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