gray scale, and ____ image contrast

A

short gray scale
high image contrast

41
Q

Contrast is the percentage of _______ vs. ______

A

absorption vs transmission

42
Q

8 factors: differential absorption

higher levels of differential absorption = ____ black and white

A

more

43
Q

8 factors: differential absorption

increased differential absorption = ____ subject contrast, and ____ gray scale

A

high subject contrast
short gray scale

44
Q

8 factors: differential absorption

decreased differential absorption = ____ subject contrast, and ___ gray scale

A

low subject contrast
long gray scale

45
Q

8 factors: differential absorption

more matter =

A

more scatter

46
Q

is scatter diagnostic?

A

no

47
Q

Scatter has what effect on contrast?

A

decreases contrast

48
Q

8 factors: Computer processing and display

Look Up Table (LUT)

A

primary controlling factor in image contrast

49
Q

8 factors: Computer processing and display

when does the LUT take place?

A

after the exposure is made and the image is being processed by the imaging system software

50
Q

8 factors: filtration

filtration

A

removes low energy photons from the x-ray beam

51
Q

8 factors: filtration

an increase in filtration = a _____ in contrast

A

decrease

52
Q

filtration and contrast have what type of relationship?

A

indirect

53
Q

8 factors: filtration

an increase in filtration = a _____ in differential absorption

A

decrease

54
Q

8 factors: filtration

a decrease in filtration = a ____ in differential absorption

A

increase

55
Q

8 factors: filtration

a increase in filtration = a ____ in differential absorption

A

decrease

56
Q

8 factors: compton scatter

compton scatter

A

an x-ray photon that interacts with the body and then scatters off of its original trajectory

57
Q

8 factors: compton scatter

does compton scatter contribute useful information

A

no

58
Q

8 factors: compton scatter

what does compton scatter do to image contrast?

A

decreases

59
Q
A

RAD1418 (5 decks)

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