Deck 11: Scatter Control

Question 1

Restriction of the primary beam to the anatomy of interest:

A) reduces patient exposure
B) is a major cause of repeated images
C) reduces the amount of scatter produced
D) A and C

Answer 1

A and C

Question 2

The probability of a Compton interaction occurring is related to:

A) the energy of the x-ray photon
B) the atomic number of the matter
C) the mAs used
D) all of the above

Answer 2

the energy of the x-ray photon

Question 3

When imaging the pelvis,changing from 14 × 17 collimation to 8 × 10 collimation requires:

A) an increase in kVp
B) a decrease in kVp
C) an increase in mAs
D) a decrease in mAs

Answer 3

an increase in mAs

Question 4

The most effective and often used radiographic beam-restriction device is the:

A) aperture diaphragm
B) collimator
C) cone or cylinder
D) none of the above

Question 5

The flat piece of lead with a hole in it is the:

A) aperture diaphragm
B) collimator
C) cone or cylinder
D) none of the above

Question 6

The most easily adjusted radiographic beam-restricting device is the:

A) aperture diaphragm
B) collimator
C) cone or cylinder
D) none of the above

Question 7

The beam-restriction device that includes a visible light projecting the x-ray field size onto the patient is the:

A) aperture diaphragm
B) collimator
C) cone or cylinder
D) none of the above

Question 8

The field shape produced by a collimator is:

A) round
B) oval
C) rectangular
D) all of the above

Question 9

As compared with lower kVp exposures,when using high kVp the energy of the scattered photon is:

A) lower
B) higher
C) the same
D) half

Question 10

A flat piece of lead with a hole in it that has a flange directed toward the patient is a(n):

A) aperture diaphragm
B) collimator
C) cone or cylinder
D) none of the above

Question 11

Decreasing collimation (opening up the field size)results in:

A) increased scatter production and higher contrast
B) increased scatter production and lower contrast
C) decreased scatter production and higher contrast
D) decreased scatter production and lower contrast

Question 12

The volume of tissue irradiated is determined by:

A) the area of collimation
B) patient thickness
C) field size
D) all of the above

Question 13

The beam-restriction device that results in images with the most unsharpness around the edge of the image is the:

A) aperture diaphragm
B) collimator
C) cone or cylinder
D) none of the above

Question 14

_____________________ collimation means _________________ field size.

A) decreasing;increasing
B) increasing;increasing
C) decreasing;decreasing
D) none of the above

Question 15

For radiographic procedures,scatter radiation is primarily the result of:

A) photoelectric interaction
B) pair production
C) Compton interaction
D) classical scattering

Question 16

When there is significant collimation,the amount of radiation reaching the IR is:

A) reduced
B) increased
C) the same
D) none of the above

Question 17

The automatic collimator:

A) automatically collimates to the anatomy of interest
B) is required by law on all new equipment
C) is seldom found on modern x-ray equipment
D) automatically collimates to the IR size

Question 18

The two major factors that affect the amount of scatter radiation produced and exiting the patient are:

A) kVp and mAs
B) volume of tissue irradiated and mAs
C) volume of tissue irradiated and kVp
D) kVp and the use of a grid

Question 19

The unrestricted primary x-ray beam is:

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

Question 20

Which of the following produces the greatest amount of scatter radiation exiting the patient?

A) low kVp and small field size
B) low kVp and large field size
C) high kVp and small field size
D) high kVp and large field size

Question 21

The higher the grid ratio,the _____________ the scatter clean up and the _____________________ the radiographic contrast.

A) better;higher
B) worse;lower
C) better;lower
D) worse;higher

Question 22

The number of lead lines per inch or centimeter is the grid:

A) number
B) ratio
C) frequency
D) rating

Question 23

The relationship between the height of the lead strips and the distance between them is the grid:

A) number
B) ratio
C) frequency
D) rating

Question 24

The material between the lead strips of a grid must be:

A) radiopaque
B) radiolucent
C) made of lead
D) made of tungsten

Question 25

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

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

Question 26

The distance between the grid and the convergent line is the:

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

Question 27

What is the grid ratio if the grid frequency is 100 lines/inch,and the lead strips are 1.8 mm high and 0.3 mm apart?

A) 5:1
B) 6:1
C) 8:1
D) 12:1

Question 28

An IR that has a grid permanently attached to its front surface is a:

A) wafer grid
B) bucky
C) grid cap
D) grid cassette

Question 29

The grid is located:

A) just below the x-ray tube window
B) between the patient and IR
C) just below the IR
D) none of the above

Question 30

Linear grids are the most commonly used because:

A) they are very inexpensive
B) the tube can be angled in all directions
C) the tube can be angled in the direction of the lead lines
D) all of the above

Question 31

Grids absorb scatter radiation because the scattered photons:

A) have high energy
B) have extremely low energy
C) travel in the same direction as the transmitted photons
D) travel at an angle to the transmitted photons

Question 32

A focused grid's lead strips are angled to match:

A) the anode angle
B) the angle of the x-rays in the primary beam
C) the angle of the scattered photons leaving the patient
D) the tube angulation

Question 33

What is the grid ratio if the lead strips are 2.4 mm high,0.03 mm wide,and 0.2 mm apart?

A) 5:1
B) 61
C) 8:1
D) 12:1

Question 34

The purpose of automatic collimation is:

A) improved image quality
B) limiting patient exposure
C) increasing the cost of equipment
D) none of the above

Question 35

A linear grid:

A) has lead strips that cross each other
B) has lead strips that travel in one direction
C) is the most common type of radiographic grid
D) B and C

Question 36

The location in space where all the lines extended from the lead strips meet is the:

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

Question 37

A grid with lead strips that run parallel to each other is a:

A) parallel grid
B) focused grid
C) nonfocused grid
D) A and C

Question 38

Grids are typically only used when the part measures more than ________ cm and ______ kVp is needed for the examination.

A) 5;50
B) 10;50
C) 10;60
D) 15;65

Question 39

Which of the following is the formula used to determine grid ratio?

A) Grid ratio = distance between the lead strips / height of the lead strips
B) Grid ratio = width of the lead strips / height of the lead strips
C) Grid ratio = height of the lead strips / distance between the lead strips
D) Grid ratio = height of the lead strips / width of the lead strips

Question 40

If all the convergent points were connected along the length of the grid they would form the:

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

Question 41

When the x-ray beam is angled across the lead strips you have _________ cutoff.

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

Question 42

The reason the grid in the bucky reciprocates is to:

A) absorb more scatter radiation
B) allow more transmitted radiation to reach the IR
C) blur out the grid lines
D) all of the above

Question 43

The grid is part of a device located just below the tabletop that also includes a tray to hold the IR.This device is the:

A) wafer grid
B) bucky
C) grid cap
D) grid cassette

Question 44

A short-dimension grid:

A) is typically used for most examinations
B) has lead strips running perpendicular to the long axis of the grid
C) has lead strips running parallel to the long axis of the grid
D) A and B

Question 45

If 24 mAs and a 6:1 grid results in an excellent radiograph,how much mAs is needed with a 5:1 grid?

A) 16 mAs
B) 20 mAs
C) 28.8 mAs
D) 36 mAs

Question 46

The formula for the grid conversion factor is:

A) GCF = mAs without grid / mAs with grid
B) GCF = mAs with grid - mAs without grid
C) GCF = mAs with grid / mAs without grid
D) GCF = mAs without grid - mAs with grid

Question 47

During the exposure,the grid in the bucky:

A) reciprocates
B) moves slightly from side to side
C) moves slightly from top to bottom
D) A and B

Question 48

The formula to use when changing from one grid to another is:

A) mAs₁/mAs₂ = GCF₂/GCF₁
B) mAs₁/mAs₂ = (GCF₂)²/GCF₁)²
C) mAs₁/mAs₂ = GCF₁/GCF₂
D) mAs₁/mAs₂ = (GCF₁)²/GCF₂)²

Question 49

Grid cutoff results in:

A) reduced exposure to the IR
B) a light film-screen image
C) possible quantum mottle
D) all of the above

Question 50

The type of grid that is usually taped to the front of an IR is the:

A) wafer grid
B) bucky
C) grid cap
D) grid cassette

Question 51

The cutoff that appears as a strip of appropriate density in the middle of the image and a significant loss of density on both sides is:

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

Question 52

If a tabletop exposure (no grid)of a humerus requires 2.5 mAs,how much mAs is needed if a 12:1 ratio grid is added?

A) 0.21 mAs
B) 0.5 mAs
C) 12.5 mAs
D) 30 mAs

Question 53

When the x-ray beam is not lined up with the center of the grid you have _________ cutoff.

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

Question 54

If 22 mAs and a 5:1 grid results in an excellent radiograph,how much mAs is needed with a 12:1 grid?

A) 8.8 mAs
B) 9.2 mAs
C) 52.8 mAs
D) 55 mAs

Question 55

When the SID is above or below the focal range you have _________ cutoff.

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

Question 56

The type of grid that includes a channel for the IR to slide into is the:

A) wafer grid
B) bucky
C) grid cap
D) grid cassette

Question 57

To compensate for the reduction of radiation reaching the IR when a grid is used,___________ is typically increased.

A) SID
B) kVp
C) mAs
D) OID

Question 58

Absorption of transmitted photons by a grid caused by misalignment is:

A) grid focus
B) grid reduction
C) grid cutoff
D) transmission reduction

Question 59

If a shoulder examination is done using an 8:1 ratio grid and 12 mAs,how much mAs should be used if the examination must be done tabletop (no grid)?

A) 1.5 mAs
B) 3 mAs
C) 48 mAs
D) 96 mAs

Question 60

To determine the amount of mAs to be increased when making grid changes,it is necessary to use the GCF,also known as the:

A) grid constancy figure
B) grid compensatory factor
C) general compensation factuals
D) grid conversion factor

Question 61

Scatter radiation is of no value in radiographic imaging.

Question 62

It is safe to assume that the x-ray beam field size and the light field size are exactly the same.

Question 63

When using automatic collimation,collimating to the anatomy of interest is an unnecessary waste of time;the beam is already collimated.

Question 64

The air gap technique reduces the amount of scatter radiation reaching the IR because:

A) more scatter is absorbed in the air
B) less scatter is produced in the patient
C) more scatter misses the IR
D) less scatter misses the IR

Question 65

Anyone in the room during an exposure must wear a lead apron to absorb the scatter radiation produced in the:

A) table
B) patient
C) air
D) beam

Question 66

The Moiré effect is also known as the _________ pattern.

A) cheetah
B) giraffe
C) lion
D) zebra

Question 67

The grid limits the amount of scatter radiation produced in the patient.

Question 68

Focused grids are more effective than parallel grids in absorbing scatter radiation and allowing transmitted radiation to reach the IR.

Question 69

Which of the following factors need to be considered when determining the grid to be used for a specific examination?

A) patient exposure
B) level of contrast improvement needed
C) focal range
D) all of the above

Question 70

Which of the following grids provides excellent scatter clean-up but requires close to perfect alignment to avoid cutoff?

A) 5:1 ratio grid
B) 8:1 ratio grid
C) 12:1 ratio grid
D) 16:1 ratio grid

Question 71

Adding a grid or increasing grid ratio results in an increase in patient dose.

Question 72

The air gap technique is based on creating a gap by increasing the ______.

A) SID
B) SOD
C) OID
D) all of the above

Question 73

The Moiré effect can be caused by:

A) using a grid with a frequency similar to the CR laser scanning frequency
B) using a focused grid upside down in the bucky
C) using a grid cassette in the bucky
D) A and C

Question 74

The grid used for the air gap technique should be high frequency.

Question 75

For a lateral lumbar spine,placing a lead shield on the table behind the area of exposure:

A) reduces the scatter exiting the patient
B) reduces the scatter reaching the IR
C) A and B
D) none of the above

Question 76

To compensate for some of the loss of recorded detail due to the large OID used with the air gap technique,the ________ should be increased as well.

A) grid ratio
B) SID
C) focal spot size
D) A and B

Question 77

Beam-restricting devices are located just above the tube housing.

Question 78

The only grid cutoff error that can occur with a parallel grid is:

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

Question 79

Grids absorb almost all of the scatter radiation and allow all of the transmitted photons to pass through to the IR.

Question 80

The air gap technique is a frequently used method for reducing the amount of scatter radiation reaching the IR.