1.
A backup timer for the AEC serves to: 1. protect the patient from overexposure.
2. protect the x-ray tube from excessive heat.
2.
A condenser (or capacitor) is a device that: stores electrical energy. The stored energy is used to operate the x-ray tube only.
3.
A CT imaging system has three component parts:: a gantry, a computer, and an operating console
4.
A device used to ensure reproducible radiographs, regardless of tissue density variations, is the: phototimer
5.
A double-focus tube has two: focal spot sizes available
6.
A generator converts: mechanical energy into electrical energy.
7.
A parallel-plate ionization chamber receives a particular charge as x-ray photons travel through it. This is the operating principle of which of the following devices?: Automatic exposure control
8.
A photostimulable phosphor plate is used with: computed radiography (CR)
9.
a series of rectifiers placed between the transformer and x-ray tube functions to: change AC to a more useful unidirectional current.
10.
Accurate operation of the AEC device is dependent on: 1. positioning of the object with respect to the photocell.
2. beam restriction.
11.
Advantages of battery-powered mobile x-ray units include their: 1. ability to store a large quantity of energy.
2. ability to store energy for extended periods of time.
12.
AECs were originally developed to: achieve more consistent and reproducible film densities
13.
All circuit devices located before the primary coil of the high-voltage transformer are said to be on the: primary, or low-voltage, side of the x-ray circuit.
14.
All of the following are components of the image intensifier: A. photocathode.
B. focusing lenses.
C. accelerating anode.
15.
All the following x-ray circuit devices are located between the incoming power supply and the primary coil of the high-voltage transformer: A. the circuit breaker.
B. the kilovoltage selector.
C. the autotransformer.
16.
although the value at the onset of the exposure may be 20 mAs and 80 kVp, at the end of the exposure the kV value will be approximately: 60
17.
An incorrect relationship between the primary beam and the center of a focused grid results in: 1. grid cutoff.
2. insufficient radiographic density.
18.
An x-ray circuit rectification system is located: between the secondary coil of the high-voltage transformer and the x-ray tube.
19.
Analog images are conventional images;: they can be converted to digital images with a device called a digitizer.
20.
Anode angle will have an effect on the: 1. severity of the heel effect.
2. focal spot size.
3. heat load capacity.
21.
Aperture diaphragms, cones, and cylinders may be placed on a collimator track so that: the illuminated crosshairs are visualized.
22.
As the anode angle is decreased (made steeper),: a larger actual focal spot may be used, while still maintaining the same small effective focal spot. Because the actual focal spot is larger, it can accommodate a greater heat load.
23.
As the anode rotates, it constantly turns a new face to the incoming electrons; this is the: focal track
24.
As the target angle decreases,: the effective (projected) focal spot becomes smaller.
25.
Autotransformers operate on the principle of self-induction and have: only one winding.
26.
Because aperture diaphragms and flare cones have a fixed aperture size and shape,: their beam restriction is not as efficient as that of the variable-size collimator.
27.
Because capacitor discharge mobile x-ray units do not carry many batteries, it is much lighter and does not need a: motor to drive or brake it
28.
Because object-image distance (OID) is an integral part of magnification radiography, the problem of: magnification unsharpness arises.
29.
Because of the anode's bevel,: the effective focal spot is foreshortened and therefore is smaller than the actual focal spot
30.
Because the high-voltage transformer has a fixed ratio, there must be a means of changing the: voltage sent to its primary coil; otherwise, there would be a fixed kVp
31.
Capacitor discharge mobile x-ray units: 1. use a grid-controlled x-ray tube.
2. provide a direct current output.
32.
Capacitor discharge mobile x-ray units use capacitors to power the: x-ray tube
33.
capacitor discharge units: x-ray tube is grid-controlled, permitting very fast (short) exposure times.
34.
capacitor discharge units are: light and therefore fairly easy to maneuver,
35.
capacitor discharge units consist of: a capacitor, or condenser, which is given a charge and then stores energy until the x-ray tube uses it to produce x-rays.
36.
capacitor discharge units permit only limited mAs values, usually: 30 to 50 mAs per charge.
37.
Capacitors: discharge a direct current (as opposed to single- or three-phase pulsating current) in which the kilovoltage decreases by a value of approximately 1 kV/mAs
38.
Cesium iodide is: the phosphor of preference for the input phosphor of an image intensifier.
39.
Cesium iodide is much more efficient in this conversion process than was the phosphor previously used:: zinc cadmium sulfide
40.
Cine and spot film cameras: record fluoroscopic events.
41.
Circuit devices that will conduct electrons in only one direction are: 1. valve tubes.
2. solid-state diodes.
42.
collimator assembly contributes approximately: 1.0 mm Al equivalent to the added filtration of the x-ray tube (because of the plastic exit portal and silver-coated reflective mirror),
43.
Components of digital imaging include: 1. computer manipulation of the image.
2. formation of an electronic image on the radiation detector.
44.
Condenser discharge mobile x-ray units do not use: batteries; this type mobile unit requires that it be charged before each exposure
45.
Cones are also used for: daylight vision
46.
CR does not use: traditional intensifying screens or film. Rather, the CR cassette contains a photostimulable IP that functions as the image receptor (rather than as film emulsion)
47.
Dedicated chest units are available that will: transport a piece of unexposed film from the magazine into position between a pair of intensifying screens, make a phototimed exposure, and transport the exposed film to the automatic processor.
48.
Dedicated radiographic units are available for: 1. chest radiography.
2. head radiography.
3. mammography.
49.
Detection efficiency is extremely high—approximately: 90 %
50.
Digital images can also be obtained in: digital subtraction angiography (DSA), nuclear medicine, and diagnostic sonography.
51.
Directly adjacent to the input phosphor is the: photocathode, which is made of a photoemissive alloy (usually a cesium and antimony compound)
52.
Directly adjacent to the input phosphor is the: photocathode, which is made of a photoemissive alloy (usually a cesium and antimony compound).
53.
disadvantages: With a smaller target angle, the anode heel effect increases; photons are more noticeably absorbed by the "heel" of the anode, resulting in a smaller percentage of x-ray photons at the anode end of the x-ray beam and a concentration of x-ray photons at the cathode end of the radiograph.
54.
disadvantages of moving grids: 1. their complex mechanism is expensive and subject to malfunction.
2. today's equipment makes possible the use of extremely short exposures, a valuable feature whenever motion may be a problem; grid mechanisms frequently are not able to oscillate rapidly enough for short exposure times, and as a result grid motion is "stopped" and lead strips are imaged.
3. patient dose is increased with moving grids. Since the central ray is not always centered to the grid because it is in motion, lateral decentering occurs (resulting in diminished density), and consequently an increase in exposure is needed to compensate (either manually or via AEC).
55.
Disadvantages of moving grids over stationary grids include which of the following?: 1. They can prohibit the use of very short exposure times.
2. They increase patient radiation dose.
56.
Double-focus x-ray tubes have two: filaments
57.
Electrons are: released from the cathode's filament, directed toward the anode by the cathode's focusing cup, and delivered at very high speed to the anode's focal track.
58.
Excessive anode heating can cause vaporized tungsten to be deposited on the port window. This can result in: 1. decreased tube output.
2. tube failure.
3. electrical sparking.
59.
Exposures less than the minimum response time of an AEC may be required when: 1. using high mA.
2. using fast film-screen combinations.
60.
Fractional-focus tubes, with a 0.3-mm focal spot or smaller, have special application in: magnification radiography
61.
Hence, the patient area viewed is: somewhat smaller and is magnified.
62.
hese scintillation crystal (cadmium tungstate or rare earth oxide ceramic crystals) photodiode assemblies convert the transmitted x-ray energy into: light
63.
How is the thickness of the tomographic section related to the tomographic angle?: The greater the tomographic angle, the thinner the section
64.
However, the minification gain has been reduced and the image is somewhat: less bright
65.
If a radiograph exposed using an AEC is overexposed because an exposure shorter than the minimum response time was required, the radiographer generally should: decrease the mA
66.
If collimation is inadequate and a field size larger than the part is used, excessive scattered radiation from the body or tabletop can cause the AEC to: terminate the exposure prematurely, resulting in an underexposed radiograph.
67.
If less than the minimum response time is required for a particular exposure, the radiograph will exhibit: excessive density.
68.
If the scintillation crystals are packed tightly together so that there is virtually no distance between them, efficiency of x-ray absorption is increased, and patient dose is: decreased
69.
In which of the following portions of the x-ray circuit is a step-down transformer located?: Filament circuit
70.
In which type of equipment does kVp decrease during the actual length of the exposure?: Condenser discharge mobile equipment
71.
Inaccurate indexing can result in: missed anatomy and/or double-exposed anatomy.
72.
inherent filtration is usually the equivalent of: 0.5 mm Al.
73.
Instead of having a single primary coil and a single secondary coil, the high-voltage transformer has: three primary and three secondary windings-one winding for each phase
74.
It is important to remember that as aluminum filtration is added to the x-ray tube, the HVL: increases
75.
It is these electrons that will become the: tube current (mA). As heat is increased, more electrons are released and mA increases.
76.
it may be stated that kV and HVL have a direct relationship:: As kV increases, HVL increases.
77.
Large exposures to a cold anode will: heat the anode surface, and the big temperature difference can cause cracking of the anode. This can be avoided by proper warming of the anode prior to use, thereby allowing sufficient dispersion of heat through the anode.
78.
Magnification radiography may be used to: demonstrate small, delicate structures that are difficult to image with conventional radiography.
79.
moving grids function to: blur the images of the lead strips on the radiographic image
80.
Myelography: requires that contrast media be instilled into the lumbar subarachnoid space and distributed via gravity to various levels of the subarachnoid space. This gravitational distribution is accomplished through the use of an x-ray table that is capable of angling or tilting during the procedure.
81.
Pluridirectional tomography refers to: conventional tomographic equipment that is capable of several x-ray tube movements.
82.
Radiographic rating charts: should be consulted, as the heat load to the anode may be critical in magnification radiography.
83.
Rare earth phosphors are much more efficient than: calcium tungstate in absorbing x-ray photons and converting their energy into fluorescent light
84.
Rare earth phosphors are not scarce: they are difficult to separate from other materials with which they are combined in the earth
85.
Rare earth phosphors that may be used in intensifying screens include: 1. gadolinium oxysulfide.
2. lanthanum oxybromide.
86.
Rectification systems are found: between the secondary coil of the high-voltage transformer and the x-ray tube.
87.
Rectifiers: change AC into unidirectional current by allowing current to flow through them in only one direction.
88.
Rectifiers are: solid-state diodes made of semiconductive materials such as silicon, selenium, or germanium that conduct electricity in only one direction.
89.
Resistors: such as rheostats or choke coils, are circuit devices used to vary voltage or current.
90.
self-induction is a characteristic of: AC only
91.
Similar to the high-frequency x-ray tubes used in projection radiography, conventional 60-Hz full-wave rectified power is converted to: a higher frequency of 500-25,000 Hz.
92.
Solid-state diodes: the types of rectifiers used in today's x-ray equipment
93.
Some x-ray circuit devices, such as the transformer and autotransformer, will operate only on: AC
94.
Special equipment is available for digital radiography (DR) or CR:: images produced by either a fan-shaped x-ray beam received by linearly arrayed radiation detectors or a traditional fan-shaped x-ray beam received by a light-stimulated phosphor plate.
95.
Star and wye configurations are related to: three-phase transformers
96.
Stereoscopy: is a technique used to produce a radiographic third dimension.
97.
Target angle has a pronounced geometric effect on the: effective, or projected, focal spot size
98.
That light is then converted into: electrical energy and finally into an electronic/digital signal.
99.
The absorption of primary radiation is termed: cutoff and results in diminished radiographic density.
100.
the actual focal spot: is always larger than the effective, or projected/apparent, focal spot
101.
The actual focal spot is a: finite area on the anode that is bombarded by electrons from the filament.
102.
The advantages of capacitor discharge mobile x-ray equipment include: 1. compact size.
2. light weight.
103.
The advantages of collimators over aperture diaphragms and flare cones include: 1. the variety of field sizes available.
2. more efficient beam restriction.
104.
The amount of increase or decrease depends on: the transformer ratio, that is, the ratio of the number of turns in the primary coil to the number of turns in the secondary coil.
105.
The anode heel effect has to do with: the variation in intensity of the x-ray beam as it is emitted from the focus.
106.
The anode heel effect is more apparent with: small anode angles
107.
The batteries in battery-operated mobile x-ray units provide power to: 1. the x-ray tube.
2. machine locomotion.
3. the braking mechanism.
108.
the battery-powered mobile unit: is capable of storing a large mAs capacity for extended periods of time. These units frequently have a capacity of 10,000 mAs, with 12 hours required for a full charge.
109.
the battery-powered mobile unit is: very heavy (largely because it carries its heavy-duty power source)
110.
The charge may not be stored for extended periods, however, because: it tends to "leak" away; the capacitor must be charged just before the exposure is made.
111.
The collimator assembly has two parts:: The prepatient, or predetector, collimator is at the x-ray tube and consists of multiple beam restrictions so that the x-ray beam diverges little.
112.
The collimator assembly has two parts:: The prepatient, or predetector, collimator is at the x-ray tube that consists of multiple beam restrictions so that the x-ray beam diverges little. This reduces patient dose and reduces the production of scattered radiation, thereby improving the CT image. The postpatient collimator, or predetector collimator, confines the exit photons before they reach the detector array and determines slice thickness.
113.
The CT high-frequency generator is often mounted in the: gantry's rotating wheel
114.
The CT x-ray tube must have: a very high short-exposure rating and must be capable of tolerating several million heat units while still having a small focal spot for optimal resolution.
115.
The device that receives the remnant beam, converts it into light, and then increases the brightness of that light is the: image intensifier
116.
The device used to change alternating current (AC) to unidirectional current is: a solid-state diode
117.
The efficient operation of the x-ray tube, however, requires the use of: unidirectional current, so current must be rectified before it gets to the x-ray tube
118.
The electrons are carefully focused, to maintain image resolution, by the: electrostatic focusing lenses, through the accelerating anode and to the output phosphor for conversion back to light.
119.
The fact that AC is constantly changing direction accounts for: the opposing current set up in the coil.
120.
The filament circuit supplies: the proper current and voltage to the x-ray tube filament for proper thermionic emission.
121.
The fluorescent light image strikes the photocathode and is converted to: an electron image
122.
The focal point, then,: moves further from the output phosphor (the diameter of the electron image is therefore smaller as it reaches the output phosphor), and the brightness gain is somewhat diminished.
123.
The functions of a picture archiving and communication system (PACS) include: 1. acquisition of digital images.
2. storage of digital images.
124.
The gantry component includes: an x-ray tube, a detector array, a high-voltage generator, a collimator assembly, and a patient couch with its motorized mechanism
125.
The glass envelope and oil coolant provide approximately: 0.5 to 1.0 mm Al equivalent filtration, which is referred to as inherent because it is a built-in, permanent part of the tube head.
126.
The high-frequency generator is: small in size, in addition to producing an almost constant potential waveform.
127.
The high-voltage generator provides high-frequency power to the CT x-ray tube, enabling: the high-speed anode rotation and the production of high-energy pulsed x-ray photons.
128.
The high-voltage transformer operates on the principle of: mutual induction.
129.
the high-voltage, or step-up, transformer decreases: amperage to milliamperage.
130.
The high-voltage, or step-up, transformer functions to: increase voltage to the necessary kilovoltage
131.
The HVL of a particular beam is defined as: that thickness of a material that will reduce the exposure rate to one half of its original value.
132.
The image intensifier's input phosphor is generally composed of: cesium iodide
133.
The input phosphor of an image intensifier: receives remnant radiation emerging from the patient and converts it to a fluorescent light image
134.
The input phosphor of an image intensifier receives remnant radiation emerging from the patient and converts it to: a fluorescent light image
135.
The input phosphor of the image intensifier tube functions to convert: x-rays to light
136.
The intensified image is then: transferred to a TV monitor for viewing
137.
The ion chamber: is positioned between the table and the cassette
138.
The light image emitted from the output phosphor: of the image intensifier is directed to the TV monitor for viewing and sometimes to recording devices such as a spot film camera or cine film.
139.
The light is directed to these places by a: beam splitter or objective lens located between the output phosphor and the TV camera tube
140.
The long exposures typical of image-intensified fluoroscopy and tomography make the use of a fractional focal spot: generally impractical and hazardous to the anode.
141.
The major disadvantage of the capacitor/condenser discharge unit is that: as the capacitor discharges its electrical charge, the kVp gradually decreases throughout the length of the exposure-therefore limiting tube output and requiring recharging between exposures
142.
The majority of the light will go: to the recording device, while a small portion goes to the TV so that the procedure may continue to be monitored during filming
143.
The master density is generally set on: normal to produce the required densities. In special cases, when this produces excessive or insufficient density, the master density may be adjusted to plus or minus density.
144.
The minimum response time, or minimum reaction time, is: the length of the shortest exposure possible with a particular AEC.
145.
The more energetic the beam (the higher the kV),: the greater the HVL thickness required to cut its intensity in half.
146.
The most commonly used types of AEC devices are the: 1. ion chamber.
2. photomultiplier tube.
147.
the most desirable condition for fluoroscopic viewing is: to have a bright enough image to permit cone (daylight) vision, for better detail perception. The image intensifier accomplishes this
148.
The most practical and efficient type is the: collimator
149.
The part of a CT imaging system made of thousands of solid-state photodiodes is the: detector array
150.
the photomultiplier: is located below the cassette
151.
The postpatient collimator, or predetector collimator: confines the exit photons before they reach the detector array and determines slice thickness.
152.
The primary parts of the cathode include the: 1. filament.
2. focusing cup.
153.
The principle of self-induction is an example of: the second law of electromagnetics (Lenz's law), which states that an induced current within a conductive coil will oppose the direction of the current that induced it.
154.
The procedure whose basic operation involves reciprocal motion of the x-ray tube and film is: tomography
155.
The process of full-wave rectification: changes the negative half cycle to a useful positive half cycle
156.
The rectification system is also located: on the high-voltage, or secondary, side of the x-ray circuit.
157.
The rectifier circuit is responsible for: changing AC to unidirectional current.
158.
The rectifiers: are placed after the secondary coil of the high-voltage transformer and before the x-ray tube
159.
The scintillation detector array is made of: thousands of solid-state photodiodes
160.
The secondary coil of the step-up transformer is located: in the high-voltage (secondary) side of the x-ray circuit.
161.
The stator and rotor are: the two principal parts of an induction motor.
162.
The step-down transformer, or filament transformer, is located: in the filament circuit and serves to regulate the voltage and current provided to heat the x-ray tube filament.
163.
The terms delta and wye (or star) refer to: the configuration of transformer windings in three-phase equipment
164.
The timer, circuit breaker, autotransformer, kilovoltage selector switch, and (prereading) kilovoltage meter are all located: in the low-voltage circuit.
165.
The tungsten deposit may also: attract electrons from the filament, creating sparking and causing puncture of the glass envelope and subsequent tube failure.
166.
The typical diode x-ray tube consists of: a positive electrode (the anode) and a negative electrode (the cathode)
167.
The use of a fractional focal spot (0.3 mm or smaller) is essential to the maintenance of: image sharpness in magnification films
168.
The visual apparatus that is responsible for visual acuity and contrast perception is the: cones within the retina
169.
The x-ray imaging system that uses a flat panel detector built into the x-ray table is: direct digital radiography
170.
The x-ray tube filament is made of: thoriated tungsten.
171.
The x-ray tube in a computed tomographic (CT) imaging system is likely to be associated with: 1. a pulsed x-ray beam.
2. high production of heat units.
3. high-speed anode rotation.
172.
The x-ray tube produces: a pulsed x-ray beam (1-5 ms) using up to about 1000 mA.
173.
There are three types of beam restrictors:: aperture diaphragms, cones and cylinders, and collimators.
174.
There are two main types of mobile x-ray equipment:: capacitor discharge and battery-powered.
175.
These focal spots are actually two: paths available on the focal track.
176.
This consistency reduces the number of: retakes, thereby reducing patient exposure dose.
177.
This is advantageous because it will: improve radiographic detail without creating a heat-loading crisis at the anode (as would occur if the actual focal spot size were reduced to produce a similar detail improvement).
178.
This problem becomes apparent when making exposures that require: very short exposure times, such as when using high milliamperage and fast film-screen combinations
179.
This reduces: patient dose and reduces the production of scattered radiation, thereby improving the CT image.
180.
Three-phase x-ray equipment often has: three autotransformers
181.
To determine secondary I:: Ns = Ip
``````` ````````
Np =Is
182.
To determine secondary V,: Vs = Ns
```` `````````
Vp =Np
183.
To help tolerate the very high production of heat units: the anode must be capable of high-speed rotation.
184.
To help tolerate the very high production of heat units, the anode must be capable of: high-speed rotation.
185.
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
186.
To resolve this problem, the radiographer should: decrease the mA rather than the kVp, in order to leave contrast unaffected.
187.
Together, the filtering effect of the x-ray tube's glass envelope and its oil coolant are referred to as: inherent filtration
188.
Tomography: produces sectional images of body parts by blurring superimposed structures above and below the section, or level, of interest.
189.
Transformers are used to: change the value of alternating current (AC).
190.
Transformers operate on the principle of: mutual induction
191.
Two x-ray circuit devices operate on the principle of self-induction:: The autotransformer operates on the principle of self-induction and enables the radiographer to vary the kilovoltage. The choke coil also operates on the principle of self-induction; it is a type of variable resistor that may be used to regulate filament current.
192.
Typical examples of digital imaging include: 1. magnetic resonance imaging (MRI).
2. computed tomography (CT).
193.
using the master control's minus-density adjustment involves decreasing the: exposure time (and this is not possible)
194.
Valve tubes: are vacuum rectifier tubes found in older equipment.
195.
Vaporized tungsten acts as: an additional filter, thereby reducing tube output.
196.
Very close to the input phosphor, separated by a thin transparent layer, is the: photocathode
197.
What device converts electrical energy to mechanical energy?: motor
198.
What equipment is mandatory for performance of a myelogram?: Tilting x-ray table
199.
What is the device that directs the light emitted from the image intensifier to various viewing and imaging apparatus?: Beam splitter
200.
What is the relationship between kilovoltage (kV) and the half-value layer (HVL)?: As kV increases, the HVL increases
201.
what makes these changes possible?: autotransformer
202.
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.
203.
When an AEC is installed in the x-ray circuit, it is calibrated to produce radiographic densities as required by: the radiologist
204.
When heated to incandescence (white hot), the filament liberates electrons-a process called: thermionic emission
205.
When kVp is selected on the control panel, the radiographer is actually adjusting the: autotransformer and selecting the amount of voltage to send to the high-voltage transformer to be stepped up.
206.
When the large focal spot is selected: the large filament is heated, and electrons are driven across to the larger portion of the focal track.
207.
When the radiographer selects kilovoltage on the control panel, which device is adjusted?: Autotransformer
208.
When the rotor is activated,: the filament current is increased to produce the required electron source (thermionic emission). Prolonged rotor time, then, can lead to shortened filament life as a result of early vaporization.
209.
When the small focal spot is selected,: the small filament is heated, and electrons are driven across to the smaller portion of the focal track
210.
When using the smaller field in a dual-field image intensifier,: 1. a smaller patient area is viewed.
2. the image is magnified.
3. the image is less bright.
211.
Which of the following circuit devices operate on the principle of self-induction?: 1. Autotransformer
2. Choke coil
212.
Which of the following contribute to inherent filtration?: 1. X-ray tube glass envelope
2. X-ray tube port window
213.
Which of the following functions to increase the mA?: Increase in heat of the filament
214.
Which of the following techniques is used to evaluate the dynamics of a part?: Fluoroscopy
215.
Which of the following will occur as a result of a decrease in the anode target angle?: 1. Decreased effective focal spot size
2. Greater photon intensity toward the cathode side of the x-ray tube
216.
While the x-ray tube is similar to direct-projection x-ray tubes, it has several special requirements:: The CT x-ray tube must have a very high short-exposure rating and must be capable of tolerating several million heat units while still having a small focal spot for optimal resolution.
217.
with steeper (smaller) anode angles,: the anode heel effect is accentuated and can compromise film coverage.
218.
X-ray tube life may be extended by: 1. using low-mAs/high-kVp exposure factors.
2. avoiding lengthy anode rotation.
3. avoiding exposures to a cold anode.
219.
X-ray tube life may be extended by using exposure factors that produce a minimum of heat, that is: a lower mAs and higher kVp combination, whenever possible.
