Ch 7 Flashcards by Nathanael Cotton

1 - 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

ANS: D - A and B

Beam-restricting devices and radiographic grids are tools that the radiographer can use to limit scatter radiation.

REF: p.179

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3 - 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

ANS: D - To reduce patient exposure by limiting the exposure field to the same size as the image receptor in the Bucky tray

Positive beam limitation (PBL), or automatic collimator, mechanically adjusts the x-ray field size to the size of the image receptor. This makes it difficult for the radiographer to open up the field beyond the image receptor, thus limiting the patient overexposure.

REF: p.187

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4 - 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

ANS: A - Collimator

The collimator, using two or three sets of lead shutters, is best at limiting unsharpness surrounding the radiographic image.

REF: p.187

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

a - greater

b - lesser

ANS: A - greater

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

REF: p.180

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5 - The unrestricted primary beam produces a(n) __________ area of exposure.

a - round

b - oval

c - square

d - rectangular

ANS: A - round

Without a collimator or other beam-restricting device, a round area of exposure would be seen.

REF: p.180

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6 - Decreasing collimation results in:

a - a smaller field size.

b - a larger field size.

c - decreased patient dose.

d - less scatter production.

ANS: B - a larger field size.

Decreased collimation is the same as less beam restriction and results in a larger field size, increased patient dose, and more scatter production.

REF: p.181

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7 - As beam restriction increases, field size and patient dose ____________________.

a - increases

b - decreases

c - does not change

ANS: B - decreases

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

REF: p.181

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

a - increases; increases

b - decreases; increases

c - decreases; decreases

d - increases; decreases

ANS: B - decreases; increases

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

REF: p.181

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

a - Collimator

b - An aperture diaphragm

c - A cylinder

d - A cone

ANS: B - An aperture diaphragm

The aperture diaphragm may be made out of a material that is pliable enough for it to be cut to the size needed.

REF: p.183

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10 - 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

ANS: C - Aperture diaphragm

The aperture diaphragm is least effective at limiting unsharpness surrounding the radiographic image.

REF: p.183

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

a - collimator

b - aperture diaphragm

c - cone

d - cylinder

ANS: D - cylinder

The cylinder is an aperture diaphragm with an attached elongated tube.

REF: p.183

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12 - 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

ANS: A - collimator

The collimator, or variable aperture diaphragm, includes two or three sets of lead shutters, some of which are adjustable.

REF: p.185

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13 - 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.

ANS: C - project a light field onto the patient.

The mirror allows the radiographer to see a light field on the patient, representing the x-ray field that will be produced.

REF: p.186

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14 - 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.

ANS: C - the radiographer must adjust the collimator to the area of interest.

Automatic collimation isn’t available with a digital flat-panel detector; it is up the radiographer to collimate the beam to the area of interest.

REF: p.187

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15 - 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.

ANS: D - grid.

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

REF: p.188

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16 - 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.

ANS: C - Increase the grid ratio.

Increasing the grid ratio will reduce the amount of scatter radiation reaching the image receptor but will have no effect on the production of scatter.

REF: p.202

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17 - 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.

ANS: C - Increase the grid ratio.

Increasing the grid ratio will absorb more of the scattered radiation and reduce the amount reaching the image receptor but will have no effect on the production of scatter.

REF: p.194

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18 - 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.

ANS: B - grid ratio.

Grid ratio is determined by dividing the height of the lead strips by the distance between them.

REF: p.189

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19 - 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.

ANS: 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.

A high ratio grid is more effective at absorbing scatter radiation. Increasing the height of the lead strips and decreasing the distance between them will result in a higher ratio grid.

REF: p.189

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20 - 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.

ANS: C - grid frequency.

The number of lead strips per inch or centimeter is a measure of grid frequency, one way of describing grid construction.

REF: p.189

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21 - 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

ANS: C - Cross-hatched grid

The cross-hatched grid is most difficult to use because it does not allow for any angulation of the x-ray beam.

REF: p.190

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22 - 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

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ANS: A - More Compton interactions

The greater the amount of tissue imaged, the greater the number of Compton interactions and the greater the amount of scatter produced.

REF: p.179

23 - 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

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ANS: A - 8:1

Grid ratio is determined by dividing the height of the lead strips by the distance between them.

REF: p.189

24 - 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.

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ANS: C - As grid ratio increases, the removal of scatter increases.

Higher ratio grids are more effective at absorbing scatter radiation.

REF: p.189

25 - 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

ANS: C - 2 and 3 only The grid conversion factor (GCF) and Bucky factor are both names for the ratio between the amount of mAs needed with and without a grid. REF: p.194

26 - 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

ANS: D - The focused grid The focused grid is designed so that the lead strips are angled to match the divergence of the x-ray beam. REF: p.194

27 - What is the grid conversion factor for a 12:1 ratio grid? a - 3 × b - 4 × c - 5 × d - 6 ×

ANS: C - 5 × The Bucky, or grid conversion, factor for a 12:1 grid is 5. This means that going from no grid to a 12:1 grid will require 5 times the mAs. REF: p.194

28 - 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

ANS: B - Grid cutoff Grid cutoff is the reduction in the number of transmitted photons that reach the image receptor, due to misalignment of the grid and the x-ray beam. REF: p.196

29 - 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

ANS: D - When part thickness exceeds 10 cm It is recommended that a grid be used when the kVp is higher than 60, along with a part that measures more than 10 cm. REF: p.200

30 - 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

ANS: B - air-gap technique The air-gap technique, using increased OID and SID, can be used to reduce the amount of scatter radiation reaching the image receptor. REF: p.203

31 - 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

ANS: B - Upside-down focused grid The upside-down focused grid will allow transmitted radiation to pass through the center portion of the grid but will increasingly absorb the radiation toward the edges. REF: p.197

32 - What is found between the lead strips in a grid? a - Lead b - Tungsten c - Radiopaque material d - Radiolucent material

ANS: D - Radiolucent material Radiolucent (X-rays can pass through it) material is found between the lead strips of the grid. REF: p.188

33 - 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

ANS: A - 2.5 mAs Because the grid conversion factor for an 8:1 grid is 4, removing the grid will only require one fourth of the original mAs, or 2.5 mAs. REF: p.194

34 - 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 - 27 mAs c - 67 mAs d - 80 mAs

ANS: B - 27 mAs Changing from a 12:1 to a 6:1 ratio grid will require less mAs. Using the formula relating mAs and the grid conversion factors, the result is that 27 mAs will be needed. REF: p.194

35 - 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

ANS: C - off-center Resulting in an overall reduction of the number of transmitted photons that reach the image receptor due to grid cutoff, the off-center grid error occurs when the central ray of the x-ray tube is not aligned (from side to side) with the focused grid. REF: p.198

36 - 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

ANS: D - 1, 2, and 3 Increasing grid ratio will require additional mAs, resulting in a higher patient dose. It will also do a better job of cleaning up the scatter radiation, resulting in an image with higher, or a shorter, scale of contrast. REF: p.196

37 - 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

ANS: B - 25 to 80 lines per centimeter Grid frequencies can range from 25 to 80 lines per centimeter. REF: p.189

38 - 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.

ANS: B - height of lead strips divided by distance between them. Grid ratio can be expressed mathematically as the height of lead strips divided between the distance between them. REF: p.189

39 - 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.

ANS: B - 4:1 to 16:1. Grid ratios range from 4:1 to 16:1. REF: p.189

40 - 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

ANS: A - decreased; decreased Decreasing grid ratio (with no change in frequency) results in decreased scatter cleanup and decreased lead content. REF: p.189

41 - 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.

ANS: C - focal range. The focal range is the recommended range of SIDs that should be used with a specific grid. REF: p.192

42 - 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.

ANS: D - A and C. Reciprocating grids, part of the Potter-Bucky diaphragm, move from side to side during the exposure. REF: p.193

43 - 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.

ANS: B - short dimension grid. A short dimension grid has lead strips running perpendicular to the long axis of the grid, or along the short axis. REF: p.193

44 - 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

ANS: C - 2 and 3 only Any time a grid is used, there is an additional exposure needed; changing from a lower to a higher ratio grid also requires additional exposure. REF: p.200

45 - 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.

ANS: D - off-level misalignment. Off-level misalignment is the most common cause of grid cutoff, especially when the grid is used on mobile or cross-table studies. REF: p.197

46 - 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.

ANS: D - off-level misalignment. Off-level misalignment is the only grid error that affects both parallel and focused grids. The other errors affect only the focused grids. REF: p.197

47 - 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.

ANS: B - less the amount of scatter produced. The smaller the volume of tissue, the less scatter is produced. REF: p.179

48 - Significant collimation requires an increase of __________ of the mAs. a - 0% b - 1% to 5% c - 10% to 20% d - 30% to 50%

ANS: D - 30% to 50% Significant collimation requires an increase of 30% to 50% of the mAs. REF: p.182

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

ANS: F Digital IRs are more sensitive to low-energy scatter radiation. REF: p.179

2 - T/F Grids do not reduce scatter production.

ANS: T Grids reduce the amount of scatter reaching the IR but not the production of scatter. REF: p.188

3 - T/F Increasing collimation results in reduced patient exposure, increased field size, and reduced scatter production.

ANS: F Increasing collimation is the same as decreasing field size. It will result in reduced patient exposure, a smaller field size, and reduced scatter production. REF: p.180

4 - T/F As collimation decreases, exposure to the IR increases.

ANS: T As collimation decreases (increased field size), there is an increased exposure to the IR. REF: p.180

5 - T/F An adult’s knee measuring 14 cm should be radiographed without a grid.

ANS: F Parts larger than 10 cm produce enough scatter radiation that a grid is recommended to improve image contrast. REF: p.188

6 - T/F The only reason a grid should be used is to increase radiographic contrast.

ANS: T There is no reason, other than improving image contrast, to include the use of a grid in a procedure. REF: p.188

Ch 7 Flashcards

(54 cards)