Grids & Contrast Practice Test

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

10 cm ; 60 kVp

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

12.5 mAs

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

12:1

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

16:1 ratio grid

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

24/x = 3/2 = 16mAs

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

3 mAs

A satisfactory radiograph is produced using 8 mAs at 85 kVp without a grid. A second film is requested using an 8:1 grid with a conversion factor of 4. What mAs is needed to produce the second radiograph?

32 mAs

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

55 mAs

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?

6:1

What is the frequency of a grid with lead strips that are 33 micrometers thick and interspace material that is 310 micrometers thick?

74 lp/inch

Which kVp selection would result in the most scattered x-rays in the image-forming beam? a. 90 kVp b. 75 kVp c. 60 kVp d. 50 kVp

90 kVp

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

A and B

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

A and C

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

A and C

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

A. better, higher

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

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. patient exposure b. level of contrast improvement needed c. focal range d. all of the above

All of the above

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

B. Between the patient and IR

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

Blur out grid lines

Image-forming x-rays include those which have been _. a. transmitted without interaction b.scattered through Compton interaction c. absorbed through photoelectric interaction d. Both A and B

Both A & B

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

Both B & C

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

Bucky

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

C. Increase in mAs

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

Convergent line

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

D. A and C

T/F: Beam-restricting devices are located just above the tube housing.

False

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

False

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

False

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

False

T/F: The grid limits the amount of scatter radiation produced in the patient.

False

T/F: The grid used for the air gap technique should be high frequency

False

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

False

Scatter radiation increases as ___________________ increases. a. photoelectric absorption b. field size c. filtration d. contrast

Field size

The distance between the grid and the convergent line is the: a. convergent line b. focal distance c. convergent point d. focal range

Focal distance

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

Focal range

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

GCF= mAs with grid / mAs without grid

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

Grid cap

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

Grid cassette

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

Grid conversion factor

Absorption of transmitted photons by a grid caused by misalignment is: a. grid focus b. grid reduction c. grid cutoff d. transmission reduction

Grid cutoff

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

Has lead strips running perpendicular to the long axis of the grid

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

MAS1/mAs2=GCF1/GCF2

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

MAs

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

More scatter misses the IR

The air gap technique is based on creating a gap by increasing the ______. a. SID b. SOD c. OID d. all of the above

OID

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

Off center

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

Off focus

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

Off level

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

Off level

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

Patient

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

Reduces the scatter reaching the IR

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

SID

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

The angle of the x-rays in the primary beam

A portable radiograph is taken of a thick body part using a 10:1 stationary grid. The image produced demonstrates a contrast factor (K) of 1.7 . A second radiograph is taken with a different grid of unknown specifications, and the K-value is 2.2. What conclusion can you reach regarding the two grids?

The second grid is more likely a higher ratio grid as the change in contrast is greater. A greater K value indicates greater contrast improvement which is related to grid ratio, grid frequency, and lead content of the grid.

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

The tube can be angled in the direction of the lead lines

T/F: Adding a grid or increasing grid ratio results in an increase in patient dose.

True

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

True

T/F: Scatter radiation is of no value in radiographic imaging.

True

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

Upside-down focused

The x-rays that are transmitted through the patient without interaction contribute to ______________. a. useful information b. film fog c. image noise d. All of the above

Useful information

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

Volume of tissue irradiated and mAs

The Moiré effect is also known as the _________ pattern. a. cheetah b. giraffe c. lion d. zebra

Zebra

The use of __________ improves contrast and reduces patient dose. a. collimation b. high kVp c. low kVp d. less filtration

collimation

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

frequency

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

grid ratio = height of the lead strips / distance between the lead strips

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

high kVp and large field size

Lowering kVp ________ patient dose and _________ image contrast. a. lowers, decreases b. increases, decreases c. lowers, increases d. increases, increases

increases; increases

Decreasing the kVp will increase ___________. a. patient dose b. image noise c. Compton scatter d. optical density

patient dose

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

radiolucent

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

ratio

Grids absorb scatter radiation because the scattered photons:

travel at an angle to the transmitted photons

How can you improve image contrast with a heavy patient without increasing patient dose?

use tight collimation

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

wafer grid