Deck 7: Scatter Control

Question 1

Which of the following is not a way to reduce the production of scatter radiation?

A) Reduce the exposure field size.
B) Reduce the tissue thickness.
C) Increase the grid ratio.
D) Ask a patient with a large abdomen to lie prone instead of supine.

Answer 1

Increase the grid ratio.

Question 2

A beam-restricting device that has two or three sets of lead shutters is a(n):

A) collimator.
B) aperture diaphragm.
C) cone.
D) cylinder.

Answer 2

collimator.

Question 3

The purpose of the mirror inside the collimator is to:

A) allow the patient to see the radiographer.
B) allow the radiographer to see the patient.
C) project a light field onto the patient.
D) none of the above.

Answer 3

project a light field onto the patient.

Question 4

Which of the following statements is true?

A) If the height of the lead strips increases and the space between the grid strips decreases, the grid will be more effective at scatter removal.
B) If the height of the lead strip decreases and the space between the grid strips increases, the grid will be more effective at removing scatter radiation.
C) A high ratio grid removes little scatter.
D) A grid decreases scatter production.

Question 5

The larger the x-ray beam field size,the _________ the amount of scatter radiation produced.

A) greater
B) lesser

Question 6

Which of the following influences the amount of scatter radiation striking the image receptor but not the production of scatter radiation?

A) Reduce the exposure field size.
B) Reduce the tissue thickness.
C) Increase the grid ratio.
D) Ask a patient with a large abdomen to lie prone instead of supine.

Question 7

As beam restriction increases,field size and patient dose _________________.

A) increases
B) decreases
C) does not change

Question 8

Which beam restriction device can be cut to the size needed?

A) A collimator
B) An aperture diaphragm
C) A cylinder
D) A cone

Question 9

Which of the following beam-restricting devices is least effective at limiting unsharpness surrounding the radiographic image?

A) Collimator
B) Cylinder cone
C) Aperture diaphragm
D) Focused grid

Question 10

A device consisting of very thin lead strips with radiolucent interspaces intended to absorb scatter radiation emitted from the patient is a:

A) collimator.
B) aperture diaphragm.
C) cone.
D) grid.

Question 11

The height of the lead strips relative to the distance between the lead strips is the measure of:

A) contrast improvement.
B) grid ratio.
C) Bucky factor.
D) grid selectivity.

Question 12

Which of the following are tools that the radiographer can use to limit scatter radiation?

A) Beam-restricting devices
B) Radiographic grids
C) Digital imaging plate
D) A and B
E) B and C

Question 13

The number of lead strips per inch in a grid is a measure of:

A) grid selectivity.
B) grid ratio.
C) grid frequency.
D) contrast improvement number.

Question 14

Which of the following beam-restricting devices is best at limiting unsharpness surrounding the radiographic image?

A) Collimator
B) Cylinder cone
C) Aperture diaphragm
D) Focused grid

Question 15

When using a digital flat-panel detector:

A) the x-ray beam will automatically collimate to the appropriate size for the part.
B) the entire detector should be exposed.
C) the radiographer must adjust the collimator to the area of interest.
D) A and C.

Question 16

Decreasing collimation results in:

A) a smaller field size.
B) a larger field size.
C) decreased patient dose.
D) less scatter production.

Question 17

An aperture diaphragm with an attached elongated tube is a(n):

A) collimator.
B) aperture diaphragm.
C) cone.
D) cylinder.

Question 18

As beam restriction increases,the quantity of scatter radiation __________ and radiographic contrast ___________.

A) increases; increases
B) decreases; increases
C) decreases; decreases
D) increases; decreases

Question 19

The unrestricted primary beam produces a(n)_________ area of exposure.

A) round
B) oval
C) square
D) rectangular

Question 20

What purpose does positive beam limitation serve?

A) To prevent the technologist from placing an image receptor in the Bucky tray that is too large for the study performed
B) To allow the technologist to use an exposure field larger than the image receptor size
C) To prevent first-year students from having to repeat studies by not aligning the Bucky tray with the image receptor
D) To reduce patient exposure by limiting the exposure field to the same size as the image receptor in the Bucky tray

Question 21

What is the result of imaging a thicker part or patient?

A) More Compton interactions
B) Decreased scatter
C) Increased radiographic contrast
D) Decreased fog

Question 22

An optimal AP abdomen radiograph can be produced using 40 mAs,75 kVp,and a 12:1 grid.How much mAs would be needed if the only grid available is a 6:1 ratio grid?

A) 20 mAs
B) 24 mAs
C) 67 mAs
D) 80 mAs

Question 23

Which of the following statements is true?

A) A high ratio grid prevents the production of scatter better than a low ratio grid.
B) A low ratio grid is more effective at removing scatter than a high ratio grid.
C) As grid ratio increases, the removal of scatter increases.
D) High ratio grids are less effective at removing scatter than low ratio grids.

Question 24

Grid ratios range from:

A) 2:1 to 6:1.
B) 4:1 to 16:1.
C) 10:1 to 24:1.
D) 20:1 to 32:1.

Question 25

Also called lateral decentering,the _____ grid error results when the central ray is not aligned to the middle of a focused grid.

A) off-level
B) off-focus
C) off-center
D) upside-down focused

Question 26

What is found between the lead strips in a grid?

A) Lead
B) Tungsten
C) Radiopaque material
D) Radiolucent material

Question 27

In general,when should a grid be used?

A) When part thickness exceeds 4 cm
B) When kV exceeds 40 kVp
C) When kV exceeds 1.02 MeV
D) When part thickness exceeds 10 cm

Question 28

What is the grid conversion factor for a 12:1 ratio grid?

A) 3 ×
B) 4 ×
C) 5 ×
D) 6 ×

Question 29

Due to increased potential grid cutoff,which would be the most challenging grid to use?

A) Focused linear grid
B) Parallel linear grid
C) Cross-hatched grid
D) Reciprocating grid

Question 30

What type of grid error results in appropriate exposure to the middle of the IR and marked underexposure along the sides of the IR?

A) Stationary grid
B) Upside-down focused grid
C) Lateral decentering
D) Off-level

Question 31

Grid frequencies can range from:

A) 10 to 30 lines per centimeter
B) 25 to 80 lines per centimeter
C) 60 to 120 lines per centimeter
D) 25 to 80 lines per inch

Question 32

Changing from an 8:1 grid to a 12:1 grid,along with making the appropriate adjustments,will result in:
1)Increased patient dose
2)An image with increased contrast
3)Using more mAs

A) 1 and 2 only
B) 1 and 3 only
C) 2 and 3 only
D) 1, 2, and 3

Question 33

The amount of mAs required with a grid divided by the amount of mAs needed without a grid is the calculation that determines the:
1)Grid ratio
2)Grid conversion factor
3)Bucky factor

A) 1 and 2 only
B) 1 and 3 only
C) 2 and 3 only
D) 1, 2, and 3

Question 34

Which grid design is manufactured to match the divergence of the x-ray beam?

A) The parallel grid
B) The crossed grid
C) The reciprocating grid
D) The focused grid

Question 35

If an excellent knee radiograph is produced using 10 mAs and an 8:1 ratio grid,how much mAs will be needed if no grid is available?

A) 2.5 mAs
B) 4 mAs
C) 8 mAs
D) 10 mAs

Question 36

Grid ratio can be expressed mathematically as:

A) thickness of lead strips divided by distance between them.
B) height of lead strips divided by distance between them.
C) height of lead strips divided by thickness of lead strips.
D) length of lead strips divided by distance between them.

Question 37

When a grid is needed but not available,the _____ may be used for certain examinations.

A) tomographic technique
B) air-gap technique
C) Seldinger technique
D) reverse collimation technique

Question 38

If the height of the grid strip is 16 mm,the distance between the strips is 2 mm,and the strip is 0.3 mm thick,what is the grid ratio?

A) 8:1
B) 10:1
C) 12:1
D) 16:1

Question 39

Decreasing grid ratio (with no change in frequency)results in _____________scatter cleanup and ____________ lead content.

A) decreased; decreased
B) decreased; increased
C) increased; decreased
D) increased; increased

Question 40

What occurs when the x-ray beam is not properly aligned with the grid strips?

A) Bucky delamination
B) Grid cutoff
C) Increased exposure to the IR
D) Nothing

Question 41

Patient dose increases when:
1)Changing from a higher to a lower grid ratio
2)Changing from a lower to a higher grid ratio
3)A grid is used

A) 1 and 2 only
B) 1 and 3 only
C) 2 and 3 only
D) 1, 2, and 3

Question 42

The only reason a grid should be used is to increase radiographic contrast.

Question 43

Increasing collimation results in reduced patient exposure,increased field size,and reduced scatter production.

Question 44

Significant collimation requires an increase of _____________ of the mAs.

A) 0%
B) 1% to 5%
C) 10% to 20%
D) 30% to 50%

Question 45

Digital IRs are less sensitive to scatter radiation than are film-screen IRs.

Question 46

An adult's knee measuring 14 cm should be radiographed without a grid.

Question 47

Grids that move during the exposure:

A) are reciprocating grids.
B) move from top to bottom.
C) are part of the Potter-Bucky diaphragm.
D) A and C.

Question 48

The only type of grid cutoff that occurs with both focused and parallel grids is due to:

A) using a focused grid upside down.
B) off-center misalignment.
C) off-focus misalignment.
D) off-level misalignment.

Question 49

The recommended SIDs that can be used with a focused grid describe the:

A) focal distance.
B) convergent point.
C) focal range.
D) convergent line.

Question 50

The smaller the volume of tissue irradiated,the:

A) greater the amount of scatter produced.
B) less the amount of scatter produced.
C) greater the need to use a grid.
D) A and C.

Question 51

As collimation decreases,exposure to the IR increases.

Question 52

A grid whose lead strips run perpendicular to the long axis of the grid is called a(n):

A) long dimension grid.
B) short dimension grid.
C) cross-hatch grid.
D) alternating grid.

Question 53

The most common cause of grid cutoff is due to:

A) using a focused grid upside down.
B) off-center misalignment.
C) off-focus misalignment.
D) off-level misalignment.

Question 54

Grids do not reduce scatter production.

Question 55

Why does the air-gap technique work?

A) The scatter photons increase in energy as a result of the distance to the image receptor.
B) The scatter photons are more likely to miss the image receptor.
C) Less scatter is produced.
D) A and C