Equipment operation and quality control Flashcards
(282 cards)
1
Q
During Bremsstrahlung
(Brems) radiation production
A
An electron approaching a positive nuclear
charge changes direction and loses energy.
2
Q
Design characteristics of x-ray tube targets that
determine heat capacity include
A
- the rotation of the anode
- the diameter of the anode
- the size of the Focal spot
3
Q
If exposure Factors of 85 kV, 400mA, and 12ms yield an output exposure of 150 mR, what is the milliroentgens per milliampere-seconds(mR/mAs)?
(A) 0.32
(B) 3.1
(C) 17.6
(D) 31
A
If the output or 4.8mAs was 150mR, then 1mAs is equal to 31.25mR (150mR ÷ 4.8mAs =31.25mR/mAs).
4
Q
If the output or 4.8mAs was 150mR, then 1mAs is equal to 31.25mR (150mR ÷ 4.8mAs =31.25mR/mAs).
A
Vs/Vp=Ns/Np
5
Q
To determine secondary I
A
Ns/Np=Ip/Is
6
Q
When using the smaller field in a dual- field image
intensifier?
A
the image is magnified
7
Q
Light-sensitive AEC devices are known as?
A
phototimers
8
Q
AEC devices has 2 types
A
1 type = ionization chamber
2 type = phototimer
9
Q
AEC devices = ionization chamber function as
A
Beneath the table top above the IR, for centering the par centered to it sensor and radiographed.
When a predetermined quantity o ionization
has occurred , the exposure terminates.
10
Q
AEC devices = phototimer
A
Small fluorescent screen, is positioned beneath the cassette. When remnant radiation emerging from the patient exposes the IR and
exits, the fluorescent screen emits light. Once a
predetermined amount o fluorescent light has
been “seen” by the photocell sensor, the exposure is
terminated automatically.
11
Q
The low product of milliampere-seconds and kilovoltage determines in single phase anode
A
heat units.
12
Q
The filament of the cathode
assembly is made of
A
thoriated tungsten
13
Q
System function to
compensate or changing patient/part thicknesses
during fluoroscopic procedures?
A
Automatic brightness control
14
Q
Increased total brightness gain does not affect
A
spatial resolution
15
Q
Delivery of large exposures to a cold anode for the use of exposures exceeding tube limitation can result in
A
-cracking to the anode
-rotor-bearing damage
16
Q
The high-voltage, or step-up, transformer functions to
A
increase voltage to the necessary kilovoltage.
17
Q
Circuit devices that permit electrons to flow in
only one direction are
A
solid-state diodes
18
Q
The slit camera is considered the standard for (annual) measurement of the
A
-effective focal-spot size.
-spatial resolution
19
Q
It cause pitting, for many small surface melts, of the anode’s focal track?
A
Repeated, frequent overloading
20
Q
There are three types of beam restrictors—aperture diaphragms.
A
cones, cylinders, and collimators.
The most practical and efficient type is the collimator.
21
Q
The type of x-ray tube designed to turn on and off rapidly, providing multiple short, precise exposures, is
A
grid-controlled
22
Q
T e device that receives the remnant beam, converts it into light, and then increases the brightness of that light is the
A
image intensifier
23
Q
A high-speed electron is decelerated as is attracted to a tungsten atom nucleus. T is results in
A
Bremsstrahlung radiation
24
Q
If the positive nucleus of a tungsten atom attracts the electron, changing its course, a certain amount of energy is released during the “braking” action. T is energy is given up in the form of an x-ray photon called
A
Bremsstrahlung (“braking”) radiation.
25
Is produced at the target when an incident electron ejects a K-shell electron, and an L-shell electron drops into its place. Energy is liberated in the form of
Characteristic ray, and its energy is representative of the deference in energy levels.
26
The rheostat is a type of variable resistor that is used to It is
change voltage or current values.
27
The procedure whose basic operation involves
reciprocal motion of the x-ray tube and IR is
tomography
28
In fluoroscopy, the automatic brightness control is used to adjust the
-kilovoltage (kV)
-milliamperage (mA)
29
When the radiographer selects kilovoltage on the control panel, which device is adjusted?
Autotransformer
30
The filament circuit supplies the proper
current and voltage to the x-ray tube for proper thermionic emission.
31
The rectifier circuit is
responsible for changing
AC to unidirectional
current.
32
Star and wye configurations are related to
three-phase transformers
33
The terms star and wye (or delta) refer to the
configuration of transformer windings in
three phase equipment.
34
high-voltage transformer windings has
three primary and three secondary windings—one winding or each phase
35
Autotransformers operate on
the principle of
self-induction and have only one winding.
36
What is the device that directs the light emitted from the image intensifier to various viewing and imaging apparatus
Beam splitter or objective lens located between the output phosphor and the TV camera tube (or CCD).
37
Characteristics of x-ray photons include
1. Fluorescent effect on certain phosphors
2. physiological effect on living tissue
38
Properties of x-ray photons are:
* X-rays are not perceptible by the senses.
* X-rays travel in straight lines.
* X-rays travel at the speed of light.
* X-rays are electrically neutral.
* X-rays have a penetrating effect on all matter.
* X-rays have a physiological effect on living tissue.
* X-rays have an ionizing effect on air.
* X-rays have a photographic effect on film
emulsion.
* X-rays produce fluorescence in certain phosphors.
* X-rays cannot be focused.
* X-rays have a spectrum of energies.
* X-rays are unaffected by a magnetic field.
39
Congruence of the x-ray beam with the light field is tested using
radiopaque objects
40
Disadvantages of moving grids over stationary
grids include which of the following?
They increase patient radiation dose.
They can prohibit the use of very short
exposure times.
41
The functions of a picture archiving and communication system (PACS) include
reception of digital images
storage of digital images
42
The kV settings on radiographic equipment must
be tested annually and must be accurate to within
+ /–4 kV
43
The device used to test the accuracy of the x-ray
timer on single phase is the
spinning top
44
The x-ray tube in a CT imaging system is most
likely to be associated with
a pulsed x-ray beam
45
Single phase full-wave-rectified symbol.
(1ϕ )
46
Exposures less than the minimum response time of an AEC may be required when
using high milliamperage
using fast imaging systems
47
Which information is necessary to determine the maximum safe kilovoltage using the appropriate x-ray tube rating chart?
Milliamperage and exposure time
Focal-spot size
48
The speed of the imaging system has no impact on the use of a
radiographic rating chart.
49
A penetrometer can be used to demonstrate effects on
kV on contrast.
50
AEC devices (phototimers and ionization chambers)
automatically terminate the x-ray exposure once a predetermined quantity of x-rays has penetrated the patient, thus ensuring consistent results.
51
Defines the remnant x-ray beam
activates the phosphor within the intensifying screens, exposing the radiography film
52
The device used to ensure reproducible radiographs, regardless of tissue density variations, is the
automatic exposure control
53
Rectifiers are solid-state diodes made of semi conductive materials such as
-silicon
-selenium
-germanium that conduct electricity in only one direction.
54
To maintain image clarity in an image-intensifier
system, the path of electron flow from the photocathode to the output phosphor is controlled by
electrostatic lenses
55
Which of the following equipment is mandatory
f or performance of a myelogram?
tilting x-ray table
56
Deposition of vaporized tungsten on the inner sur-face of the x-ray tube glass window
acts as additional filtration
57
The brightness level of the fluoroscopic image can vary with
milliamperage
kilovoltage
patient thickness
58
Bremsstrahlung radiation or “braking” x-ray is produce at
high-speed electron, accelerated
toward a tungsten atom, is attracted (and
“braked,” i.e., slowed down) by the positively
charged nucleus and therefore is defected from
its original course with a resulting loss o energy.
59
Brems radiation comprises
70% to 90% of the x-ray beam.
60
Characteristic radiation comprises
very little of the x-ray beam between
(10–30%)
61
Characteristic radiation is produced at
high-speed electron encounters the tungsten atom and ejects a K-shell electron, leaving a vacancy in the K shell. An electron from a shell above (e.g., the L shell) shells the vacancy and in doing so emits a K-characteristic ray.
62
That portion of the x-ray beam striking the IR
and representing image anatomy is referred to
the
Signal
63
A high SNR meaning
(more signal, less noise).
64
SNR increases as
mAs increases
65
A computed tomographic (CT) imaging system
has three component parts:
a gantry
a computer
operator console.
66
A technique chart should be prepared for each
AEC x-ray unit and should contain which of
the following information for each type of
examination?
Photocell(s) used
Optimum kilovoltage
Backup time
67
Moving the image intensifier closer to the patient during fluoroscopy
decreases the SID
decreases patient dose
improves image quality
68
Although the stated focal-spot size is measured
directly under the actual focal spot, focal-spot
size actually varies along the length of the x-ray
beam. At which portion of the x-ray beam is the
effective focal spot the smallest?
At the anode end
69
The effective focal spot is always
smaller than the actual focal spot.
70
The total brightness gain of an image intensifier is the product of
flux gain*minification gain
71
Associated with magnification fluoroscopy?
Higher patient dose than nonmagnifcation
fluoroscopy
Higher voltage to the focusing lenses
Image intensifier focal point closer to the input
phosphor
72
Advantages of battery-powered mobile x-ray units include their
ability to store a large quantity o energy
ability to store energy for extended periods of
time
73
Off - focus is
responsible for indistinct images outside the collimated field
74
Off - focus, for extra focal, radiation is produced
as
electrons strike metal surfaces other than the
focal track and produce x-rays that emerge with
the primary beam at a variety of angles.
75
Which is/are components of the
secondary, or high voltage, side of the x-ray circuit?
Rectification system
76
The secondary coil of the step-up transformer and the rectification system are located in the
high- voltage (secondary) side of the x-ray circuit.
77
The timer, autotransformer, and (prereading)
kilovoltage meter are all located in the
low-voltage circuit.
78
A three-phase timer can be tested for accuracy
using a synchronous spinning top. The resulting
image looks like a
solid arc, with the angle (in degrees) representative of the exposure time
79
Anode angle will have an effect on the
severity of the heel effect
focal-spot size
heat-load capacity
80
The minimum response time of an automatic
exposure control (AEC)
is its shortest possible exposure time
81
Function to increase the
milliamperage?
Increase in heat of the lament
82
Formula would the radiographer use to determine the total number of heat
units produced with a given exposure using three phase, six-pulse equipment
mA × time × kV × 1.2
83
Heat units (HU) for a single-phase x-ray unit are determined by using the formula
HU = mA × kV × time.
84
For three-phase and high- frequency x-ray
equipment are determined by using the formula
HU = mA × kV × time × 1.4
85
Images using a particular single-phase, full-wave rectified x-ray unit were made, using known correct exposures. A spinning-top test was per formed at 200 mA, 0.05 s, and 70 kV, and 8 dots were visualized.
The 0.05-s time station is inaccurate.
86
The spinning-top test is used to test
timer accuracy for rectifier operation.
87
Because single-phase, full-wave-rectified current
has 120 useful impulses per second, a 1-s exposure of the spinning top should demonstrate 120 dots.
Therefore, a 0.05-s exposure should demonstrate six dots. Anything more or less than this indicates that the time station needs calibration. If exactly one-half the expected number of dots appears, rectifier failure is suspected.
88
The smaller the Focal spot
the more limited the anode is with respect to the quantity of heat it can safely accept.
89
Target angle and effective focal spot are
directly proportional
90
Target angle and actual focal spot are
inversely
91
Combination that will offer the
greatest heat-loading capability?
low degree target angle, high mm actual focal spot
92
The image-intensifier tube’s input phosphor functions
receives the remnant radiation emerging from the patient and converts it into a fluorescent light image.
(kinetic energy to light)
93
Very close to the input phosphor, separated by a thin, transparent layer, is the
photocathode.
94
Would be appropriate IP front material(s)?
Magnesium
Bakelite
95
The collimator light field and the actual x-ray field—they must be congruent (i.e., match) to within
2% of the SID.
96
Reproducibility testing should specify that radiation output be consistent to within
+ /–5%.
97
Examples of equipment components that are tested annually are the
-focal-spot size
-linearity
-reproducibility
-filtration
-kV
-exposure time
98
Kilovoltage settings can most effectively be tested using an electronic kV meter; to meet required standards, the kV should be accurate to within
+ /–4 kV.
99
The photocathode is made of
Antimony and cesium compound.
100
The fluorescent light image strikes the photocathode and is converted to an
electron image that is focused by the electrostatic lenses to the output phosphor.
101
If collimation is inadequate
and a field size larger than the part is used
excessive scattered radiation from the body for tabletop can cause the AEC to terminate the exposure prematurely, resulting in an underexposed image.
102
Accurate operation of the AEC device depends on
-positioning of the object with respect to the
photocell
-beam restriction
103
The AEC automatically adjust the
exposure required for body parts with different thicknesses and densities
104
T e image intensifier’s input phosphor generally is composed of
cesium iodide crystals
105
A photostimulable phosphor plate is used with
CR
106
radiography exposure refers to the
amount of the hit produce inside the x ray tube
107
Hit is the majority of energy that is produce
on a radiography exposure
108
An incorrect relationship between the primary
beam and the center of a focused grid results in
grid cutoff
insufficient receptor exposure
109
Spinning-top test is used to
test
timer accuracy or rectifier function in threephase equipment.
110
QA was being performed on a three-phase,
full-wave-rectified x-ray unit. A synchronous
spinning-top test was performed using 300 mA,
60 ms, and 70 kV. A 22-degree arc is observed on the test image. Which o the following statements regarding these results is most correct?
The test results are satisfactory.
111
Three-phase, fullwave-rectified current would expose a
360-degree arc each second, a 60-ms (0.06-s) exposure should expose a 21.6-degree arc (360 degrees × 0.06 = 21.6 degrees).
112
Will most likely to produce the highest quality radiographic image?
high SNR
113
In the production of characteristic radiation, the projectile electron interacts with ?
inner shell electron of the target atom
114
The useful, or primary, beam is
those x-rays emitted through the window
the portion of the x-ray beam before interaction with matter
115
A high-speed projectile electron that interacts with a tungsten target is attracted to the nucleus of the tungsten atom and decelerated. The resulting energy production is
Bremsstrahlung radiation
116
Inside the x-ray tube occurs two type of radiation production
Characteristic and Bremsstrahlung radiation
117
Bremsstrahlung radiation occurs at the
Nucleus of tungsten atom
118
Characteristic radiation interact with
the orbital electrons of the nucleus
119
4 principal factor(s) influence x-ray quantity?
mAs
kVp
SID
filtration
120
Factors have an influence over the effective energy level of the x-ray beam?
added filtration
kVp
121
The x-ray emission spectrum is represent by a
vertical line on bar graphic
122
The vertical line on bar graphic has two way
shifts it to the right
shifts it to the left
123
The vertical line on bar graphic that shifts it to the right represent the
increase of the energy level of the x ray beam
124
The vertical line on bar graphic that shifts it to the left represent the
decrease of the energy level in x ray beam
125
Amplitude and x ray quantity are directly proportional to the
mAs
126
How does added filtration affect the CHARACTERISTIC x-ray emission spectrum?
decreases its amplitude
127
The only factor that influence the right or left shifts in characteristic x ray emission spectrum is
Changing the target material
128
Which of the following transformers is found on the filament circuit?
step down
129
Single phase unit will container
tree transformers
130
Tree phase unit will container
five transformers
131
The step up transformers is locate on the
high voltage section of the circuit
132
The transformer is the electromagnetic devise that can
increase or decrease voltage and current
133
Increase or decrease voltage and current is the
turn ratio (on transformers)
134
A transformer that has a greater number of turns on secondary side compare to the primary side is the
step up transformer {750:1}
135
The turn ratio for calculate
S/P
136
On transformers turns ratio an voltage are
direct proportional
137
The relationship between current and turn ratio is
inversely
138
Which of the following pairs of x-ray interactions with matter processes occurs most frequently in diagnostic radiography?
Compton scattering and photoelectric interaction
139
Both the step up transformer and filament transformer (step down) are
constant (turn ratio do not change)
140
kVp and mA selection adjusts which of the following radiographic unit devices?
autotransformer
141
Both the step up transformer and filament transformer (step down) only change the
voltage and current that are supply to them by the autotransformer
142
Radiographic generators has a voltage ripple of 100%?
any single phase
143
Voltage ripple is
the amount of fluctuation in power of the radiography unit while that unit is energize
144
any single phase of the radiography unit has the 100% voltage ripple because
Has only one wave of the electrical power running through the system
145
Tree phase 6 pulse unit has voltage ripple of
13%
146
The three-phase, 12-pulse has a voltage ripple of
3-4%
147
Single-phase, half rectification biographic units have _______ energy pulses per second and have a voltage ripple of ________%.
60; 100
148
A transformer has 2000 turns on the primary side and 100 turns on the secondary side. If the input current is 400 mA, what is the current produced on the secondary side?
SN/PN=PI/SI
1/20=400/S=8000 mA (8000/1000)=8A
149
A radiographic grid contains lead strips that are 1.0 mm high, 0.5 mm thick, and 0.1 mm apart. What is the ratio for this grid?
H/D
150
Half rectification means that
the negative cycle of pulse will be eliminated and only the positive are use (60)
151
Which of the following extension cone or cylinder parameters will restrict the x-ray beam the greatest?
increased length; smaller diameter
152
input current is =
primary CURRENT
153
The beam restricting device that absorbs scatter radiation after the primary beam has interacted with the patient but before the remnant beam has interacted with the image receptor is the
grid
154
Is a disadvantage of the line focus principle?
the anode heel effect
155
Advantage of line focus principal
it reduces the effective focal spot size
156
The line focus principle require
angling the target area in the anode
157
Angling the target area in the anode
increase the hit capacity of the x ray tube
158
Increase the hit capacity of the x ray tube results in
decrease decrease the actual focal spot size
159
Decrease decrease the actual focal spot size results in
decrease the image quality
160
The accumulation of to mush hit cant damage the
x ray tube on the anode or cathode
161
For tree phase 12 pulse unit the radio correction factor is
1.41
162
For tree phase 6 pulse unit the factor correction is
1.35
163
correction formula for 6 pulse is
kV*mA*s*1.35
164
A wire mesh device is used to evaluate which of the following?
film-screen contact
165
To determine how quickly an x-ray tube will dissipate its heat following a radiographic exposure
anode cooling chart
166
Poor film-screen contact can result from which of the following?
damaged cassette
warped cassette
dirt or dust within the cassette
167
Cassettes that contain intensifying screens typically have a back cover comprised of a high atomic number material. The purpose of this is to
absorb backscatter radiation
168
The invisible changes that take place in radiographic film after the emulsion has been exposed but before the film is processed is called
latent image
169
Manifest image
Is the image that appear after prosses taken place
170
Remnant image
is the will be interact with the image receptor
171
Emulsion image reffers to the
active layer in the radiography film (terms are not use in typical radiology terminology)
172
Photocathode of an image intensification tube function
converts visible light to electrons
173
Extension cone or cylinder are
a type of beam restricting devise attached directly to the collimator housing mechanism
174
The number of grid lines or lead strips per inch or centimeter describes
grid frequency
175
NOT need to be included in a technique chart prepared for an automatic exposure control (AEC) x-ray unit?
mAs
176
An electrical device that allows current to flow only in one direction is a
rectifier
177
The base of most modern radiographic film is composed of
polyester
178
Is a rare earth phosphor used in intensifying screens
gadolinium oxysulfide
179
Radiographic procedures would require an intensifying screen cover with a very low atomic number?
mammography
180
Is NOT vital information when determining the maximum safe exposure using a radiographic rating chart?
SID
181
A star pattern test is designed to measure ?
focal spot size
182
kVp accuracy is measure by
filters in ion chambers or photodiodes
183
Function to protect the patient from excessive radiation exposure if the phototimer fails to terminate an exposure?
backup timer or backup mAs
184
On single phase transformer timer accuracy can be measure by
spinning top test
185
A procedure is performed utilizing exposure factors of 75 kVp, 200 mA, and 0.25 second exposure time. If the output exposure is 300 mR, what is the mR/mAs?
output exposure / mAs= 300/50=6
186
The image intensification component that maintains an accurate path of electron flow from the photocathode to the output phosphor is the
electrostatic lenses
187
Input phosphor covert the remain radiation from the patient in
visible light
188
Cesium iodide is a substance that comprises which of the following fluoroscopic components?
input phosphor
189
Output phosphor will convert the electrons
in light photons
190
Is produced in the greatest quantity during radiation production on x ray tube
heat
191
The device that converts alternating current into direct current is a
rectifiers
192
Have no impact on the number of x-ray photons produced at the target area of the anode?
SID
193
Impacting on the number of x-ray photons produced at the target area of the anode?
number of electrons at the filament
target material
kilovoltage selection
194
Which of the following x-ray unit generators has a voltage ripple of less than 1%?
high frequency
195
The device that can increase or decrease the voltage and current in an electrical circuit is called a
transformer
196
If the primary coil of a transformer contains 1000 turns and is supplied with 150 volts, and the secondary coil contains 500,000 turns, what is the voltage induced on the secondary side of this transformer?
75000volts to 75 kilovolts
197
If an exposure time of 0.5 second is used on a single phase, half rectification radiographic generator, how many pulses of energy will be produced?
30
198
If an exposure time of 0.1 second is used with a three phase, six pulse fully rectified radiographic unit, how many pulses of energy will be produced?
36
199
Silver halide crystals in radiographic film are comprised of which of the following substances
silver bromide and silver iodide
200
Appropriate material to comprise the front cover of a cassette?
magnesium
201
The light-absorbing dye that is frequently incorporated during the manufacture of intensifying screens is designed to
reduce the diffusion of fluorescent light
202
The target material used in most modern diagnostic x-ray machines that operate above 50 kVp is
tungsten
203
Concerning the LINE FOCUS PRINCIPLE is true
requires an angled target
204
Example of digital imaging
CT
MRI
Computed Radiography
205
A conventional fluoroscopic unit typically operates at a milliamperage of
less than 5 mA
206
A spinning top is used to measure which of the following?
exposure timer accuracy for a single phase generator
207
For measure the exposure time accuracy on tree phase generator
synchrony time is most be use
208
Ion chamber and filters photodiodes are use to measure the
kVp accuracy
209
Which of the following is not a component of an image intensification tube?
filament
210
the base part of image intensification tube include the
anode
input phosphor
photocathode
output phosphor
electrostatic lenses
211
To comprise the front cover of a cassette the material need most
low number
212
To comprise the back cover of a cassette the material need
high atomic number (lead, calcium
tungsten, lead)
213
A conventional fluoroscopic unit typically operates at a milliamperage
very mA levels 1-5
214
The filament is a component of the
x ray tube not belong to intensifier fluoroscopy tube
215
Converts visible light to electrons
photocathode
216
The output phosphor of an image intensification tube allow significant
brightness
217
Converts x-rays or remnant radiation front patient to visible light
input phosphors
218
The output phosphor of an image intensification tube is typically composed of
zinc cadmium sulfide
219
Doesn't exist part on intensification tube that convert the
converts visible light to x-rays
220
If the temperature of the developer is increased, assuming all other factors remain the same, which of the following would have to occur in order to maintain the same optical density on the finished radiograph?
decrease developer time
221
The input phosphors is compose by
cesium diode
222
Beam restricting devices is the simplest
aperture diaphragm
223
A spinning top tool is
a metal disk with a small hole in its outer edge that is placed on a pedestal about 6 in high.
224
Images using a particular single-phase, full-wave rectified x-ray unit were made, using known correct exposures. A spinning-top test was per formed at 200 mA, 0.05 s, and 70 kV, and 8 dots were visualized. Which of the following is indicated?
The 0.05-s time station is inaccurate.
EX=Therefore, a 0.05-s exposure should demonstrate six dots. Anything more or less than this indicates that the time station needs calibration. If exactly one-half the expected number of dots appears, rectifier failure is
suspected.
225
The input phosphor of image intensifiers is
usually for each x-ray photon absorbed by cesium iodide, approximately
5,000 light photons are emitted.
226
Devise that converts visible light to electrons in fluoroscopy tube is the
photocathode
227
Input screen diameters is
5 to 12 in are available. Although smaller diameter input screens improve resolution
228
To achieve magnification, the voltage to the focusing lenses is
increased and a smaller portion of the input phosphor is used, thereby resulting in a smaller FOV.
229
As number of electrons from the photocathode
are released
230
Electrons from photocathode are focused toward the output side of the image tube by
voltage applied to the negatively charged electrostatic focusing lenses.
231
The output phosphor is small about output
(0.5–1 in)
232
The entire assembly is enclosed
within a
2- to 4-mm thick vacuum glass envelope
233
The image on the output phosphor will be
minified
234
Electron focusing on the output phosphor
causes
Electron focusing on the output phosphor
causes
235
Photoemission is the process that occurs in
photocathode tube part of fluoroscopy
236
Photoemission consist in
emission of electrons extimulated by cesium iodide layer of input phosphor
237
Thermionic emission refers to
electrons emission by heat on cathode side of x ray tube
238
When a dual- Field image intensifier is switched
to the smaller field
the electrostatic focusing lenses are given a greater charge to focus the electron image more tightly.
239
When using the smaller field in a dual- field image intensifier
the image is magnified
240
When using the smaller field in a dual- field image intensifier and image is magnified the focal point moves
further from the output phosphor (the diameter of the electron image is, smaller as it reaches the output phosphor)
241
When image is magnified and focal point moves further from the output phosphor the brightness gain is
diminished. Hence, the patient area viewed is somewhat smaller and is magnified. However, the minification gain has been reduced, and the image is less bright.
242
An image’s spatial resolution refers to its
recorded detail.
243
the smaller the input phosphor
diameter
the greater is the spatial resolution.
A brighter image is easier to see but does not affect resolution.
244
The product of milliampere-seconds and kilovoltage determines
heat units.
245
Which of the Following combinations would pose the least hazard to a particular single phase anode?
(A) 1.2-mm Focal spot, 92 kV, 1.5 mAs
(B) 0.6-mm Focal spot, 80 kV, 3 mAs
(C) 1.2-mm Focal spot, 70 kV, 6 mAs
(D) 0.6-mm Focal spot, 60 kV, 12 mAs
(A) produces 138 HU
(B) produces 240 HU
(C) produces 420 HU,
(D) produces 720 HU.
The least hazardous group of technical factors is (A). Group (A) is also delivering its heat to the large focal spot, thereby decreasing the heat load to the anode.
246
A large quantity of heat applied to a cold anode
can cause
enough surface heat to crack the anode.
247
Excessive heat to the target can cause
pitting or
localized melting o the ocal track.
248
Localized melts can result in
vaporized tungsten deposits on the glass envelope
249
Vaporized tungsten deposits on the glass envelope can cause a
filtering effect, decreasing tube output.
250
Excessive heat also can be conducted to the
rotor bearings, causing increased friction and tube failure.
251
Rectifiers change AC into
unidirectional current by fallowing current to flow through them in only one direction.
252
Valve tubes are
vacuum rectifier tubes found in older equipment.
253
Solid-state diodes are the types of
rectifiers used in today’s x-ray equipment.
254
Rectification systems are found between the
secondary coil of the high-voltage
transformer and the x-ray tube.
255
Resistors, such as rheostats or choke coils, are circuit devices operating on the principle of
mutual induction
256
Autotransformers, operating on the principle of self-induction
enable us to select the required kilovoltage
257
Resistors, such as rheostats or choke coils, are circuit devices used to
change the voltage and current to useful levels.
258
Spatial resolution is most affected by
focal spot size.
259
A slit camera, as well as a star pattern, or pinhole camera, are used to test
focal-spot size
260
The slit camera is considered the standard for
(annual) measurement of the effective focal-spot size.
261
A parallel line–type resolution test pattern can be used to test the
resolution capability of intensifying screens.
262
As the lament ages, vaporized tungsten may
be deposited on the port window act as
an additional filter.
263
This process can causes pitting, for many small sur face melts, of the anode’s focal track
Repeated, frequent overloading
264
Vaporized tungsten on the glass envelope is the result of
anode abuse
265
The advantages of collimators over aperture diaphragms and are cones include
the variety of field sizes available
more efficient beam restriction
266
The patient is the principal scattered, and grids function to
clean up scattered radiation generated by the patient.
267
In digital imaging, x-rays Form an
electronic image on a special radiation detector.
268
A CCD converts .
visible light to an electrical
charge that is then sent to the analog-to-digital converter
(ADC) or processing
269
In digital fluoroscopy (DF), the image-intensifier
output screen image is coupled via a
charge coupled device (CCD) or viewing on a display
monitor.
270
CCD cameras have replaced analog cameras such as the
Vidicon and Plumbicon in new fluoroscopic equipment.
271
When output screen light strikes the CCD cathode, a proportional number of electrons are released by the cathode and stored as
digital values by the CCD.
272
The CCD’s rapid discharge time virtually eliminates image lag and is particularly useful in high-speed imaging procedures such as
cardiac
catheterizations.
273
CCDs are more sensitive to the light emitted by the output phosphor (than the analog cameras) and are associated with less
“noise.”
274
DF also offers
“road-mapping” capability.
275
“Road-mapping” capability is a technique useful in procedures involving
guidewire/catheter placement.
276
During the fluoroscopic examination
the image is stored
on the monitor, reducing the need for continuous x-ray exposure offering significant reductions in patient and personnel radiation exposure.
277
Device used to control voltage by varying resistance is the
Rheostat
278
brightness and contrast controls on the monitor that the radiographer can regulate.
different thicknesses and densities are scanned with the image intensifier
279
What is Information not necessary to determine the maximum safe kilovoltage using the appropriate x-ray tube rating chart is the
The speed of the imaging system has no impact on the use o a radiographic rating chart.
280
281
282
