Module 5 Exam

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)?

3 mAs

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

Patient exposure. Level of contrast improvement needed. Focal range.

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

The purpose of automatic collimation is

limiting patient exposure

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

16:1 ratio grid

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

false

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

false

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

false

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

false

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

false

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

mAs

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

mAs must be increased

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

patient

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

Restriction of the primary beam to the anatomy of interest

reduces patient exposure reduces the amount of scatter produced

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

reduces the scatter reaching the IR

The unrestricted primary x-ray beam is

round

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

true

Scatter radiation is of no value in radiographic imaging.

true

To overcome the decrease in sharpness caused by the air gap technique, an increase in SID is required.

true

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

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

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

Calculate the new mAs to be used with the grid change. If the original mAs is 24, the original grid was a 5:1, and the new grid is a 16:1, what should the new mAs be to compensate for the change in grid?

72 mAs

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

10; 60

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

False

The formula for the grid conversion factor is

GCF = mAs with grid/mAs without grid

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

Grid ratio = height of the lead strips/distance between the lead strips.

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

convergent line

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

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

aperture diaphragm

The simplest type of beam-restricting device is a flat piece of lead with a hole in it called a(n)

aperture diaphragm

The automatic collimator

automatically collimates to the IR size

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

better; higher

The grid is located

between the patient and IR

The reason the grid in the bucky reciprocates is to

blur out the 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 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

For radiographic procedures, scatter radiation is primarily the result of

compton interaction

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

cone or cylinder

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

convergent point

Increasing collimation (decreasing the field size) results in

decreased scatter production and higher contrast

_____________________ collimation means _________________ field size.

decreasing; increasing

The distance between the grid and the convergent line is the

focal distance

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 is permanently mounted but 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 increased 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

A short-dimension grid

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

A linear grid

has lead strips that travel in one direction is the most common type of radiographic grid

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

high kVp and large field size

As compared with lower kVp exposures, when using high kVp will result in a scattered photon that is of ________ energy.

higher

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

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

parallel grid or unfocused grid

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

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

During the exposure, the grid in the bucky

reciprocates or moves slightly from side to side

The field shape produced by a collimator is

rectangular

A significant amount of collimation will have what effect on the amount of radiation reaching the IR

reduced

Grid cutoff results in

reduced exposure to the IR a light film-screen image possible quantum mottle

A focused grid's lead strips are angled to match

the angle of the x-rays in the primary beam

The volume of tissue irradiated is determined by

the area of collimation patient thickness field size

The probability of a Compton interaction occurring is related to

the energy of the xray photon

Linear grids are the most commonly used because

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

Grids absorb scatter radiation because the scattered photons

travel at an angle to the transmitted photons

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

true

The Moiré effect can be caused by

using a grid with a frequency similar to the CR laser scanning frequency

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

volume of tissue irradiated and kVp

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

wafer grid

The Moiré effect is also known as the _________ pattern.

zebra