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Physics 2 > Ch. 12 Scatter Control > Flashcards

Ch. 12 Scatter Control Flashcards

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1
Q

scatter in diagnostic x-ray is primarily due to this type of interaction

A

Compton effect

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2
Q

what are the 2 major factors that affect scatter production

A
  • tissue volume
  • kVp
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3
Q

what is tissue volume dependent on

A

part thickness and field size

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4
Q

scatter adds unwanted radiation to the image, what do we call this

A

fog

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5
Q

beam restrictions do these two things

A
  • limits patient dose
  • reduces scatter production
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6
Q

relationship between collimation and field size

A

inverse

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7
Q

increasing collimation does what to field size

A

decrease field size

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8
Q

increasing collimation does what to scatter production

A

decreases scatter production

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9
Q

significant changes in collimation will require this

A

adjusted mAs

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9
Q

going from a 14x17 field size to a 4x4 field size may require what

A

more mAs

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10
Q

essentially a flat piece of lead with a small hole in it, attaches to the collimator

A

aperture diaphragms

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11
Q

long tube/cone that attaches to the collimator, most often used for dental imaging today, can also be used for small parts such as nasal bones and fingers. These devices help to limit both scatter and beam divergence

A

cones/cylinders

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12
Q

most used form beam restriction, this is the part of the x-ray tube that we use to set field size. Typically consists of 2-3 lead shutters that can be adjusted using controls on the collimator

A

collimators

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13
Q

also called positive beam-limiting devices (PBL). these are essentially the same as standard collimators, the difference is that these automatically set selected field size depending on what exam is being completed. a lot of collimators today are a form of PBL

A

automatic collimators

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14
Q

who invented the radiographic grid and when

A

Gustave Bucky - 1913

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15
Q

number of lead strips per unit length

A

grid frequency

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16
Q

the ratio of the height of the lead strips and the distance between them

A

grid ratio

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17
Q

what are the 2 types of grid focus

A
  • parallel grid
  • focused grid
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18
Q

what are the 4 types of grid

A
  • wafer grid
  • grid cassette
  • grid cap
  • reciprocating grid
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19
Q

stationary, same size as IR, usually taped to secure it to IR

A

wafer grid

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20
Q

stationary, IR with a permanent grid mounted to the front surface

A

grid cassette

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21
Q

stationary, very similar to the wafer, but is designed to hold the IR, so no tape is required to secure it. Most common grid type

A

grid cap

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22
Q

dynamic, they slightly move while the image is being taken, so as to blur out grid lines. these are built into wall stands and table buckys

A

reciprocating grid

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23
Q

the decrease in the number of transmitted photons that reach the IR due to grid misalignment

A

grid cutoff

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24
Q

because focused grids are designed to match beam divergence, if they are place upside down, then they will cutoff most of the radiation before it can reach the IR

A

upside down focused

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25
Q

most common type of cutoff, happens when the IR with grid is tilted and the CR is not adjusted to match. also the only type that can occur with both focused and parallel grids

A

off-level

26
Q

happens with focused grids when the CR is not aligned to the center of the IR, once again, because focused grids are designed to work with beam divergence

A

off-center

27
Q

occurs when SID is outside of the focal range of the focused grid, meaning the tube is either too close or too far away from the IR at the time of exposure. This results in images with not enough exposure along the edges of the image

A

off focused

28
Q

zebra stripe pattern that occurs when the grid frequency of a stationary grid used in CR imaging is similar to the laser scanning frequency of the CR reader

A

moire effect

29
Q

what can help eliminate moire effect

A
  • using higher frequency grids
  • using moving grids with CR
30
Q

method for limiting the scatter reaching the image receptor. scatter will miss the image receptor if there is increased distance between the patient and the image receptor (increased OID)

A

air gap technique

31
Q

the simplest type of beam-restricting device, constructed of a flat piece of lead that has a hole in it

A

aperture diaphragm

32
Q

automatically limits the size and shape of the primary beam to the size and shape of the image receptor

A

automatic collimator

33
Q

changes the shape and size of the primary beam; located just below the x-ray tube housing

A

beam-restricting device

34
Q

refers to a decrease in the size of the projected radiation field also known as collimation

A

beam restriction

35
Q

the potter-bucky diaphragm located directly below the radiographic tabletop, which contains the grid and holds the image receptor

A

bucky

36
Q

can be used to determine the adjustment in milliampere/second needed when changing from using a grid to non-grid (or vice versa) or for changing to grids with different grid ratios

A

bucky factor

37
Q

refers to a decrease in the size of the projected radiation field, also known as beam restriction

A

collimation

38
Q

located immediately below the tube window where the entrance shutters limit the x-ray beam field size

A

collimator

39
Q

essentially an aperture diaphragm that has an extended flange attached

A

cone

40
Q

an imaginary line if points were connected along the length of a linear focused grid

A

convergent line

41
Q

an imaginary point, if imaginary lines were drawn from each of the lead lines in a linear focused grid

A

convergent point

42
Q

has lead line that run at a right angle to one another

A

cross-hatched grid; crossed grid

43
Q

essentially an aperture diaphragm that has an extended flange attached to it

A

cylinder

44
Q

the distance between the grid and the convergent line or point; also known as the grid radius

A

focal distance

45
Q

the recommended range of SID measurements that can be used with a focused grid

A

focal range

46
Q

has lead line that are angled, or canted, to approximately match the angle of divergence of the primary beam

A

focused grid

47
Q

a device that has very thin lead strips with radiolucent interspaces; intended to absorb scatter radiation emitted from the patient before it strikes the IR

A

grid

48
Q

contains a permanently mounted grid and allows the IR to slide in behind it

A

grid cap

49
Q

an IR that has a grid permanently mounted to its front surface

A

grid cassette

50
Q

can be used to determine the adjustment in milliampere/second needed when changing from using a grid to non-grid (or vice versa) or for changing to grids with different grid ratios; also called the bucky factor

A

grid conversion factor (GCF)

51
Q

a decrease in the number of transmitted photons that reach the image receptor because of some misalignment of the grid

A

grid cutoff

52
Q

the orientation of a grid’s lead lines to one another

A

grid focus

53
Q

expresses the number of lead lines per unit length in inches, centimeters, or both

A

grid frequency

54
Q

refers to the linear pattern of the lead lines of a grid

A

grid pattern

55
Q

the ratio of the height of the lead strips to the distance between them

A

grid ratio

56
Q

radiolucent strips between the lead lines of a grid, generally made of aluminum

A

interspace material

57
Q

changes the shape and size of the projected x-ray field; similar to an aperture diaphragm

A

lead mask

58
Q

has lead lines that run in one direction only

A

linear grid

59
Q

a zebra pattern artifact that can occur during computed radiography imaging if the grid frequency is similar to the laser scanning frequency or if a grid cassette is placed in a bucky

A

Moire effect

60
Q

has lead lines that run parallel to one another; also called a parallel grid

A

non-focused grid

61
Q

has lead lines that run parallel to one another; also called a non-focused grid

A

parallel grid

62
Q

automatically limits the size and shape of the primary beam to the size and shape of the image receptor; also called automatic collimator

A

positive beam-limiting (PBL) device

63
Q

a stationary grid placed on top of the image receptor

A

wafer grid

Physics 2 (16 decks)

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