Chapter 12

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

A. the energy of the x-ray photon

The grid is located: A. just below the x-ray tube window B. between the patient and the IR C. just below the IR D. none of the above

B. between the patient and the IR

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&B

B. has lead strips running perpendicular to the long axis of the grid

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

B. the angle of the x-rays in the primary beam

For radiographic procedures, scatter radiation is primarily the result of: A. photoelectric interaction B. pair production C. Compton interaction D. classical scattering

C. Compton Interaction

When imaging the pelvis, changing from a 14x17 collimation to 8x10 collimation requires: A. an increase in kVp B. a decrease in kVp C. an increase in mAs D. a decrease in mAs

C. an increase in mAs

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

C. the tube can be angled in the direction of the lead lines

The higher the grid ratio, the __________ the scatter clean up and the ____________ the radiographic contrast.

better; higher

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

collimator

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

collimator

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

collimator

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

cone or cylinder

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

convergent line

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

convergent point

________________ collimation means __________________ field size.

decreasing; increasing

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

focal distance

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

mAs

The Moiré effect is also known as the __________ pattern

zebra

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

10; 60 (70)

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

12.5 mAs

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

16 mAs

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

3 mAs

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

55 mAs

The unrestricted primary x-ray beam is: A. round B. oval C. square D. rectangular

A. round

As compared with lower kVp exposures, when using a high kVp the energy of the scattered photon is: A. lower B. higher C. the same D. half

B. higher

Decreasing collimation (opening 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

B. increased scatter production and lower contrast

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

B. limiting patient exposure

The material between the lead strips of a grid must be: A. radiopaque B. radiolucent C. made of lead D. made of tungsten

B. radiolucent

The 2 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

C. volume of tissue irradiated and kVp

Which of the following grids provides excellent scatter clean-up but requires close to perfect alignment to avoid cutoff? A. 5:1 grid B. 8:1 grid C. 12:1 grid D. 16:1 grid

D. 16:1 grid

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&B

D. A&B

A grid with lead strips that run parallel to each other is a: A. parallel grid B. focused grid C. nonfojcused grid D. A&C

D. A&C

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&C

D. A&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&C

D. A&C

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&C

D. B&C

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

D. High kVp and large field size

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

D. all of the above

The volume of tissue irradiated is determined by: A. the area of collimation B. patient thickness C. field size D. all of the above

D. all of the above

Which of the following factors need to be considered when determining the grid to be used for a specific exam? A. patient exposure B. level of contrast improvement needed C. focal range D. all of the above

D. all of the above

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

D. automatically collimates to the IR size

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

D. travel at an angle to the transmitted photons

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

False

T/F: Grid absorbs almost all of the scatter radiation and allow all of the transmitted photons to pass through 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

The formula for the grid conversion factor is:

GCF=mAs with grid/mAs without grid

What is the formula to determine grid ratio?

GR= height of lead strips/distance between them

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?

GR=h/d GR=1.8/0.3 GR=6 6:1

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

GR=h/d GR=2.4/0.2 GR=12 12:1

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

OID

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.

SID

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 radiations of no value in radiographic imaging.

True

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

Wafer grid

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

aperture diaphragm

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

aperture diaphragm

The reason the grid in the bucky reciprocates is to:

blur out grid lines

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:

bucky

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

focal range

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

frequency

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

grid cap

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

grid cassette

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

grid conversion factor

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

grid cutoff

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

mAs1/mAs2=GCF1/GCF2

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

more scatter misses the IR

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

off-center

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

off-focus

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

off-level

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

off-level

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

patient

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

ratio

The field shape produced by a collimator is:

rectangular

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

reduced

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

reduces the scatter reaching the IR

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:

upside-down focused