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X-ray Physics > Test #2 > Flashcards

Test #2 Flashcards

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1
Q

This refers to the overall blackening of the finished radiograph

A

Radiographic/Optical density

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2
Q

As the mAs is increased, the quantity of radiation is _______ & the optical density is ______

A

Increased: Increased

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3
Q

Increasing kVp does what to density?

A

Increases it

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4
Q

What is the 15% rule?

A

A 15% increase in kVp will have the same effect on density as doubling the mAs. A 15% decrease in kVp will have the same effect on density as decreasing the mAs by 1/2

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5
Q

What is the Inverse Square Law?

A

The intensity of the x-ray beam is inversely proportionate to the square distance from the source

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6
Q

Increase in SID requires that what is increased to maintain density?

A

mAs

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7
Q

A faster film-screen system speed does what to density?

A

Increases it

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8
Q

What is the variation in densities on the radiograph called?

A

Radiographic contrast

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9
Q

Radiographic contrast is the product of what 2 major factors?

A

Film contrast

Subject contrast

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10
Q

What is a controlling factor of contrast?

A

kVp

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11
Q

What are controlling factors of density?

A

Milliamperage

Time

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12
Q

How do influencing factors affect contrast?

A

By controlling the amount of scatter that reaches the film

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13
Q

How do grids affect contrast?

A

By absorbing much of the scatter that exits the pt before it reaches the film

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14
Q

How does collimation affect contrast?

A

Less collimation irradiates more tissue causing more scatter which causes less contrast

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15
Q

How does tissue thickness affect contrast?

A

Increase the thickness of tissue increases scatter causing decrease in contrast

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16
Q

What is geometric unsharpness along the edges of the film called? It’s greatest on the cathode side of the tube.

A

Penumbra

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17
Q

What effect does an increase in focal spot size have on recorded detail?

A

Increases unsharpness which decreases in recorded detail

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18
Q

What does increasing the SID do to recorded detail?

A

Decreases unsharpness which increases recorded detail

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19
Q

What does increasing the OID do to recorded detail?

A

Increases unsharpness which decreases recorded detail

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20
Q

Misrepresentation of either the size or shape of the anatomical part

A

Distortion

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21
Q

Distortion is caused by what?

A

d/t inaccurate alignment of the central ray w/ the part being images or the film

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22
Q

What is the function of beam restrictors?

A

Changes the size & shape of the primary beam

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23
Q

What are the types of beam restrictors?

A

Aperture diaphram
Cones & cylinders
Variable aperture diaphragm/collimator

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24
Q

This type of beam restrictor has fixed field sizes, is heavy, and is used for dental & skull xrays

A

Cones & cylinders

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25
Q

This is the M/C’ly used beam restricting device. It has 2 adjustable sets of shutter leaves.

A

Variable aperture diaphragm/collimator

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26
Q

This is the simplest of beam restrictors. Only produces one field size. Used in dedicated chest equipt., tomo., & CT

A

Aperture diaphram

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27
Q

When the film is clamped into the tray, this sensing device in the tray sends a signal to the collimator & it automatically restricts the beam to film size & provides unexposed borders all around the film

A

Positive Beam Limiting Device (PBL)

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28
Q

This device is placed b/w the pt & the film to decrease the amount of scatter reaching the film

A

Grid

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29
Q

Grids w/ “good clean-up” will attenuated what % of scatter?

A

80-90%

30
Q

A higher grid ratio does what to scatter?

A

More effectively cleans scatter

31
Q

A 5:1 grid cleans up what % of scatter?

A

85%

32
Q

A 16:1 grid cleans up what % of scatter?

A

97%

33
Q

This is the number of lead strips per inch or cm.

A

Grid frequency

34
Q

What is the M/C grid frequency?

A

60-110 lines per inch

35
Q

What are the 3 types of grids?

A

Linear
Cross Grid (Cross hatched)
Focused grid

36
Q

This type of grid is commonly used. It allows for t.t. w/o attenuation of the primary beam

A

Linear grid

37
Q

This type of grid cleans up more scatter than the linear type. Central axis of the beam must be in the center of the grid. Can’t use t.t.

A

Crossed grid

38
Q

This type of grid must be used at specific focal film distances. The required distance is marked on the grid but you can vary the distance 10cm either way & still maintain qulaity

A

Focused grid

39
Q

These are undesirable images of lead strips on the film

A

Grid lines

40
Q

This is a moving grid/Bucky grid

A

Potter Bucky diaphram

41
Q

What type of grids can a potter bucky diaphram be used w/?

A

Linear & focused grids only

42
Q

This is undesirable absorption of the primary beam by the grid. Causes the edges of the film to be light

A

Grid cut off

43
Q

What is the M/C film size to see grid cut off?

A

14x17 or larger

44
Q

What are 3 types of grid cutoff?

A

Upside down focused grid
Lateral decentering
Distance decentering

45
Q

Type of grid cutoff caused by the tube side of the grid not facing the tube. Causes a plus density (dark stripe) down the center of the film.

A

Upside down focused grid cutoff

46
Q

What are the 3 causes of lateral decentering?

A

Grid is off level
Tube is angled against the lead lines
Central ray is not in the center of a focused grid

47
Q

Type of grid cutoff caused by using the focused grid outside of the recommended SID

A

Distance decentering

48
Q

When light strikes the silver halide crystals in the emulsion it creates what type of image?

A

Latent image (metallic silver)

49
Q

When the film is chemically processed, the latent images b/co what?

A

Manifest image (elemental silver)

50
Q

Transparent plastic that provides support for the emulsion. Light blue tint which makes it easy on the eyes & enhances contrast

A

Film base

51
Q

This geltin is clear, gives structure, & holds the silver halide crystals

A

Emulsion

52
Q

What is the primary active ingredient in silver halide crystals?

A

Silver bromide

53
Q

This is the gelatinous covering that protects the emulsion from scratching, pressure, & contamination

A

Supercoat

54
Q

What are the 3 types of film?

A

Screen film
Direct exposure film
Duplicating film

55
Q

What is the M/C type of film used in medical imaging? It’s designed to be used w/ intensitfying screens & usually has double emulsion

A

Screen film

56
Q

Type of film primarily used for extremities. Doesn’t use screens, has a cardboard cassette, is thicker. & has a high concentration of silver halide crystals

A

Direct exposure film

57
Q

Type of film has emulsion on one side that is exposed to UV light through the existing radiograph

A

Duplicating film

58
Q

Increasing the ______ or _____ of silver halide crystals increases film speed/sensitivity

A

Number; size

59
Q

The color of light to which a particular film is most sensitive is called what?

A

Spectral sensitivity

60
Q

This is a silver halide film that responds to blue & violet light. Uses calcium tunstate screens

A

Blue sensitive

61
Q

This is an orthochromatic film that responds to blue & green light. Uses rare earth screens

A

Green sensitive

62
Q

Lights w/ a colored filter that provide some illumination in the dark room

A

Safe lights

63
Q

The safe light filter must be based on what?

A

Spectral sensitivity of the film

64
Q

The wavelength of the safe light must be what?

A

Above the spectral response of the film (If not, it leaves a fog on the film

65
Q

What is the closest distance a safelight can be to film?

A

4ft

66
Q

What is the watt range a safelight can be?

A

7.5-15 watts

67
Q

Type of safelight used for blue sensitive film?

A

Amber Filter/Wratten 6B filter

68
Q

Type of safelight used for blue or green sensitive film

A

Red filter/GBX filter

69
Q

Type of safelight used for green sensitive film

A

Wratten 1A filter

70
Q

What temp, should you store films in?

A

<68F

71
Q

How long can you refrigerate films for?

A

Up to 1yr at 50F

72
Q

What does a humidity level >60% do to the films?

A

Decrease contrast

X-ray Physics (4 decks)

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