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Rare earth screens are most effective in reducing patient dose in

abdominal radiography

Of the following elements, which has the highest atomic number?

tungsten

Rare earth phosphors have conversion efficiencies ______Those of calcium tungstate

3-4 times

Which of the following spectra is discrete?

rare earth emission

Rare earth screens

Show higher x-ray absorption in the diagnostic range than calcium tungstate screens

When diagnostic x-rays interact with rare earth phosphors,

The lower the x-ray energy the more probable is photoelectric absorption

When using rare earth intensifying screens.

The abrupt change in absorption at an energy equal to the K-shell binding energy called the K-shell absorption edge.

By comparison with calcium tungstate, when an x-ray is absorbed in an rare earth screen

the more light will be emitted

In comparison with calcium tungstate screens, rare earth screens

absorb three to five times as many x-rays

Rare earth intensifying screens

Are more expensive than calcium tungstate screens

Which of the following statements concerning intensifying screens is correct?

All have conversion efficiencies greater than one

What is the principal limitation of the rare earth intensifying screen?

quantum mottle

Stains in intensifying screens from processing chemicals are likely to result in ______ in the radiograph

light blotches

In the proper design and use of a film cassette.

The front cover should be made of low Z material to minimize x-ray attenuation

Carbon fiber is particularly useful in x-ray imaging because of its

lower atomic number

The routine care of screens requires that they be

periodically cleaned

Remnant x-ray include those that

exit the patient toward the image receptor

Which of the following factors can both affect the level of scatter radiation and be ready controlled by the radiologic Technologist?

inherent filtration field size

As the kVp of operation increases the absolute level of scatter radiation will

decrease because of less compton interaction

At 100kVp what is the approximate percent of x-rays that are transmitted through 100m of soft tissue?

When kVp is increased with a compensating reduction in mAs, then _____ is reduced

patient dose

If a constant radiographic density is maintained while increasing KVp

patient dose will increase

As the field size is increased, scatter radiation

is increased

One factor that influences the production of scatter radiation that is generally not under the control of the technologist is

patient thickness

Which of the following is not a device designed to reduce the level of scatter radiation Reaching the film?

a test pattern

Scatter radiation chiefly influences radiographic quality by reducing

contrast

The x-ray photons that the technologist would like to have interact with the image receptor Are those that are _______ the body

transmitted through

as kVp is increased from 70-80,

There will be a higher proportion of scatter radiation

In conventional radiography, most of the photons that reach the image receptor are

compton-scattered photons

Remnant radiation consist of all emerging from the patient in the direction of the Image receptor.

photons

As kVp increases from 70-90, all other factors remaining constant.

quantity of absorbed photons will decrease

As the field size of the x-ray beam increases the ______ increases

patient exposure

In general, as the thickness of the part being radiographed increases.

the patient exposure increases

Remnant x-rays include those transmitted and ________ By the patient

scattered forward

In radiography, one would like to employ very low KVp because

scattered radiation would be low

In fact, it is necessary to use higher kVp in order that ___________ be at an acceptable level.

patient dose

In general, if an increase in radiographic technique is required because of patient size, patient dose will be lowest if

only kVp is increase

X-ray beam restriction to the area of interest is principally required to reduce

patient dose

Which of the following is not a beam-restricting device?

added filtration

An aperture diaphragm should allow x-rays to expose an area

just smaller than the image receptor

An aperture diaphragm is used

x-ray field cutoff can occur if the diaphragm is not properly positioned.

Dental radiographic cones are usually designed for either ________or _______ source-to- image receptor distances(SID).

20cm,40cm

The least desirable dental cone is

short,plastic pointer cone

Off-focus radiation

degrade the image receptor

In a light-localizing, variable-aperture collimator,

Periodic checks of x-ray beam and light-field coincidence are necessary

The simplest of all beam restricting devices is

aperture diaphragm

Which of the following devices is normally designed to limit off-focus radiation?

First stage shutters of a variable of a variable-aperture collimator

Which of the following could be considered a beam-resisting device?

fluoroscopic shutter

Cone cutting

Occurs if the axis if the cone, tube and image receptor are not aligned

if a fixed aperture, rectangular, beam – restricting device is used, then

An unexposed border should be visible on all four sides of the radiograph

A properly designed light-localizing, variable-aperture collimator will

be design to reduce off-focus radiation

Radiographic cones and cylinder are employed principally to reduce

patient dose

in dental radiography

the x-ray beam diameter should not exceed 7cm

Which of the following is most useful in dental radiography?

rectangular aperture diaphragm

PBL stands for

positive beam limiting

One helpful feature of a light localizing collimator is increased

filtration

A diaphragm is machined to just match image receptor size. If an unexposed border is required on the radiograph, the diaphragm opening will

have to be reduced

A dental cone diaphragm assembly must restrict the circular x-ray beam to 7cm diameter at the tip of the cone. If the source-to-cone tip distance is 20cm and the source-16- Diaphragm distance is 4in what should the diameter of the diaphragm be?

1.4 cm

An aperture diaphragm is designed for 10x12 in film. If the SID is 36 inches and the source-to-diaphragm distance is 4cm, what should the diameter of the diaphragm be?

in x 1.3 in

A room to be used exclusively to produce 14 in x17 in chest radiographs is being installed The SID is 180 cm and the source-to-diaphragm distance is 10cm, What size should be the opening of the diaphragm be?

0.8 cm x 0.9 in

The principal reason for using a grid is to

increase radiographic contrast

Which of the following will not enhance radiographic contrast?

the use of added filtration

If one had to select the single most important grid characteristics, it would be

grid ratio

In a grid that has lead strips 0.5mm apart and 4mm high, the grid ratio is

8:1

In a grid that has lead strips 0 5mm apart and 8mm high, the grid ratio is

16:1

The use of a grid will result in

control scatter radiation

The design of a radiographic grid, the

interpace material is radiolucent

X-ray grids are principally effective in attenuating

x-rays following compton interaction

If the interspace dimension is constant, increasing the grid ratio will.

make grid thicker

As grid frequency increases,

The interspace width becomes thinner if the width of the grid, remains constant

Grid with a high ratio

are more effective than those with low ratio

The efficiency of a grid for reducing scatter radiation is related principally to the

grid ratio

The patient dose increases as

as the atomic number of interspace material increase

Radiographic grids

must be place between the patient and the image receptor

Added filtration influences selection of

high energy x-rays

If only scatter radiation reached the image receptor

radiographic contrast would be very low

A grid has the following characteristics grid ratio – 10:1. Grid strip = 25um, interspace width =300um, contrast improvement factor = 1.8 What percentage of the incident radiation will be intercepted?

7.7%

A grid has the following characteristics grid frequency = 40lines/cm, grid strip width= 30um, grid height 3.0mm. The grid ratio is approximately

14:1

A grid has the following characteristics grid ratio=81 Grid strip width=50um, grid height -3.2mm. The grid frequency is approximately

22 lines/cm

Which of the following is the least important indicator of a grid performance?

grid strip height

The contrast improvement factor is defined a the radiographic contrast obtained.

with a grid compared to that obtained without one

383. As the ratio of grids increases, The __________also increases

contrast improvement factor

The use of high-frequency grids result in

increased contrast improvement factor

Radiographic grids with high contrast improvement usually

increased radiographic contrast

A radiograph is made at 76kVp 25 mAs without a grid. If an 8:1 ratio grid is added, the mAs required would the be approximately

75 mAs

The simplest type of grid is the

linear grid

The undesirable absorption of primary-beam x-rays by a grid is called

grid cut off

Which of the following would be included in the three major classifications of moving grids?

reciprocating

If one had two grids whose characteristics were unknown, but grid B weighed twice as Much as grid A, one might conclude that grid B would have a

higher contrast improvement factor

Focused grids

Cut off two edges of an image if placed too far from the tube

One factor that does not affect the percentage of scatter radiation reaching the image receptor is

mAs

The efficiency of a grid for scatter radiation cleanup is related principally to the grid

ratio

Radiographic grid

Usually have grid ratios between 5:1 and 16:1

The contrast improvement factor

varies with the kVp of operation

Generally the selectivity of a grid will depend principally on

grid mass

Which the moving-grid technique, the appearance of grid lines could indicate that before the grid moved

the exposure started

The average gradient of an image receptor is 2 1 With a 10:1 grid having 50lines/cm frequency, the average gradient is increased to 3.2 What is the contrast improvement factor?

1.5

Bucky factor is a measure of

penetrability of a beam through a grid

The value of the Bucky factor increases with

increasing x-ray quality

100

Which of the following is not a grid positioning error?

air-gap grid

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