Equipment Ops & QC Flashcards

Question 1

Q

Digital fluoroscopy units use which of the following devices in lieu of a television camera tube?

Answer

A

photomultiplier tube

EXPLANATION: In a digital fluoroscopy unit, a charge-coupled device (CCD) (A) is mounted on the output phosphor of the image intensifier tube and is coupled via fiber optics or a lens system. The sensitive layer of crystalline silicon within the CCD responds to the light from the output phosphor, creating an electrical charge. The charges are sampled, pixel by pixel, and then manipulated to produce a digital image. A photometer (B) is used to measure luminance response and uniformity of monitors used in digital imaging. Two types are commonly used: near-range and telescopic. Near-range photometers are used for measuring a monitor’s luminance at close range, whereas telescopic photometers measure this from a distance of one meter. Background ambient light should be kept constant when either photometer is used. A photomultiplier tube (C) receives light energy from the scanned IP in a CR reader and converts it into an electrical (analog) signal that can then be converted to a binary signal in the analog-to-digital convertor (ADC). This binary signal is then processed by a computer to develop a diagnostic image. Newer CR readers may use a charged-coupled device (CDC) to convert the light energy in to an electrical signal. The light gate (or channeling guide) (D) in a CR reader channels the light energy released by the image plate as it is scanned by the laser beam to the photomultiplier tube (D). (Bushong, 9th ed., p. 439).

Question 2

Q

All the following statements regarding three-phase current are true except

Answer

A

three-phase current is constant-potential direct current.

EXPLANATION: Three-phase current is obtained from three individual alternating currents superimposed on, but out of step with, one another by 120 degrees. The result is an almost constant potential current, with only a very small voltage ripple (4%–13%), producing more x-rays per milliampere-second. (Bushong, 10th ed., p. 243)

Question 3

Q

Tungsten alloy is the usual choice of target material for radiographic equipment because it

has a high atomic number
has a high melting point
can readily dissipate heat

Answer

A

1, 2, and 3

EXPLANATION: The x-ray anode may be a molybdenum disk coated with a tungsten–rhenium alloy. Tungsten, with a high atomic number (74), produces high-energy x-rays quite efficiently. Since a great deal of heat is produced at the target, its high melting point (3410°C) helps to avoid damage to the target surface. Heat produced at the target should be dissipated readily, and tungsten’s conductivity is similar to that of copper. Therefore, as heat is applied to the focus, it can be conducted throughout the disk to equalize the temperature and thus avoid pitting, or localized melting, of the focal track. (Selman, 9th ed., p. 138)

Question 4

Q

Digital fluoroscopy units use which of the following devices in lieu of a television camera tube?

Answer

A

charge-coupled device (CCD)

EXPLANATION: In a digital fluoroscopy unit, a charge-coupled device (CCD) (A) is mounted on the output phosphor of the image intensifier tube and is coupled via fiber optics or a lens system. The sensitive layer of crystalline silicon within the CCD responds to the light from the output phosphor, creating an electrical charge. The charges are sampled, pixel by pixel, and then manipulated to produce a digital image. A photometer (B) is used to measure luminance response and uniformity of monitors used in digital imaging. Two types are commonly used: near-range and telescopic. Near-range photometers are used for measuring a monitor’s luminance at close range, whereas telescopic photometers measure this from a distance of one meter. Background ambient light should be kept constant when either photometer is used. A photomultiplier tube (C) receives light energy from the scanned IP in a CR reader and converts it into an electrical (analog) signal that can then be converted to a binary signal in the analog-to-digital convertor (ADC). This binary signal is then processed by a computer to develop a diagnostic image. Newer CR readers may use a charged-coupled device (CDC) to convert the light energy in to an electrical signal. The light gate (or channeling guide) (D) in a CR reader channels the light energy released by the image plate as it is scanned by the laser beam to the photomultiplier tube (D). (Bushong, 9th ed., p. 439).

Question 5

Q

Inadequate collimation in CR imaging can result in an image that is too

light
dark
noisy

Answer

A

1, 2, and 3

EXPLANATION: It is important to note that histogram appearance as well as patient dose can be affected by the radiographer’s knowledge and skill using digital imaging, in addition to his or her degree of accuracy in positioning and centering. Collimation is exceedingly important to avoid histogram analysis errors. Lack of adequate collimation can result in signals outside the anatomical area being included in the exposure data recognition/histogram analysis. This can result in a variety of histogram analysis errors, including excessively light, dark, or noisy images.

Question 6

Q

Phosphors classified as rare earth include

lanthanum oxybromide.
gadolinium oxysulfide.
cesium iodide.

Answer

A

1 and 2 only

EXPLANATION: Rare earth phosphors have a greater conversion efficiency than do other phosphors. Lanthanum oxybromide is a blue-emitting phosphor, and gadolinium oxysulfide is a green-emitting phosphor. Cesium iodide is the phosphor used on the input screen of image intensifiers; it is not a rare earth phosphor. (Shephard, p. 66)

Question 7

Q

A three-phase timer can be tested for accuracy using a synchronous spinning top. The resulting image looks like a

Answer

A

solid arc, with the angle (in degrees) representative of the exposure time

EXPLANATION: When a spinning top is used to test the efficiency of a single-phase timer, the result is a series of dots or dashes, with each representing a pulse of radiation. With full-wave-rectified current and a possible 120 dots (pulses) available per second, one should visualize 12 dots at 1/10 s, 24 dots at 1/5 s, 6 dots at 1/20 s, and so on.
However, because three-phase equipment is at almost constant potential, a synchronous spinning top must be used, and the result is a solid arc (rather than dots). The number of degrees formed by the arc is measured and equated to a particular exposure time.
A multitude of small, mesh-like squares describes a screen contact test. An aluminum step wedge (penetrometer) may be used to demonstrate the effect of kilovoltage on contrast (demonstrating a series of gray tones from white to black), with a greater number of grays demonstrated at higher kilovoltage levels. (Selman, 9th ed., p. 106)

Question 8

Q

Which of the following is most likely to occur as a result of using a 30-in. SID with a 14 x 17 in. IR to radiograph a fairly homogeneous structure?

Answer

A

Density variation between opposite ends of the IR

EXPLANATION: Since x-ray photons are produced at the tungsten target, they more readily diverge toward the cathode end of the x-ray tube. As they try to diverge toward the anode, they interact with and are absorbed by the anode “heel.” Consequently, there is a greater intensity of x-ray photons at the cathode end of the x-ray beam. This phenomenon is known as the anode heel effect. Because shorter SIDs and larger IR sizes require greater divergence of the x-ray beam to provide coverage, the anode heel effect will be accentuated. (Bushong, 8th ed., pp. 138–140)

Question 9

Q

A star pattern is used to measure

focal spot resolution.
intensifying-screen resolution.
SID resolution.

Answer

A

1 only

EXPLANATION: A quality control program requires the use of a number of devices to test the efficiency of various components of the imaging system. A star pattern is a resolution testing device that is used to test the effect of focal spot size. A parallel-line-type resolution test pattern is used to test the resolving capability of intensifying screens. (Selman, p 210)

Question 10

Q

Excessive anode heating can cause vaporized tungsten to be deposited on the port window. This can result in

decreased tube output.
tube failure.
electrical sparking.

Answer

A

1, 2, and 3

EXPLANATION: Vaporized tungsten may be deposited on the inner surface of the glass envelope at the tube (port) window. It acts as an additional filter, thereby reducing tube output. The tungsten deposit may also attract electrons from the filament, creating sparking and causing puncture of the glass envelope and subsequent tube failure. (Selman, pp 137–138)

Question 11

Q

Circuit devices that permit electrons to flow in only one direction are

Answer

A

solid-state diodes

EXPLANATION: Rectifiers change AC into unidirectional current by allowing current to flow through them in only one direction. Valve tubes are vacuum rectifier tubes found in older equipment. Solid-state diodes are the types of rectifiers used in today’s x-ray equipment. Rectification systems are found between the secondary coil of the high-voltage transformer and the x-ray tube. Resistors, such as rheostats or choke coils, are circuit devices used to vary voltage or current. Transformers, operating on the principle of mutual induction, change the voltage (and current) to useful levels. Autotransformers, operating on the principle of self-induction, enable us to select the required kilovoltage. (Selman, 9th ed., p. 101)

Question 12

Q

A device used to ensure reproducible radiographs, regardless of tissue-density variations, is the

Answer

A

phototimer

EXPLANATION: Radiographic reproducibility is an important concept in producing high-quality diagnostic films. Radiographic results should be consistent and predictable not only in terms of positioning accuracy but also with respect to exposure factors. 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. (Shephard, p. 274)

Question 13

Q

Which of the following are typical sizes of fluoroscopic photospot camera film?

Answer

A

70 mm and 105 mm

EXPLANATION: A photospot camera uses film sizes of 70 mm and 105 mm (B). Answers A, C and D include sizes not used for fluoroscopic photospot camera film. (Bushong, 10th ed., p. 413).

Question 14

Q

The trend in spot filming in conventional fluoroscopy is to use a:

Answer

A

Photospot camera film

EXPLANATION: Photospot camera film (D) is similar to that used in a movie camera except only one frame is exposed when activated. This film receives its light image from the output phosphor of the image intensifier tube. The photospot camera provides adequate image quality without interruption of the fluoroscopic examination, and can produce up to twelve exposures in one second. A cassette-loaded spot film (A) is positioned in a lead-lined compartment between the patient and the image intensifier. When a spot-film exposure is desired, the radiologist must actuate a control that properly positions the cassette in the X-ray beam and changes the operation of the X-ray tube from low fluoroscopic milliamperes (mA) to high radiographic mA, at which time the rotating anode is energized to a higher rotation speed. A flat panel image receptor (FPIR) (B) composed of cesium iodide and amorphous silicon pixel detectors can be used in place of an image intensifier in digital fluoroscopy for real-time imaging. Images created from this device are digitized and, therefore, can be stored in a PACS, but this device is not considered a recording system in itself. It only generates the image to be recorded. Cine film (C) is almost exclusively used in cardiac catheterization fluoroscopic procedures. Cine film typically comes in 35 mm rolls of 100 and 500 feet in length and is exposed by the light from the output phosphor of the image intensifier tube, similar to that of the photospot camera film, but while rapidly moving to expose each frame of the film strip. The exposed frames can then be played back as a continuous strip of images to produce a dynamic reproduction of the fluoroscopic images, similar to how one would draw various, slightly different images, on the same spot on multiple blank pieces of paper, and then flip these pieces of paper rapidly to produce what appears to be a moving image. Because of the rapid transition to digital imaging, the use of cine film is rapidly declining. (Bushong, 10th ed., p. 413).

Question 15

Q

Congruence of the x-ray beam with the light field is tested using

Answer

A

radiopaque objects

EXPLANATION: Radiographic results should be consistent and predictable with respect to positioning accuracy, exposure factors, and equipment operation. X-ray equipment should be tested and calibrated periodically as part of an ongoing quality assurance (QA) program. The focal spot should be tested periodically to evaluate its size and its impact on recorded detail; this is accomplished using a slit camera, a pinhole camera, or a star pattern. To test the congruence of the light and x-ray fields, a radiopaque object such as a paper clip or a penny is placed at each corner of the light field before the test exposure is made. After processing, the corners of the x-ray field should be exactly delineated by the radioopaque objects. (Carlton and Adler, 4th ed., p. 484)

Question 16

Q

All of the following can permanently record the images in conventional fluoroscopy, except a:

Answer

A

Flat panel image receptor

EXPLANATION: A flat panel image receptor (FPIR) (B) composed of cesium iodide and amorphous silicon pixel detectors can be used in place of an image intensifier in digital fluoroscopy for real-time imaging. Images created from this device are digitized and, therefore, can be stored in a PACS, but this device is not considered a recording system in itself. It only generates the image to be recorded. A cassette-loaded spot film (A) is positioned in a lead-lined compartment between the patient and the image intensifier. When a spot-film exposure is desired, the radiologist must actuate a control that properly positions the cassette in the X-ray beam and changes the operation of the X-ray tube from low fluoroscopic milliamperes (mA) to high radiographic mA, at which time the rotating anode is energized to a higher rotation speed. Photospot camera film (C) is similar to that used in a movie camera except only one frame is exposed when activated. This film receives its light image from the output phosphor of the image intensifier tube and therefore requires less patient exposure than that required when using the cassette-loaded spot film image recording method. Cine film (D) is almost exclusively used in cardiac catheterization fluoroscopic procedures. Cine film typically comes in 35 mm rolls of 100 and 500 feet in length and is exposed by the light from the output phosphor of the image intensifier tube, similar to that of the photospot camera film, but while rapidly moving to expose each frame of the film strip. The exposed frames can then be played back as a continuous strip of images to produce a dynamic reproduction of the fluoroscopic images, similar to how one would draw various, slightly different images, on the same spot on multiple blank pieces of paper, and then flip these pieces of paper rapidly to produce what appears to be a moving image. Because of the rapid transition to digital imaging, the use of cine film is rapidly declining. (Bushong, 10th ed., pp. 412-413).

Question 17

Q

Focal-spot blur is greatest

Answer

A

toward the cathode end of the x-ray beam

EXPLANATION: Focal-spot blur, or geometric blur, is caused by photons emerging from a large focal spot. Because the projected focal spot is greatest at the cathode end of the x-ray tube, geometric blur is also greatest at the corresponding part (cathode end) of the radiograph. The projected focal-spot size becomes progressively smaller toward the anode end of the x-ray tube. (Bushong, 8th ed., p. 140)

Question 18

Q

An automatic exposure control (AEC) device can operate on which of the following principles?

A photomultiplier tube charged by a fluorescent screen
A parallel-plate ionization chamber charged by x-ray photons
Motion of magnetic fields inducing current in a conductor

Answer

A

1 and 2 only

EXPLANATION: A phototimer is one type of automatic exposure control (AEC) that actually measures light. As x-ray photons penetrate and emerge from a part, a fluorescent screen beneath the cassette glows, and the fluorescent light charges a photomultiplier tube. Once a predetermined charge has been reached, the exposure terminates automatically. A parallel-plate ionization chamber is another type of AEC. A radiolucent chamber is beneath the patient (between the patient and the IR). As photons emerge from the patient, they enter the chamber and ionize the air within it. Once a predetermined charge has been reached, the exposure is terminated automatically. Motion of magnetic fields inducing a current in a conductor refers to the principle of mutual induction. (Fauber, 2nd ed., pp. 232–233)

Question 19

Q

The image-intensifier tube’s input phosphor functions to convert

Answer

A

x-rays to light

EXPLANATION: The image intensifier’s input phosphor receives the remnant radiation emerging from the patient and converts it into a fluorescent light image. Very close to the input phosphor, separated by a thin, transparent layer, is the photocathode. The photocathode is made of a photoemissive alloy, usually an antimony and cesium compound. 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. (Bushong, 8th ed., p. 360)

Question 20

Q

In which type of equipment does kilovoltage decrease during the actual length of the exposure?

Condenser-discharge mobile equipment
Battery-operated mobile equipment
Fixed x-ray equipment

Answer

A

1 only

EXPLANATION: Mobile x-ray machines are compact and cordless and are either the battery-operated type or the condenser-discharge type. Condenser-discharge mobile x-ray units do not use batteries; this type of mobile unit requires that it be charged before each exposure. A condenser (or capacitor) is a device that stores electrical energy. The stored energy is used to operate the x-ray tube only. Because this machine does not carry many batteries, it is much lighter and does not need a motor to drive or brake it. The major disadvantage of the capacitor/condenser-discharge unit is that as the capacitor discharges its electrical charge, the kilovoltage gradually decreases throughout the length of the exposure—therefore limiting tube output and requiring recharging between exposures. (Frank, Long, and Smith, 11th ed., vol. 3, p. 235)

Question 21

Q

With three-phase equipment, the voltage across the x-ray tube

drops to zero every 180 degrees
is 87% to 96% of the maximum value
is at nearly constant potential

Answer

A

2 and 3 only

EXPLANATION: With single-phase, full-wave-rectified equipment, the voltage is constantly changing from 0% to 100% of its maximum value. It drops to 0 every 180 degrees (of the AC waveform); that is, there is 100% voltage ripple. With three-phase equipment, the voltage ripple is significantly smaller. Three-phase, six-pulse equipment has a 13% voltage ripple, and three-phase, 12-pulse equipment has a 3.5% ripple. Therefore, the voltage never falls below 87% to 96.5% of its maximum value with three-phase equipment, and it closely approaches constant potential [direct current (DC)]. (Carlton and Adler, 4th ed., pp. 91–93)

Question 22

Q

Which of the following is a device that can be used in lieu of an image intensifier/charge-coupled device combination in digital fluoroscopy?

A. Charge-coupled device
B. Flat panel image receptor
C. photometer
D. photomultiplier tube

Answer

A

Flat panel image receptor

EXPLANATION: A flat panel image receptor (FPIR) (B) composed of cesium iodide and amorphous silicon pixel detectors can be used in place of an image intensifier in digital fluoroscopy. There are several advantages of FPIR imaging over image intensifier/CCD imaging, including distortion free images, constant image quality and contrast resolution over the entire image, high detective quantum efficiency (DQE) at all dose levels, a rectangular image area coupled to a similar shaped image monitor, and its immunity to external magnetic fields. A charge-coupled device (CCD) (A) is mounted on the output phosphor of the image intensifier tube and is coupled via fiber optics or a lens system. The sensitive layer of crystalline silicon within the CCD responds to the light from the output phosphor, creating and electrical charge. The charges are sampled, pixel by pixel, and then manipulated to produce a digital image. A photometer (C) is used to measure the luminance response and uniformity of monitors used in digital imaging. A photomultiplier tube receives light energy from the scanned IP plate in a CR reader and converts it into an electrical (analog) signal that can then be converted to a binary signal in the analog-to-digital convertor (ADC). This binary signal is then processed by a computer to develop a diagnostic image. Newer CR readers may use a charged-coupled device (CDC) (D) to convert the light energy into an electrical signal. (Bushong, 9th ed., pp. 441-442).

Question 23

Q

The advantages of collimators over aperture diaphragms and flare cones include

the variety of field sizes available
more efficient beam restriction
better cleanup of scattered radiation

Answer

A

1 and 2 only

EXPLANATION: There are three types of beam restrictors—aperture diaphragms, cones and cylinders, and collimators. The most practical and efficient type is the collimator. Its design makes available an infinite number of field-size variations that are not available with the other types of beam restrictors. 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. Aperture diaphragms, cones, and cylinders may be placed on a collimator track so that the illuminated crosshairs are visualized. Although the 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), its functions are unrelated to the cleanup of scattered radiation. This is so because the patient is the principal scatterer, and grids function to clean up scattered radiation generated by the patient. (Bushong, 8th ed., pp. 241–243)

Question 24

Q

Which of the following x-ray circuit devices operate(s) on the principle of mutual induction?

High-voltage transformer
Filament transformer
Autotransformer

Answer

A

1 and 2 only

EXPLANATION: In mutual induction, two coils are in close proximity, and a current is supplied to one of the coils. As the magnetic field associated with every electric current expands and “grows up” around the first coil, it interacts with and “cuts” the turns of the second coil. This interaction, motion between magnetic field and coil (conductor), induces an electromotive force (emf) in the second coil. This is mutual induction, the production of a current in a neighboring circuit. Transformers, such as the high-voltage transformer and the filament (step-down) transformer, operate on the principle of mutual induction. The autotransformer operates on the principle of self-induction. Both the transformer and the autotransformer require the use of alternating current. (Bushong, 8th ed., p. 99)

Question 25

Q

Radiographs from a particular three-phase, full-wave-rectified x-ray unit, made using known correct exposures, were underexposed. A synchronous spinning top test was performed using 200 mA, 1/12 second, and 70 kVp, and a 20° arc is observed on the test film. Which of the following is most likely the problem?

Answer

A

The 1/12-second time station is inaccurate.

EXPLANATION: A synchronous spinning top test is used to test timer accuracy or rectifier function in three-phase equipment. Because three-phase, full-wave-rectified current would expose a 360° arc each second, a 1/12-second exposure should expose a 30° arc. Anything more or less indicates timer inaccuracy. If exactly one half of the expected arc appears, one should suspect rectifier failure. (Saia, p 434)

Question 26

Q

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 kVp, and a 22-degree arc is observed on the test film. Which of the following statements regarding these results is most correct?

Answer

A

The test results are satisfactory.

EXPLANATION: A synchronous spinning-top test is used to test timer accuracy or rectifier function in three-phase equipment. Because three-phase, full-wave-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 x 0.06 = 21.6 degrees). Anything more or less indicates timer inaccuracy. If exactly one-half the expected arc appears, rectifier failure should be suspected. (Selman, 9th ed., p. 106)

Question 27

Q

All of the following are maintenance steps that should be performed on digital receptors, except:

A. All receptors should be erased before each shift
B. The equipment and its environment should be cleaned periodically
C. The technique charts should be revised on a monthly basis to align with the gain settings
D. A properly calibrated exposure indicator should be used to conduct periodic checks of the automatic exposure control (AEC)

Answer

A

The technique charts should be revised on a monthly basis to align with the gain settings

EXPLANATION: It may be tempting for one to revise the established technique chart (C) in response to gain setting fluctuations. However, the system gain settings should rather be adjusted accordingly to align with the technique chart that was initially established upon installation and calibration of the equipment. The digital receptors should be erased before each shift (A) to avoid ghost images on subsequent exposures. By cleaning the equipment and its environment (B), artifacts in radiographic images may be avoided. The AEC system should be checked periodically (D) using a properly calibrated exposure indicator. (Seeram, 1st ed., p. 232).

Question 28

Q

Using a multifield image intensifier tube, which of the following input phosphor diameters will provide the best spatial resolution?

Answer

A

12 cm

EXPLANATION: Multifield image intensifier tubes are usually either dual-field or tri-field and are designed this way in order to permit magnification imaging. As voltage is applied to the electrostatic focusing lenses, the focal point moves back—closer to the input phosphor—and a smaller portion of the input phosphor is utilized. As a result, the FOV decreases and magnification increases, producing better spatial resolution. At the same time, brightness is decreased requiring an increase in mA (therefore increased patient dose). This increase in mA increases image quality. It can be likened to an increase in signal-to-noise ratio (SNR), with mA being the signal. (Seeram, p 103)

Question 29

Q

Star and wye configurations are related to

Answer

A

three-phase transformers

EXPLANATION: The terms star and wye (or delta) refer to the configuration of transformer windings in three-phase equipment. 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 (Figure 5–13). Autotransformers operate on the principle of self-induction and have only one winding. Three-phase x-ray equipment often has three autotransformers. (Selman, 9th ed., p. 163)

Question 30

Q

When the radiographer selects kilovoltage on the control panel, which device is adjusted?

Answer

A

Autotransformer

EXPLANATION: 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 kilovoltage. The autotransformer makes these changes possible. When kilovoltage is selected on the control panel, the radiographer actually is adjusting the autotransformer and selecting the amount of voltage to send to the high-voltage transformer to be stepped up (to kilovoltage). The filament circuit supplies the proper current and voltage to the x-ray tube filament for proper thermionic emission. The rectifier circuit is responsible for changing AC to unidirectional current. (Selman, 9th ed., pp. 88–89)

Question 31

Q

The type of x-ray tube designed to turn on and off rapidly, providing multiple short, precise exposures, is

Answer

A

grid-controlled

EXPLANATION: X-ray tubes are diode tubes; that is, they have two electrodes—a positive electrode called the anode and a negative electrode called the cathode. The cathode filament is heated to incandescence and releases electrons—a process called thermionic emission. During the exposure, these electrons are driven by thousands of volts toward the anode, where they are suddenly decelerated. That deceleration is what produces x-rays. Some x-ray tubes, such as those used in fluoroscopy and in capacitor-discharge mobile units, are required to make short, precise—sometimes multiple—exposures. This need is met by using a grid-controlled tube. A grid-controlled tube uses the molybdenum focusing cup as the switch, permitting very precise control of the tube current (flow of electrons between cathode and anode). (Bushong, 8th ed., p. 132)

Question 32

Q

Disadvantages of moving grids over stationary grids include which of the following?

They can prohibit the use of very short exposure times.
They increase patient radiation dose.
They can cause phantom images when anatomic parts parallel their motion.

Answer

A

1 and 2 only

EXPLANATION: One generally thinks in terms of moving grids being totally superior to stationary grids because moving grids function to blur the images of the lead strips on the radiographic image. Moving grids do, however, have several disadvantages. First, their complex mechanism is expensive and subject to malfunction. Second, today’s sophisticated x-ray equipment makes possible the use of extremely short exposures, a valuable feature whenever motion may be a problem (as in pediatric radiography). However, grid mechanisms frequently are not able to oscillate rapidly enough for the short exposure times, and as a result, the grid motion is “stopped,” and the lead strips are imaged. Third, 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). (Shephard, p. 249)

Question 33

Q

When using the smaller field in a dual-field image intensifier,

the image is magnified
the image is brighter
a larger anatomic area is viewed

Answer

A

1 only

EXPLANATION: 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. 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. Hence, the patient area viewed is somewhat smaller and is magnified. However, the minification gain has been reduced, and the image is somewhat less bright. (Bushong, 8th ed., p. 363)

Question 34

Q

Europium-activated barium fluorohalide is associated with

Answer

A

PSP storage plates

EXPLANATION: Computed radiography (CR) cassettes use no intensifying screens or film—hence, the term filmless radiography. The Image Plates (IPs) have a protective function (for the PSP/storage plate within) and can be used in the Bucky tray or directly under the anatomic part; they need not be light-tight because the PSP is not light sensitive. The IP has a thin lead-foil backing (similar to traditional cassettes) to absorb backscatter. Inside the IP is the photostimulable phosphor (PSP) storage plate. This PSP storage plate within the IP has a layer of europium-activated barium fluorohalide that serves as the IR as it is exposed in the traditional manner and receives the latent image. The PSP can store the latent image for several hours; after about 8 hours, noticeable image fading will occur. (Carlton and Adler, 4th ed., p. 358)

Question 35

Q

The brightness level of the fluoroscopic image can vary with

milliamperage
kilovoltage
patient thickness

Answer

A

1, 2, and 3

EXPLANATION: The thicker and more dense the anatomic part being studied, the less bright will be the fluoroscopic image. Both milliamperage and kilovoltage affect the fluoroscopic image in a way similar to the way in which they affect the radiographic image. For optimal contrast, especially taking patient dose into consideration, higher kilovoltage and lower milliamperage are generally preferred. (Bushong, 8th ed., p. 363)

Question 36

Q

All the following x-ray circuit devices are located between the incoming power supply and the primary coil of the high-voltage transformer except

A. the timer
B. the kilovoltage meter
C. the milliamperage meter
D. the autotransformer

Answer

A

the milliamperage meter

EXPLANATION: 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. The timer, autotransformer, and (prereading) kilovoltage meter are all located in the low-voltage circuit. The milliampere meter, however, is connected at the midpoint of the secondary coil of the high-voltage transformer. When studying a diagram of the x-ray circuit, it will be noted that the milliampere meter is grounded at the midpoint of the secondary coil (where it is at zero potential). Therefore, it may be placed in the control panel safely. (Selman, 9th ed., pp. 150–151)

Question 37

Q

If the primary coil of the high-voltage transformer is supplied by 220 V and has 200 turns, and the secondary coil has 100,000 turns, what is the voltage induced in the secondary coil?

Answer

A

110 kV

EXPLANATION: The high-voltage, or step-up, transformer functions to increase voltage to the necessary kilovoltage. It decreases the amperage to milliamperage. 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. The transformer law is as follows:
To determine secondary V,
To determine secondary I:
Substituting known values,
(Selman, pp 84–85)

Question 38

Q

The ability of an x-ray unit to produce constant radiation output, at a given mA, using various combinations of mAs and time is called

Answer

A

linearity.

EXPLANATION: Each of the four factors are used as part of a complete quality assurance (QA) program. Linearity means that a given mA, using different mA stations with appropriate exposure time adjustments, will provide consistent intensity. Reproducibility means that repeated exposures at a given technique must provide consistent intensity. Sensitometry and densitometry are used in evaluation of the film processor, part of a complete QA program. ((Bushong,10th ed, p 550))

Question 39

Q

Off-focus, or extrafocal, radiation is minimized by

Answer

A

restricting the x-ray beam as close to its source as possible

EXPLANATION: Off-focus, or extrafocal, 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. This radiation is responsible for indistinct images outside the collimated field. Mounting a pair of shutters as close to the source as possible minimizes off-focus radiation. (Bushong, 8th ed., p. 140)

Question 40

Q

Which device is used to control voltage by varying resistance?

Answer

A

Rheostat

EXPLANATION: The autotransformer operates on the principle of self-induction and functions to select the correct voltage to be sent to the high-voltage transformer to be “stepped up” to kilovoltage. The high-voltage transformer increases the voltage and decreases the current. The rheostat is a type of variable resistor that is used to change voltage or current values. It is found frequently in the filament circuit. A fuse is a device used to protect the circuit elements from overload by opening the circuit in the event of a power surge. (Selman, 9th ed., pp. 90–91)

Question 41

Q

Which of the following combinations will offer the greatest heat-loading capability?

A. 17-degree target angle, 1.2-mm actual focal spot

B. 10-degree target angle, 1.2-mm actual focal spot

C. 17-degree target angle, 0.6-mm actual focal spot

D. 10-degree target angle, 0.6-mm actual focal spot

Answer

A

10-degree target angle, 1.2-mm actual focal spot

EXPLANATION: The smaller the focal spot, the more limited the anode is with respect to the quantity of heat it can safely accept. As the target angle decreases, the actual focal spot can be increased while still maintaining a small effective focal spot. Therefore, group (B) offers the greatest heat-loading potential, with a steep target angle and a large actual focal spot. It must be remembered, however, that a steep target angle increases the heel effect, and IR coverage may be compromised. (Selman, 9th ed., pp. 145–146)

Question 42

Q

Which of the following is/are components of the secondary, or high voltage, side of the x-ray circuit?

Rectification system
Autotransformer
kV meter

Answer

A

1 only

EXPLANATION: 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. The timer, autotransformer, and (prereading) kilovoltage meter are all located in the low-voltage circuit.
The secondary/high-voltage side of the circuit begins with the secondary coil of the high-voltage transformer. The mA meter is connected at the midpoint of the secondary coil of the high-voltage transformer. Following the secondary coil is the rectification system, and the x-ray tube. (Selman, 9th ed., pp. 150–151)
Transformers are used to change the value of alternating current (AC). They operate on the principle of mutual induction. The secondary coil of the step-up transformer is located in the high-voltage (secondary) side of the x-ray circuit. 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. The rectification system is also located on the high-voltage, or secondary, side of the x-ray circuit. (Selman, 9th ed., pp. 155–156)

Question 43

Q

The condition that results from a persistent fetal foramen ovale is

Answer

A

an atrial septal defect

EXPLANATION: Atrial septal defect is a small hole (the remnant of the fetal foramen ovale) in the interatrial septum. It usually closes spontaneously in the first months of life; if it persists or is unusually large, surgical repair is necessary. The ductus arteriosus is a short fetal blood vessel connecting the aorta and pulmonary artery that usually closes within 10 to 15 hours after birth. A patent ductus arteriosus is one that persists and requires surgical closure. Ventricular septal defect is a congenital heart condition characterized by a hole in the interventricular septum that allows oxygenated and unoxygenated blood to mix. Some interventricular septal defects are small and close spontaneously; others require surgery. Coarctation of the aorta is a narrowing or constriction of the aorta. (Tortora and Derrickson, 11th ed., p. 794)

Question 44

Q

Primary radiation barriers must be at least how high?

Answer

A

8 ft

EXPLANATION: Radiation protection guidelines have established that primary radiation barriers must be 7 ft high. Primary radiation barriers are walls that the primary beam might be directed toward. They usually contain 1.5 mm of lead (1/16 in.), but this may vary depending on use factor, and so on. (Bushong, 8th ed., pp. 571–572)

Question 45

Q

If the primary coil of a high-voltage transformer is supplied by 220 V and has 400 turns and the secondary coil has 100,000 turns, what is the voltage induced in the secondary coil?

Answer

A

55 kV

EXPLANATION: The high-voltage, or step-up, transformer functions to increase voltage to the necessary kilovoltage. It decreases the amperage to milliamperage. 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. The transformer law is as follows: To determine secondary V,

Question 46

Q

Recorded detail is directly related to

SID.
tube current.
focal-spot size.

Answer

A

1 only

EXPLANATION: As SID increases, so does recorded detail because magnification is decreased. Therefore, SID is directly related to recorded detail. As focal spot size increases, recorded detail decreases because more penumbra is produced. Focal spot size is thus inversely related to radiographic sharpness or recorded detail. Tube current affects radiographic density and is unrelated to recorded detail. (Fauber, 2nd ed., pp. 79, 81)

Question 47

Q

A lesion with a stalk projecting from the intestinal mucosa into the lumen is a(n)

Answer

A

polyp

EXPLANATION: A polyp is a tumor with a pedicle (stalk) that is found commonly in vascular organs projecting inward from its mucosal wall. Polyps usually are removed surgically because, although usually benign, they can become malignant. A diverticulum is an outpouching from the wall of an organ, such as the colon. A fistula is an abnormal tube-like passageway between organs or between an organ and the surface. An abscess is a localized collection of pus as a result of inflammation. (Bontrager and Lampignano, 6th ed., p. 499)

Question 48

Q

Which of the following is (are) demonstrated in an AP projection of the cervical spine?

Intervertebral disk spaces
C3–7 cervical bodies
Apophyseal joints

Answer

A

1 and 2 only

EXPLANATION: The AP projection of the cervical spine demonstrates the bodies and intervertebral spaces of the last five vertebrae (C3–7). The cervical apophyseal joints are 90 degrees to the MSP and, therefore, are demonstrated in the lateral projection. (Frank, Long, and Smith, 11th ed., vol. 1, pp. 398–399)

Question 49

Q

Symptoms of impending diabetic coma include
increased urination.
sweet-smelling breath.
extreme thirst.

Answer

A

1, 2, and 3

EXPLANATION: When a diabetic patient misses an insulin injection, the body loses its ability to metabolize glucose, and ketoacidosis can occur. If this is not corrected quickly, the patient may become comatose. Symptoms of impending coma include increased urination, sweet (fruity) breath, and extreme thirst. Other symptoms are weakness and nausea. (Torres et al., 6th ed., p. 170)

Question 50

Q

What is the name of the condition that results in the forward slipping of one vertebra on the one below it?

Answer

A

Spondylolisthesis

EXPLANATION: The forward slipping of one vertebra on the one below it is called spondylolisthesis. Spondylolysis is the breakdown of the pars interarticularis; it may be unilateral or bilateral and results in forward slipping of the involved vertebra—the condition of spondylolisthesis. Inflammation of one or more vertebrae is called spondylitis. Spondylosis refers to degenerative changes occurring in the vertebra. (Frank, Long, and Smith, 11th ed., vol. 1, p. 388)

Question 51

Q

Shoulder arthrography is performed to

evaluate humeral luxation

demonstrate complete or partial rotator cuff tear

evaluate the glenoid labrum

Answer

A

2 and 3 only

EXPLANATION: Shoulder arthrograms (Figure 2–64) are used to evaluate rotator cuff tear, glenoid labrum (a ring of fibrocartilaginous tissue around the glenoid fossa), and frozen shoulder. Routine radiographs demonstrate arthritis, and the addition of a transthoracic humerus or scapular Y projection would be used to demonstrate luxation (dislocation). (Frank, Long, and Smith, 11th ed., vol. 2, p. 16)

Question 52

Q

Which of the following account(s) for an x-ray beam’s heterogeneity?
Incident electrons interacting with several layers of tungsten target atoms
Energy differences among incident electrons
Electrons moving to fill different shell vacancies

Answer

A

1, 2, and 3

EXPLANATION: The x-ray photons produced at the tungsten target make up a heterogeneous beam, a spectrum of photon energies. This is accounted for by the fact that the incident electrons have differing energies. Also, the incident electrons travel through several layers of tungsten target material, lose energy with each interaction, and, therefore, produce increasingly weaker photons. During characteristic x-ray production, vacancies may be filled in the K, L, or M shells, which differ from each other in binding energies, and, therefore, photons with varying amounts of energy are emitted. (Bushong, 8th ed., pp. 144–146)

Question 53

Q

An axial projection of the clavicle is often helpful in demonstrating a fracture that is not visualized using a perpendicular CR. When examining the clavicle in the PA position, how is the CR directed for the axial projection?

Answer

A

Caudad

EXPLANATION: With the patient in the AP position, the CR is directed cephalad 25 to 30 degrees. This serves to project the clavicle away from the pulmonary apices and ribs, projecting most of the clavicle above the thorax. The reverse is true when the patient is examined in the PA position. The PA projection can be useful to obtain better recorded detail because of reduced OID. (Bontrager and Lampignano, 6th ed., p. 202)

Question 54

Q

While performing mobile radiography on a patient, you note that the requisition is for a chest image to check placement of a Swan–Ganz catheter. A Swan–Ganz catheter is a(n)

Answer

A

IV catheter.

EXPLANATION: A Swan–Ganz catheter is a specific type of IV catheter used to measure the pumping ability of the heart, to obtain pressure readings, and to introduce medications and IV fluids. A pacemaker is a device that is inserted under the patient’s skin to regulate heart rate. Pacemakers may be permanent or temporary. Chest tubes are used to remove fluid or air from the pleural cavity. Any of these items may be identified on a chest radiograph, provided that the IP is properly positioned and the correct exposure factors are employed. If the physician is interested in assessing the proper placement of a Swan–Ganz catheter, the lungs may have to be slightly overexposed to clearly delineate the proper placement of the tip of the Swan–Ganz catheter, which will overlap the denser cardiac silhouette. A urinary catheter will not appear on a chest radiograph. (Adler and Carlton, 5th ed., p. 189, 229)

Question 55

Q

Which of the following will be demonstrated best in the 45-degree right anterior oblique (RAO) position?

Answer

A

Left axillary ribs

EXPLANATION: The axillary portions of ribs are demonstrated in a 45-degree oblique position. In order to place the axillary portions parallel to the image receptor (IR), the affected side is away from the IR in the PA oblique (RAO and LAO) positions and toward the IR in the AP oblique (RPO and LPO) positions. Radiography of the sternum, in the slight RAO position, requires greater obliquity for thinner patients and lesser obliquity for thicker patients. The scapular Y position of the shoulder is performed to demonstrate dislocation and requires a rotation of 45–60 degrees, with the affected side closest to the IR. (Frank, Long, and Smith, vol. 1, pp. 494–495)

Question 56

Q

The first carpometacarpal joint is formed by the articulation of the base of the first metacarpal and the

Answer

A

trapezium.

EXPLANATION: The bases of the proximal row of phalanges articulate with the heads of the metacarpals to form the (condyloid) metacarpophalangeal joints, which permit flexion and extension, abduction and adduction, and circumduction. The bases of the metacarpals articulate with each other and the distal row of carpals at the carpometacarpal joints. The first carpometacarpal joint (thumb) is a saddle joint, permitting flexion and extension, abduction and adduction, and circumduction; it is formed by the articulation of the base of the first metacarpal and the trapezium. (Tortora, 11th ed, p 274)

Question 57

Q

Biologic material is most sensitive to radiation exposure under which of the following conditions?

Answer

A

Oxygenated

EXPLANATION: Tissue is most sensitive to radiation exposure when it is in an oxygenated condition. Anoxic refers to a general lack of oxygen in tissue; hypoxic refers to tissue with little oxygen. Anoxic and hypoxic tumors typically are avascular (with little or no blood supply) and, therefore, more radioresistant. (Bushong, 8th ed., p. 496)

Question 58

Q

The function(s) of the developer in film processing is (are) to

remove the unexposed silver bromide crystals

change the exposed silver bromide crystals to black metallic silver

harden the emulsion

Answer

A

2 only

EXPLANATION: X-ray film processing consists of four parts: development, fixing, wash, and dry. Developing agents change the exposed silver bromide crystals (latent image) to black metallic silver, thus producing a manifest image. The fixer solution removes the unexposed silver bromide crystals from the emulsion and hardens the gelatin emulsion, thus ensuring permanence of the radiograph. (Fauber, p. 167)

Question 59

Q

Capacitor-discharge mobile x-ray units use capacitors to power the

x-ray tube

machine locomotion

braking mechanism

Answer

A

1 only

EXPLANATION: Mobile x-ray machines are smaller and more compact than their fixed counterparts in the radiology department. It is important that they be relatively easy to move, that their size allows entry into patient rooms, and that their locks enable securing of the x-ray tube into the required positions. Mobile x-ray machines are cordless and are either the battery-operated type or the condenser-discharge type. Condenser-discharge mobile x-ray units do not use batteries; this type of mobile unit requires that it be charged before each exposure. A condenser (or capacitor) is a device that stores electrical energy. The stored energy is used to operate the x-ray tube only. Because this machine does not carry many batteries, it is much lighter and does not need a motor to drive or brake it. The major disadvantage of the capacitor/condenser-discharge unit is that as the capacitor discharges its electrical charge, the kilovoltage gradually decreases throughout the length of the exposure—hence, the need for recharging between exposures. (Frank, Long, and Smith, 11th ed., vol. 3, p. 235)

Question 60

Q

Which of the following combinations is most likely to be associated with quantum mottle?

 A. Decreased milliampere-seconds, decreased SID, fast-speed screens
 B. Increased milliampere-seconds, decreased kilovoltage, slow-speed screens
 C. Decreased milliampere-seconds, increased kilovoltage, fast-speed screens
 D. Increased milliampere-seconds, increased SID, fast-speed screens

Answer

A

Decreased milliampere-seconds, increased kilovoltage, fast-speed screens

EXPLANATION: Quantum mottle is a grainy appearance on a finished image that is seen especially in fast-imaging systems. It is very similar in appearance to an enlarged photograph taken with fast film; it has a spotted or freckled appearance. Fast imaging systems (fast film and fast screens, as well as CR/DR systems) with low-milliampere-seconds and high-kilovoltage factors are most likely to be the cause of quantum mottle. (Bushong, 8th ed., p. 273)

Question 61

Q

Skeletal conditions characterized by faulty bone calcification include

osteoarthritis.
osteomalacia.
rickets.

Answer

A

2 and 3 only

EXPLANATION: Rickets and osteomalacia are skeletal disorders characterized by abnormal calcification processes. In osteomalacia, bones become soft and are easily misshapen. Rickets affects the growing bones of children and is also characterized by soft, misshapened bones—as a result of calcium salts not being deposited in bone matrix. Osteoarthritis is a degeneration of articular cartilage; when these surfaces then attempt to articulate and move, bone friction and pain occur. (Tortora & Derrickson, pp 189-190)

Question 62

Q

When blue-emitting rare earth screens are matched properly with the correct film emulsion, what type of safelight should be used in the darkroom?

Red

GBX-2

Ultraviolet

Answer

A

1 and 2 only

EXPLANATION: Most radiographic film (i.e., green- and blue-sensitive) is orthochromatic, that is, sensitive to all colors but red. The GBX-2 is a red filter that is safe with orthochromatic film emulsion. Blue-sensitive film is also sensitive to violet and ultraviolet as well as blue. Green-sensitive film is also sensitive to blue, violet, and ultraviolet, as well as green. (Shephard, p. 90)

Question 63

Q

Which of the following will produce the most significant increase in patient dose?

Answer

A

Decreased SID

EXPLANATION: One of the most important ways to decrease exposure to ionizing radiation is to increase the distance between the source and the individual exposed. As the distance between the radiation source and the irradiated individual decreases, tissue exposure increases dramatically according to the Inverse Square Law of radiation.
An increase in mAs will increase patient dose proportionally. An increase in filtration will decrease patient skin dose, as low energy photons are removed from the x-ray beam. An increase in kVp will increase the number of high energy photons, thereby increasing patient dose. However, when accompanied by an appropriate decrease in mAs, increased kVp serves to decrease patient dose. (Bushong, 8th ed, p 552)

Question 64

Q

Which of the following methods can be used effectively to decrease differential absorption, providing a longer scale of contrast in the diagnostic range?

Using high peak kilovoltage and low milliampere-seconds factors

Using compensating filtration

Using factors that increase the photoelectric effect

Answer

A

1 and 2 only

EXPLANATION: When differences in absorption characteristics are decreased, body tissues absorb radiation more uniformly, and as a result, more grays are seen on the radiographic image. A longer scale of contrast is produced. High-kilovoltage and low-milliamperage factors achieve this. Compensating filtration is also used to “even out” densities in uneven anatomic parts, such as the thoracic spine. The photoelectric effect is the interaction between x-ray photons and matter that occurs at low-peak kilovoltage levels—levels that tend to produce short-scale contrast. (Shephard, pp. 193, 197, 199)

Answer 65

A

Aliasing

EXPLANATION: An artifact associated with digital imaging and grids is “aliasing” or the “moiré effect.” If the direction of the lead strips and the grid lines per inch (i.e., grid frequency) matches the scan frequency of the scanner/reader, this artifact can occur. Aliasing (or Moiré effect) appears as superimposed images slightly out of alignment, an image “wrapping” effect. This most commonly occurs in mobile radiography with stationary grids and can be a problem with DR flat panel detectors.

Answer 66

A

1, 2, and 3

EXPLANATION: Elective booking of a radiologic examination after inquiring about the patient’s previous menstrual cycle is the most effective means of preventing accidental exposure of a recently fertilized ovum. Patient questionnaires obtain this information from the patient and are also used often in an informed consent form. Patient postings in waiting and changing areas alert patients to advise the radiographer if there is any chance of pregnancy. These three safeguards replace the earlier 10-day rule, which is now obsolete. (Bushong, 8th ed., p. 559)

Answer 67

A

1, 2, and 3

EXPLANATION: Technique charts are exposure factor guides that help technologists produce radiographs with consistent density and contrast. They suggest a group of exposure factors to be used at a particular SID with a particular grid ratio, screen–film combination, focal-spot size, and CR angulation. Technique charts do not take into account the nature of the part (disease and atrophy). (Shephard, p. 298)

Answer 68

A

2 and 3 only

EXPLANATION: Target angle has a pronounced geometric effect on the effective, or projected, focal spot size. As the target angle decreases, the effective (projected) focal spot becomes smaller. 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). There are disadvantages, however. 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. (Shephard, p 221)

Answer 69

A

2 and 3 only

EXPLANATION: Somatic effects are those induced in the irradiated body. Genetic effects of ionizing radiation are those that may not appear for many years (generations) following exposure. Formation of cataracts or cancer (such as leukemia) and embryologic damage are all possible long-term somatic effects of radiation exposure. A fourth is life-span shortening. Blood changes are generally early effects of exposure to large quantities of ionizing radiation. (Bushong, 9th ed., pp. 551–558)

Answer 70

A

0.5 mm Mo

EXPLANATION: Soft tissue radiography requires the use of long-wavelength, low-energy x-ray photons. Very little filtration is used in mammography. Certainly, anything more than 1.0 mm of aluminum would remove the useful soft photons, and the desired high contrast could not be achieved. Dedicated mammographic units usually have molybdenum targets (for the production of soft radiation) and a small amount of molybdenum filtration. (Carlton & Adler, p 581)

Answer 71

A

2 and 3 only

EXPLANATION: Late effects of radiation can occur in cells that have survived a previous irradiation months or years earlier. These late effects, such as carcinogenesis and genetic effects, are “all-or-nothing” effects—either the organism develops cancer or it does not. Most late effects do not have a threshold dose; that is, any dose, however small, theoretically can induce an effect. Increasing that dose will increase the likelihood of the occurrence but will not affect its severity; these effects are termed stochastic. Nonstochastic effects are those that will not occur below a particular threshold dose and that increase in severity as the dose increases. (Bushong, 8th ed., p. 532)

Answer 72

A

As SID increases, exposure rate decreases and radiographic density decreases.

EXPLANATION: According to the inverse-square law of radiation, the intensity or exposure rate of radiation is inversely proportional to the square of the distance from its source. Thus, as distance from the source of radiation increases, exposure rate decreases. Because exposure rate and radiographic density are directly proportional, if the exposure rate of a beam directed to an IR is decreased, the resulting radiographic density would be decreased proportionately. (Selman, 9th ed., p. 117)

Answer 73

A

1 and 2 only

EXPLANATION: Computed radiography (CR) offers wide latitude and automatic optimization of the radiologic image. When AEC is not used, CR can compensate for about 80% underexposure and 500% overexposure. This can be an important advantage in trauma and mobile radiography. The radiographer still must be vigilant in patient dose considerations—overexposure, though correctable, results in increased patient dose; underexposure results in decreased image quality owing to increased image noise. CR systems provide an exposure indicator: an S (sensitivity) number, exposure index EI, or other relative exposure index depending on the manufacturer used. The manufacturer usually provides a chart identifying the acceptable range the exposure indicator numbers should be within for various examination types. For example, a high S number often is related to underexposure, whereas a high EI number is related to overexposure. Field of view (FOV) refers to the anatomic area being visualized. (Bontrager and Lampignano, 6th ed., p. 52)

Answer 74

A

First metacarpal

EXPLANATION: The first metacarpal, on the lateral side of the hand, articulates with the most lateral carpal of the distal carpal row, the greater multangular/trapezium. This articulation forms a rather unique and very versatile saddle joint named for the shape of its articulating surfaces. (Bontrager and Lampignano, 6th ed., p. 136)

Answer 75

A

1 and 3 only

EXPLANATION: Diarthrotic, or synovial, joints, such as the knee and the TMJ, are freely movable. Most diarthrotic joints are associated with a joint capsule containing synovial fluid. Diarthrotic joints are the most numerous in the body and are subdivided according to type of movement. Amphiarthrotic joints are partially movable joints whose articular surfaces are connected by cartilage, such as intervertebral joints. Synarthrotic joints, such as the cranial sutures, are immovable. (Bontrager and Lampignano, 6th ed., pp. 10–13)

Answer 76

A

1, 2, and 3

EXPLANATION: Differential absorption refers to the x-ray absorption characteristics of neighboring anatomic structures. The radiographic representation of these structures is referred to as radiographic contrast; it may be enhanced with high-contrast technical factors, especially using low kilovoltage levels. At low-kilovoltage levels, the photoelectric effect predominates. (Bushong, 8th ed., pp. 181–184)

Answer 77

A

1 only

EXPLANATION: The scaphoid can be difficult to image because its curved shape lends itself to foreshortening and self-superimposition. The lateral carpals, especially the scaphoid, are well demonstrated in the PA oblique projection. The ulnar flexion maneuver helps to overcome the scaphoid’s self-superimposition. The scaphoid may also be demonstrated with less foreshortening with the wrist PA and elevated 20 degrees. The CR is directed perpendicular to the carpal scaphoid.
The medial carpals, especially the pisiform, are well demonstrated in the AP oblique projection with the radial flexion maneuver. (Bontrager and Lampignano, 6th ed., pp. 161–162)

Answer 78

A

AP (medial) oblique

EXPLANATION: In the direct PA projection of the wrist, the carpal pisiform is superimposed on the carpal triquetrum. The AP oblique projection (medial surface adjacent to the IR) separates the pisiform and triquetrum and projects the pisiform as a separate structure. The pisiform is the smallest and most palpable carpal. (Frank, Long, and Smith, vol. 1, 11th ed., p. 129)

Answer 79

A

2 and 3 only

EXPLANATION: Facsimile transmission of health information is convenient but should be used only to address immediate and urgent patient needs—and every precaution must be taken to ensure its confidentiality. It should be used only with prior patient authorization, when urgently needed for patient care, or when required for third-party payer ongoing hospitalization certification. These recommendations are made by the American Health Information Management Association (AHIMA). (Adler and Carlton, 4th ed., p. 368)

Answer 80

A

There is greater patient dose with three-phase equipment than with single-phase equipment.

EXPLANATION: If the same kilovoltage is used with single-phase and three-phase equipment, the three-phase unit will require about 50% fewer milliampere-seconds to produce similar radiographs. Because three-phase equipment has much higher effective voltage than single-phase equipment, the three-phase radiograph will have lower contrast. A lower milliampere-seconds value can be used with three-phase equipment, so heat units are not built up as quickly. When technical factors are adjusted to obtain the same density and contrast, there is no difference in patient dose. (Selman, 9th ed., pp. 162–164)

Answer 81

A

1 only

EXPLANATION: Kilovoltage is the qualitative regulating factor; it has a direct effect on photon energy. That is, as kilovoltage is increased, photon energy increases. Photon energy is inversely related to wavelength. That is, as photon energy increases, wavelength decreases. Photon energy is unrelated to milliamperage. (Shephard, pp. 173, 178)

Answer 82

A

1, 2, and 3

EXPLANATION: There are several advantages of electronic/digital fluoroscopy. Electronic/digital fluoroscopic images are produced with less patient exposure and can be postprocessed (windowed to improve/enhance the image). The fluoroscopic still-frame images can be stored and/or transmitted to a TV monitor. Another advantage is the ability to perform “road-mapping.” In this procedure, the most recent fluoroscopic image is retained on the screen/monitor (last image hold) is retained on the screen/monitor. Road-mapping is particularly useful in procedures that require guidewire/catheter placement. The frame-hold function eliminates the need for continuous fluoroscopy, thereby reducing patient exposure. (Hendee and Ritenour, p. 244)

Answer 83

A

Coronoid process

EXPLANATION: The axial trauma lateral (Coyle) position is described. If routine elbow projections in extension are not possible because of limited part movement, these positions can be used to demonstrate the coronoid process and/or radial head. With the elbow flexed 90 degrees and the CR directed to the elbow joint at an angle of 45 degrees medially (i.e., toward the shoulder), the joint space between the radial head and capitulum should be revealed. With the elbow flexed 80 degrees and the CR directed to the elbow joint at an angle of 45 degrees laterally (i.e., from the shoulder toward the elbow), the elongated coronoid process will be visualized. (Bontrager and Lampignano, 6th ed., p. 174)

Answer 84

A

1 and 3 only

EXPLANATION: Hypoglycemic reactions can be very severe and should be treated with an immediate dose of sugar in the form of juice or candy. Symptoms of hypoglycemia include fatigue, restlessness, irritability, and weakness. Diabetic patients who have not taken their insulin prior to a fasting examination should be given priority, and their examinations should be expedited as quickly as possible. (Torres et al., 6th ed., pp. 169–170)

Answer 85

A

apposition

EXPLANATION: Various terms are used to describe the position of fractured ends of long bones. The term apposition is used to describe the alignment, or misalignment, between the ends of fractured long bones. The term angulation describes the direction of misalignment. The term luxation refers to a dislocation. A sprain refers to a wrenched articulation with ligament injury. (Bontrager and Lampignano, 6th ed., p. 600)

Answer 86

A

a solid-state diode

EXPLANATION: Some x-ray circuit devices, such as the transformer and autotransformer, will operate only on AC. 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. The process of full-wave rectification changes the negative half-cycle to a useful positive half-cycle. An x-ray circuit rectification system is located between the secondary coil of the high-voltage transformer and the x-ray tube. Rectifiers are solid-state diodes made of semiconductive materials such as silicon, selenium, or germanium that conduct electricity in only one direction. Thus, a series of rectifiers placed between the transformer and x-ray tube function to change AC to a more useful unidirectional current. (Bushong, 8th ed., p. 119)

Answer 87

A

Photospot camera film

EXPLANATION: Photospot camera film (C) is similar to that used in a movie camera. Only one frame is exposed when activated, but this can be done in succession to expose up to twelve images per second. This film receives its light image from the output phosphor of the image intensifier tube. A cassette-loaded spot film (A) is positioned in a lead-lined compartment between the patient and the image intensifier. When a spot-film exposure is desired, the radiologist must actuate a control that properly positions the cassette in the X-ray beam. Only one image can be recorded on either a portion of the film or the entire film. The images cannot be recorded in rapid succession, as the cassette must be mechanically repositioned within a lead-lined compartment before another exposure can be made. This repositioning of the cassette, along with energizing the X-ray tube to make an exposure, generally takes at least a couple of seconds. A flat panel image receptor (FPIR) (B) composed of cesium iodide and amorphous silicon pixel detectors can be used in place of an image intensifier in digital fluoroscopy for real-time imaging. Images created from this device are digitized and, therefore, can be stored in a PACS, but this device is not considered a recording system in itself. It only generates the image, to be recorded. In the past, direct exposure film (D) was manufactured for use without screens. They were primarily used for radiography of small anatomical parts, such as the hands and feet. Since these films were exposed by X-rays rather than the light emitted from intensifying screens, a much larger exposure was required to produce the desired optical density, when compared to screen film. By limiting use of the direct exposure film to radiography of smaller body parts, images of inherent high subject contrast could be produced, superior resolution was realized (due to no light divergence from an intensifying screen), and there was low radiation risk when compared to radiation exposure to other, more radiosensitive, body parts. (Bushong, 10th ed., p. 413).

Answer 88

A

AP and scapular Y

EXPLANATION: The AP projection will give a general survey and show mediolateral and inferosuperior joint relationships. The scapular Y position (LAO or RAO) is employed to demonstrate anterior (subcoracoid) or posterior (subacromial) humeral dislocation. The humerus normally is superimposed on the scapula in this position; any deviation from this may indicate dislocation. Rotational views must be avoided in cases of suspected fracture. The AP and scapular Y combination is the closest to two views at right angles to each other. (Frank, Long, and Smith, 11th ed., vol. 1, pp. 178, 189)

Answer 89

A

phosphorescence

EXPLANATION: Fluorescence occurs when an intensifying screen absorbs x-ray photon energy, emits light, and then ceases to emit light as soon as the energizing source ceases. Phosphorescence occurs when an intensifying screen absorbs x-ray photon energy, emits light, and continues to emit light for a short time after the energizing source ceases. Quantum mottle is the freckle-like appearance on some radiographs made using a very fast imaging system. The brightness of a fluoroscopic image is amplified through image intensification. (Bushong, 8th ed., p. 221)

Answer 90

A

Horizontal beam lateral

EXPLANATION: When a cervical spine radiograph is requested to rule out subluxation or fracture, the patient will arrive in the radiology area on a stretcher. The patient should not be moved before a subluxation is ruled out. Any movement of the head and neck could cause serious damage to the spinal cord. A horizontal beam lateral projection is performed and evaluated. The physician then will decide what further images are required. (Frank, Long, and Smith, 11th ed., vol. 2, p. 35)

Answer 91

A

must be supported parallel to the IR

EXPLANATION: The fingers must be supported parallel to the IR (e.g., on a finger sponge) in order that the joint spaces parallel the x-ray beam. When the fingers are flexed or resting on the cassette, the relationship between the joint spaces and the IR changes, and the joints appear “closed.” (Frank, Long, and Smith, 11th ed., vol. 1, pp. 118–119)

Answer 92

A

0.08 second.

EXPLANATION: First, evaluate the change(s): The kVp was decreased by about 15% [95–15% = 80.7]. A 15% decrease in kVp will cut the radiographic density in half; therefore, it is necessary to use twice the original mAs to maintain the original density. The original mAs was 21, and so we now need 42 mAs, using the 500-mA station. Because mA x s = mAs,
500x = 42
x = 0.084 second
(Fauber, pp 55, 59–60)

Answer 93

A

Use 0.02 second

EXPLANATION: With three-phase equipment, the voltage never drops to zero, and x-ray intensity is significantly greater. When changing from single-phase to three-phase, six-pulse equipment, two-thirds of the original milliampere-seconds value is required to produce a radiograph with similar density. When changing from single-phase to three-phase, 12-pulse equipment, only half the original milliampere-seconds value is required. In this problem, we are changing from three-phase, 12-pulse to single-phase equipment; therefore, the milliampere-seconds value should be doubled (from 4–8 mAs). (Carlton and Adler, 4th ed., p. 96)

Answer 94

A

Upper-limb venogram

EXPLANATION: The cephalic, basilic, and subclavian veins should be demonstrated on an upper limb venogram. Venography of the upper limb usually is performed to rule out venous obstruction or thrombosis. The injection site is usually in the hand or wrist, and images should be obtained up to the area of the superior vena cava. (Frank, Long, and Smith, 11th ed., vol. 3, p. 51)

Answer 95

A

1 and 2 only

EXPLANATION: Radiographic contrast is defined as the degree of difference between adjacent densities. These density differences represent sometimes very subtle differences in the absorbing properties of adjacent body tissues. The type of film emulsion used also brings with it its own contrast characteristics. Different types of film emulsions have different degrees of contrast “built into” them chemically. The technical factor used to regulate contrast is kilovoltage. Radiographic contrast is unrelated to milliampere-seconds. (Selman, 9th ed., pp. 218–220)

Answer 96

A

stored in a radiation-free area

EXPLANATION: The control badge that comes with the month’s supply of dosimeters is used as a standard for comparison with the used personal badges. The control badge should be stored in a radiation-free area, away from the radiographic rooms. When it has been processed, its density is compared with the densities of the monitors worn in radiation areas. Densities greater than the density of the radiation-free monitor are reported in millirem units. (Bushong, 8th ed., p. 596)

Answer 97

A

1 and 2 only

EXPLANATION: The AP projection of the clavicle should demonstrate the clavicular body/shaft and its two extremities: the sternal extremity and its associated sternoclavicular articulation, and the acromial extremity and its associated acromioclavicular articulation. The sternocostal joint is the articulation between the sternum and rib and is not delineated in the AP clavicle image. (Bontrager and Lampignano, 6th ed., p. 202)

Answer 98

A

1 and 2 only

EXPLANATION: The spinning-top test is used to evaluate timer accuracy or rectifier failure. With single-phase, full-wave-rectified equipment (120 pulses/s), for example, 12 dots should be visualized when using the 1/10-s time station. A few dots more or less indicate timer inaccuracy. If the test demonstrated exactly six dots, rectifier failure is strongly suspected. With three-phase equipment, a special synchronous spinning top (or oscilloscope) is used, and a solid black arc is obtained rather than dots. The length of this arc is measured and compared with the known correct arc. (Selman, 9th ed., pp. 105–106)

Answer 99

A

Between the draped patient and the instrument table

EXPLANATION: When radiographs in the surgical suite are required, the radiographer is responsible for ensuring that surgical asepsis is maintained. This requires proper dress, cleanliness of equipment, and restricted access to certain areas. An example of a restricted area is the “sterile corridor,” which is located between the draped patient and the instrument table and is occupied only by the surgeon and the instrument nurse. (Adler & Carlton, p 220)

Answer 100

A

0.03 s

EXPLANATION: The use of high kilovoltage with a fairly low-ratio grid will be ineffective in ridding the remnant beam of scattered radiation. To improve contrast in this example, it has been decided to decrease the kilovoltage by 15%, thus making it necessary to increase the milliampere-seconds from 5 mAs to 10 mAs. Because an increase in the grid ratio to 12:1 is also desired, another change in milliampere-seconds will be required (remember, 10 mAs is now the old mAs):

EXPLANATION: Thus, x = 12.5 mAs at 90 kVp. Now determine the exposure time required with 400 mA to produce 12.5 mAs:

EXPLANATION: (Selman, 9th ed., p. 214)

Answer 101

A

1 and 3 only

EXPLANATION: In a lateral projection of the ankle, the tibia and fibula are superimposed, and the foot is somewhat dorsiflexed to better demonstrate the talotibial joint. The talofibular joint is not visualized because of superimposition with other bony structures. It may be well visualized in the medial oblique projection of the ankle. (Frank, Long, and Smith, 11th ed., vol. 1, p. 286)

Answer 102

A

1, 2, and 3

EXPLANATION: Focal-spot size affects recorded detail by its effect on focal-spot blur: The larger the focal-spot size, the greater is the blur produced. Recorded detail is affected significantly by distance changes because of their effect on magnification. As SID increases and as OID decreases, magnification decreases and recorded detail increases. SOD is determined by subtracting OID from SID. (Shephard, p. 215)

Answer 103

A

1, 2, and 3

EXPLANATION: Ionization is the fundamental principle of operation of both the film badge and the pocket dosimeter. In the film badge, the film’s silver halide emulsion is ionized by x-ray photons. The pocket dosimeter contains an ionization chamber, and the number of ionizations taking place may be equated to the exposure dose. TLDs contain lithium fluoride crystals that undergo characteristic changes on irradiation. When the crystals are subsequently heated, they emit a quantity of visible (thermo) luminescence/light in proportion to the amount of radiation absorbed. OSL dosimeters contain aluminum oxide crystals that also undergo characteristic changes on irradiation. When the Al2O3 crystals are stimulated by a laser, they emit (optically stimulated) luminescence/light in proportion to the amount of radiation absorbed. (Bushong, 8th ed., p. 593)

Answer 104

A

Femoral neck

EXPLANATION: The dome of the acetabulum lies midway between the ASIS and the symphysis pubis. On an adult of average size, a line perpendicular to this point will parallel the plane of the femoral neck. In an AP projection of the hip, the CR should be directed to a point approximately 2 inches down that perpendicular line so as to enter the distal portion of the femoral head. (Frank, Long, and Smith, 11th ed., vol. 1, p. 341)

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