Equipment Operation and Quality Assurance - Rad Review

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 3. lightness and ease of maneuverability

1 and 2 only

Bone densitometry is often performed to 1. measure degree of bone (de)mineralization 2. evaluate results of osteoporosis treatment/therapy 3. evaluate condition of soft tissue adjacent to bone

1 and 2 only

Components of digital imaging include 1. computer manipulation of the image 2. formation of an electronic image on the radiation detector 3. formation of an x-ray image directly on the emulsion

1 and 2 only

What information must be included on an x-ray image for it to be considered as legitimate legal evidence? 1. Name of facility where exam performed 2. Examination date 3. Date of birth

1 and 2 only

Which of the following is/are components of the secondary, or high voltage, side of the x-ray circuit? 1. Rectification system 2. Autotransformer 3. kV meter

1 only -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.

Deposition of vaporized tungsten on the inner surface of the x-ray tube glass window 1. acts as additional filtration 2. results in increased tube output 3. results in anode pitting

1 only -Through the action of thermionic emission, as the tungsten filament continually gives up electrons, it gradually becomes thinner with age. This evaporated tungsten frequently is deposited on the inner surface of the glass envelope at the tube window. When this happens, it acts as an additional filter of the x-ray beam, thereby reducing tube output. Also, the tungsten deposit actually may attract electrons from the filament, creating a tube current and causing puncture of the glass envelope

Characteristics of DR imaging include 1. solid-state detector receptor plates 2. a direct-capture imaging system 3. immediate image display

1, 2, and 3

Characteristics of the metallic element tungsten include 1. ready dissipation of heat 2. high melting point 3. high atomic number

1, 2, and 3

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.

1, 2, and 3

Image quality in digital fluoroscopy is influenced by 1. pixel size. 2. contrast. 3. noise.

1, 2, and 3

Inadequate collimation in CR imaging can result in an image that is too 1. light 2. dark 3. noisy

1, 2, and 3

The batteries in battery-operated mobile x-ray units provide power to 1. the x-ray tube 2. machine locomotion 3. the braking mechanism

1, 2, and 3

The brightness level of the fluoroscopic image can vary with 1. milliamperage 2. kilovoltage 3. patient thickness

1, 2, and 3

X-ray tube life may be extended by 1. using low-milliampere-seconds/high- kilovoltage exposure factors 2. avoiding lengthy anode rotation 3. avoiding exposures to a cold anode

1, 2, and 3

Anode angle will have an effect on the 1. severity of the heel effect 2. focal-spot size 3. heat-load capacity

1, 2, and 3 -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. However, with steeper (smaller) anode angles, the anode heel effect is accentuated and can compromise film coverage.

As the image intensifier's FOV is reduced, how is the resulting image affected? 1. Magnification increases 2. Brightness decreases 3. Quality increases

1, 2, and 3 -As voltage is applied to the electrostatic focusing lenses, the focal point moves back—closer to the input phosphor—and, as a result, the FOV decreases and magnification increases. 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

Which part of an induction motor is located within the x-ray tube glass envelope?

Rotor -The anode is made to rotate through the use of an induction motor. An induction motor has two main parts, a stator and a rotor. The stator is the part located outside the glass envelope and consists of a series of electromagnets occupying positions around the stem of the anode. The stator's electromagnets are supplied with current, and the associated magnetic fields function to exert a drag or pull on the rotor within the glass envelope.

The device used to test the accuracy of the x-ray timer is the?

Spinning top -The spinning-top test may be used to test timer accuracy in single-phase equipment. A spinning top is a metal disk with a small hole in its outer edge that is placed on a pedestal about 6 in. high. An exposure is made (e.g., 0.1 s) while the top spins. Because a full-wave-rectified unit produces 120 x-ray photon impulses per second, in 0.1 s the film should record 12 dots (if the timer is accurate). Because three-phase equipment produces almost constant potential rather than pulsed radiation, the standard spinning top cannot be used. An oscilloscope or synchronous spinning top must be employed to test the timers of three-phase equipment.

Which part of an induction motor is located outside the x-ray tube glass envelope?

Stator

In digital imaging, the maximum spatial resolution is equal to:

The Nyquist frequency, which is 1/2X the pixel pitch (mm) -With digital systems, the spatial resolution is related to pixel pitch. The maximum spatial resolution is equal to the Nyquist frequency, 1/2X the pixel pitch (mm) (A). The wavelength of the electrical signal in an analog-to-digital convertor (ADC) is constant, and not affected by the pixel pitch of the matrix

A test pattern, such as the TG 18-CT test pattern, is used to qualitatively evaluate?

The luminance response of a digital display monitor

Cassetteless digital systems have a fixed spatial resolution determined by:

The thin film transistor (TFT) detector element (DEL) size

One reason why only one image is preferred per image plate is:

To allow the radiologist to split the PACS monitor and display the current image and a prior image side-by-side for comparison

The device used to change alternating current to unidirectional current is?

a solid-state diode

IRs/cassettes frequently have a lead-foil layer behind the rear screen that functions to

absorb backscatter

The term windowing describes the practice of?

changing the image contrast and/or brightness

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

charge-coupled device (CCD)

The part of a CT imaging system made of thousands of solid-state photodiodes is the?

detector array

The x-ray imaging system that uses a flat panel detector is?

direct digital radiography

To maintain image clarity, the path of electron flow from photocathode to output phosphor is controlled by?

electrostatic lenses

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 -The input phosphor of an image intensifier receives remnant radiation emerging from the patient and converts it to a fluorescent light image. Directly adjacent to the input phosphor is the photocathode, which is made of a photoemissive alloy (usually a cesium and antimony compound). The fluorescent light image strikes the photocathode and is converted to an electron image. 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

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

grid-controlled

As the CR laser scanner/reader recognizes the phosphostimulated luminescence (PSL) released by the PSP storage plate, it constructs a graphic representation of pixel value distribution called a?

histogram

The filtering effect of the x-ray tube's glass envelope and its oil coolant are referred to collectively as?

inherent filtration

The image intensifier's input phosphor differs from the output phosphor in that the input phosphor

is much larger than the output phosphor

In fluoroscopy, the automatic brightness control is used to adjust the?

kVp and mA

The continued emission of light by a phosphor after the activating source has ceased is termed?

phosphorescence

Off-focus, or extrafocal, radiation is minimized by?

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

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

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

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

solid-state diodes -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

The most common cause of x-ray tube failure is?

vaporized tungsten on glass envelope

A star pattern is used to measure 1. focal spot resolution. 2. scatter resolution. 3. SID resolution.

1 only -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

Electronic imaging terms used to indicate the intensity of radiation reaching the IR include 1. exposure index 2. sensitivity (S) number 3. field of view (FOV)

1 and 2 only -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.

Types of moving grid mechanisms include 1. oscillating. 2. reciprocating. 3. synchronous.

1 and 2 only -Grids are devices constructed of alternating strips of lead foil and radiolucent interspacing material. They are placed between the patient and the IR, and they function to remove scattered radiation from the remnant beam before it forms the latent image. Stationary grids will efficiently remove scattered radiation from the remnant beam; however, their lead strips will be imaged on the radiograph. If the grid is made to move (usually in a direction perpendicular to the lead strips) during the exposure, the lead strips will be effectively blurred. The motion of a moving grid, or Potter-Bucky diaphragm, may be reciprocating (equal strokes back and forth), oscillating (almost circular direction), or catapult (rapid forward motion and slow return). Synchronous refers to a type of x-ray timer.

Which of the following x-ray circuit devices operate(s) on the principle of mutual induction? 1. High-voltage transformer 2. Filament transformer 3. Autotransformer

1 and 2 only -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

Which of the following x-ray circuit devices operate(s) on the principle of mutual induction? 1. High-voltage transformer 2. Filament transformer 3. Autotransformer

1 and 2 only -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 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.

The total brightness gain of an image intensifier is the product of 1.flux gain 2. minification gain 3. focusing gain

1 and 2 only -The brightness gain of image intensifiers is 5,000 to 20,000. This increase is accounted for in two ways. As the electron image is focused to the output phosphor, it is accelerated by high voltage (about 25 kV). The output phosphor is only a fraction of the size of the input phosphor, and this decrease in image size represents brightness gain, termed minification gain. The ratio of the number of x-ray photons at the input phosphor compared to the number light photons at the output phosphor is termed flux gain. Total brightness gain is equal to the product of minification gain and flux gain

The output phosphor can be coupled with the Vidicon TV camera or charge-coupled device (CCD) via 1. fiber optics. 2. an image distributor or lens. 3. closed-circuit TV.

1 and 2 only -The output phosphor of the image intensifier displays the brighter, minified, and inverted image. From the output phosphor, the light image is conveyed to its destination by some kind of image distributor—either a series of lenses and a mirror or via fiber optics. Fiber optics is often the method of choice where equipment size is of concern (e.g., mobile equipment). The image distributor, that is, the lens or fiber optics, then sends the majority of light to the TV monitor for direct viewing and the remaining light (about 10%) to the IR (e.g., photospot camera).

Which of the following statements regarding dual x-ray absorptiometry is (are) true? 1. Radiation dose is low. 2. Only low-energy photons are used. 3. Photon attenuation by bone is calculated.

1 and 3 only -Dual x-ray absorptiometry (DXA) imaging is used to evaluate bone mineral density (BMD). It is the most widely used method of bone densitometry—it is low-dose, precise, and uncomplicated to use/perform. DXA uses two photon energies—one for soft tissue and one for bone. Since bone is denser and attenuates x-ray photons more readily, photon attenuation is calculated to represent the degree of bone density. Bone densitometry DXA can be used to evaluate bone mineral content of the body, or part of it, to diagnose osteoporosis or to evaluate the effectiveness of treatments for osteoporosis.

Capacitor-discharge mobile x-ray units 1. use a grid-controlled x-ray tube 2. are typically charged before the day's work 3. provide a direct-current output

1 and 3 only -There are two main types of mobile x-ray units—capacitor-discharge and battery-powered. The 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. 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. Its x-ray tube is grid-controlled, permitting very fast (short) exposure times. 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. Thus, although the value at the onset of the exposure may be 20 mAs and 80 kVp, at the end of the exposure, the kilovoltage value will be approximately 60 kVp.

Which of the following voltage ripples is (are) produced by single-phase equipment 1. 100% voltage ripple 2. 13% voltage ripple 3. 3.5% voltage ripple

1 only

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.

1, 2, and 3 -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.

Which of the following combinations would pose the least hazard to a particular anode?

1.2-mm focal spot, 85 kVp, 15 mAs -Radiographic rating charts enable the operator to determine the maximum safe milliamperage, exposure time, and peak kilovoltage for a particular exposure using a particular x-ray tube. An exposure that can be made safely with the large focal spot may not be safe for use with the small focal spot of the same x-ray tube. The total number of heat units that an exposure generates also influences the amount of stress (in the form of heat) imparted to the anode

If 85 kV and 20 mAs were used for a particular abdominal exposure with single-phase equipment, what mAs would be required to produce a similar radiograph with 3-phase, 12-pulse equipment.

10 -Single-phase radiographic equipment is much less efficient than three-phase equipment because it has a 100% voltage ripple. With three-phase equipment, voltage never drops to zero, and x-ray intensity is significantly greater. To produce similar receptor exposure, only two thirds of the original mAs would be used for three-phase, six-pulse equipment (2/3 × 20 = 13 mAs). With 3-phase, 12-pulse equipment, the original mAs would be cut in half; thus, 10 mAs should be used.

The functions of a picture archiving and communication system (PACS) include 1. storage of analog images 2. retrieval of digital images 3. storage of digital images

2 and 3 only

The primary parts of the cathode include the 1. focal track. 2. filament. 3. focusing cup.

2 and 3 only

Which of the following would be appropriate IP front material(s)? 1. Tungsten 2. Magnesium 3. Bakelite

2 and 3 only

With three-phase equipment, the voltage across the x-ray tube 1. drops to zero every 180 degrees 2. is 87% to 96% of the maximum value 3. is at nearly constant potential

2 and 3 only

Delivery of large exposures to a cold anode or the use of exposures exceeding tube limitation can result in 1. increased tube output 2. cracking of the anode 3. rotor-bearing damage

2 and 3 only -A large quantity of heat applied to a cold anode can cause enough surface heat to crack the anode. Excessive heat to the target can cause pitting or localized melting of the focal track. Localized melts can result in vaporized tungsten deposits on the glass envelope, which can cause a filtering effect, decreasing tube output. Excessive heat also can be conducted to the rotor bearings, causing increased friction and tube failure

Use of a portion of the input phosphor during fluoroscopy, rather than the entire input phosphor, will result in 1. a larger field of view (FOV). 2. a magnified image. 3. improved spatial resolution.

2 and 3 only -Multifield image intensifier tubes are usually either dual-field or trifield 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 used. As a result, the FOV decreases and magnification increases, producing better spatial resolution. At the same time, brightness is decreased, requiring an increase in milliamperage (therefore increased patient dose). This increase in milliamperage increases image quality. It can be likened to an increase in signal-to-noise ratio (SNR), with milliamperes being the signal.

Which of the following will occur as a result of a decrease in the anode target angle? 1. Less pronounced anode heel effect 2. Decreased effective focal spot size 3. Greater photon intensity toward the cathode side of the x-ray tube

2 and 3 only -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 spatial resolution without creating a heat-loading crisis at the anode (as would occur if the actual focal spot size were reduced to produce a similar resolution 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.

The collimator light and actual irradiated area must be accurate to within what percentage of the SID?

2% -Restriction of field size is one important method of patient protection. However, the accuracy of the light field must be evaluated periodically as part of a QA program. Guidelines set forth for patient protection state that the collimator light and actual irradiated area must be accurate to within 2% of the SID.

The voltage ripple associated with a three-phase, 12-pulse rectified generator is about?

4% -Voltage ripple refers to the percentage drop from maximum voltage each pulse of current experiences. In single-phase rectified equipment, the entire pulse (half-cycle) is used; therefore, there is first an increase to the maximum (peak) voltage value and then a decrease to zero potential (90° past peak potential). The entire waveform is used; if 100 kV were selected, the actual average kilovoltage output would be approximately 70. Three-phase rectification produces almost constant potential, with just small ripples (drops) in maximum potential between pulses. Approximately a 13% voltage ripple (drop from maximum value) characterizes the operation of three-phase, six-pulse generators. Three-phase, 12-pulse generators have about a 3.5% voltage ripple.

If the distance from the focal spot to the center of the collimator's mirror is 6 in., what distance should the illuminator's light bulb be from the center of the mirror?

6 in. -The collimator assembly includes a series of lead shutters, a mirror, and a light bulb (Figure 5-14). The mirror and light bulb function to project the size, location, and center of the irradiated field. The bulb's emitted beam of light is deflected by a mirror placed at an angle of 45 degrees in the path of the light beam. In order for the projected light beam to be the same size as the x-ray beam, the focal spot and the light bulb must be exactly the same distance from the center of the mirror

Which of the following combinations would pose the most hazard to a particular anode? A. 0.6 mm focal spot, 75 kVp, 30 mAs B. 0.6 mm focal spot, 85 kVp, 15 mAs C. 1.2 mm focal spot, 75 kVp, 30 mAs D. 1.2 mm focal spot, 85 kVp, 15 mAs

A. 0.6 mm focal spot, 75 kVp, 30 mAs -Radiographic rating charts enable the operator to determine the maximum safe mA, exposure time, and kVp for a particular exposure using a particular x-ray tube. An exposure that can be made safely with the large focal spot may not be safe for use with the small focal spot of the same x-ray tube. The total number of HU that an exposure generates also influences the amount of stress (in the form of heat) imparted to the anode. The product of mAs and kVp determines HU. Groups A and C produce 2250 HU; groups B and D produce 1275 HU. Groups B and D deliver less heat load, but group D delivers it to a larger area (actual focal spot) making this the least hazardous group of technical factors. The most hazardous group of technical factors is group A because it delivers the greatest heat (2,250 HU) with the small focal spot.

Which of the following combinations would pose the least hazard to a particular anode? A. 1.2-mm focal spot, 92 kVp, 1.5 mAs B. 0.6-mm focal spot, 80 kVp, 3 mAs C. 1.2-mm focal spot, 70 kVp, 6 mAs D. 0.6-mm focal spot, 60 kVp, 12 mAs

A. 1.2-mm focal spot, 92 kVp, 1.5 mAs -Radiographic rating charts enable the operator to determine the maximum safe milliamperage, exposure time, and kilovoltage for a particular exposure using a particular x-ray tube. An exposure that can be made safely with the large focal spot may not be safe for use with the small focal spot of the same x-ray tube. The total number of heat units that an exposure generates also influences the amount of stress (in the form of heat) imparted to the anode.

Which of the following devices converts electrical energy to mechanical energy? A. Motor B. Generator C. Stator D. Rotor

A. Motor

Which of the following devices converts electrical energy to mechanical energy? A. Motor B. Generator C. Stator D. Rotor

A. Motor

The luminescent light emitted by the PSP is converted to a digital image by the?

ADC -The exposed IP is placed into the CR scanner/reader, where the PSP is removed automatically. The latent image appears as the PSP is scanned by a narrow, high-intensity helium-neon laser to obtain the pixel data. As the PSP plate is scanned in the CR reader, it releases a violet light—a process referred to as photostimulated luminescence (PSL). The luminescent light is converted to electrical energy and sent to the analog-to-digital converter (ADC), where it is digitized and becomes the digital image. After a short delay the DAC (digital to analog converter) displays the recognizable analog image on a high-resolution monitor and/or printed out by a laser printer. The digitized images can also be manipulated in postprocessing, transmitted electronically, and stored/archived.

Although the stated focal-spot size is measured directly under the actual focal spot, focal-spot size in fact varies along the length of the x-ray beam. At which portion of the x-ray beam is the effective focal spot the largest?

At the cathode end

Histogram data that is skewed relative to the values of interest (VOI) of the histogram analysis used for a particular exam may be caused by all of the following, except: A. Anatomical structures not centered to the IP B. Excessive windowing C. The X-ray beam is not correctly aligned to the edges of the IP D. The beam edge is irregular because of overlap of a radiopaque shadow, such as a gonadal shield

B. Excessive windowing

Which of the following cells is the least radiosensitive? A. Myelocytes B. Myocytes C. Megakaryocytes D. Erythroblasts

B. Myocytes

All the following statements regarding beam restriction are true except A. beam restriction improves contrast resolution B. beam restriction improves spatial resolution C. field size should never exceed IR dimensions D. beam restriction reduces patient dose

B. beam restriction improves spatial resolution

"Saturation" of an image in CR means that:

Beyond a certain exposure level, a large number of pixels will be at maximum digital value (black), resulting in loss of visibility of anatomical structures in that region.

Which of the following combinations would deliver the least amount of heat to the anode of a three-phase, 12-pulse x-ray unit? A. 400 mA, 0.12 s, 90 kVp B. 300 mA, ½ s, 70 kVp C. 500 mA, 1/30 s, 85 kVp D. 700 mA, 0.06 s, 120 kVp

C. 500 mA, 1/30 s, 85 kVp -Radiographic rating charts enable the operator to determine the maximum safe milliamperage, exposure time, and kilovoltage for a particular exposure using a particular x-ray tube. An exposure that can be made using the large focal spot may not be safe when the small focal spot of the same x-ray tube is used. The total number of heat units an exposure generates also influences the amount of stress (in the form of heat) imparted to the anode. Single-phase heat units are determined by the product of milliampere-seconds and kilovoltage. A correction factor is required to determine the HU of three-phase equipment and high frequency equipment. Unless the equipment manufacturer specifies otherwise, three-phase and high frequency equipment heat units are determined by multiplying mA × second × kV × 1.4. In the examples given, then, group (A) produces 6,048 HU, group (B) produces 14,700 HU, group (C) produces 1,983 HU, and group (D) produces 7,056 HU. Therefore, group (C) exposure factors will deliver the least amount of heat to the anode.

Quality Control (QC) testing is used to evaluate digital display monitors in all of the following ways, except A. Display luminance response B. Display resolution C. Display matrix size D. Display noise

C. Display matrix size

Which of the following may occur if the X-ray exposure field is not properly collimated, positioned, and sized? A. Modulation transfer function failure B. Moiré artifact C. Exposure field recognition errors may occur D. Ghost artifact

C. Exposure field recognition errors may occur

Geometric blur can be evaluated using all the following devices except A. star pattern B. slit camera C. penetrometer D. pinhole camera

C. Penetrometer -Focal-spot size accuracy is related to the degree of geometric blur, that is, edge gradient or penumbra. Manufacturer tolerance for new focal spots is 50%; that is, a 0.3-mm focal spot actually may be 0.45 mm. Additionally, the focal spot can increase in size as the x-ray tube ages—hence the importance of testing newly arrived focal spots and periodic testing to monitor focal-spot changes. Focal-spot size can be measured with a pinhole camera, slit camera, or star-pattern-type resolution device.

Which of the following devices is used to control voltage by varying resistance? A/ Autotransformer B. High-voltage transformer C. Rheostat D. Fuse

C. Rheostat -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

Which of the following digital post-processing methods remove high-frequency noise from the image? A. Edge enhancement B. Windowing C. Smoothing D. Aliasing

C. Smoothing

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

C. the milliamperage meter

The X-ray scintillator layer used with indirect flat-panel digital detectors is usually either _____________ or ______________.

Cesium iodide, gadolinium oxysulfide

Using a multifield image intensifier tube, which of the following input phosphor diameters will require the highest patient dose? A. 35 cm B. 25 cm C. 17 cm D. 12 cm

D. 12 cm -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.

Which of the following possesses the widest dynamic range? A. ALARA B. PBL C. AEC D. CR

D. CR

Which of the following waveforms has the lowest percentage voltage ripple? A. Single-phase B. Three-phase, six-pulse C. Three-phase, 12-pulse D. High-frequency

D. High-frequency -high-frequency current is almost constant potential, having less than 1% voltage ripple

Objectionable widening of the histogram in CR can be caused by all of the following, except: A. Off-focus and scatter radiation outside of the exposure field B. Windowing C. Improper pre-exposure anatomical selection D. Subtraction

D. Subtraction

One advantage of a battery-powered mobile radiographic unit is:

Electrical power is available to drive itself

The safe approach to avoid an exposure field recognition error when using CR is to:

Expose one image on the smallest IP available with collimation margins aligned parallel to the edges of the IP

The long axis of the laser beam moving transversely back and forth across the image plate in a CR reader is called the:

Fast scan direction

The optimal alignment of the anatomical part being imaged for all digital receptors should be:

Field centered to IP with four collimation margins parallel to the IP edges

An important feature of the pixel in a flat-panel TFT digital detector active matrix array is the:

Fill factor -The fill factor (B) is defined as the ratio of the sensing area of the pixel to the area of the pixel itself. The sensing area of the pixel receives the data from the layer above it, which captures X-rays that are subsequently converted to light (indirect flat-panel detectors) or electrical charges (direct flat-panel detectors).

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

Flat panel image receptor

A type of laser used in CR scanners is?

Helium-neon

Before a flat-panel detector can be used for a radiographic exposure, it must be prepared. This preparation is referred to as:

Initialization

The pre-contrast image used to subtract pixel values from the post-contrast image showing contrast-filled blood vessels in digital subtraction angiography is called the:

Mask image

Europium-activated barium fluorohalide is associated with?

PSP storage plates -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

A device contained within many CR readers that functions to convert light energy released by the PSP into electrical energy, is called a:

Photomultiplier tube -A photomultiplier tube (B) receives light energy from the scanned PSP 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) to convert the light energy into an electrical signal. The light gate (C), (or channeling guide,) 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.

Pixel size and spacing determine the spatial resolution of the digital image. This is known as:

Pixel pitch

Sampling frequency in computed radiography (CR) is expressed as:

Pixels/mm or pixel density

The electron beam in a television cathode ray tube (CRT) is projected onto the output phosphor in a:

Raster pattern