Exposures Chapter 10 Quiz - Grids and Beam Limitation

When a focused grid is used, the appearance of grid cut-off is is NOT associated with which of the following

tube angulations directed along the grid strips

Which of the following errors in grid use will have the same results as an angulation error?

off-level or tilted grid error

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

volume of tissue irradiated and kVp

What is the main advantage of the use of a moving grid over a stationary grid?

grid lines will be blurred and not visible with a moving grid

The only grid cut-off error that can occur with a parallel grid is:

off-level

As a general rule, a radiographic grid is employed for:

part thicknesses above 10 cm

Penumbra is _____ when the field size is _____

reduced; decreased

When a beam-restricting device is used to limit field size, technical factors may need to _____ to compensate for the change in image receptor exposure

be increased

The most common type of grid pattern is the:

focused grid

Grids absorb scatter radiation because the scattered photons:

travel at an angle to the transmitted photons

Which one of these grid ratios will absorb the most scattered radiation?

A. 6:1

B. 8:1

C. 5:1

D. 12:1

12:1

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

A. 8:1

B. 5:1

C. 12:1

D. 6:1

6:1

(grid ratio = height/depth; grid ratio = 1.8/0.3)

A radiograph is produced in a table Bucky. The tube was properly centered to the image receptor in the Bucky tray, yet grid lines were seen. A probable cause is:

insufficient grid speed

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?

12.5 mAs

The _____ the atomic number of the irradiated material, the _____ number of photoelectric absorption interactions that occur.

higher; higher

The use of a grid on a radiograph has what effect on contrast?

increases it

During the exposure, the grid in the bucky:

A. moves slightly from side to side

B. reciprocates

C. moves slightly from top to bottom

A and B

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

collimator

Which kVp selection would result in the most scattered x-rays in the image-forming beam?

- 50 kVp

- 75 kVP

- 60 kVp

- 90 kVp

90 kVp

The field shape produced by a collimator is:

rectangular

A technologist acquires an x-ray of the pelvis using 100 kilovoltage peak (kVp), 10 milliampere-seconds (mAs), 40 inches source-to-image distance (SID), and no grid. The exposure level is good, but the contrast is too low.

If the exam is repeated using a 16:1 grid, what new technique should be employed?

A. 85 kVp and 15 mAS

B. 100 kVp and 15 mAs

C. 100 kVp and 60 mAs

D. 85 kVp and 60 mAs

100 kVp and 60 mAs

(mAs new = mAs old x grid conversion factor new/grid conversion factor old; mAs new = 10 mAs x 6/1 = 60 mAs)

A type of grid in which the grid lines are situated parallel to the divergent rays of the x-ray beam is termed a:

focused grid

All of the following are true of positive beam limitation (PBL) EXCEPT:

- may be overridden hy the radiographer in select instances

- is possible with portable radiography

- senses the size and orientation of the receptor

- automatically collimates the beam

is possible with portable radiography

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

frequency

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

reduces the scatter reaching the IR

Which of the following combination of factors is most likely to be associated with a radiographic image possessing the highest radiographic contrast?

- 300 mA, 30 msec, 68 kVp, 12:1 grid ratio

- 200 mA, 50 msec, 84 kVp. 10:1 grid ratio

- 600 mA, 15 msec, 98 kVp, 12:1 grid ratio

- 400 mA, 25 msec, 87 kVp, 8:1 grid ratio

300 mA, 30 msec, 68 kVp, 12:1 grid ratio

Which one of these grid pattens is the most restrictive for angling the central ray?

A. criss-cross grid

B. parallel grid

C. focused grid

criss-cross grid

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

A. parallel grid

B. focused grid

C. non-focused grid

both A and C

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

Compton interation

Which of these statements is true about scattered radiation?

1. Scattered radiation has less energy than primary radiation.

2. Scattered radiation is produced in the x-ray tube.

3. Scattered radiation puts additional energy on the image receptor.

4. Scattered radiation travels in a different direction from primary radiation.

5. Scattered radiation increases radiographic contrast.

1, 3, and 4 (Scattered radiation has less energy than primary radiation, scattered radiation puts additional energy on the image receptor, scattered radiation travels in a different direction from primary radiation)

A patient has been brought to the imaging department for a radiograph of his knee. Previously, the patient had a portable knee exam completed in the emergency department, using 70 kilovoltage (kV) 2.5 milliampere-seconds (mAs), and a 6:1 grid. In the x-ray room, the exposure will be completed with the image receptor in the Bucky tray with a 12:1 grid. What new mAs will be required for the exposure in the department to compensate for the higher ratio grid?

- 4.16 mAs

- 7.5 mAs

- 1.5 mAs

- 12.6 mAs

4.16 mAs

(mAs new = mAs old x grid conversion factor new/grid conversion factor old; mAs new = 2.5 x 5/3 = 4.16 mAs)

A radiographic image that has excessive fogging due to scatter radiation would be described as:

low contrast

When an x-ray beam passes through the body,

A. it will be absorbed by the body

B. it will pass through the body unaffected

C it will interact with the body and change direction

all of the above

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

A. focal range

B. level of contrast improvement needed

C. patient exposure

all of the above

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

convergent point

Which one of these maneuvers would produce grid cut-off?

angling the central ray against the grid lines

Which type of grid pattern will result in a radiograph with the least amount of primary beam cut-off?

focused grid

Photon absorption within the body occurs as the result of:

photoelectric interactions

Lower kVp _____ patient dose and _____ image contrast

increases; increases

A grid that has lead strips with a height of 4 mm that are spaced 0.5 mm apart will have a grid ratio of:

- 8:1

- 16:1

- 4:1

- 2:1

8:1

(4/0.5 = 8)

A Potter-Bucky diaphragm must move the grid in a direction that is _____ to the direction of the grid lines.

perpendicular

Grid cut-off results in:

- a light film-screen image

- reduced exposure to the IR

- possible quantum mottle

all of the above

The name of the man who invented the grid is:

Gustave Bucky

Which situation is most likely to result in grid errors?

- tabletop radiography

- stationary radiography at the table bucky

- stationary radiography at the upright bucky

- mobile radiography

mobile radiography

What is the advantage of a focused grid as compared to a non-focused grid?

decreased grid cut-off

The ability of a grid to absorb scattered radiation after it exits from the patient is termed the:

grid efficiency

The tolerance range of acceptable source-image distances that can be used with a focused grid is the:

focal range

The positive beam limiting device (PBL) assures that the x-ray beam is collimated to _____

the image receptor size

The greatest source of scatter during a radiographic examination is the:

patient

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

- low kVp and large field size

- low kVp and small field size

- high kVp and large field size

- high kVp and small field size

high kVp and large field size

Which grid error results in grid cut-off and loss of exposure on the outside edges of the image receptor (IR)?

incorrect source-to-image distance (SID) with a focused grid

A radiographer can best reduce the amount of scatter radiation from reaching the receptor by:

A. collimating

B. beam restriction

C. utilizing a grid

all of the above

The ratio of the height of the lead strips to the distance between the lead strips is the grid:

ratio

A device that moves the grid during a radiographic exposure is called a:

Potter-Bucky diaphragm

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

more scatter misses the IR

Linear grids are the most commonly used because:

tube can be angled in the direction of the lead lines

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

aperture diaphragm

When grids are utilized, the technical factors must be adjusted to maintain the IR exposure because:

1. The amount of scatter produced in the patient decreases.

2. The amount of scatter reaching the image receptor decreases.

3. The SID must be increased.

2 only

The minimum kVp that requires use of a grid is:

60

The distance at which a focused grid can be used is most closely related to the:

convergence line