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RADT 171 - Phys. 2 > Scatter Radiation > Flashcards

Scatter Radiation Flashcards

1
Q

Factors that influence scatter

A

kVp, patient size, field size

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2
Q

Source of occupational exposure

A

Compton scatter

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3
Q

As ___ increases, Compton interactions also increase

A

kVp (energy)

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4
Q

T/F: Modern digital filming is more sensitive to scatter than older filming modalities

A

True

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5
Q

T/F: Field size and collimation are inversely related

A

True

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6
Q

Automatic collimators use ____ to match the light field with the cassette size

A

Positive beam limiting (PBL)

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7
Q

Go on the tube head/window to limit the beam coming out

A

Aperture diaphragm

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8
Q

“Cleans up” scatter radiation using lead strips that absorb scattered x-rays

A

Grids

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9
Q

Use of a grid requires more ___

A

mAs

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10
Q

Increase in patient size [increases/decreases] amount of scatter

A

increases

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11
Q

Grid Ratio =

A

h/D
(h= height of lead strips)
(d= distance between them)

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12
Q

Use of a grid is recommended for anatomy greater than:

A

4 inches (10 cm) thickness

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13
Q

Number of lead lines per unit length

A

Grid frequency

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14
Q

T/F: The higher grid frequency, the more distinct grid lines on x-ray image

A

False

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15
Q

Two types of grid patterns:

A

Cross-hatched and linear

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16
Q

An aperture diaphragm that has an extended flange attached to it

A

Cone/cylinder

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17
Q

The orientation of the lead lines relative to one another

A

Grid focus

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18
Q

Grid conversion factor =

A

mAs with grid / mAs without grid

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19
Q

A decrease in the number of transmitted photons that reach the IR because of some misalignment of the grid

A

Grid cutoff

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20
Q

Occurs when using an SID outside the recommended focal range

A

Off-focus grid cutoff

21
Q

Concept that much of the scatter will miss the IR if there is an increased distance between the patient and the IR

A

Air gap technique

22
Q

mAs should be increased __% for every centimeter of air gap

A

10

23
Q

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

A

Collimator

24
Q

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

A

Grid

25
Q

A larger the x-ray beam field size results in:

A

increase in scatter produced and increase in fog

26
Q

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

A

True

27
Q

Changing from an 8:1 grid to a 12:1 grid, along with making the appropriate adjustments, will result in:
A: an image with increased contrast
B: using more mAs
C: Increased patient dose

A

A, B, and C

28
Q

T/F: Digital IRs are not sensitive to scatter radiation

A

False

29
Q

Grids that move during the exposure:

A

are reciprocating grids and are part of the Potter-Bucky diaphragm

30
Q

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

31
Q

T/F: Placing a lead shield behind the patient’s lower back during lumbar spine imaging absorbs the scatter and reduces the amount striking the IR.

A

True

32
Q

Significant collimation requires an increase of _____________ of the mAs.

A

30 - 50%

33
Q

The most common cause of grid cutoff is due to:

A

off-level misalignment.

34
Q

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

A

round

35
Q

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

A

5 x

36
Q

Why does the air-gap technique work?

A

The scatter photons are more likely to miss the image receptor.

37
Q

T/F: A good alternative to collimation is electronic masking.

A

False

38
Q

A larger field size will result in ___ scatter production

A

Increased

39
Q

An increase in collimation results in a [increase/decrease] in radiographic contrast

A

Increase

40
Q

When making a significant increase in collimation, _____ should be increased

A

mAs

41
Q

The purpose of a grid in radiography is to:

A

Increase image contrast

42
Q

With which one of the following grids would a convergent line be formed if imaginary lines from its grid lines were drawn in space above it?

A

Linear focused

43
Q

With exposure technique compensation, which of the following would result in the greatest radiation exposure to the patient?

A

a 12:1 grid ratio

44
Q

Off-focus grid cutoff occurs by using an SID that is not:

A

within the focal range of the grid

45
Q

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

A

beam-restricting devices and radiographic grids

46
Q

What purpose does positive beam limitation serve?

A

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

47
Q

As beam restriction increases:
a. less volume of tissue is irradiated and higher image contrast
b. less scatter is produced and higher image contrast
c. less scatter is produced and less volume of tissue is irradiated
d. all options are correct

A

D

48
Q

Which of the following is not a way to reduce the production of scatter radiation?
a. Reduce the tissue thickness.
b. Reduce the exposure field size.
c. Increase collimation.
d. Increase the grid ratio.

A

D

49
Q

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

A

More Compton interactions

RADT 171 - Phys. 2 (10 decks)

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