Chapter 18 Flashcards
The primary purpose of using a radiographic grid is to
a. intercept remnant radiation.
b. remove undesired primary photons.
c. remove a percentage of scatter photons.
d. decrease skin exposure to patients.
remove a percentage of scatter photons
A radiographic grid absorbs
a. primary radiation.
b. all scatter and secondary electrons.
c. scatter electrons.
d. scatter radiation.
scatter radiation
When an x-ray beam passes through the body,
a. it will pass through the body unaffected.
b. it will be absorbed by the body.
c. it will interact with the body and change direction.
d. all of the above.
all of the above
Photons that pass through the body unaffected produce
a. scatter radiation.
b. radiographic contrast.
c. secondary radiation.
d. radiographic distortion.
radiographic contrast
Photon absorption within the body occurs as the result of
a. Compton interactions.
b. characteristic interactions.
c. photoelectric interactions.
d. Bremsstrahlung interactions.
photoelectric interactions
The atomic interaction that produces scatter radiation is
a. Bremsstrahlung.
b. photoelectric.
c. Compton.
d. photodisintegration.
compton
As kVp increases,
a. secondary radiation increases.
b. scatter radiation increases.
c. image receptor exposure increases.
d. all of the above.
all of the above
The greatest source of scatter during a radiographic examination is the
a. patient.
b. table top material.
c. image receptor.
d. AEC detector.
patient
The amount of scatter radiation produced increases with a/an
a. increase in patient thickness.
b. larger field size.
c. decrease in atomic number of the tissue.
d. all of the above.
all of the above
As a general rule, a radiographic grid is employed
a. for procedures below 60 kVp.
b. for part thicknesses above 10 cm.
c. for pediatric studies to improve contrast.
d. in order to improve positioning latitude.
for part thickness above 10 cm
The use of a radiographic grid requires
a. attention to central ray angulation.
b. an awareness of the SID.
c. an increase in exposure factors.
d. all of the above.
all of the above
Which statement about radiographic grids is incorrect?
a. Grids may have grid strips running in perpendicular directions.
b. A grid is a series of lead strips that alternate with radiopaque interspace strips.
c. The radiopaque strips are typically made of thin lead.
d. The interspace strips are usually made of aluminum.
a Grid is a series of lead strips that alternate with radiopaque interspace strips
The purpose of moving the grid during the radiographic exposure is to
a. activate the digital detector.
b. remove unwanted contrast.
c. blur out the radiopaque strips.
d. activate the AEC detectors.
blur out the radiopaque strips
The radiopaque strips
a. absorb scatter.
b. are made of radiodense material.
c. have a high atomic number.
d. all of the above.
all of the above
The ratio of the height of the lead strips to the distance between the lead strips is the grid
a. selectivity.
b. ratio.
c. frequency.
d. speed.
ratio
Which grid would have the greatest distance between lead strips?
a. 15:1
b. 12:1
c. 8:1
d. 6:1
6:1
Which grid would most effectively reduce scatter?
a. 6:1
b. 8:1
c. 12:1
d. 15:1
15:1
The number of grid lines per inch is the grid
a. focus.
b. ratio.
c. frequency.
d. speed.
frequency
As the lead content of a grid increases,
a. the contrast improvement factor decreases.
b. the ability of the grid to remove scatter increases.
c. the K-factor decreases.
d. exposure to the image receptor increases.
the ability of the grid to remove scatter increases
When the lead strips run in a single direction in a grid, the grid pattern is described as
a. criss-cross.
b. linear.
c. cross-hatched.
d. Tangential.
linear
Angulation across the long axis of a linear grid causes
a. grid shadowing.
b. cross-hatched impressions.
c. grid cut-off.
d. grid convergence.
grid cut off
For a grid to be properly focused, the x-ray tube must be located along the ____ line.
a. convergence
b. divergence
c. tangent
d. resolution
convergence
A device that moves the grid during a radiographic exposure is called a(n)
a. oscillator.
b. alternator.
c. Potter-Bucky diaphragm.
d. focussed grid.
potter-bucky diapgragm
A Potter-Bucky diaphragm must move the grid in a direction that is ____ to the direction of the grid lines.
a. perpendicular
b. parallel
c. at a 45° angle
d. at a 37° angle
perpendicular
When using a radiographic grid with computed radiography (CR),
a. the Moire effect is a consideration.
b. higher frequency grids are undesirable.
c. radiographic grids are unnecessary.
d. none of the above.
the moire effect is a consideration
With digital detector technology, final image contrast is primarily due to the application of
a. very high kVp values
b. Look-Up-Tables(LUTs)
c. faster receptor speeds
d. very low kVp, high mAs exposures
look up tables
Grid cut-off artifacts are a particular problem when performing radiographic exams using digital detectors. Even a small degree of cut-off can show up on the final image. This is primarily due to the
a. very small mAs exposures typically used with fast digital receptors
b. high grid ratios required with digital detectors
c. extreme sensitivity of the digital receptors, to scatter radiation
d. high kVp photons penetrating the grid strips
very small mAs exposures typically used with fast digital receptors
Grid replacement software is designed to
a. hide the grid lines from the viewer
b. allow the radiographer to select a grid ratio for postprocessing
c. create a nongrid image that looks like a grid was employed
d. all of the following
create a nongrid image that looks like a grid was employed
Grid suppression software is intended to
a. remove the visibility of grid lines
b. blur out the grid lines through dynamic visual motion
c. lower image contrast for the viewer, to reveal low contrast objects
d. amplify the visibility of the radiopaque grid strips
remove the visibility of grid lines
In an emergency situation when a radiographic grid is unavailable, a convenient practice to employ, that creates a “grid-like image” when one was not used is
a. grid suppression software
b. to turn the digital detector over, to use the back of the detector as an absorber
c. increase the OID to create an air-gap
d. all of the above
increase the OID to create an air-gap
