問題一覧
1
Rare earth screens are most effective in reducing patient dose in
abdominal radiography
2
Of the following elements, which has the highest atomic number?
tungsten
3
Rare earth phosphors have conversion efficiencies ______Those of calcium tungstate
3-4 times
4
Which of the following spectra is discrete?
rare earth emission
5
Rare earth screens
Show higher x-ray absorption in the diagnostic range than calcium tungstate screens
6
When diagnostic x-rays interact with rare earth phosphors,
The lower the x-ray energy the more probable is photoelectric absorption
7
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.
8
By comparison with calcium tungstate, when an x-ray is absorbed in an rare earth screen
the more light will be emitted
9
In comparison with calcium tungstate screens, rare earth screens
absorb three to five times as many x-rays
10
Rare earth intensifying screens
Are more expensive than calcium tungstate screens
11
Which of the following statements concerning intensifying screens is correct?
All have conversion efficiencies greater than one
12
What is the principal limitation of the rare earth intensifying screen?
quantum mottle
13
Stains in intensifying screens from processing chemicals are likely to result in ______ in the radiograph
light blotches
14
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
15
Carbon fiber is particularly useful in x-ray imaging because of its
lower atomic number
16
The routine care of screens requires that they be
periodically cleaned
17
Remnant x-ray include those that
exit the patient toward the image receptor
18
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
19
As the kVp of operation increases the absolute level of scatter radiation will
decrease because of less compton interaction
20
At 100kVp what is the approximate percent of x-rays that are transmitted through 100m of soft tissue?
5%
21
When kVp is increased with a compensating reduction in mAs, then _____ is reduced
patient dose
22
If a constant radiographic density is maintained while increasing KVp
patient dose will increase
23
As the field size is increased, scatter radiation
is increased
24
One factor that influences the production of scatter radiation that is generally not under the control of the technologist is
patient thickness
25
Which of the following is not a device designed to reduce the level of scatter radiation Reaching the film?
a test pattern
26
Scatter radiation chiefly influences radiographic quality by reducing
contrast
27
The x-ray photons that the technologist would like to have interact with the image receptor Are those that are _______ the body
transmitted through
28
as kVp is increased from 70-80,
There will be a higher proportion of scatter radiation
29
In conventional radiography, most of the photons that reach the image receptor are
compton-scattered photons
30
Remnant radiation consist of all emerging from the patient in the direction of the Image receptor.
photons
31
As kVp increases from 70-90, all other factors remaining constant.
quantity of absorbed photons will decrease
32
As the field size of the x-ray beam increases the ______ increases
patient exposure
33
In general, as the thickness of the part being radiographed increases.
the patient exposure increases
34
Remnant x-rays include those transmitted and ________ By the patient
scattered forward
35
In radiography, one would like to employ very low KVp because
scattered radiation would be low
36
In fact, it is necessary to use higher kVp in order that ___________ be at an acceptable level.
patient dose
37
In general, if an increase in radiographic technique is required because of patient size, patient dose will be lowest if
only kVp is increase
38
X-ray beam restriction to the area of interest is principally required to reduce
patient dose
39
Which of the following is not a beam-restricting device?
added filtration
40
An aperture diaphragm should allow x-rays to expose an area
just smaller than the image receptor
41
An aperture diaphragm is used
x-ray field cutoff can occur if the diaphragm is not properly positioned.
42
Dental radiographic cones are usually designed for either ________or _______ source-to- image receptor distances(SID).
20cm,40cm
43
The least desirable dental cone is
short,plastic pointer cone
44
Off-focus radiation
degrade the image receptor
45
In a light-localizing, variable-aperture collimator,
Periodic checks of x-ray beam and light-field coincidence are necessary
46
The simplest of all beam restricting devices is
aperture diaphragm
47
Which of the following devices is normally designed to limit off-focus radiation?
First stage shutters of a variable of a variable-aperture collimator
48
Which of the following could be considered a beam-resisting device?
fluoroscopic shutter
49
Cone cutting
Occurs if the axis if the cone, tube and image receptor are not aligned
50
if a fixed aperture, rectangular, beam – restricting device is used, then
An unexposed border should be visible on all four sides of the radiograph
51
A properly designed light-localizing, variable-aperture collimator will
be design to reduce off-focus radiation
52
Radiographic cones and cylinder are employed principally to reduce
patient dose
53
in dental radiography
the x-ray beam diameter should not exceed 7cm
54
Which of the following is most useful in dental radiography?
rectangular aperture diaphragm
55
PBL stands for
positive beam limiting
56
One helpful feature of a light localizing collimator is increased
filtration
57
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
58
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
59
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
60
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
61
The principal reason for using a grid is to
increase radiographic contrast
62
Which of the following will not enhance radiographic contrast?
the use of added filtration
63
If one had to select the single most important grid characteristics, it would be
grid ratio
64
In a grid that has lead strips 0.5mm apart and 4mm high, the grid ratio is
8:1
65
In a grid that has lead strips 0 5mm apart and 8mm high, the grid ratio is
16:1
66
The use of a grid will result in
control scatter radiation
67
The design of a radiographic grid, the
interpace material is radiolucent
68
X-ray grids are principally effective in attenuating
x-rays following compton interaction
69
If the interspace dimension is constant, increasing the grid ratio will.
make grid thicker
70
As grid frequency increases,
The interspace width becomes thinner if the width of the grid, remains constant
71
Grid with a high ratio
are more effective than those with low ratio
72
The efficiency of a grid for reducing scatter radiation is related principally to the
grid ratio
73
The patient dose increases as
as the atomic number of interspace material increase
74
Radiographic grids
must be place between the patient and the image receptor
75
Added filtration influences selection of
high energy x-rays
76
If only scatter radiation reached the image receptor
radiographic contrast would be very low
77
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%
78
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
79
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
80
Which of the following is the least important indicator of a grid performance?
grid strip height
81
The contrast improvement factor is defined a the radiographic contrast obtained.
with a grid compared to that obtained without one
82
383. As the ratio of grids increases, The __________also increases
contrast improvement factor
83
The use of high-frequency grids result in
increased contrast improvement factor
84
Radiographic grids with high contrast improvement usually
increased radiographic contrast
85
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
86
The simplest type of grid is the
linear grid
87
The undesirable absorption of primary-beam x-rays by a grid is called
grid cut off
88
Which of the following would be included in the three major classifications of moving grids?
reciprocating
89
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
90
Focused grids
Cut off two edges of an image if placed too far from the tube
91
One factor that does not affect the percentage of scatter radiation reaching the image receptor is
mAs
92
The efficiency of a grid for scatter radiation cleanup is related principally to the grid
ratio
93
Radiographic grid
Usually have grid ratios between 5:1 and 16:1
94
The contrast improvement factor
varies with the kVp of operation
95
Generally the selectivity of a grid will depend principally on
grid mass
96
Which the moving-grid technique, the appearance of grid lines could indicate that before the grid moved
the exposure started
97
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
98
Bucky factor is a measure of
penetrability of a beam through a grid
99
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