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trisemester 3 TCC > test 2 xray physics > Flashcards

test 2 xray physics Flashcards

1
Q

What is the function of the circulation system of automatic processing systems?

A

Mixes and filters solutions

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2
Q

What is the function of the replenishment system of automatic processing systems?

A

Adds fresh chemistry each time a film is processed

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3
Q

What are the lines that are longitudinally orientated in the direction of the transport film called?

A

guide shoe artifacts (guide lines)

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4
Q

What is the purpose of intensifying screens?

A

Reduce exposure necessary to make image by converting x-ray energy to visible light

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5
Q

What is the term for visible light emission in response to outside stimulation?

A

Luminescence

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6
Q

_____% of x-rays incident on x-ray film will interact with the film

_____% of x-rays incident on screen will interact to produce visible light

A

_____% of x-rays incident on x-ray film will interact with the film

_____% of x-rays incident on screen will interact to produce visible light

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7
Q

Doster: “What protects the intensifying screen from physical damage?”

Answer: _______________

A

Protective coating

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8
Q

What layer of the intensifying screen produces light?

A

Phosphor layer

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9
Q

Does the phosphor layer of intensifying screens fluoresce or phosphoresce?

A

Fluoresce

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10
Q

What layer of the intensifying screen projects light toward film?

A

Reflective layer

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11
Q

What parts make up intensifying screens?

A

Protective coating

Phosphor layer

Reflective layer

Base (plastic)

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12
Q

What are some requirements that help the phosphor layer of intensifying screens interact?

A

High atomic # - increase probability of photoelectric interaction

Spectral matching - produce light in blue/green spectrum

High conversion efficiency

Minimum afterglow

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13
Q

What type of compounds are used for the phosphor layer of of intensifying screens?

A

Rare earth phosphors such as

Lanthanum
Yttrium
Gadolinium

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14
Q

Rare earth phosphors become more efficient as what increase?

A

kVp (>60kVp)

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15
Q

What is the formula for intensification factor?

A

Exposure without screen divided by exposure with screen needed to produce optical density of 1

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16
Q

Exposure without screen divided by exposure with screen needed to produce optical density of 1 is known as what?

A

Intensification factor

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17
Q

Pertaining to intensifying screens, increased crystal concentration, size, and thickness of phosphor layer will ______ speed and ________ resolution

A

increase speed and decrease resolution

It is analogous to film

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18
Q

Spatial Resolution of intensifying screens are expressed as what?

A

Line pairs per millimeter (lp/mm)

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19
Q

Normal spatial resolution regarding line pairs/mm range from what to what?

A

7 to 15 lp/mm

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20
Q

As screen speed increases, what happens to resolution?

A

Resolution decreases

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21
Q

What has better resolution? The x-ray film or the screen?

A

X-ray film has better resolution, the screen has most influence on system speed

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22
Q

Do screens “wear out”?

A

no

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23
Q

How do you clean cassettes?

A

Mild soap/water or special cleaning solutions

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24
Q

When putting x-ray film on the screen, should they be in contact?

A

Yes! They could have complete contact, a blurred area suggest poor film/screen contact
When putting x-ray film on the screen, should they be in contact?

25
Q

What are the 3 operator control panel settings that are non-physical?

A

Kilovoltage peak (kVp)
Milliamperage (mA)
Time (fractions of seconds)

26
Q

What is a physical factor that controls exposure?

A

Source-image distance

27
Q

What does kVp control regarding the x-ray beam?

A

X-ray beam quality

The quality controls the ability to penetrate
and quantity but not a proportional level

28
Q

As kVp increases, what happens to differential absorption?

A

Differential absorption decreases, which causes contrast to decrease

29
Q

What happens to contrast as kVp increases?

A

Contrast decreases

30
Q

What does mA determine in relation to x-rays?

A

X-ray beam quantity

31
Q

mA and time can be combined as a product called _______.

A

mAs

32
Q

When mA or time is changed, what is affected in relation to the x-ray beam?

A

ONLY the quantity

proportional

33
Q

What determines the area impacted by the projectile electrons?

A

Focal spot size - it is on the anode

34
Q

Does smaller or larger focal spot size affect the quantity or quality of photon production at a given kVp and mAs?

A

No it does not affect quantity or quality!

BUT

It determines the area over which projectile electron energy is distributed…. It can be a limiting factor for how much kVp and mAs can be safely used without heat damage to the anode

35
Q

What is the fixed amount of filtering that is built into the x-ray machine to meet government safety standards?

A

Inherent filtration

36
Q

What is the additional aluminum or leaded plexiglass filters added to the collimator?

A

Added filtration

37
Q

What are the 3 basic types of high voltage generators that are still in use?

A

Single phase (full wave rectified)

Three phase

High frequency (latest and greatest technology - reduces voltage ripple)

38
Q

What is the most efficient type of high voltage generator that has the lowest voltage ripple, most efficient x-ray production, and lower patient dose?

A

High frequency

39
Q

What are some patient factors that affect x-ray technique?

A

Body Habitus - radiographic exposure charts correlate patient measurements with correct selection of kVp and mAs

Part thickness - thickness of the tissue to be x-rayed determines the exposure factor setting

Composition of tissue - some tissues have more inherent contrast

Pathology - tissue density can be increased or decreased by disease processes

40
Q

Why are patient measurements taken in centimeters and not inches?

A

Because centimeters are smaller than inches and less likely to give you fractional values

41
Q

What is patient body habitus?

A

Radiographic exposure charts that correlate patient measurements with correct selection of kVp and mAs

42
Q

Optical density of x-ray image refers to what?

A

How much light can pass through

43
Q

Overexposed x-ray film appears what color?

A

black

44
Q

Underexposed x-ray film appears what color?

A

white

45
Q

What is the primary control of optical density of the image?

A

mAs

46
Q

If a film is over or underexposed enough to have to repeat the x-ray, by how much percentage do you have to change the mAs by in order for it to be a “visible change” to the optical density?

How about if the change needs to be significant?

A

greater than 30%

If the change needs to be significant, the mAs should be doubled or halved

47
Q

What is the 15% rule?

A

15% increase in kVp will approximately double exposure of the image receptor

48
Q

In order to make a visible change in an image, which requires a greater change? kVp or mAs?

A

mAs

kVp requires a much SMALLER change to get the same result as changing mAs

49
Q

If you wanted to double the exposure of the image receptor with a kVp of 80, what would you change the kVp to? why?

A

92 kVp - the 15% rule states if you increase kVp by 15% it will double the exposure to the image recepto

50
Q

Resolution has 2 components known as what?

A

Spatial resolution

Contrast resolution

51
Q

Spatial resolution of x-ray film is __________ than resolution of the intensifying screens

A

Greater

52
Q

What is the undesirable fluctuation or alteration of optical density?

A

Noise

53
Q

What are the four components of noise?

A

Film grain - film crystal size

Structure mottle - screen crystal size

Quantum mottle - distribution of photons

Scatter (most important)

54
Q

When x-raying the trunk of a larger patient, is it better to have them in a recumbent position or an upright position?

A

Recumbent position

55
Q

Source-Image Distance

SID

A

Distance between the source and the film

56
Q

Source-Object Distance

SOD

A

Distance between the source and object you are xraying

57
Q

Object-Image Distance

OID

A

Distance of object and xray film

58
Q

1/2 shadow

Created by objects that are outside of the xray beam and intern does not have edge sharpness

A

Penumbra

59
Q

How can you decrease the magnification effect?

A

Increase SID and decrease OID

trisemester 3 TCC (25 decks)

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