image eq and eqip

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 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. The product of milliampere-seconds and kilovoltage determines heat units. Group (A) produces 138 HU, group (B) produces 240 HU, group (C) produces 420 HU, and group (D) produces 720 HU. The least hazardous group of technical factors is, therefore, group (A). Group (A) is also delivering its heat to the large focal spot, thereby decreasing the heat load to the anode. (Selman, 9th ed., pp. 144-145)

Which among the following components is (are) part of the gantry of a CT imaging system? X-ray tube Detector array Control panel A 1 only B 1 and 2 only C 2 and 3 only D 1, 2, and 3

B

The AEC device operates on which of the following principles? 1. Delivery of the required exposure time 2. A parallel-plate ionization chamber charged by x-ray photons 3. Motion of magnetic fields inducing current in a conductor A 1 only B 2 only C 1 and 2 only D 1, 2, and 3

Correct Answer is: C A parallel-plate ionization chamber is the most commonly used 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 automatically terminated. AEC determines exposure time; the radiographer must determine optimum kV and mA. Motion of magnetic fields inducing a current in a conductor refers to the principle of mutual induction. (Fauber, 2nd ed., pp 232-233)

What x-ray tube component does the number 8 in Figure 5-11 indicate? A Anode stem B Rotor C Stator D Focal track

Correct Answer is: D The figure illustrates the component parts of a rotating-anode x-ray tube enclosed within a glass envelope (number 3) to preserve the vacuum necessary for x-ray production. Number 4 is the rotating anode with its beveled focal track at the periphery (number 8) and its stem (at number 5). Numbers 6 and 7 are the stator and rotor, respectively—the two components of an induction motor—whose function it is to rotate the anode. Number 1 is the filament of the cathode assembly, which is made of thoriated tungsten and functions to liberate electrons (thermionic emission) when heated to white hot (incandescence). Number 2 is the nickel focusing cup, which functions to direct the liberated filament electrons to the focal spot. (Shephard, pp. 5-6; B

Which part of an induction motor is located within the x-ray tube glass envelope? A Filament B Focusing cup C Stator D Rotor

D

A new full-wave rectified x-ray machine is being installed at the outpatient imaging center downtown. Engineers and electricians from the manufacturer recommend wiring to a 220 V power supply from the building's electrical system. The operator's manual states that the maximum kilovoltage for the unit will be 150 kVp, and the rectifier will contain 4 diodes. It further states that the autotransformer uses 300 turns when it supplies unadjusted line voltage for maximum output to the step up transformer. What is the turns ratio (S:P) for the high voltage transformer for this machine? A 600:1 B 682:1 C 8,250:1 D 440:1

Expressed as Secondary to Primary (S:P): 682:1 (B). The 300 turns on the autotransformer and the 4 diodes were extra information unnecessary to the solution. Utilizing it in any way may yield some of the other choices. A full-wave rectified machine is the standard schematic in the ARRT content outline. It creates high voltage by sending a measured and selected voltage from the autotransformer to the step-up, or high voltage, transformer. The high voltage transformer is constructed with a great deal more coil windings on the secondary side than the primary side; the transformer law explains that such a ratio will lead to an increase in voltage, proportional to the magnitude of the turns ratio. If we have the maximum output voltage and the maximum input voltage, we have the voltage ratio, which is said to be equal to the turns ratio. Remember to convert 150 kilovolts back to volts (multiply by 103) before you begin. The G.U.E.S.S. method is a systematic way of solving word problems in a standardized, ordered process. The student may find it useful, but like any tool, you should practice with it a couple times to get the feel for it. The other answer choices are incorrect as per the previous explanation (A, C, and D). (Bushong, 11th ed., pp. 79-80)

Which of the following pathologic conditions would require a decrease in exposure factors? A Empyema B Osteoporosis C Pleural effusion D Hemothorax

In radiography, a pathologic condition is categorized as either destructive or additive pathology. Destructive pathology refers to an abnormal decrease in mass density in the affected area, and therefore requires the radiographer to decrease the exposure factors from what would be used for a healthy patient with an anatomical part of the same thickness. Osteoporosis is a destructive pathological condition that requires the radiographer to use a lower kVp setting than that used for healthy bone. Healthy bone is constantly being broken down and replaced. However, osteoporosis occurs when the creation of new bone fails to keep up with the removal of old bone. This results in a decrease in bone density and strength, which places the affected person at higher risk for fractures (B).Additive pathology refers to an abnormal increase in mass density, such as that caused by additional tissue (e.g., tumor mass), fluid, or other condition that effectively increases the mass density of the affected area. Therefore, the radiographer must increase the exposure factors to properly expose the IR. Empyema is a collection of pus in the pleural cavity caused by infection (A). A pleural effusion is a collection of fluid in the pleural space caused by a variety of underlying abnormal conditions including inflammation and congestive heart failure (C). Hydrothorax is a type of pleural effusion in which transudate accumulates in the pleural cavity, most commonly caused by congestive heart failure, pneumonia, malignancies, and pulmonary embolism (D). (Eisenberg and Johnson, 6th. ed., pp. 108-109)

Which of the following examinations might require the use of 70 kV? AP abdomen Chest radiograph Barium-filled stomach A 1 only B 2 only C 1 and 2 only D 2 and 3 only

It is appropriate to perform an AP abdomen radiograph with lower kilovoltage because it has such low subject contrast. Abdominal tissue densities are so similar that it takes high- or short-scale contrast (using low kilovoltage) to emphasize the little difference there is between tissues. However, high-kilovoltage factors are used frequently to even out densities in anatomic parts having high tissue contrast (e.g., the chest). However, since high kilovoltage produces added scattered radiation, it generally must be used with a grid. Barium-filled structures frequently are radiographed using 120 kV or more to penetrate the barium—to see through to posterior structures (Carlton and Adler, 4th ed., pp. 423-424)

ort the steps of image formation if an indirect DR system is used: Unordered List Technologist selects body part and projection from the control console's APR menu. TFT array sorts and transmits electronic signal to the image processing software. Processing software applies body part/projection-specific LUT to incoming data stream. Remnant beam exits the patient and interacts with the cesium iodide layer of the image receptor. Exposure switch is fully pressed, generating and broadcasting an x-ray beam that exits the tube. Light emission from the scintillation layer is converted to electric charge at the photodetector. Adjusted data set is sent to console display. Ordered List

Technologist selects body part and projection from the control console's APR menu. Exposure switch is fully pressed, generating and broadcasting an x-ray beam that exits the tube. Remnant beam exits the patient and interacts with the cesium iodide layer of the image receptor Light emission from the scintillation layer is converted to electric charge at the photodetector. TFT array sorts and transmits electronic signal to the image processing software. Processing software applies body part/projection-specific LUT to incoming data stream. Adjusted data set is sent to console display. Ordered List

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

The Correct Answer is: A A motor is the device used to convert electrical energy to mechanical energy. The stator and rotor are the two principal parts of an induction motor. A generator converts mechanical energy into electrical energy. (Selman, p 78)

A star pattern is used to measure 1. focal spot resolution. 2. scatter resolution. 3. SID resolution. A 1 only B 1 and 2 only C 1 and 3 only D 1, 2, and 3

The Correct Answer is: A 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. (Selman, p 210)

Which of the following is/are components of the secondary, or high voltage, side of the x-ray circuit? Rectification system Autotransformer kV meter A 1 only B 1 and 2 only C 2 and 3 only D 1, 2, and 3

The Correct Answer is: A 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)

The CR should be directed to the center of the part of greatest interest to avoid A rotation distortion B magnification C foreshortening D elongation

The Correct Answer is: A Anatomic details placed away from the path of the CR will be exposed by more divergent rays, resulting in rotation distortion. This is why the CR must be directed to the midpoint of the part of greatest interest. For example, if bilateral hands are requested, they should be examined individually; if imaged simultaneously, the CR will be directed to no anatomic part (between the two hands) and rotation distortion will occur. Magnification occurs when an OID is introduced, or with a decrease in SID. Foreshortening and elongation are the two types of shape distortion—caused by nonalignment of the x-ray tube, part/subject, and IR.

Spatial resolution is directly related to 1. source-image distance (SID). 2. tube current. 3. focal spot size. A 1 only B 1 and 2 only C 2 and 3 only D 1, 2, and 3

The Correct Answer is: A As SID increases, so does spatial resolution, because magnification is decreased. Therefore, SID is directly related to spatial resolution. As focal spot size increases, spatial resolution decreases because more blur/penumbra is produced. Focal spot size is thus inversely related to spatial resolution. Tube current affects receptor exposure and is unrelated to spatial resolution. (Fauber, 2nd ed., pp. 79, 81)

A part whose width is 6 inches will be imaged at 44 inches SID. The part to be imaged lies 9 inches from the IR. What will be the magnification factor? A 1.25 B 1.86 C 4.9 D 7.3

The Correct Answer is: A As the object-to-image receptor distance (OID) increases, magnification of that object increases. Depending upon the information provided, we can determine the magnification factor, the percentage magnification, and image width. In the stated scenario, we are looking for image width. The formula used to determine magnification factor is: MF = SID/SOD Substituting known factors the equation becomes: MF = 44/35 MF = 1.257 The "1" in the answer represents the actual object, while the ".257" represents the degree of magnification. The percent magnification can be determined by moving the decimal two places to the right. Thus, the percent magnification is 25.7%. (Shephard, p 230)

Any images obtained using dual x-ray absorptiometry (DXA) bone densitometry are used to evaluate accuracy of the region of interest (ROI) are used as evaluation for various bone/joint disorders reflect the similar attenuation properties of soft tissue and bone A 1 only B 1 and 2 only C 1 and 3 only D 1, 2, and 3

The Correct Answer is: A DXA imaging is used to evaluate 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, their attenuation is calculated to represent the degree of bone density. Soft tissue attenuation information is not used to measure bone density. Any images obtained in DXA/bone densitometry are strictly to evaluate the accuracy of the region of interest (ROI); they are not used for further diagnostic purposes—additional diagnostic examinations are done for any required further evaluation. 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. (Frank, Long, and Smith, 11th ed., vol. 3, pp. 455-456)

To compensate for variations in gain across a digital receptor, which of the following maintenance steps should be taken? A Conduct a calibration correction for image nonuniformity B Increase or decrease the exposure factors to compensate C Install a variable resistor to adjust the electrical supply to the unit D Keep a log for at least 30 days to confirm consistent variations before making any adjustments

The Correct Answer is: A Digital systems require that a uniformity correction (A) be applied to compensate for variations in gain across the receptor. This calibration for nonuniformity (also called shading correction) must be repeated on a periodic basis; the frequency depends on the digital device and ranges from daily to semi-annually. The exposure factors should not be adjusted (B) as a result of gain variations. This would be an unacceptable practice, especially if the exposure is increased, as this will cause unnecessary patient radiation dosage. Technologists should never alter the electrical supply (C) to the digital unit. Gain adjustments can be made to the equipment by simply adjusting the gain setting. Keeping a log for 30 days (D) to track the variations in gain would not facilitate timely correction to ensure that optimal diagnostic images are being produced. (S

The ability of an x-ray unit to produce constant radiation output at a given mAs, using various combinations of mA and time is called A linearity. B reproducibility. C densitometry. D sensitometry.

The Correct Answer is: A Each of the four factors are used as part of a complete quality assurance (QA) program. Linearity means that a given mAs, 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))

If a lateral projection of the chest is being performed on an asthenic patient and the outer photocells are selected, what is likely to be the outcome? A Decreased receptor exposure B Increased receptor exposure C Scattered radiation fog D Motion blur

The Correct Answer is: A If a lateral projection of the chest is being performed on an asthenic patient and the outer photocells are selected incorrectly, the outcome is likely to be an underexposed image. The patient is thin, and the lateral photocells have no tissue superimposed on them. Therefore, as soon as the lateral photocells detect radiation (which will be immediately), the exposure will be terminated, resulting in insufficient exposure. (Shephard, pp. 280-281)

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: A Mask image B Ghost (phantom) image C Moiré image D Latent image

The Correct Answer is: A In digital image subtraction, the pixel values from post-contrast images are electronically subtracted from pixel values from the first pre-contrast (mask) image (A) to show contrast-filled blood vessels with the other structures (e.g., bone) removed in order to enhance the diagnostic impressions of the radiologist. A ghost (or phantom) image (B) is an image artifact. The appearance of ghost images can be seen when CR image plates are incompletely erased. If an image plate has not been used for 24 hours, its phosphor storage plate should be erased again before using it for a diagnostic radiographic exposure. If a radiographic grid has a frequency that approximates the CR scan frequency and the grid strips are oriented in the same direction as the scan, the Moiré artifact may be observed (C); to decrease the possibility of this effect, high frequency grids are recommended for digital imaging. The latent image (D) is the image that exists in a radiographic film prior to chemical processing. It represents the collection of silver atoms around the sensitivity specks within the film emulsion. Upon chemical processing in a darkroom, the film will reveal an anatomical image with densities representing the varying levels of radiation exposure to the sensitivity specks contained within the film's emulsion. (Seeram, p. 36).

The purpose of magnification fluoroscopy is to: A Enhance the image in order to facilitate diagnostic interpretation B Decrease patient dosage C Decrease fluoroscopy time D Increase efficiency of X-ray production

The Correct Answer is: A Magnification of the image is an important feature of the image intensifier. The purpose of magnification fluoroscopy is to enhance the image in order to assist the radiologist in diagnostic interpretation (A). Magnification mode in fluoroscopy actually increases patient dosage (B), as more radiation is necessary to produce the brightness levels needed to view the images. The magnification mode should therefore be used only when necessary to enhance diagnostic interpretation of small specific anatomical areas in question. Fluoroscopy time should be limited in order to ensure the practice of ALARA. However, the time needed to evaluate the anatomical areas in question is not limited to a certain time (C). Magnification fluoroscopy neither increases or decreases fluoroscopic evaluation time. X-ray production efficiency is a function of the generator and X-ray tube providing the necessary X-ray energy to produce the fluoroscopic image. Magnification fluoroscopy, therefore, does not alter the efficiency of X-ray production (D). (Seeram, p. 134).

n 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 A 1 only B 1 and 2 only C 2 and 3 only D 1, 2, and 3

The Correct Answer is: A 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)

Capacitor-discharge mobile x-ray units use capacitors to power the x-ray tube machine locomotion braking mechanism A 1 only B 2 only C 1 and 2 only D 1, 2, and 3

The Correct Answer is: A 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., v

Which of the following focal-spot sizes should be employed for magnification radiography? A 0.2 mm B 0.6 mm C 1.2 mm D 2.0 mm

The Correct Answer is: A Proper use of focal spot size is of paramount importance in magnification radiography. A magnified image that is diagnostic can be obtained only by using a fractional focal spot of 0.3 mm or smaller. The amount of blur or geometric unsharpness produced by focal spots that are larger in size render the radiograph undiagnostic. (Selman, 9

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

The Correct Answer is: A 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.

The movement of the IP through the transport system of a CR reader is referred to as the: A Slow-scan direction B Charge-coupled direction C Nyquist direction D Fast-scan direction

The Correct Answer is: A The IP moves slowly through the transport system of a CR reader and this movement is considered the slow-scan direction (A). The laser light in the reader is rapidly reflected by an oscillating polygonal mirror that redirects the beam through a special lens called the f-theta lens, which focuses the light on a cylindrical mirror that reflects the light toward the PSP (photostimulable phosphor). This light moves back and forth very rapidly to scan the PSP transversely, in a raster pattern, and this movement of the laser beam across the PSP is therefore called the fast-scan direction (D). Charge-coupled direction (B) is not a term used to describe laser scanning in the CR reader. Charge-coupled devices are used in digital image receptors. Nyquist direction (C) is not a term used to describe laser scanning in the CR reader. With digital systems, the spatial resolution is related to pixel pitch. The maximum spatial resolution is equal to the Nyquist frequency, or 1/2X the pixel pitch (mm). (Seeram p. 54; Shephard p.

Incomplete erasure of CR plates can contribute to a A Ghost artifact B Moiré artifact C Static artifact D Grid cutoff artifact

The Correct Answer is: A The appearance of ghost artifacts (A) can be seen when CR image plates are incompletely erased. If an image plate has not been used for 24 hours, its phosphor storage plate should be erased again before using it for a diagnostic radiographic exposure. If a radiographic grid has a frequency that approximates the CR scan frequency and the grid strips are oriented in the same direction as the scan, the Moiré artifact may be observed (B); to decrease the possibility of this effect, high frequency grids are recommended for digital imaging. Grid cutoff artifacts (D) are seen as a decrease in receptor exposure on one side of the image when the CR is off-centered or not perpendicular to the grid - or, on both sides when the central ray is properly centered but the focal range is exceeded when using a focused grid. Static artifacts (C) may be seen on radi

Backscatter on a digital image can cause an artifact called a A Phantom image artifact B Moiré artifact C Static artifact D Grid cutoff artifact

The Correct Answer is: A The appearance of phantom image artifact (A) can be seen when excessive backscatter exposes the image receptor. The back side of the image receptor should be shielded with lead to reduce exposure to backscatter radiation. If a radiographic grid has a frequency that approximates the CR scan frequency and the grid strips are oriented in the same direction as the scan, the Moiré artifact may be observed (B). Grid cutoff artifacts are seen as a decrease in receptor exposure on one side of the image when the central ray is off-centered or not perpendicular to either a non-focused or focused grid, or on both sides when the central ray is properly centered but the focal range is exceeded (caused by improper SID) when using a focused grid (D). Static artifacts may be seen on radiographic film imaging (Bushong, 9 t

The image intensifier's input phosphor differs from the output phosphor in that the input phosphor A is much larger than the output phosphor B emits electrons, whereas the output phosphor emits light photons C absorbs electrons, whereas the output phosphor absorbs light photons D is a fixed size, and the size of the output phosphor can vary

The Correct Answer is: A The image intensifier's input phosphor is 6 to 9 times larger than the output phosphor. It receives the remnant radiation emerging from the patient and converts it into a fluorescent light image. Very close to the input phosphor, separated only by a thin, transparent layer, is the photocathode. The photocathode 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, which is focused by the electrostatic lenses to the small output phosphor. (Bushong, 8th ed., pp. 360-363)

The following are disadvantages of a capacitor-discharge mobile unit, except: A The mAs increases during the exposure, called "mAs creep" B The capacitor may continue to discharge after the exposure C The actual kilovoltage achieved during an exposure is significantly lower than the set kVp D At lower kVp settings, the capacitors discharge more slowly and, therefore, a considerable residual kV may exist after the desired exposure time

The Correct Answer is: A The mAs does not increase during an exposure (A) using a capacitor discharge mobile unit, but rather, the kVp decreases during the exposure. A disadvantage of a capacitor discharge unit is that the capacitor may continue to discharge after the usable exposure is made (B). Exposure begins at peak kV and then decreases during the exposure. The end of the exposure is called wavetail cutoff. The actual kilovoltage achieved during an exposure is significantly lower than the set kVp (C), approximately one kVp per mAs lower than the set kVp. At lower kVp settings, the capacitors discharge more slowly and, therefore, a considerable residual kV may exist after the desired exposure time (D). This can create a leakage of radiation, although there are several devices that are designed to avoid this problem. For instance, grid-biased X-ray tubes can be used to terminate the X-ray photon emission at a set time by reversing the charge polarity of a wire grid positioned in front of the cathode filament. Additionally, some tube collimators are designed to automatically close its lead shutters after the desired exposure is made, thus stopping radiation leakage. (Carlton and Adler, 5 th ed., p. 102).

Pixel size and spacing determine the spatial resolution of the digital image. This is known as: A Pixel pitch B Focal resolution C Nyquist resolution D Frequency modulation

The Correct Answer is: A The pixel size and spacing (i.e., pixel pitch, which is the distance from the midpoint of one pixel to the midpoint of the adjacent pixel) determine the spatial resolution of the image (A). The number of pixels can be obtained by multiplying the horizontal number of pixels by the vertical number of pixels in the image matrix (A). Focal resolution (B) is not a term used to describe spatial resolution in a digital radiographic image. However, the focal "spot" size does have an influence on image resolution. The smaller focal spot sizes should be used for smaller anatomical parts, whenever involuntary motion is absent. Nyquist "resolution" (C) is not a term used to describe spatial resolution in a digital radiographic image. However, the Nyquist "frequency," which is 1/2X the pixel pitch (mm) is equivalent to the spatial resolution. Frequency modulation (D) is not a term used to describe spatial resolution in a digital radiographic image. However, modulation transfer function (MTF) measures the ability of a detector to transfer its spatial resolution characteristics to the image. (Seeram, 1 st ed., p. 110)

The safe approach to avoid an exposure field recognition error when using CR is to: A Expose one image on the smallest IP available with collimation margins aligned parallel to the edges of the IP B Expose multiple images on one IP, but make sure all collimation margins overlap C Expose one image on the IP, but do not collimate D Expose multiple images on one IP, but make sure all collimation margins are parallel to each other and do not overlap

The Correct Answer is: A The safe approach to avoid an exposure field recognition error when using CR is to acquire one image on the smallest IP available. Collimation margins should also be parallel to the edges of the cassette (A). Exposing multiple images on one image plate (B) with overlapping collimation borders can result in an exposure field recognition error. The ALARA principle should be applied for every radiographic exposure. Collimation is critical to minimize patient exposure and dose (C). It is best to expose one image on the smallest image plate that will include all pertinent anatomy. Making multiple exposures on one image plate, regardless of attention to proper collimation can result in an exposure field recognition error (D). (Seeram, 1 st ed., p. 92)

The filtering effect of the x-ray tube's glass envelope and its oil coolant are referred to collectively as A inherent filtration B added filtration C compensating filtration D port filtration

The Correct Answer is: A The x-ray photons emitted from the anode focus are heterogeneous in nature. The low-energy photons must be removed because they are not penetrating enough to contribute to the image and because they do contribute to the patient's skin dose. The glass envelope and oil coolant provide approximately 0.5- to 1.0-mm Al equivalent filtration, which is referred to as inherent because it is a built-in, permanent part of the tube head. (Selman, 9th ed., p. 132)

All the following statements regarding three-phase current are true except A three-phase current is constant-potential direct current. B three-phase equipment produces more x-rays per milliampere-second. C three-phase equipment produces higher-average-energy x-rays than single-phase equipment. D the three-phase waveform has less ripple than the single-phase waveform.

The Correct Answer is: A 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)

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 A 1 only B 1 and 3 only C 2 and 3 only D 1, 2, and 3

The Correct Answer is: A 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)

In digital imaging, the maximum spatial resolution is equal to: A The Nyquist frequency, which is 1/2X the pixel pitch (mm) B The wavelength of the detector system's analog-to-digital convertor's electrical signal C The distance between the silver halide crystals in the image receptor D The detective quantum efficiency of the imaging system; this should be at least 2X the frequency of the analog-to-digital convertor electrical signal

The Correct Answer is: A 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 (B). Digital imaging does not use receptors with silver halide crystals. These crystals are used in radiographic film (C). Spatial resolution depends on the pixel sizes and pitch in the image matrix. Detective quantum efficiency (DQE) is a measure of the efficiency of a digital system to detect the X-ray photons and convert them into an image signal, regardless of the size and pitch of the image matrix pixels (D). (Seeram, 1 st ed., p. 97)

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 A 1 only B 2 only C 2 and 3 only D 1, 2, and 3

The Correct Answer is: A With single-phase, full-wave-rectified equipment, the voltage drops to zero every 180° (of the AC waveform); that is, there is 100% voltage ripple. With three-phase equipment, the voltage ripple is significantly smaller. Three-phase, 6-pulse equipment has a 13% voltage ripple, and three-phase, 12-pulse equipment has only a 3.5% ripple. Three-phase, 12-pulse equipment comes closest to constant potential, as the voltage never falls below 96.5% of maximum value. (Selman, p 96

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

The Correct Answer is: B 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, 9 th ed., pp. 441-442).

A device contained within many CR readers that functions to convert light energy released by the PSP into electrical energy, is called a: A Transilluminator B Photomultiplier tube C Light gate D Penetrometer

The Correct Answer is: B 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 (CCD) 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. A penetrometer (D) (or aluminum step wedge) is a device used for quality control testing in film radiography. After an exposure of this device is made while it rests on top of a film cassette, the film within the cassette is chemically processed. The resultant image demonstrates multiple steps of densities. The densities can be measured by a densitometer to determine the film contrast index and other processing-related factors. A sensitometer, which is an electrical device, can be used in lieu of the penetrometer and projects a preset light exposure on the film in the darkroom. After the film is processed, multiple steps of densities, similar to those achieved using the penetrometer, are demonstrated and can then be measured by a densitometer in the same fashion. A transilluminator is a device used for imaging of fluorescent DNA and proteins in a molecular biology lab (A). (Seeram p. 54; Shephard p. 328-329; Carter and Veale p. 72) Explanation Peer Comparison

A satisfactory radiograph was made using a 36-in. SID, 12 mAs, and a 12:1 grid. If the examination will be repeated at a distance of 42 in. and using a 5:1 grid, what should be the new milliampere-seconds value to maintain the original receptor exposure? A 5.6 B 6.5 C 9.7 D 13

The Correct Answer is: B According to the exposure-maintenance formula, if the SID is changed to 48 in., 16.33 mAs is required to maintain the original radiographic receptor exposure: mas for formula mas/mas2 di/di2 Bucky factor formula

The smallest digital detectors (approximately 100 microns) provide the best spatial resolution and, therefore, are best-suited for use in: A Fluoroscopy procedures B Mammography C Pediatric radiography D Long bone measurement to ensure measurement accuracy

The Correct Answer is: B Although spatial resolution is important in all radiographic or fluoroscopic applications, the systems affording the maximum spatial resolution are applied to those examinations such as mammography (B) where microscopic lesions must be detected. Lesions typically detected in fluoroscopic images (A) are at the macroscopic level. Maximum spatial resolution in cassetteless digital systems is limited by the size of the digital detectors. In the case of mammography, the best possible spatial resolution is required to ensure the detection and display of micro-calcifications, which may be suggestive of malignant lesions (B). Spatial resolution is important in pediatric imaging (C) and those systems used for this application provide sufficient resolution to display diagnostically acceptable images. The spatial resolution is not as important for long-bone measurement (D) as it is in mammography. These radiographic procedures, regardless of the spatial resolution, are intended to provide measurements from one joint to another, which does not require optimal spatial resolution. (Seeram, 1 st ed., p. 98)

An increase in kilovoltage will have which of the following effects? More scattered radiation will be produced. The exposure rate will increase. Radiographic contrast will increase. A 1 only B 1 and 2 only C 2 and 3 only D 1, 2, and 3

The Correct Answer is: B An increase in kilovoltage (photon energy) will result in a greater number (i.e., exposure rate) of scattered photons (Compton interaction). These scattered photons carry no useful information and contribute to radiation fog, thus decreasing radiographic contrast. (Selman, 9th ed., p. 117)

In an AP abdomen taken at 105-cm SID during an IV urography series, one renal shadow measures 9 cm in width. If the OID is 18 cm, what is the actual width of the kidney? A 5 cm B 7.5 cm C 11 cm D 18 cm

The Correct Answer is: B As OID increases, magnification increases. Viscera and structures within the body will be varying distances from the image receptor, depending on their location within the body and the position used for the exposure. The size of a particular structure or image can be calculated using the following formula: Substituting known quantities,

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

The Correct Answer is: B Beam restriction is used to determine the size of the x-ray field. This size never should be larger than the IR size. Because the size of the irradiated area can be made smaller, patient dose is reduced. Beam restriction reduces the production of scattered radiation that leads to fog and, therefore, improves contrast resolution. Spatial resolution is related to factors affecting recorded detail, not contrast resolution. (Bushong, 8th ed., pp. 243, 244)

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

The Correct Answer is: B Bergonié and Tribondeau theorized in 1906 that all precursor cells are particularly radiosensitive (e.g., stem cells found in bone marrow). There are several types of stem cells in bone marrow, and the different types differ in degree of radiosensitivity. Of these, red blood cell precursors, or erythroblasts, are the most radiosensitive. White blood cell precursors, or myelocytes, follow. Platelet precursor cells, or megakaryocytes, are even less radiosensitive. Myocytes are mature muscle cells and are fairly radioresistant. (Bushong, 8th ed., p. 495)

Electronic imaging terms used to indicate the intensity of radiation reaching the IR include exposure index sensitivity (S) number field of view (FOV) A 1 only B 1 and 2 only C 2 and 3 only D 1, 2, and 3

The Correct Answer is: B 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)

An exposed image plate will retain its original image quality for about A 2 hours B 8 hours C 24 hours D 48 hours

The Correct Answer is: B Computed radiography image plates (IP) have a protective function (for the PSP 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 to absorb backscatter. Inside the IP is the photostimulable phosphor (PSP) storage plate. This PSP 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, 4t

Which of the following mobile radiography applications enables the radiographer to view the radiographic image before leaving the patient? A Fixed digital units of any type B Tethered or wireless flat-panel digital mobile units C Portable units using conventional radiographic film D Battery operated conventional radiography mobile units

The Correct Answer is: B Detectors in mobile digital units may use either tethered or wireless flat-panels (B), which allows the radiographer to view the radiographic image at the patient's bedside. An acceptable image may then be sent to a PACS system for physician review. Fixed digital units (A) are found in the radiology department and cannot be used for mobile applications. Portable units using conventional radiographic film (C) requires the radiographer to chemically process the film in a darkroom located in the radiology department. Battery operated conventional radiography mobile units (D) are used with conventional radiographic film and, therefore, the film must be chemically processed in the darkroom located in the radiology department. (Carlton and Adler, 5 th ed., p. 52

Bone densitometry is often performed to measure degree of bone (de)mineralization evaluate results of osteoporosis treatment/therapy evaluate condition of soft tissue adjacent to bone A 1 only B 1 and 2 only C 2 and 3 only D 1, 2, and 3

The Correct Answer is: B Dual x-ray absorptiometry (DXA) imaging is used to evaluate bone mineral density (BMD). 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. 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, the attenuation is calculated to represent the degree of bone density. Soft tissue attenuation information is not used to measure bone density. (Frank, Long, and Smith, 11th ed., vol. 3, pp. 454-455)

One reason why only one image is preferred per image plate is: A To ensure that the anatomical part is properly centered to avoid undercutting of the image B To allow the radiologist to split the PACS monitor and display the current image and a prior image side-by-side for comparison C To ensure optimal radiation safety, since only one image is exposed on one image plate D To reduce the chances of grid cutoff artifacts

The Correct Answer is: B Exposing only one image on one image plate does not ensure proper centering (A). This is a technical skill required of the radiographer to ensure the anatomical part is properly centered. One reason to collect only one image per IP (B) is the ability of the radiologist to then split the PACS monitor and display the current image and the prior image side by side for comparison. Radiation safety is not optimized by exposing one image on one imaging plate. The required number of projections (exposures) is required, regardless (C). Grid cutoff artifacts can occur with faulty tube/image receptor alignment or improper SID for any radiographic exposure, regardless of the number of projections taken on an image plate (D). (Seeram, 1 st ed., p. 93)

Due to the high sensitivity of digital detectors to low intensity radiation (background, scatter and/or off-focus radiation), there is likely to be scatter and off-focus radiation contributing to the image outside the collimation margins. Since many radiologists find this distracting, the most appropriate radiographer action would be to: A Use film-screen imaging only B Apply a black border to the image before it is printed or sent to PACS C Expose the anatomical parts as is; there is nothing that can be done to improve the presentation of the image(s) due to the inherent sensitivity of the system D Reduce exposure factors by one-half to ensure minimal scatter and off-focus radiation

The Correct Answer is: B Film-screen radiography has been abandoned in most hospitals and imaging centers. Most of these institutions no longer maintain a darkroom or resources to produce film-screen images (A). Many radiologists find scatter and off-focus radiation distracting when viewing images. The appropriate response to scatter and off-focus exposure outside the collimation margin is to apply a black border to the image before it is printed or sent to PACS (B). Close collimation should be used to minimize scatter radiation (C). The exposure factors must be appropriate for the anatomical part being imaged. Halving the appropriate mAs or kVp (D) will result in image mottle or inadequate penetration of the part, respectively. (Seeram, 1 st ed

The continued emission of light by a phosphor after the activating source has ceased is termed A fluorescence B phosphorescence C image intensification D quantum mottle

The Correct Answer is: B 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)

Focal-spot blur is greatest A toward the anode end of the x-ray beam B toward the cathode end of the x-ray beam C directly along the course of the CR D as the SID is increased

The Correct Answer is: B 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)

Which of the following requires two exposures to evaluate focal-spot accuracy? A Pinhole camera B Slit camera C Star pattern D Bar pattern

The Correct Answer is: B 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. The pinhole camera is rather difficult to use accurately and requires the use of excessive tube (heat) loading. With a slit camera, two exposures are made; one measures the length of the focal spot, and the other measures the width. The star pattern, or similar resolution device, such as the bar pattern, can measure focal-spot size as a function of geometric blur and is readily adaptable in a QA program to monitor focal-spot changes over a period of time. It is recommended that focal-spot size be checked on installation of a new x-ray tube and annually thereafter. (Bushong, 8th ed., p. 462)

Which of the following information is necessary to determine the maximum safe kilovoltage using the appropriate x-ray tube rating chart? Milliamperage and exposure time Focal-spot size Imaging-system speed A 1 only B 1 and 2 only C 2 and 3 only D 1, 2, and 3

The Correct Answer is: B Given the milliamperage and exposure time, a radiographic rating chart enables the radiographer to determine the maximum safe kilovoltage for a particular exposure. Because the heat load an anode will safely accept varies with the size of the focal spot and the type of rectification, these variables must be identified. Each x-ray tube has its own radiographic rating chart. The speed of the imaging system has no impact on the use of a radiographic rating chart. (Selman, 9th ed., p. 145)

TV camera tubes used in image intensification, such as the Plumbicon and Vidicon, function to A increase the brightness of the input-phosphor image. B transfer the output-phosphor image to the TV monitor. C focus and accelerate electrons toward the output phosphor. D record the output-phosphor image on the IR.

The Correct Answer is: B Image intensification is a process that converts the dim fluoroscopic image into a much brighter image, much like normal daylight. As x-ray photons emerge from the patient and enter the image intensifier, they first encounter the input phosphor, which is generally composed of cesium iodide phosphors. At the input phosphor, x-ray photons are converted to light photons, which, in turn, strike the photocathode. The photocathode is a photoemissive metal (usually antimony and cesium compounds); when struck by light, it emits electrons in proportion to the intensity of the light striking it. The electrons then are directed to the output phosphor via the electrostatic focusing lenses, speeded up in the neck of the tube by the accelerating anode and directed to the output phosphor for further amplification. Most image intensifiers offer brightness gains of 5,000-20,000. From the output phosphor, the image is taken by the TV camera, most often a Plumbicon or Vidicon tube, and transferred to the TV monitor. (Thompson et al., p. 370)

The term windowing describes the practice of A varying the automatic brightness control B changing the image contrast and/or brightness C varying the FOV D increasing resolution

The Correct Answer is: B In electronic imaging (CR/DR), the radiographer can manipulate the digital image displayed on the CRT through postprocessing. One way to alter image contrast and/or brightness is through windowing. This refers to some change made to window width and/or window level. Change in window width changes the number of gray shades, that is, image contrast. Change in window level changes the image brightness. Windowing and other postprocessing mechanisms permit the radiographer to produce "special effects" such as edge enhancement, image stitching, and image inversion, rotation, and reversal. A digital image is formed by a matrix of pixels in rows and columns. A matrix having 512 pixels in each row and column is a 512 × 512 matrix. The term field of view is used to describe how much of the patient (e.g., 150-mm diameter) is included in the matrix. The matrix or field of view can be changed without affecting the other, but changes in either will change pixel size. Automatic brightness control is associated with image intensification. (Fosbinder and Kelsey, p. 289; Selman, 9th ed., pp. 190-191)

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 A 1 only B 1 and 2 only C 1 and 3 only D 1, 2, and 3

The Correct Answer is: B 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. (Bushong, 8th ed

Before a flat-panel detector can be used for a radiographic exposure, it must be prepared. This preparation is referred to as: A Propagation B Initialization C Augmentation D Instrumentation

The Correct Answer is: B In order to prepare a flat-panel detector for an X-ray exposure, it must be initialized, where all switching elements are held in an "off" state by the appropriate control voltage (e.g., -5 volts) (B). Once the x-ray exposure is made, the pixel's sensing area contains the image information. That information is obtained, line by line, by changing the control voltage (e.g., +10 volts). The resulting signal is digitized and stored. Propagation (A) refers to energy travelling through a medium, such as an anatomical part. In medical imaging, the term "augmentation" (C) refers to either forced accelerated venous blood return to the heart by manually compressing a patient's leg during a venous ultrasound Doppler procedure or, in mammography, when imaging augmented breasts. Instrumentation (D) is a general term that refers to devices used in medical procedures or the development, and safe and effective use of medical technology. (Seeram, 1 st ed., p. 114)

Magnification fluoroscopy is only possible with: A Decreased patient dosage B Multifield image intensifiers C Decreased fluoroscopic time D Increased efficiency of X-ray production

The Correct Answer is: B Magnification fluoroscopy requires that a multifield image intensifier (B) be used to allow reduction of the X-ray field size to the input phosphor area. Smaller input phosphor field sizes produce magnified images of the anatomical areas being evaluated at the output phosphor. Magnification mode in fluoroscopy actually increases patient dosage (A), as more radiation is necessary to produce the brightness levels needed to view the images. The magnification mode should therefore be used only when necessary to enhance diagnostic interpretation of small anatomical areas in question (e.g., the gallbladder or duodenal bulb). Fluoroscopy time should be limited to that which is absolutely necessary in order to ensure proper practice of ALARA. However, the time needed to evaluate the anatomical areas in question is not limited to a certain time. Magnification fluoroscopy neither increases or decreases fluoroscopic evaluation time (C). X-ray production efficiency is a function of the generator and X-ray tube (D) providing the necessary X-ray energy to produce the fluoroscopic image. Magnification fluoroscopy, therefore, does not alter the efficiency of X-ray production. (Seeram, p. 134).

IRs/cassettes frequently have a lead-foil layer behind the rear screen that functions to A improve penetration B absorb backscatter C preserve resolution D increase the screen speed

The Correct Answer is: B Many cassettes/IRs have a thin lead-foil layer behind the rear screen to absorb backscattered radiation that is energetic enough to exit the rear screen, strike the metal back, and bounce back to fog the image. When this happens, the IR's metal hinges or straps may be imaged in high-kilovoltage radiography. The lead foil absorbs the backscatter before it can fog the film. (Shephard, pp. 41-42)

The advantages of capacitor-discharge mobile x-ray equipment include compact size light weight high kilovoltage capability A 1 only B 1 and 2 only C 2 and 3 only D 1, 2, and 3

The Correct Answer is: B 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)

All the following statements regarding mobile radiographic equipment are true except A the exposure cord must permit the operator to stand at least 6 ft from the patient, x-ray tube, and useful beam B exposure switches must be the two-stage type C a lead apron should be carried with the unit and worn by the radiographer during exposure D the radiographer must alert individuals in the area before making the exposure

The Correct Answer is: B NCRP Report No. 102 states that the exposure switch on mobile radiographic units shall be so arranged that the operator can stand at least 2 m (6 ft) from the patient, the x-ray tube, and the useful beam. An appropriately long exposure cord accomplishes this requirement. The fluoroscopic and/or radiographic exposure switch or switches must be of the "dead man" type; that is, the exposure will terminate should the switch be released. A lead apron should be carried with every mobile x-ray unit for the operator to wear during the exposure. Lastly, the radiographer must be certain to alert individuals in the area, enabling unnecessary occupants to move away, before making the exposure. (NCRP Report No. 102, p. 25)

Off-focus and scatter radiation outside of the exposure field when using CR can cause: A Narrowing of the histogram B Widening of the histogram C Improper alignment of the exposure field D High contrast

The Correct Answer is: B Off-focus and scatter radiation outside of the exposure field would be detected as additional information and, therefore, would widen the histogram (B), resulting in a processing error. Histogram analysis errors can result in rescaling errors and exposure indicator determination errors. Alignment of the exposure field (C) is set by the radiographer prior to the exposure. Any off-focus and scatter radiation exposure outside of the exposure field will not change this alignment. Scatter radiation decreases image contrast (D). (Seeram

The device used to change alternating current to unidirectional current is a A capacitor B solid-state diode C transformer D generator

The Correct Answer is: B 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)

To ensure proper operation of the digital image display monitor, all of the following are important in order to develop a quality control (QC) program, except: A Routine quality control tests by the QC technologist B Disassembly and cleaning of the internal monitor control devices by the QC technologist C Periodic review of the QC program by a qualified medical physicist D Annual and post-repair medical physics performance evaluations

The Correct Answer is: B The QC technologist should never disassemble the monitor to expose its control devices for cleaning (B). Any malfunctions and undesirable results should be reported to the medical physicist and/or manufacturer. Routine quality control tests by the QC technologist (A) ensure that the display monitor accurately reveals diagnostic images. Periodic review of the integrity of the QC program should be evaluated by a qualified medical physicist (C) who may either make recommendations for revisions or approve the existing program. Annual and post-repair medical physics performance evaluations (D) should be performed by a qualified medical physicist. (Bushong, 9 th ed., p. 485).

A test pattern, such as the TG 18-CT test pattern, is used to qualitatively evaluate A Radiographic film-screen contact B The luminance response of a digital display monitor C The X-ray exposure field alignment D The exposure rate in an X-ray beam

The Correct Answer is: B The TG 18-CT test pattern is used to qualitatively evaluate the luminance response of a digital display monitor (B). Luminance response refers to the comparison of input to the display device and the actual displayed luminance value. The displayed luminance value varies between L min and L max and is impacted by ambient light as well (L amb ). The pattern in TG 18-CT testing device includes 16 low-contrast targets that should be visible on the display. The test pattern should be viewed from a distance of approximately 30 cm. One frequent observation is inability to visualize one or more shades in the darker regions. Radiographic film-screen (A) contact is evaluated by exposing a wire mesh screen on top of a conventional radiographic cassette holding an unexposed film. Any blurred areas of the wire mesh would indicate that there is poor film-screen contact in that particular area. The X-ray exposure field alignment (C) can be tested by using a square or rectangular leaded test pattern. An exposure is made with this test pattern device positioned on top of the receptor with collimator light field adjusted to match the size of the test pattern. The resultant image is then inspected to determine if the X-ray exposure field is congruent with the borders of the test pattern. The exposure rate (D) in an X-ray beam is measured with a calibrated radiation dosimeter that contains an ionization chamber or photodiode.

Which of the following is a type of television camera tube that converts a visible image on the output phosphor of the image intensifier into an electronic signal? A Ionization chamber B Vidicon C Charge-coupled device D Cathode ray tube

The Correct Answer is: B The Vidicon (B) is a television camera tube used in television fluoroscopy. It is a cylindrical glass vacuum tube that contains a cathode and anode. The cathode (also called the electron gun) is responsible for thermionic emission of electrons, which are accelerated through an electrostatic field that focuses them on a target assembly (anode). The target assembly consists of three layers: the window (thin part of the glass envelope), a metal or graphite signal plate, and a photoconductive layer called the target. When visible light from the output phosphor of the image intensifier tube strikes the anode target assembly, the photoconductive layer of the target conducts electrons. Therefore, in the presence of light, the electrons emitted from the cathode are able to pass through the target to the signal plate and, from there, out of the tube as the video signal. Ionization chambers (A) are found in an automatic exposure control (AEC) system. Air in these chambers is ionized in proportion to the number of X-rays interacting with the air and an electrical signal is generated. This signal, once it reaches a specific magnitude, initiates an exposure timer in the X-ray circuit, which terminates the exposure according to the radiographer's preselected density setting. A major change from conventional television fluoroscopy to digital fluoroscopy is the use of a charge-coupled device (CCD) (C) in lieu of a television camera tube. The CCD is mounted directly to the output phosphor of the image intensifier tube and is coupled through fiber optics or a lens system to receive the light from the output phosphor. The cathode ray tube (CRT) (D) is a television monitor tube that is viewed by the operator during fluoroscopic evaluation of the anatomy of interest. (Bushong, 9 th ed., pp. 353-354).

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? A 3 in. B 6 in. C 9 in. D 12 in.

The Correct Answer is: B 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. (Carlton and Adler, 4th ed., p. 232)

An important feature of the pixel in a flat-panel TFT digital detector active matrix array is the: A Nyquist frequency B Fill factor C Image lag D Modulation transfer function

The Correct Answer is: B 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). The Nyquist frequency (A) is 1/2X the pixel pitch (mm) and is equivalent to the spatial resolution in digital systems. A pixel contains generally three components: the TFT, the capacitor, and the sensing area. Image lag (C) is an undesirable phenomenon that refers to the persistence of the image, that is, a charge is still being produced in a digital detector after the radiation beam from the X-ray tube has been turned off. The modulation transfer function (D) is a mathematical function that measures the ability of the digital detector to transfer its spatial resolution characteristics to the image. (Seeram, 1 st ed., p. 111)

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? A 40 kV B 110 kV C 40 V D 110 V

The Correct Answer is: B 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,

An advantage of coupling the image intensifier to the TV camera or CCD via a fiber-optic coupling device is its compact size durability ability to accommodate auxilary imaging devices A 1 only B 1 and 2 only C 1 and 3 only D 1, 2, and 3

The Correct Answer is: B The image intensifier can be coupled to the TV camera via a fiber-optic bundle or via a lens coupling device. The fiber-optic connection offers less fragility, more compactness, and ease of maneuverability. The objective lens can use the, now infrequently used, auxiliary imaging devices such as a cine camera or spot-film camera. (Bushong, 8th ed., p. 366)

To maintain image clarity in an image-intensifier system, the path of electron flow from the photocathode to the output phosphor is controlled by A the accelerating anode B electrostatic lenses C the vacuum glass envelope D the input phosphor

The Correct Answer is: B 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. (Carlton and Adler, 4th ed., pp. 569-570)

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

The Correct Answer is: B 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). (Bushong, 8th ed., p. 366)

Star and wye configurations are related to A autotransformers B three-phase transformers C rectification systems D AECs

The Correct Answer is: B 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)

he direction of electron travel in the x-ray tube is A filament to cathode B cathode to anode C anode to focus D anode to cathode

The Correct Answer is: B The x-ray tube is a diode tube; that is, it has two electrodes—a negative and a positive. The cathode assembly is the negative terminal of the x-ray tube, and the anode is the positive terminal. Electrons are released by the cathode filament (thermionic emission) as it is heated to incandescence. When kilovoltage is applied, the electrons are driven across to the anode's focal spot. Upon sudden deceleration of electrons at the anode surface, x-rays are produced. Hence, electrons travel from cathode to anode within the x-ray tube. (Bushong, 9th ed., pp. 122-125)

Fluorescent light is collected from the image intensifier output phosphor and converted to an electronic video signal by the 1. TV camera tube. 2. CCD. 3. coaxial cable. A 1 only B 1 and 2 only C 2 and 3 only D 1, 2, and 3

The Correct Answer is: B There are two devices that can take the fluorescent image from the image intensifier output phosphor and convert it to an electronic video signal: a TV camera tube and a CCD. A TV camera tube is found on older fluoroscopic equipment. Today's newer fluoroscopic equipment uses a CCD (charge-coupled device) to accomplish this task. The CCD is a solid-state device that offers much better spatial resolution and less image noise. A coaxial cable follows the TV camera or CCD in the fluoroscopic chain. It is used to connect the TV camera or CCD to the TV monit

Advantages of battery-powered mobile x-ray units include their ability to store a large quantity of energy ability to store energy for extended periods of time lightweight quality A 1 only B 1 and 2 only C 2 and 3 only D 1, 2, and 3

The Correct Answer is: B There are two main types of mobile x-ray equipment—capacitor-discharge and battery-powered. Although capacitor-discharge units are light, and therefore fairly easy to maneuver, the battery-powered mobile unit is very heavy (largely because it carries its heavy-duty power source). It is, however, capable of storing a large milliampere-seconds capacity for extended periods of time. These units frequently have a capacity of 10,000 mAs, with 12 hours required for a full charge. (Carlton and Adler, 4th ed., pp. 558-561)

A three-phase timer can be tested for accuracy using a synchronous spinning top. The resulting image looks like a A series of dots or dashes, each representative of a radiation pulse B solid arc, with the angle (in degrees) representative of the exposure time C series of gray tones, from white to black D multitude of small, mesh-like squares of uniform sharpness

The Correct Answer is: B 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 e

The radiograph illustrated in the figure below was made using a single-phase, full-wave-rectified unit with a timer and rectifiers that are known to be accurate and functioning correctly. What exposure time was used to produce this image? A 1/10 second B 0.05 second C 1/12 second D 0.025 second

The Correct Answer is: B When a spinning top is used to test the timer efficiency of full-wave-rectified single-phase equipment, the result is a series of dots or dashes, with each dot 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 second, 6 dots at 0.05 second, 10 dots at 1/12 second, and 3 dots at 0.025 second. Because three-phase equipment is at almost constant potential, a synchronous spinning top must be used for timer testing, and the result is a solid arc (rather than dots). The number of degrees covered by the arc is measured and equated to a particular exposure time. (Selman, 9th ed., p. 106)

A backup timer for the AEC serves to protect the patient from overexposure protect the x-ray tube from excessive heat adjust image contrast A 1 only B 1 and 2 only C 2 and 3 only D 1, 2, and 3

The Correct Answer is: B When an AEC is installed in an x-ray circuit, it is calibrated to deliver the most appropriate receptor as required by the radiologist. Once the part being radiographed has been exposed to produce the correct receptor exposure, the AEC automatically terminates the exposure. The manual timer should be used as a backup timer; in case the AEC fails to terminate the exposure, the backup timer would protect the patient from overexposure and the x-ray tube from excessive heat load. Image contras in CR/DR is determined by computer software.

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 A 1 only B 1 and 2 only C 2 and 3 only D 1, 2, and 3

The Correct Answer is: B 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 cont

Cassetteless digital systems have a fixed spatial resolution determined by: A The image plate laser divergence B The focal spot size used C The thin film transistor (TFT) detector element (DEL) size D The proximity of the phosphor screen crystals

The Correct Answer is: C A cassetteless system refers to direct or indirect digital systems where no cassette/IP is used. CR uses an IP containing a PSP (photostimulable phosphor plate). Laser divergence is a negative factor that occurs in computed radiography (CR) readers (A). However, with cassetteless digital systems, the spatial resolution of the detector elements (DEL) determines the maximum image resolution that can be obtained and is important in both CR and direct or indirect digital imaging systems. The thin film transistor (TFT) or detector element (DEL) size is fixed and, therefore, the maximum spatial resolution is defined by the physical size of the individual elements and their proximity to each other (C). The focal spot size (B) appropriate for the anatomical part being imaged is important to render optimal image resolution. Proximity of the phosphor screen crystals refers to conventional film-screen radiography (D). (Seeram, 1 st ed., p. 97)

Grid interspace material can be made of plastic lead aluminum A 1 only B 1 and 2 only C 1 and 3 only D 1, 2, and 3

The Correct Answer is: C A grid is a thin wafer placed between the patient and the IR to collect scattered radiation. It is made of alternating strips of lead and a radiolucent material such as plastic or aluminum. If the interspace material also were made of lead, little or no radiation would reach the IR, and no image would be formed. (Shephard, pp. 244-245)

Delivery of large exposures to a cold anode or the use of exposures exceeding tube limitation can result in increased tube output cracking of the anode rotor-bearing damage A 1 only B 1 and 2 only C 2 and 3 only D 1, 2, and 3

The Correct Answer is: C 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. (Selman, 9th ed., p. 1

he radiograph shown in Figure 5-5 was made using a A three-phase, 6-pulse rectified unit B three-phase, 12-pulse rectified unit C single-phase, full-wave rectified unit D high-frequency rectified unit

The Correct Answer is: C A spinning top is used to test the timer efficiency of full-wave-rectified single-phase equipment. The result should be a series of dots or dashes, with each dot representing a pulse of x-radiation. With full-wave-rectified current there should be 120 dots/pulses seen per second. One should visualize 12 dots/pulses at 1 / 10 s, 6 dots at 0.05 s, 10 dots at 1 / 12 s, and 3 dots at 0.025 s. If an incorrect number of dots/pulses is obtained, it is an indication of either timer malfunction or rectifier failure. Because three-phase equipment is at almost constant potential, a synchronous spinning top must be used for timer testing, and the result is a solid arc (rather than dots). The number of degrees covered by the arc is measured and equated to a particular exposure time; one second exposure should demonstrate 360 degrees. (Selman, 9th ed., p. 106)

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

The Correct Answer is: C 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)

The x-ray tube in a CT imaging system is most likely to be associated with A low-energy photons B an unrestricted x-ray beam C a pulsed x-ray beam D a large focal spo

The Correct Answer is: C Although the CT x-ray tube is similar to direct-projection x-ray tubes, it has several special requirements. The CT x-ray tube must have a very high short-exposure rating and must be capable of tolerating several million heat units while still having a small focal spot for optimal resolution. To help tolerate the very high production of heat units, the anode must be capable of high-speed rotation. The x-ray tube produces a pulsed x-ray beam (1-5 ms) using up to about 1,000 mA. The collimator assembly has two parts: The prepatient, or predetector, collimator is at the x-ray tube and consists of multiple beam restrictions so that the x-ray beam diverges little. This reduces patient dose and reduces the production of scattered radiation, thereby improving the CT image. The postpatient collimator, or predetector collimator, confines the exit photons before they reach the detector array and determines slice thickness. (Bushong, 8th ed., pp. 429-430)

To determine how quickly an x-ray tube will disperse its accumulated heat, the radiographer uses a(n) A technique chart. B radiographic rating chart. C anode cooling curve. D spinning top test.

The Correct Answer is: C An anode cooling curve identifies how many HU the anode can accommodate and the length of time required for adequate cooling between exposures. A radiographic rating chart is used to determine if the selected mA, exposure time, and kVp are within safe tube limits. A technique chart is used to determine the correct exposure factors for a particular part of the body of a given thickness. A spinning top test is used to test for timer inaccuracy or rectifier failure. (Selman, p 147)

Recently, dual-sided reading technology has become available in more modern CR readers, in which two sets of photodetectors are used to capture light released from the front and back sides of the phosphor storage plate, or PSP (photostimulable phosphor). This technology enables improved: A Slow-scan direction speed B Modulation transfer function C Signal-to-noise ratio D Fast-scan direction speed

The Correct Answer is: C By incorporating two sets of light guides and photodetectors on either side of the IP as it travels through the CR reader, a single laser beam can effectively stimulate release of stored energy from both sides of the phosphor plate. This increases the amount of energy that may be released and used in the form of light to be converted by the photodetectors to an electrical (analog) signal. Therefore, the higher signal intensity increases the SNR, i.e. signal-to-noise ratio (C). Slow scan direction speed refers to the linear travel speed of the phosphor plate through the CR reader (A). The laser light in the CR reader is rapidly reflected by an oscillating polygonal mirror that redirects the beam through a special lens called the f-theta lens, which focuses the light on a cylindrical mirror that reflects the light toward the IP. This light moves back and forth very rapidly to scan the plate transversely, in a raster pattern, and this movement of the laser beam across the IP is therefore called the fast-scan direction (D). The modulation transfer function is a mathematical function that measures the ability of the digital detector to transfer its spatial resolution characteristics to the image (B). (Seeram p. 56)

dvantages of direct digital radiography over computed radiography (CR) include direct digital is less expensive. direct digital has immediate readout. PSPs are not needed for direct digital . A 1 only B 1 and 2 only C 2 and 3 only D 1, 2, and 3

The Correct Answer is: C Computed radiography (CR) is less expensive primarily because it is compatible with existing equipment. Direct digital radiography requires existing equipment to be modified or new equipment purchased. The image plate (IP) can also be used for mobile studies, though direct digital is currently available for mobile imaging as well. After image processing, the PSP is erased and reused. DR offers the advantage of immediate visualization of the x-ray image; in CR there is a short delay. (Shephard, p. 335)

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

The Correct Answer is: C 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. (Frank, Long, and Smith, 11th ed., vol. 3, pp. 455-456)

In the radiographic rating charts shown below, what is the maximum safe mA that may be used with 0.1-second exposure and 120 kVp, using the three-phase, 2-mm focal spot x-ray tube? A 400 B 500 C 600 D 700

The Correct Answer is: C Find the correct chart for the three-phase, 2-mm focal spot x-ray tube. Locate 0.1 second on the horizontal (seconds) axis and follow it up to where it intersects with the 120-kVp line on the vertical (kVp) axis. They intersect midway between the 600- and 700-mA curves, at approximately 650 mA. Thus, 600 mA is the maximum safe milliamperage for this particular group of exposure factors and x-ray tube. (Selman, p 145)

All of the following are factors that cause low contrast in CR images, except: A High kVp B Inadequate grid efficiency or no grid C Excessive beam limiting (collimation) D Incomplete erasure of the image plate

The Correct Answer is: C High kVp (beyond that which is optimal for the anatomical part being imaged) provides scattered X-ray photons enough energy to exit the anatomical part in various directions to strike the image receptor (A). This scatter radiation contributes nothing to the "true" anatomical image, but causes decreased contrast in the image. Inadequate grid efficiency, or not using a grid when needed (B), allows scatter radiation to strike the image receptor, causing decreased contrast. Many of the factors that cause low contrast in film-screen systems also cause low contrast in CR images: high kVp, inadequate grid efficiency or no grid, insufficient beam limiting, and incomplete erasure of the image plate (C). Incomplete erasure of an image plate from a previous exposure or background radiation will result in extraneous exposure data that reduces image contrast in the successive image (D). (Seeram, 1 st ed., p. 96)

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

The Correct Answer is: C If the X-ray exposure field is improperly collimated, positioned, and sized, exposure field recognition errors can occur (C). These can lead to histogram analysis errors due to signals generated from outside of the exposure field. This may result in dark, light, or noisy images. The MTF, or modulation transfer function (A) is a mathematical function that measures the ability of a digital detector to transfer its spatial resolution characteristics of the image. If a radiographic grid has a frequency that approximates the CR scan frequency and the grid strips are oriented in the same direction as the scan, the Moiré artifact may be observed (B). The appearance of ghost artifacts can be seen when CR image plates are incompletely erased. If an image plate has not been used for 24 hours, it should be erased again before using it for a diagnostic radiographic exposure (A). (Bushong, 9 th ed., p. 493)

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

The Correct Answer is: C Image smoothing (C) is a type of spatial frequency filtering performed during digital image post-processing. Also known as low-pass filtering, smoothing can be achieved by averaging each pixel's frequency with surrounding pixel values to remove high-frequency noise. The result is reduction in noise and contrast. Smoothing (low-pass filtering) is useful for viewing small structures such as fine bone tissues. Edge enhancement (A) is a type of post-processing image manipulation, which can be effective for enhancing fractures and small, high-contrast tissues. In digital imaging, after the signal is obtained for each pixel, the signals are averaged to shorten processing time and decrease storage needs. The larger the number of pixels involved in the averaging, the smoother the image appears. The signal strength of one pixel is averaged with the strength of its neighboring pixels. Edge enhancement is achieved when fewer neighboring pixels are included in the signal average. Therefore, the smaller the number of neighboring pixels, the greater the edge enhancement. Windowing (B) is a post-processing method of adjusting the brightness and contrast in the digital image. There are two types of windowing: level and width. Window level adjusts the overall image brightness. Window width adjusts the ratio of white to black, thereby changing image contrast. Narrow window width provides higher contrast (short-scale contrast), whereas wide window width will produce an image with less contrast (long-scale contrast). Aliasing (D) is an image artifact that occurs when the spatial frequency is greater than the Nyquist frequency and the sampling occurs less than twice per cycle. This causes loss of information and a fluctuating signal and wrap-around image is produced, which appears as two superimposed images that are slightly out of alignment, resulting in a moiré effect. The Nyquist theorem states that when sampling a signal (such as the conversion from the analog to digital image), the sampling frequency must be greater than twice the bandwidth of the input signal so that reconstruction of the original image properly displays the anatomy of interest. (Carter and Veal

All of the following are equipment options that may be used to record the anatomical image in mobile radiography, except: A Tethered flat panel B Remote (wireless) digital flat panel array C Scanned projection radiography (SPR) D Conventional radiograph

The Correct Answer is: C In scanned projection radiography (SPR) (A), typically of the chest, the X-ray beam is collimated to a thin fan by pre-patient collimators. Post-patient image-forming X-rays likewise are collimated to a thin fan that corresponds to a detector array consisting of a scintillation phosphor, usually NaI or CsI, which is married to a linear array of CCDs through a fiberoptic path. This type of unit is a fixed unit located in the radiology department. Answers A, B and D can be used with mobile radiographic units to record the anatomical image. (Carlton and Adler, 5 th ed., p. 528).

The x-ray imaging system that uses a flat panel detector is A film emulsion system. B computed radiography. C direct digital radiography. D fluoroscopy.

The Correct Answer is: C Medical imaging is experiencing rapid technological growth, and x-ray images can be obtained in a number of ways. Film/screen systems are rarely used today. Imaging systems used today include computed radiography (CR) and direct digital radiography (DR). CR uses an Image Plate (IP) that encloses the photostimulable phosphor (PSP). When the PSP is exposed, it stores the image; a scanner-reader then converts the PSP image to a digital image; the image is then displayed on a computer monitor. Direct digital radiography (DR) eliminates the IP and PSP. The x-ray image is captured by a flat panel detector in the x-ray table and converts it to a digital image; the x-ray image is displayed immediately on a computer monitor. Fluoroscopy is a "live action" or "real-time" examination where the dynamics (motion) of parts can be evaluated; "still" images can be made during the fluoroscopic exam. (Ballinger and Frank, 10th ed, vol 1, p 3)

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. A 1 only B 1 and 2 only C 2 and 3 only D 1, 2, and 3

The Correct Answer is: C 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. (Fosbinder and Kelsey, p. 262)

The functions of a picture archiving and communication system (PACS) include storage of analog images retrieval of digital images storage of digital images A 1 only B 1 and 2 only C 2 and 3 only D 1, 2, and 3

The Correct Answer is: C PACS refers to a picture archiving and communication system. Analog images (conventional images) can be digitized with a digitizer. PACS systems receive digital images and display them on monitors for interpretation. These systems also store images and allow their retrieval at a later time. (Shephard, pp. 365-367)

Congruence of the x-ray beam with the light field is tested using A a pinhole camera B a star pattern C radiopaque objects D a slit camera

The Correct Answer is: C 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 spatial resolution; 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. Upon viewing, the corners of the x-ray field should be exactly delineated by the radioopaque objects. (Carlton and Adler, 4th ed., p. 484)

Types of shape distortion include magnification elongation foreshortening A 1 only B 1 and 2 only C 2 and 3 only D 1, 2, and 3

The Correct Answer is: C Size distortion (magnification) is inversely proportional to SID and directly proportional to OID. Increasing the SID and decreasing the OID decreases size distortion. Aligning the tube, part, and IR so that they are parallel reduces shape distortion. There are two types of shape distortion—elongation and foreshortening. Angulation of the part with relation to the IR results in foreshortening of the object. Tube angulation causes elongation of the object. (Shephard, pp. 228, 231-234)

If obtaining multiple images on one image plate, it is important to: A Allow for X-ray tube cooling between successive exposures B Avoid shielding of the image plate at all times to avoid field recognition errors C Properly shield each exposed and unexposed area during the imaging of each individual image D Expose the AP or PA projection in the right lower portion of the image plate

The Correct Answer is: C Successive static exposures taken on one or more image plates rarely would cause overheating of the X-ray tube (A). Shielding of the image plate for multiple exposures is important to avoid intrafield scatter radiation exposure and a possible field recognition error (B). The keys to multiple fields on one IP are symmetry and uniform distribution. One should only use 3-on-1 distribution for fingers and toes where the amount of intrafield scatter is low. If larger body structures are done 3-on-1, the intrafield scatter will reduce the contrast unless the unexposed areas are shielded between exposures (C). The specific location of any projection on an image plate does not discount the importance of including one projection on one image plate (D). (Seer

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 A 1 only B 1 and 2 only C 2 and 3 only D 1, 2, and 3

The Correct Answer is: C 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. (Shephard, p 221)

Which of the following would be appropriate IP front material(s)? 1. Tungsten 2. Magnesium 3. Bakelite A 1 only B 1 and 2 only C 2 and 3 only D 1, 2, and 3

The Correct Answer is: C The IP is used to support the PSP plate. The IP front should be made of a sturdy material with a low atomic number, because attenuation of the remnant beam is undesirable. Bakelite (the forerunner of today's plastics) and magnesium (the lightest structural metal) are commonly used for IP fronts. The high atomic number of tungsten makes it inappropriate as an IP front material. (Shephard, p. 41)

During CR imaging, the latent image present on the PSP is changed to a digital signal by the A PSP B Scanner-reader C ADC D helium-neon laser

The Correct Answer is: C The exposed CR cassette is placed into the CR scanner/reader, where the PSP (SPS) 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 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 representing the analog image. The electrical energy is sent to an analog-to-digital converter (ADC), where it is digitized and becomes the digital image that is displayed eventually (after a short delay) 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. (Carlton and Adler, 4th ed., p. 358)

The luminescent light emitted by the PSP is converted to a digital image by the A DAC B scanner-reader C ADC D helium-neon laser

The Correct Answer is: C 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. (Carlton and Adler, 4th ed., pp. 357-358; Bushong 9th ed., p. 421, p. 443)

Major components of a CR reader include all of the following, except: A Laser source B Image plate transport mechanism C Thin-film transistor D Analog-to-digital convertor

The Correct Answer is: C The laser source (A) is a major component of a CR reader because it is this light energy that, when distributed on the image plate's PSP (photostimulable phosphor), releases the stored energy from the X-ray exposure to the PSP, which can then be used to produce the diagnostic anatomical image. The major components of a computed radiography (CR) reader include the laser source, image plate (IP) transport mechanism (B), light channeling guide, photodetector (photomultiplier tube), and the analog-to-digital convertor (ADC). The TFT, i.e. thin-film transistor (C), is a component found in flat-panel detector type digital systems. The analog-to-digital convertor (D) is a device that receives the analog signal from the CR reader and converts this signal into binary code to be used by the computer for read-out and post-processing. (Seeram, p. 54)

The primary parts of the cathode include the 1. focal track. 2. filament. 3. focusing cup. A 1 only B 1 and 2 only C 2 and 3 only D 1, 2, and 3

The Correct Answer is: C The typical diode x-ray tube consists of a positive electrode (the anode) and a negative electrode (the cathode). Electrons are released from the cathode's filament, directed toward the anode by the cathode's focusing cup, and delivered at very high speed to the anode's focal track. (Bushong, 8th ed, p 131)

The voltage ripple associated with a three-phase, six-pulse rectified generator is about A 100% B 32% C 13% D 3%

The Correct Answer is: C 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-degree past-peak potential). The entire waveform is used; if 100 kV were selected, the actual average kilovoltage output would be approximately 70 kV. 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. (Selman, 9th ed., p. 162)

f 82 kVp, 300 mA, and 0.05 second were used for a particular exposure using 3-phase, 12-pulse equipment, what mAs would be required, using single-phase equipment, to produce a similar radiograph? A 7.5 B 20 C 30 D 50

The Correct Answer is: C 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 mAs is required to produce a radiograph with similar receptor exposure. When changing from single-phase to three-phase, 12-pulse equipment, only one-half of the original mAs is required. In this problem, we are changing from three-phase, 12-pulse to single-phase equipment; therefore, the mAs should be doubled (from 15 to 30 mAs). (Carlton & Adler, p 98)

X-ray tube life may be extended by using high milliampere-second, low- kilovoltage exposure factors. avoiding lengthy anode rotation. avoiding exposures to a cold anode. A 1 only B 1 and 2 only C 2 and 3 only D 1, 2, and 3

The Correct Answer is: C X-ray tube life may be extended by using exposure factors that produce a minimum of heat (a lower milliampere-seconds and higher kilovoltage combination) whenever possible. When the rotor is activated, the filament current is increased to produce the required electron source (thermionic emission). Prolonged rotor time, then, can lead to shortened filament life owing to early vaporization. Large exposures to a cold anode will heat the anode surface, and the temperature difference between surface and interior can cause cracking of the anode. This can be avoided by proper warming of the anode prior to use, thereby allowing sufficient dispersion of heat through the anode. (Selman, 9th ed., pp. 147-148)

Although the stated focal-spot size is measured directly under the actual focal spot, focal-spot size actually varies along the length of the x-ray beam. At which portion of the x-ray beam is the effective focal spot the largest? A At its outer edge B Along the path of the central ray C At the cathode end D At the anode end

The Correct Answer is: C X-ray tube targets are constructed according to the line-focus principle—the focal spot is angled (usually 12-17 degrees) to the vertical (Figure 4-34). As the actual focal spot is projected downward, it is foreshortened; thus, the effective focal spot is always smaller than the actual focal spot. As it is projected toward the cathode end of the x-ray beam, the effective focal spot becomes larger and approaches the actual size. As it is projected toward the anode end, it gets smaller because of the anode heel effect. (Selman, 9th ed., p. 139)

In conventional fluoroscopy, all of the following are methods of permanently recording the images, except: A Cassette-loaded spot film B Photospot camera film C Cine film D Flat panel image receptor

The Correct Answer is: D A flat panel image receptor (FPIR) (D) 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 (B) is similar to 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 is almost exclusively used in cardiac catheterization fluoroscopic procedures. Cine film (C) 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, 9 th ed., pp. 441-442).

X-ray tubes used in CT imaging systems must be capable of high short-exposure rating tolerating millions of heat units high-speed anode rotation A 1 only B 1 and 2 only C 1 and 3 only D 1, 2, and 3

The Correct Answer is: D Although the CT x-ray tube is similar to direct-projection x-ray tubes, it has several special requirements. The CT x-ray tube must have a very high short-exposure rating and must be capable of tolerating several million heat units while still having a small focal spot for optimal resolution. To help tolerate the very high production of heat units, the anode must be capable of high-speed rotation. The x-ray tube produces a pulsed x-ray beam (1-5 ms) using up to about 1,000 m

node angle will have an effect on the severity of the heel effect focal-spot size heat-load capacity A 1 only B 2 only C 1 and 2 only D 1, 2, and 3

The Correct Answer is: D 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. (Selman, 9th ed., pp. 138-139)

As the image intensifier's FOV is reduced, how is the resulting image affected? 1. Magnification increases 2. Brightness decreases 3. Quality increases A 1 only B 1 and 2 only C 2 and 3 only D 1, 2, and 3

The Correct Answer is: D 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. (Selman, 9th ed, pp 263-264)

A type of laser used in CR scanners is A Cesium-iodide B Helium-halide C Barium-fluorohalide D Helium-neon

The Correct Answer is: D Cesium iodide (A) is used in the scintillation layer of an indirect flat-panel digital detector (FPD). Helium halide (B) is not used in either computed or digital radiography. Barium fluorohalide (C) is a phosphor used in the CR PSPs which are housed within the image plate (IP). Energy is stored in a PSP plate after X-ray exposure and is then released in the CR reader when stimulated by a helium-neon laser (D) beam striking it in a raster pattern (transversely across the plate). In some newer units, solid-state laser diodes may be used to achieve the same purpose. (Seeram p. 54; Shephard p. 327; Carter and Veale p. 70)

Which of the following is (are) tested as part of a QC program? Beam alignment Reproducibility Linearity A 1 only B 1 and 2 only C 1 and 3 only D 1, 2, and 3

The Correct Answer is: D Each of the three is included in a good QC program. The QC deals with imaging equipment. (QA deals with people and management practices.) Beam alignment must be accurate to 2% of the SID. Reproducibility means that repeated exposures at a given technique must provide consistent intensity. Linearity means that a given milliampere-seconds value, using different milliamperage stations with appropriate exposure-time adjustments, will provide consistent intensity. (Bushong, 11th ed., pp. 344, 345)

Design characteristics of x-ray tube targets that determine heat capacity include the rotation of the anode diameter of the anode size of the focal spot A 1 only B 1 and 2 only C 1 and 3 only D 1, 2, and 3

The Correct Answer is: D Each time an x-ray exposure is made, less than 1% of the total energy is converted to x-rays, and the remainder (more than 99%) of the energy is converted to heat. Thus, it is important to use target material with a high atomic number and high melting point. The larger the actual focal-spot size, the larger is the area over which the generated heat is spread, and the more tolerant the x-ray tube is. Heat is particularly damaging to the target if it is concentrated or limited to a small area. A target that rotates during the exposure is spreading the heat over a large area, the entire surface of the focal track. If the diameter of the anode is greater, the focal track will be longer, and heat will be spread over an even larger area. (Bushong, 8th ed., pp. 135

Which of the following factors is/are related to grid efficiency? Grid ratio Number of lead strips per inch Amount of scatter transmitted through the grid A 1 only B 2 only C 1 and 2 only D 1, 2, and 3

The Correct Answer is: D Grid ratio is defined as the ratio of the height of the lead strips to the width of the interspace material; the higher the lead strips, the more scattered radiation they will trap and the greater is the grid's efficiency. The greater the number of lead strips per inch, the thinner and less visible they will be on the finished radiograph. The function of a grid is to absorb scattered radiation in order to improve radiographic contrast. The selectivity of a grid is determined by the amount of primary radiation transmitted through the grid divided by the amount of scattered radiation transmitted through the grid. (Selman, 9th ed., pp. 236-237)

All of the following are daily quality control (QC) steps to ensure optimal diagnostic images on a digital display monitor, except: A Turn on the monitor and allow it to warm up B Evaluate luminance, reflection, noise and glare C Make sure that the monitor is dust-free on the viewing surface D Evaluate the QC patterns at the periphery and verify that all letters and numbers appear

The Correct Answer is: D In order to ensure optimal diagnostic images on a digital display monitor, the QC pattern should be evaluated at the center and corners to verify that all letters and numbers can be visualized (D). Turning on the monitor and allowing it to warm up (A) prior to evaluating images is an important step in daily quality control efforts. Evaluating the luminance, reflection, noise and glare (B) at the beginning of each day is important to ensure optimal image clarity for the radiologists and other physicians. It is important that the monitor viewing surface is dust-free (C) in order to provide a clear optical evaluation. (Carter and Veale, 1 st ed., pp. 199-200).

In order to avoid background radiation artifacts when using CR, it is important to: A Erase all image plates that have not been used for 48 hours B Erase all image plates if there is any question about how long it has been since the plate has been erased C Erase an image plate if there is any doubt as to when it was last erased, especially in the case of pediatric radiography D All of these are correct actions

The Correct Answer is: D It is important to be aware of the necessity of erasing image plates that have not been used for 24 hours. If there is any question about how long it has been since the plate has been through the read/erase cycle, one should erase the plate, especially if pediatric images are being performed. One should also be aware if images suddenly begin to exhibit low contrast, because the erasure system may have failed (D). (Bushong, 9 th ed., p. 487; Seeram, p. 96).

Magnification fluoroscopy provides: A Decreased resolution and decreased patient dose B Decreased resolution and increased patient dose C Increased resolution and decreased patient dose D Increased resolution and increased patient dose

The Correct Answer is: D Magnification fluoroscopy requires that a multifield image intensifier be used to allow reduction of the x-ray field size to the input phosphor area. Smaller input phosphor field sizes produce magnified images of the anatomical areas being evaluated at the output phosphor. Magnification fluoroscopy provides increased resolution, but at the expense of increased patient dosage (D). In fact, the increase in dosage is about 2.2 times that used in the full-field operation mode. The magnification mode should therefore be used only when necessary to enhance diagnostic interpretation of small anatomical areas in question (e.g., the gallbladder or duodenal bulb). (Seeram, p. 135).

he batteries in battery-operated mobile x-ray units provide power to the x-ray tube machine locomotion the braking mechanism A 1 only B 2 only C 1 and 2 only D 1, 2, and 3

The Correct Answer is: D 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. The battery-operated type is probably the most commonly used where consistent and high-energy output is required. Two sets of batteries are used in these mobile units: One set is used for operating the motor that drives the unit and operates the braking mechanism ("dead man" brake), and the other set is used for operating the x-ray tube. Periodic recharging of the batteries is required. (Frank, Long, and Smith, 11th ed., vol. 3, p. 234)

Using a multifield image intensifier tube, which of the following input phosphor diameters will provide the greatest magnification? A 35 cm B 25 cm C 17 cm D 12 cm

The Correct Answer is: D 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)

One advantage of a battery-powered mobile radiographic unit is: A It requires less kilovoltage to penetrate the anatomical part of interest B It produces radiographic images of much better image quality C It is much lighter than other mobile units D Electrical power is available to drive itself

The Correct Answer is: D One advantage of a battery-powered unit is that electrical power is available to drive itself (D). Some of the stored electrical power resulting from charging the unit can be used to operate the motor that propels the unit to the patient's room. Since this unit is self-driven, the radiographer must be especially careful when driving the unit down a hallway or around corners to avoid injury to others and structures. The kilovoltage (A) produced with battery-operated mobile radiography units is similar to that of other mobile units. The radiographer is responsible for selecting an adequate kilovoltage necessary to penetrate the anatomical part of interest. The battery-operated unit produces X-ray beams and image quality (B) similar to that produced with other mobile radiographic units. The quality of the radiographic image depends on the radiographer's control settings, positioning, X-ray beam alignment, and source distance, as it does when using any other mobile unit. Since the battery-operated mobile units contain several large batteries, the unit is very heavy (C). Care must be taken when driving these units to ensure the safety of others and to avoid damaging structures within the facility. (Carlton and Adler, 5 th ed., p. 528).

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

The Correct Answer is: D One of the biggest advantages of CR is the dynamic range, or latitude, it offers. In CR, there is a linear relationship between the exposure given the PSP and its resulting luminescence as it is scanned by the laser. This affords much greater exposure latitude, and technical inaccuracies can be effectively eliminated. Overexposure of up to 500% and underexposure of up to 80% are reported as recoverable, thus eliminating most retakes. This surely affords increased efficiency; however, this does not mean that images can be exposed arbitrarily. The radiographer must keep dose reduction in mind. AEC refers to automatic exposure control and is unrelated to dynamic range or latitude. PBL refers to positive beam limitation and is unrelated to dynamic range or latitude. ALARA is a radiation protection concept referring to keeping occupational dose as low as reasonably achievable.

Too much edge enhancement of the image in digital systems can cause an unwanted artifact called the: A Photoelectric effect artifact B Scaling artifact C Hounsfield artifact D Halo effect artifact

The Correct Answer is: D One of the problems seen with too much edge enhancement is an effect called the "halo" effect (D). This effect can cause loss of anatomical information and artifacts that may interfere with proper diagnoses. The photoelectric effect (A) occurs when an X-ray photon interacts with an inner shell electron of an atom and its energy is completely absorbed by the atom. This interaction is responsible for producing diagnostic information in a radiographic image and contributing to patient dosage. A scaling artifact is not an artifact seen in digital imaging (B). A Hounsfield artifact is not an artifact seen in digital imaging (C). (Seeram p. 120)

Which of the following is (are) correct regarding care of protective leaded apparel? Lead aprons should be fluoroscoped yearly to check for cracks. Lead gloves should be fluoroscoped yearly to check for cracks. Lead aprons should be hung on appropriate racks when not in use. A 1 only B 1 and 2 only C 1 and 3 only D 1, 2, and 3

The Correct Answer is: D Proper care of leaded protective apparel is required to ensure its continued usefulness. If lead aprons and gloves are folded, cracks will develop, and this will decrease their effectiveness. Both items should be fluoroscoped annually to check for the formation of cracks. (Bushong, 8th ed., pp. 596, 597)

Which of the following combinations would pose the least 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

The Correct Answer is: D 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. The product of milliampere-second and peak kilovolts 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). (Selman, 9th ed., p. 145)

To be used more efficiently by the x-ray tube, alternating current is changed to unidirectional current by the A filament transformer. B autotransformer. C high-voltage transformer. D rectifiers.

The Correct Answer is: D Rectifiers (solid-state or the older valve tubes) permit the flow of current in only one direction. They serve to change AC, which is needed in the low-voltage side of the x-ray circuit, to unidirectional current. Unidirectional current is necessary for the efficient operation of the x-ray tube. The rectification system is located between the secondary coil of the high-voltage transformer and the x-ray tube. The filament transformer functions to adjust the voltage and current going to heat the x-ray tube filament. The autotransformer varies the amount of voltage being sent to the primary coil of the high-voltage transformer so that the appropriate kVp can be obtained. The high-voltage transformer "steps up" the voltage to the required kilovoltage and steps down the amperage to milliamperage. (Carlton & Adler, p 78)

Shape distortion is influenced by the relationship between the x-ray tube and the part to be imaged. body part to be imaged and the IR. IR and the x-ray tube. A 1 and 2 only B 1 and 3 only C 2 and 3 only D 1, 2, and 3

The Correct Answer is: D Shape distortion is caused by misalignment of the x-ray tube, the body part to be radiographed, and the IR. An object can be falsely imaged (foreshortened or elongated) as a result of incorrect placement of the tube, the part, or the IR. Only one of the three need be misaligned for distortion to occur. (Selman, 9th ed., pp. 225-226)

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. A 40 B 25 C 20 D 10

The Correct Answer is: D 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. (Saia, pp 329, 330)

The long axis of the laser beam moving transversely back and forth across the image plate in a CR reader is called the: A Scan/translation mode B Zig-zag scan mode C Slow scan direction D Fast scan direction

The Correct Answer is: D Slow scan direction (C) speed refers to the linear travel speed of the image plate through the CR reader. The IP moves slowly through the transport system of a CR reader and this movement is considered the slow-scan direction. The laser light in the reader is rapidly reflected by an oscillating polygonal mirror that redirects the beam through a special lens called the f-theta lens, which focuses the light on a cylindrical mirror that reflects the light toward the IP. This light moves back and forth very rapidly to scan the plate transversely, in a raster pattern, and this movement of the laser beam across the IP is therefore called the fast-scan direction (D). Scan/translation mode (A) and Zig-zag mode (B) are not terms used to describe the laser beam movement back and forth across the image plate while it travels through the CR reader (A). (Seeram p. 54; Shephard p. 327; Carter and Veale p. 70)

Dedicated radiographic units are available for 1. chest radiography. 2. dental radiography. 3. mammography. A 1 only B 2 only C 1 and 2 only D 1, 2, and 3

The Correct Answer is: D Special units have been designed to accommodate examinations with high patient volume. Dedicated chest units are available with high frequency generator and digital flat-panel detector. Dedicated head units are available for cone beam and panoramic digital dental imaging. High-quality mammographic examinations are available with dedicated mammographic units having molybdenum or rhodium target material and other beneficial features.

Sampling frequency in computed radiography (CR) is expressed as: A The TFT array size B An inverse relationship between focal spot size and matrix size C The light spread between the image plate and the light guide of the scanner D Pixels/mm or pixel densit

The Correct Answer is: D The TFT array is found in direct and indirect digital detector systems, not in computed radiography (CR) (A). The focal spot size (B) influences image resolution but has no influence on the number of pixels per millimeter that determines the sampling frequency. The light spread between the image plate and the light guide of the scanner (C) refers to computed radiography (CR) systems, not direct or indirect digital detector systems. Sampling frequency, also referred to as pixel density (pixels/mm), is expressed as pixels per millimeter. The sampling frequency determines the pixel pitch, which, in turn, determines the spatial resolution (D). (Seeram, 1 st ed., p. 98).

The optimal alignment of the anatomical part being imaged for all digital receptors should be: A Field centered to IP with at least two collimation margins and parallel to the IP edges B Centered anywhere on the IP, but having four distinct collimation margins, regardless of parallel orientation to the IP edges C Centered to the IP with at least one collimation margin aligned to nearest edge of IP D Field centered to IP with four collimation margins parallel to the IP edges

The Correct Answer is: D The optimal alignment when using CR is field centered to the plate with four collimation margins parallel to the IP edges (D). Otherwise, the exposure field may not be correctly identified, resulting in a processing error. An exposure field with only two collimation margins and parallel to the IP edges (A) results in extraneous radiation exposure in the top and bottom portions of the receptor. This exposure information may cause misidentification of the exposure field, causing a processing error. Simply exposing an anatomical part anywhere on the receptor (B) has the potential to cause misidentification of the exposure field, causing a processing error. If only one collimation margin is included on the receptor (C), the radiographer has improperly centered the anatomical part. This may result in misidentification of the exposure field and therefore, cause a processing error. (Seeram, 1 st ed., p. 91).

Acceptable method(s) of minimizing motion unsharpness is (are) suspended respiration short exposure time patient instruction A 1 only B 1 and 2 only C 1 and 3 only D 1, 2, and 3

The Correct Answer is: D The shortest possible exposure time should be used to minimize motion unsharpness. Motion causes unsharpness that destroys spatial resolution. Careful and accurate patient instruction is essential for minimizing voluntary motion. Suspended respiration eliminates respiratory motion. Using the shortest possible exposure time is essential for decreasing involuntary motion. Immobilization is also very useful in eliminating motion unsharpness. (Carlton and Adler, 4th ed., p. 451)

Image quality in digital fluoroscopy is influenced by 1. pixel size. 2. contrast. 3. noise. A 1 only B 1 and 2 only C 2 and 3 only D 1, 2, and 3

The Correct Answer is: D The smaller the pixel size and larger the matrix, the better the image's spatial resolution. For example, an image matrix of 1024 × 1024 will provide better resolution than a matrix of 700 × 700. The 1024 × 1024 matrix has a larger number of smaller pixels, therefore a less "pixelly" image. As in analog x-ray imaging, a range of diagnostic grays representing the various tissue densities is desirable. In CR and DR the image can be manipulated (i.e., "windowed") to provide the desired scale of grays and brightness. Noise is degrading to both traditional and digital images. It can result from a number of causes including insufficient mA (i.e., signal) causing graininess/mottle, and scattered radiation fog. (Selman, 9th ed, pp 311-312)

The device used to test the accuracy of the x-ray timer is the A densitometer B sensitometer C penetrometer D spinning top

The Correct Answer is: D 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. (Selman, 9th ed., p. 106)

Characteristics of the metallic element tungsten include ready dissipation of heat high melting point high atomic number A 1 only B 1 and 2 only C 2 and 3 only D 1, 2, and 3

The Correct Answer is: D The x-ray anode may be a molybdenum disk coated with a tungsten-rhenium alloy. Because tungsten has a high atomic number (74), it produces high-energy x-rays more efficiently. Since a great deal of heat is produced at the target, tungsten's high melting point (3,410°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, 11th ed., p. 110)

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 arcing. A 1 only B 2 only C 1 and 2 only D 1, 2, and 3

The Correct Answer is: D 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 arcing and causing puncture of the glass envelope and subsequent tube failure. (Selman, pp 137-138)

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. A 1 only B 1 and 3 only C 2 and 3 only D 1, 2, and 3

The Correct Answer is: D 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)

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 A 1 only B 2 only C 1 and 2 only D 2 and 3 only

The Correct Answer is: D 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)

Significant over- or underexposure of the digital receptor is likely to result in (select the three that apply) A quantum mottle B increased brightness C information loss D saturation E magnification F structural blur

The answer is A, C, and D. Digital processing usually compensates for over- or underexposure. An exposure can exceed the processing capabilities. Significant overexposure will result in saturation (very dark image); underexposure results in quantum mottle (A and D). In both cases, there is loss of diagnostic information (C). Magnification and structural blur are spatial resolution factors and not associated with over- or underexposure of the digital receptor (E and F). (Carroll, 2nd ed., p. 546)

Histogram analysis errors can result from (select the three that apply): A selection of incorrect anatomical part/algorithm B excessively long backup time C incorrect centering D inadequate beam restriction E use of large focal spot

The answer is A, C, and D. Factors affecting histogram appearance, and reflected in the EI, include selection of the correct processing algorithm (e.g., chest vs. femur vs. cervical spine), and changes in scatter, SID, OID, and collimation—in short, anything that affects scatter and/or dose (A, C, and D). Inadequate collimation results in signals outside the anatomic area being included in the exposure data recognition (EDR)/ histogram analysis, potentially resulting in a variety of analysis errors including excessively light, dark, or noisy images. One other factor is delay in PSP processing. A delay in processing can result in fading of the image. Histogram analysis errors are less common in DR systems where only exposed pixels are analyzed, rather than entire plate analysis as in CR systems. Backup time is related to AEC (B). Focal spot size is related to spatial resolution (E). Neither of these is related to histogram analysis. (Saia, PREP 9th ed., p. 378; Carroll, 2nd ed., p. 487)

Which of the following statements regarding direct digital imaging are correct? (select the three that apply) A The TFT array collects and stores electrical charges B Spatial resolution decreases with an increase in fill factor C Spatial resolution is variable in direct digital D The DEL is the sensing element of the TFT E Spatial resolution increases with a decrease in DEL size F Direct digital utilizes amorphous silicon

The answer is A, D, and E. Direct conversion FPDs utilize no scintillation; x-rays are directly converted to electric signals by amorphous selenium (a-Se)—most commonly used because of its excellent x-ray absorption/conversion properties and spatial resolution (F). Below the a-Se layer is a TFT array that functions to collect and store the electrical charges, which are transmitted to the ADC for digitization (A). There is no diffusion of electrons, so spatial resolution is unaffected. The spatial resolution of direct digital systems is fixed and is related to the detector element (DEL) size of the TFT and its fill factor (C). The DEL is the sensing element of the TFT, and it is desirable that its largest portion is used for just that purpose (D). If 25% of the DEL is used for other functions, the DEL is said to have a fill factor of 75%. The greater the fill factor, the better the spatial resolution and SNR (B). The smaller the TFT DEL size, and the larger the fill factor, the better the spatial resolution (E). A DEL size of 100 μm provides a spatial resolution of about 5 lp/mm (available only in some digital mammography systems). A DEL size of 200 μm provides a spatial resolution of about 2.5 lp/mm (general radiography)—lower than that achieved with a 400-speed intensifying screen system in analog systems. A 100-speed-intensifying screen system offers a spatial resolution of about 10 lp/mm—significantly greater than, and currently unachievable in, digital imaging. Spatial resolution in digital imaging is fixed, but it is very important that radiographers are alert to the opportunities they have to utilize and control the remaining recorded detail factors (motion and geometric fac

Dynamic range is a function of the image receptor computer software kV brightness level A 1 and 2 only B 1 and 3 only C 2 and 4 only D 2, 3, and 4 only

The answer is A. The ability of the computer software and the detector to distinguish and make available various pixel values for image formation is termed dynamic range (1 and 2). Contrast and brightness are controlled principally by computer software in digital imaging (3 and 4). (Carroll, 2nd ed., p. 461)

X-ray energy is directly controlled by which of the following factors? A kVp B mAs C SID D OID

The answer is A. The controlling factor of x-ray energy (quality) is the applied kilovoltage used during a radiographic exposure (A). Increased kilovoltage in the x-ray circuit produces higher kinetic energy filament (projectile) electrons bombarding the anode of the x-ray tube. The increased kinetic energy results in the production of bremsstrahlung x-rays that are of higher energy (shorter wavelength) and can therefore penetrate the inherent and added filtration of the tube and collimator assembly, penetrate the patient, and expose the image receptor. The quantity (intensity) of x-ray photons in the x-ray beam is controlled by the mA, time, or mAs settings (B). The SID controls the quantity (intensity) of x-ray photons, based on the inverse square law, reaching the anatomical area of interest and affecting magnification distortion, geometric unsharpness (penumbra), and spatial resolution (detail) of the projected image, and is therefore considered both an exposure factor and geometric image factor (it is primarily classified as a geometric image factor, however) (C). The OID primarily affects magnification distortion of the anatomical area of interest and secondarily affects the exposure level from scatter radiation if an air-gap technique is used. SID and OID should be primarily regarded as geometric image factors (D). (Bushong, 11th ed., pp. 130-131)

When performing quality control checks on the x-ray beam collimator, each dimension and edge of the light field must be congruent within _____ percent of the source-image-distance (SID). A 2 B 3 C 4 D 5

The answer is A. U.S. federal guidelines specify that all x-ray beam collimators must demonstrate light field‒x-ray field congruency within 2 percent of the source-image-distance (SID) (A). Quality control test results, which identify congruency beyond 2 percent, would not be in regulation and would require service. The other answer choices are incorrect as per the previous explanation (B, C, and D). (Johnston and Fauber, 2nd ed., p. 145)

Consider a step-up transformer that increases the voltage induced on the secondary side of the transformer. What is the relationship of the primary side current to the secondary side current? A The secondary current is stepped up. B The secondary current is decreased. C There is no change in the current through the step-up transformer. D The secondary current is increased.

The answer is B. Current has an inverse relationship to both the turns ratio and the voltage ratio through a transformer. This manifests as a special consideration of the conservation of energy. For electrical devices, power, measured in watts, is equal to the product of the voltage and the amperage. Power must remain constant throughout the circuit. Thus, a device, like a transformer, that is employed to amplify voltage, will always decrease current in an inverse proportion (B). A device that increases one or both does not exist, because such a device would output more energy than it took in, and energy would not be conserved. In the choices above, the impossible energy device is represented by choices (A), (C), and (D); "stepped-up" is synonymous with increased, within the nomenclature of electric circuits. No change in current would still increase power, and thus energy. (Bushong, 11th ed., p. 80)

The standard developed to establish a universal, standardized public format and protocol for communicating biomedical imaging files is A PACS B DICOM C RIS D HIS

The answer is B. DICOM is an acronym for Digital Imaging and Communications in Medicine standard (B). It originated in 1983 as a collaborative effort between the American College of Radiology (ACR) and the National Electrical Manufacturers' Association (NEMA) to establish a standardized public format and protocol for communicating biomedical imaging files. PACS is an acronym for Picture, Archiving and Communication System and denotes a networked group of computers, servers, and archives to manage digital images for storing, retrieving, and distributing medical images (A). RIS is an acronym for Radiology Information System and HIS is an acronym for Hospital Information System; both of these relate to Biomedical Informatics (BMI) platforms used in radiology departments and healthcare facilities respectively (C and D). (Carlton/Adler/Balac, 6th ed., p. 329)

Which three (3) of the following statements are true regarding image manipulation? Window level controls brightness and darkness The wider the window width, the lower the contrast Window level controls contrast (i.e., white and black ratio) The higher the window level, the darker the image Window width controls brightness and darkness A 1, 2, and 3 are correct B 1, 2, and 4 are correct C 2, 3, and 5 are correct D 1, 4, and 5 are correct

The answer is B. Post processing image manipulation and enhancement functions can include annotating, orientation functions such as rotation and flipping, window level and/or width adjustments, magnification, and zoom. Adjustments of window level and/or width are probably most common. The window level controls the degree of brightness; the higher the window level, the darker the image (1, 3, and 4). The window width controls contrast; the wider the window width, the lower the contrast (2 and 5). (Carter and Veale, Digital Radiography and PACS

Which of the following is the formula used to determine magnification factor (MF)? A MF = source-image-distance / object-image-distance B MF = source-image-distance / source-object-distance C MF = source-object-distance / source-image-distance D MF = object-image-distance / source-image-distance

The answer is B. The magnification factor (MF) indicates how much size distortion or magnification is demonstrated on a radiograph. The magnification factor (MF) is found by applying the following formula, MF = source-image-distance (SID) / source-object-distance (SOD) (B). If, for example, the SID was 40 inches and there was a source-object-distance (SOD) of 30 inches, the MF would equal 40" / 30" or 1.33. SOD is found by subtracting OID from SID (SOD = SID ‒OID). The other answer choices are incorrect as per the previous explanation (A, C, and D). (Johnston and Fauber, 2n

During the processing of the PSP image, what layer of the imaging plate is responsible for sending the emitted blue light toward the processor's light collecting optics and photodetector? A Conductive layer B Reflective layer C Barium fluorohalide phosphor layer D Backing layer

The answer is B. To minimize signal loss, a reflective layer is immediately underneath the active phosphor layer in a PSP imaging plate system (B). While it is true that the blue light originates in the barium fluorohalide layer, remember than it spreads in all directions, or isotropically, as it forms (C). The light photon heading away from the reader optics will hit a mirror-like surface at the reflective layer and return the light photon from the direction it came. The net result is that most of the blue light exits the front surface of the phosphor layer, passes through the protective layer, and is captured as useful signal. The conductive layer captures stray electrons that choose to wander off after getting loose from the trap, which keeps static electricity within the plate low (A). The backing layer is typically an aluminum sheet, to offer structural rigidity and back shielding, which reduces unwanted scatter radiation from being recorded in the phosphor (D). (Carter &Veale, 3rd ed., pp. 47)

Increasing the overall brightness of a radiographic digital image is accomplished by A raising the window level B lowering the window level C increasing the window width D decreasing the window width

The answer is B. Windowing is a postprocessing operation that changes the contrast and brightness of the digital image on the monitor. The brightness and contrast of the digital image depends on the shades of gray, which are controlled by varying the numerical values of each pixel. Modifying the window level will change the brightness of the image; raising/increasing the window level will decrease brightness and lowering/decreasing the level will increase brightness. Changing the window width will modify the grayscale (contrast) of the image; increasing the window width lengthens the grayscale (lower contrast) and decreasing the window width will shorten the grayscale (higher contrast). (Carroll 3rd ed p469, Carter and Veale 3rd ed p32)

Within the x-ray tube, why do we need a robust current passing through the cathode filament during exposure? A To pull electrons toward the anode B To rectify the voltage waveform C To create thermionic emission D To limit the space charge effect

The answer is C. Heat generated within a filament is directly proportional to the current passing through it. Breaking the word apart, in similar fashion to medical terminology, yields "therm-," which means heat, "ion-," which means an unbound charged particle, and "-ic," which means pertaining to. Thus, the entire word means "pertaining to the formation of unbound charged particles by applying heat." Robust current implies robust heat; robust heat implies many available electrons (C). Electrons are only pulled toward the anode if there is a large positive charge, created by activating the high voltage circuit (A). Rectification is undertaken in the high voltage circuit, between the step-up transformer and the tube, not within the tube (B). Finally, the space charge effect is more likely with large mA (robust) and is the natural result of "like" charges repelling (D). Excited electrons in the space charge inhibit additional electrons from joining them, via the coulomb force. It's not something we need to create for the production of x-rays, it's more of an unwanted side effect. (Bushong, 11th ed., p. 107)

Order the following PSP layers correctly from top to bottom Reflective layer Protective coat Conductive layer Support layer Phosphor layer A 4, 5, 3, 1, 2 B 4, 2, 5, 1, 3 C 2, 5, 1, 3, 4 D 2, 1, 5, 4, 3

The answer is C. The layers of the PSP include the outer layer, the protective coat of clear plastic(2). Next is the phosphor layer (5). The thinner the phosphor layer, the less the light spread and the better the spatial resolution/detail. A common PSP phosphor is europium-doped barium fluorohalide (BaF:Eu2 mixed with a binder). Needle-shaped phosphors also reduce diffusion of light, improving resolution. The phosphor layer is followed by the reflective layer, which directs the emitted light toward the CR reader (1). Next is the conductive layer that functions to reduce static electrical buildup, and then the color layer, which also reflects the emitted light (PSL/ photostimulable luminescence) while absorbing the stimulating laser light (3). The backing layer is a support layer that provides a reinforcement for the entire PSP (4). A narrow monochromatic high-intensity (red) helium-neon laser or a solid-state laser beam scans back and forth multiple times across the PSP while it is simultaneously being pulled under the laser to progressively read the entire PSP. The PSP movement is referred to as translation. The PSL signal represents varying tissue densities and the latent image. The PMT or photodiode (PD) detects the PSL and converts it to electrical signals, which is then transferred to an analog-to-digital converter (ADC)—converting the analog electrical signal to digital data. This digital data is then transferred to a digital-to-analog converter (DAC) to be converted to a perceptible analog image on the display monitor. (Carter and Veale, Digital Radiography and PACS 3rd ed., p. 51)

According to the line-focus principle, to produce an effective focal spot smaller than the actual focal spot the anode target angle must be less than ______ degrees. A 15 B 35 C 45 D 60

The answer is C. When the anode target angle is less than 45 degrees the effective focal spot is smaller than the actual focal spot (C). This is accomplished by the line-focus principle. A target angle of 60 degrees would not produce an effective focal spot smaller than the actual focal. The other answer choices are incorrect as per the previous explanation (A, B, and D). (Carlton, Adler, and Balac, 6th ed., p. 84)

What is the purpose of the aluminum layer in a CR (photostimuable phosphor) cassette? A The aluminum layer is used to filter low energy x-rays in the primary beam, saving patient dose. B The aluminum layer reflects blue light toward the photomultiplier tube during image processing. C The aluminum layer traps the electrons, which are later released via stimulation with red laser light. D The aluminum layer absorbs backscatter radiation, preserving the signal-to-noise ratio for the image.

The answer is D. In the CR cassette, an aluminum backing layer is employed to absorb scatter radiation generated when a high energy x-ray photon transmits through room air, patient, image receptor, and only then interacts with something behind the image receptor (D). If this interaction is Compton scattering, there is a probability that a lower energy x-ray photon will travel back toward the IR. This phenomenon is called backscattering and can add noise and artifact to the image. For example, a metal bed railing, used to hold a CR cassette vertically during a cross-table projection, may send backscatter into the cassette to project an image of the railing structure over the patient's anatomy, ruining the image. An aluminum layer behind the active phosphor layer will absorb much of this lower energy backscatter. Aluminum is also used in the collimator assembly, but the question is specifically asking about the metal's use within a CR cassette (A). Choices (B) and (C) describe functions of the reflective and barium fluorohalide layers, respectively. (Carter and Veale, 3rd ed.

An Indirect DR system will always have a lower detective quantum efficiency and a lower spatial resolution than an equivalent Direct DR system. This is because A the indirect DR detector utilizes an electron trap to capture the signal. B the direct DR system converts the remnant beam to visible light. C the indirect DR system stores the image data as an analog signal. D the indirect DR system converts the remnant beam to visible light.

The answer is D. Indirect DR exposure capture and processing is a two-step process: The remnant x-ray beam is converted to light at the scintillator, and then the light is converted to an electronic signal in the photodiodes of the DELs on the TFT array (D). While the signal is light, it spreads from its point of origin within the scintillator, via the inverse-square law. A thicker scintillation layer will cause a noticeable decrease in spatial frequency. Each time energy is converted, some of the energy is lost as heat. The direct system, with less steps in the data capture process, necessarily will transmit more of the original signal to the CPU with less heat loss; thus, it will have a higher DQE than the indirect process (B). Electron traps are utilized only in PSP systems (A). Neither system is capable of storing an analog signal in memory (C). Direct systems do not convert the remnant beam to light, but rather straight to an electronic signal via an amorphous selenium layer. (Carter and Veale, 3rd ed., pp. 23, 66-67)

Biomedical repair technicians often perform repairs of diagnostic imaging equipment without a complaint of malfunction, but rather to test and replace parts of the machine known to experience wear and tear with normal operation. These types of repairs are called A acceptance testing. B quality assurance repairs. C service call repairs. D preventive maintenance.

The answer is D. Preventive maintenance is a quality control practice where equipment that is operating normally is tested and evaluated to find minor malfunctions before they affect the diagnostic quality of the images produced (D). It is commonly employed in diagnostic imaging departments to keep the equipment operating smoothly and avoid extended maintenance downtimes. Acceptance testing refers to testing that is conducted independently of the manufacturer, as the equipment is first installed, but before it is utilized on patients (A). While manufacturers are trusted to deliver, assemble, and test new exam rooms, it is recommended that the purchaser independently verify that the equipment is functioning properly before it is utilized in a clinical setting. Quality assurance refers to people, training, communication, and workflow issues, and would not be used to describe equipment repair (B). Service call repairs begin with a complaint of malfunction; usually by the radiologic technologist noticing erratic behavior or a loss in diagnostic quality while using the equipment (C). (Carter and Veale, 3rd ed., p. 164)

Which of the following cassette-less digital image receptors uses a scintillator to produce visible light? Indirect capture with charge-coupled device (CCD) Indirect capture with amorphous silicon photodetector Direct capture with amorphous selenium photoconductor A 1 only B 2 only C 3 only D 1 and 2 only

The answer is D. The cassette-less digital imaging systems, which use the indirect capture method, utilize scintillators or phosphor elements, which emit light when struck by x-rays. Light emitted is then read by either a charge-coupled (CCD) device or an amorphous silicon photoconductor to convert the light energy to an electrical signal (1 and 2). In the direct capture method, x-rays are converted directly to an electrical signal in the amorphous selenium photoconductor (3). This method does not utilize scintillators or phosphor elements to convert the x-ray energy to light. (Johnston and Fauber, 2nd ed., p. 158-160)

f a 30/23/15 cm trifocus image intensifier is operated in the 15-cm mode, the fluoroscopic image will be magnified by a factor of A 1.0 B 1.3 C 1.5 D 2.0

The answer is D. The degree of magnification (magnification factor [MF]) is found by dividing the full-size input diameter (30 cm) by the selected input diameter (15 cm). MF = 30 cm / 15 cm = 2.0 (D). If the image intensifier was operated in the 23-cm mode, the MF would be 30 cm / 23 cm = 1.3 (B). If the image intensifier was operated in the 30-cm mode, the MF would be 30 cm / 30 cm = 1.0 (A). (Johnston and Fauber, 2nd ed., p. 208)

A device used to measure the luminance response and uniformity of monitors used in digital imaging is called a A Penetrometer B Densitometer C Sensitometer D Photometer

The correct answer is (D). Two types of photometers (D) are commonly used to measure the luminance response and uniformity of monitors used in digital imaging: near-range and telescopic. Near-range photometers are used for measuring the 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 penetrometer (or aluminum step wedge) (A) is a device used for quality control testing in film radiography. After making an exposure of this device while it rests on top of a film cassette, the film within the cassette is chemically processed. The resultant image demonstrates multiple steps of densities. The densities can be measured by a densitometer (B) to determine the film contrast index and other processing-related factors. A sensitometer (C), which is an electrical device, can be used in lieu of the penetrometer and projects a preset (visible light) exposure on the film in the darkroom. After the film is processed, multiple steps of densities, similar to those achieved using the penetrometer, are demonstrated and can then be measured by a densitometer in the same fashion (A, B, C). (Bushong, 9 th ed., p. 480).

The X-ray scintillator layer used with indirect flat-panel digital detectors is usually either _____________ or ______________. A Silicon dioxide, silver halide B Cesium iodide, gadolinium oxysulfide C Yttrium oxysulfide, barium fluoride D Amorphous silicon dioxide, barium platinocyanide

The correct answer is: (B) The X-ray scintillator used in the indirect flat-panel digital detector is usually either cesium iodide (CsI) or gadolinium oxysulfide (Gd 2 O 2 S). These phosphors are not new to x-ray imaging; they have been used in x-ray image intensifiers (CsI) and in rare-earth intensifying screens (Gd 2 O 2 S) for many years (B). Silicon dioxide is a substance used in sonographic imaging, whereas silver halide was found in radiographic film emulsions (A). Yttrium oxysulfide was a phosphor material used in rare earth radiographic screens, whereas barium fluoride is a component of barium fluoride bromide crystals coated with europium in computed radiography (CR) PSPs (C). Amorphous silicon dioxide is a material used in the photodiodes used in indirect digital flat panel detectors, whereas barium platinocyanide was a phosphor material used in experiments conducted by Wilhelm Roentgen. (Seeram, 1 st ed., p. 108)

he housing surrounding an x-ray tube functions to retain heat within the glass envelope protect from electric shock keep leakage radiation to a minimum A 1 and 2 only B 1 and 3 only C 2 and 3 only D 1, 2, and 3

The correct answer is: (C) When high-speed electrons strike surfaces other than the tungsten target, x-rays may be produced and emitted in all directions. X-ray tubes, therefore, have a lead-lined metal protective housing to absorb much of this "leakage radiation." Leakage radiation must not exceed 100 mR/h at a distance of 1 m from the tube. Because the production of x-radiation requires the use of exceedingly high voltage, the tube housing also serves to protect from electric shock. The production of x-rays involves the production of large quantities of heat, which can be damaging to the x-ray tube. Therefore, an oil coolant surrounds the x-ray tube to further insulate it and to absorb heat from the x-ray tube structures. (Bushong, 8th ed., p. 131)

Quality control testing of digital display monitors should be conducted A Daily B Weekly C Monthly D Annually

a

Which of the following is most likely to produce a radiograph with a long scale of contrast? A Increased photon energy B Increased OID C Increased mAs D Increased SID

ahe Correct Answer is: A An increase in photon energy accompanies an increase in kilovoltage. Kilovoltage regulates the penetrability of x-ray photons; it regulates their wavelength—the amount of energy with which they are associated. The higher the related energy of an x-ray beam, the greater its penetrability (kilovoltage and photon energy are directly related; kilovoltage and wavelength are inversely related). Adjustments in kilovoltage can have a big impact on radiographic contrast in analog imaging: As kilovoltage (photon energy) is increased, the number of grays increases, thereby producing a longer scale of contrast. An increase in OID would, if anything (air-gap), result in an increase in contrast. An increase in mAs is frequently accompanied by an appropriate decrease in kilovoltage, which would also shorten the contrast scale. SID and image contrast are unrelated. (Shephard, p 204)

The part of a CT imaging system made of thousands of solid-state photodiodes is the A gantry. B detector array. C collimator assembly. D x-ray tube.

b

With milliamperage adjusted to produce equal exposures, all the following statements are true except A a single-phase examination done at 10 mAs can be duplicated with three-phase, 12-pulse at 5 mAs. B There is greater patient dose with three-phase equipment than with single-phase equipment. C Three-phase equipment can produce comparable radiographs with less heat unit (HU) buildup. D Three-phase equipment produces lower-contrast radiographs than single-phase equipment.

b

ontinuous rotation of the CT x-ray tube and detector array, with simultaneous movement of the CT couch, has been accomplished through implementation of A additional cables. B slip rings. C multiple rows of detectors. D electron beam CT.

b

A particular milliampere-seconds value, regardless of the combination of milliamperes and time, will reproduce the same receptor exposure. This is a statement of the A line-focus principle B inverse-square law C reciprocity law D law of conservation of energy

c

All of the following are steps that should be used to accomplish quality control (QC) in digital radiography, except: A Acceptance testing B Establishment of baseline performance C Monitoring patient size to evaluate variations in equipment performance D Diagnosis of changes in performan

c

All the following are components of the image intensifier except A the photocathode B the focusing lenses C the TV monitor D the accelerating anode

c

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 circuit breaker. B the kilovoltage selector. C the rectifiers. D the autotransformer.

c

Component parts of a CT gantry include high-voltage generator multidetector array x-ray tube A 1 only B 1 and 2 only C 2 and 3 only D 1, 2, and 3

d

Component parts of a CT imaging system include a(n) high-frequency generator x-ray tube operator console A 1 only B 1 and 2 only C 1 and 3 only D 1, 2, and 3

d

The voltage ripple associated with a three-phase, 12-pulse rectified generator is about A 100%. B 32%. C 13%. D 4%.

d

X-ray tubes used in CT differ from those used in x-ray, in that CT x-ray tubes must have a very high short-exposure rating be capable of tolerating several million heat units have a small focal spot for optimal resolution A 1 only B 1 and 2 only C 2 and 3 only D 1, 2, and 3

d

sing a multifield image intensifier tube, which of the following input phosphor diameters will provide the best spatial resolution? A 35 cm B 25 cm C 17 cm D 12 cm

d

What is the single most important factor controlling size distortion? A Tube, part, IR alignment B IR dimensions C SID D OID

e Correct Answer is: D Shape distortion (foreshortening, elongation) is caused by improper alignment of the tube, part, and image receptor. Size distortion, or magnification, is caused by too great an object-image distance or too short a source-image distance. OID is the primary factor influencing magnification, followed by SID. (Bushong, 8th ed, p 2

Perhaps the simplest of beam restriction devices, a sheet of lead with a single fenestration, is also known as A an aperture diaphragm. B a fenestrated drape. C a cylinder. D a variable-aperture collimator.

e answer is A. Beam restricting devices come in three basic forms: cylinders and cones, aperture diaphragms, and variable aperture collimators (A). Cylinders and cones are lead or lead lined structures, which restrict the useful beam to a required diameter (C). Variable aperture collimators are the most common device, which feature pairs of lead shutters that can be adjusted to configure the desired length and width of the beam (D). Finally, the aperture diaphragm is, just as the question says, a sheet of lead with a hole in the middle. The hole, or fenestration, is of a fixed size. A fenestrated drape is not a beam restricting device, but is a sterile drape commonly used in surgery to frame the area of the body to be surgically repaired (B). (Bushong, 11th ed., p. 193)

Which of the following devices is used to overcome severe variation in patient anatomy or tissue density, providing more uniform radiographic density? A Compensating filter B Grid C Collimator D Protective filter

he Correct Answer is: A A compensating filter is used when the part to be radiographed is of uneven thickness or tissue density (in the chest, mediastinum vs. lungs). The filter (made of aluminum or lead acrylic) is constructed in such a way that it will absorb much of the x-ray beam directed toward the low tissue-density area while not affecting the x-ray photons to directed toward the high tissue-density area. A collimator is used to decrease the production of scattered radiation by limiting the volume of tissue irradiated. The grid functions to trap scattered radiation before it reaches the IR, thus reducing scattered radiation fog. Protective filtration absorbs low energy x-ray photons that contribute only to patient (skin) dose and would never reach the image receptor. (Selman, 9th ed., pp. 254-25

All of the following are potential digital pre-processing problems, except: A Edge enhancement B Defective pixel C Image lag D Line noise

he Correct Answer is: A Edge enhancement (A) is a type of post-processing image manipulation, which can be effective for enhancing fractures and small, high-contrast tissues. Answers B, C and D are problems that may be encountered in pre-processed digital images. (Bushong, 10 th ed., p. 326).

While indirect digital detectors use a scintillator (phosphor) to convert X-ray energy, direct detectors use a: A Photoconductor B Scintillator C Charged coupled device D Histogram detector screen

he Correct Answer is: A Indirect digital systems use scintillators/phosphors (B) to convert X-ray energy, whereas direct digital systems use a photoconductor (A) to covert this energy. In the two types of indirect systems this energy is subsequently converted by either a charged coupled device (CCD) array or photodiode array (coupled with a thin film transistor array) , or by a TFT array in a direct system. Finally, both indirect and direct digital system conversions result in an analog signal that is converted to a digital signal by the analog-to-digital convertor (ADC). A scintillator (phosphor) receives X-ray energy and converts it to light in an indirect digital detector system. In direct conversion digital detectors, an X-ray photoconductor (B) is used to convert this energy. Some indirect digital detectors use charged coupled devices (CCD), but a scintillator (phosphor) converts the X-ray energy and, through light optics, transfers this energy to the CCD (C). The histogram (D) is a computerized graphic display of the X-ray intensities received by the detectors in direct or indirect digital detector systems (or by the image plate in CR systems). There is no histogram detector screen (D). (Seeram, 1 st ed., p. 106)

Which of the following systems function(s) to compensate for changing patient/part thicknesses during fluoroscopic procedures? A Automatic brightness control B Minification gain C Automatic resolution control D Flux gain

he Correct Answer is: A Parts being examined during fluoroscopic procedures change in thickness and density as the patient is required to change positions and as the fluoroscope is moved to examine different regions of the body that have varying thickness and tissue densities. The automatic brightness control functions to vary the required milliampere-seconds and/or kilovoltage as necessary. With this method, patient dose varies, and image quality is maintainMinification and flux gain contribute to total brightness gain. (Bushong, 8th ed., p. 360)

The collimator light and actual irradiated area must be accurate to within what percentage of the SID? A 2% B 5% C 10% D 15%

he Correct Answer is: A 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. (Thompson et al., p. 403)

The image intensifier's input phosphor generally is composed of A cesium iodide B zinc cadmium sulfide C gadolinium oxysulfide D calcium tungstate

he Correct Answer is: A The image intensifier's input phosphor receives the remnant beam from the patient and converts it to a fluorescent light image. To maintain resolution, the input phosphor is made of cesium iodide crystals. Cesium iodide is much more efficient in this conversion process than was the phosphor used previously, zinc cadmium sulfide. Calcium tungstate was used in intensifying screens in film screen imaging for many years prior to the development of rare earth phosphors such as gadolinium oxysulfide. (Bushong, 8th ed., p. 360)

In the CR reader, some of the laser light is redirected to a reference detector by way of a(n): A Beam splitter B Analog-to-digital converter C Photomultiplier tube D f-theta lens

he Correct Answer is: A The laser beam in a CR reader is directed to a reference detector by way of a beam splitter (A). Optical components called beam splitters are used to divide input light into two separate parts. Beam splitters are found in many laser or illumination systems, and light can be split according to overall intensity or by wavelength. A reference detector enables the CR reader to monitor the laser beam intensity and make adjustments for any fluctuations that may occur, thereby ensuring constant laser beam intensity and uniform release of stored phosphor energy. The PMT, or photomultiplier tube (C), receives the light emitted from a CR phosphor plate as it is scanned by the laser beam, which, in turn, sends an electronic signal to the ADC. The ADC, or analog-to-digital convertor (B), receives an electrical signal from a photomultiplier tube that receives the light emitted from a CR image plate as it is scanned by the laser beam. The ADC changes this electrical (analog) signal to a binary (digital) signal to be used by the processing computer. The f-theta lens in a CR reader focuses the laser light onto a cylindrical mirror, which, in turn, reflects this light toward the image plate as it traverses the scanning section of the CR reader (D). (Shephard p. 327)

Deposition of vaporized tungsten on the inner surface of the x-ray tube glass window acts as additional filtration results in increased tube output results in anode pitting A 1 only B 1 and 2 only C 2 and 3 only D 1, 2, and 3

he Correct Answer is: A 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. (Selman, 9th ed., pp. 137-138)

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 A processing algorithm B histogram C lookup table D exposure index

he Correct Answer is: B 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 photostimulable storage phosphor (PSP) within the IP is the image receptor (IR). The PSP is a europium-doped barium fluorohalide coated storage plate. When the PSP is exposed by x-ray photons, the x-ray energy interacts with the crystals and a small amount of visible light is emitted, but most of the x-ray energy is stored (hence, the term storage plate). This stored energy represents the latent image. The IP is placed in the CR scanner/reader where a helium-neon, or solid-state, laser beam scans the PSP and its stored energy is released as blue-violet light (phosphostimulated luminescence [PSL]). This light signal represents varying tissue densities and the latent image that is then transferred to an analog-to-digital converter (ADC)—converting the signal to a digital (electrical) one. The PSL values will result in numerous image brightness values that represent various tissue densities (i.e., x-ray attenuation properties), for example, bone, muscle, blood-filled organs, air/gas, pathologic processes, and so on. The CR scanner/reader recognizes all these values and constructs a representative gray-scale histogram of them corresponding to the anatomical characteristics of the imaged part. Thus, all PA chest histograms will be similar, all lateral chest histograms will be similar, all pelvis histograms will be similar, and so on. A histogram is a graphic representation of pixel-value distribution. The histogram analyzes all the densities from the PSP and represents them graphically—demonstrating the quantity of exposure, the number of pixels, and their value. Histograms are generated that are unique to each body part that can be imaged. After a part is exposed/imaged, its PSP is read/scanned and its own histogram is developed and analyzed. The resulting analysis, and histogram of the actual imaged part, is compared to the programmed representative histogram for that part. Over time, if required diagnostic image characteristics change, a histogram can be updated to reflect the latest required characteristics. (Carlton and Adler, 4th ed., pp. 361-362)

Referring to the anode cooling chart in Figure 5-9, if the anode is saturated with 300,000 heat units (HU), how long will the anode need to cool before another 160,000 HU can be safely applied?eproduced, with permission, from Dunlee Tech Data Publication 50014. A 3 minutes B 4 minutes C 5 minutes D 7 minutes

he Correct Answer is: B Each x-ray exposure made by the radiographer produces hundreds or thousands of heat units at the target. If the examination requires several consecutive exposures, the potential for extreme heat load is increased. Just as each x-ray tube has its own radiographic rating chart, each tube also has its own anode cooling curve to describe its unique heating and cooling characteristics. An x-ray tube generally cools most rapidly during the first 2 minutes of nonuse. First, note that the tube is saturated with heat at 300,000 HU. In order for another 160,000 HU to be safely applied, the x-ray tube must first release 160,000 HU, which means that it has to cool down at least to 140,000 HU. Find the 140,000 HU point on the vertical axis and follow across to where it intersects with the cooling curve. It intersects at about the 4-minute point. (Selman, 9th ed., p. 147)

For the same FOV, spatial resolution will be improved using A a smaller matrix B a larger matrix C fewer pixels D shorter SID

he Correct Answer is: B Field of view (FOV) refers to the area being viewed. The FOV can be increased or decreased. As the FOV is increased, the part being examined is magnified; as the FOV is decreased, the part returns closer to actual size. Pixel size is affected by changes in either the FOV or matrix size. For example, if the matrix size is increased, for example, from 256 × 256 to 512 × 512, pixel size must decrease. If FOV increases, pixel size must increase. Pixel size is inversely related to resolution. As pixel size decreases, resolution increases. Decreasing SID would decrease spatial resolution. (Fosbinder and Kelsey, p. 285)

Characteristics of low ratio focused grids include the following: 1. they have a greater focal range 2. they are less efficient in collecting SR 3. they can be used inverted A 1 only B 1 and 2 only C 2 and 3 only D 1, 2, and 3

he Correct Answer is: B Grid ratio compares the height of the lead strip to the distance between the lead strips. Focused grids have their lead strips angled so as to parallel the divergent x-ray beam. The higher the grid ratio, the greater the grid's efficiency in absorbing scattered radiation before it reaches the image receptor—but the more critical the centering and distance specifications. Although higher ratio focused grids absorb more SR they have a narrower focal range (focusing distance) and grid/tube centering becomes much more critical. Focused grids must not be accidentally inverted—to do so would cause the lead strips to be placed exactly in the path of the lead strips (grid cutoff), everywhere but in the center of the grid. (Ballinger & Frank, vol 3, p 235)

Types of moving grid mechanisms include 1. oscillating. 2. reciprocating. 3. synchronous. A 1 only B 1 and 2 only C 1 and 3 only D 2 and 3 only

he Correct Answer is: B 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). Synchronou

Which of the following is used in digital fluoroscopy, replacing the image intensifier's television camera tube? A Solid-state diode B Charge-coupled device C Photostimulable phosphor D Vidicon

he Correct Answer is: B In digital fluoroscopy (DF), the image-intensifier output screen image is coupled via a charge-coupled device (CCD) for viewing on a display monitor. A CCD converts visible light to an electrical charge that is then sent to the analog-to-digital converter (ADC) for processing. When output screen light strikes the CCD cathode, a proportional number of electrons are released by the cathode and stored as digital values by the CCD. The CCD's rapid discharge time virtually eliminates image lag and is particularly useful in high-speed imaging procedures such as cardiac catheterizations. CCD cameras have replaced analog cameras (such as the Vidicon and Plumbicon) in new fluoroscopic equipment. CCDs are more sensitive to the light emitted by the output phosphor (than the analog cameras) and are associated with less "noise." DF eliminates the need for cassette-loaded spot films and/or 100-mm spot films. DF photo-spot images, which are simply still-frame images, need no chemical processing, require less patient dose, and offer postprocessing capability. DF also offers "road-mapping" capability. "Road-mapping" is a technique useful in procedures involving guidewire/catheter placement. During the fluoroscopic examination, the most recent fluoroscopic image is stored on the monitor, thereby reducing the need for continuous x-ray exposure. This technique can offer significant reductions in patient and personnel radiation exposure. (Bushong, 8th ed., p. 410)

Which of the following circuit devices operate(s) on the principle of self-induction? Autotransformer Choke coil High-voltage transformer A 1 only B 1 and 2 only C 2 and 3 only D 1, 2, and 3

he Correct Answer is: B The principle of self-induction is an example of the second law of electromagnetics (Lenz's law), which states that an induced current within a conductive coil will oppose the direction of the current that induced it. It is important to note that self-induction is a characteristic of AC only. The fact that AC is constantly changing direction accounts for the opposing current set up in the coil. Two x-ray circuit devices operate on the principle of self-induction. The autotransformer operates on the principle of self-induction and enables the radiographer to vary the kilovoltage. The choke coil also operates on the principle of self-induction; it is a type of variable resistor that may be used to regulate filament current. The high-voltage transformer operates on the principle of mutual induction. (Selman, 9th ed., p. 89) Explanation Peer Comparison

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

he Correct Answer is: B 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)

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

he Correct Answer is: B X-ray images are often subpoenaed as court evidence in cases of medical litigation. In order to be considered as legitimate legal evidence, each x-ray image must contain certain essential and specific patient information. Essential information that must be included on each image is patient identification, the identity of the facility where the x-ray study was performed, the date that the study was performed, and a right- or left-side marker. Other useful information that may be included, but that is not considered essential, is additional patient demographics such as their date of birth, the identity of the referring physician, the time of day that the study was performed, and the identity/initials of the radiographer performing the examination.

Conditions that contribute to x-ray tube damage include lengthy anode rotation exposures to a cold anode low-milliampere-seconds/high- kilovoltage exposure factors A 1 only B 1 and 2 only C 1 and 3 only D 1, 2, and 3

he Correct Answer is: B X-ray tube life may be extended by using exposure factors that produce a minimum of heat, that is, a lower milliampere-seconds and higher kilovoltage combination, whenever possible. When the rotor is activated, the filament current is increased to produce the required electron source (thermionic emission). Prolonged rotor time, then, can lead to shortened filament life as a result of early vaporization. Large exposures to a cold anode will heat the anode surface, and the big temperature difference can cause cracking of the anode. This can be avoided by proper warming of the anode prior to use, thereby allowing sufficient dispersion of heat through the anode. (Selman, 9th ed., pp. 143-145)

The type of x-ray tube designed to turn on and off rapidly, providing multiple short, precise exposures, is A high speed B grid-controlled C diode D electrode

he Correct Answer is: B 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 nickel 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)

All of the following are advantages of digital fluoroscopic imaging systems over conventional fluoroscopic imaging systems, except: A Post-processing capability to enhance image contrast B Increased image acquisition speed C No need for pulsed or continuous radiation exposure D Higher milliamperage settings can be used

he Correct Answer is: C All fluoroscopic imaging (conventional and digital) requires either pulsed or continuous X-ray exposure (C) to provide a dynamic image of the anatomical area of interest. In digital fluoroscopic units, the X-ray tube actually operates in the radiographic mode. However, multiple exposures are made in succession to produce the dynamic image. In these systems, the X-ray generator must be capable of switching on (also called interrogation time) and off (also called extinction time) rapidly in less than 1 ms. The digitized image in a digital fluoroscopy system can be post-processed to enhance image contrast (A), similar to the post-processing that can be done with computed and direct capture static radiographic images. One of the advantages of a digital fluoroscopic system over a conventional fluoroscopic system is the elimination of the television camera tube from the imaging chain, thereby increasing image acquisition speed (B). Either a charge-coupled device or a flat panel image receptor is used to generate electrical signals that can be digitized in a much faster and efficient way, when compared to conventional fluoroscopy. During digital fluoroscopy, the X-ray tube actually operates in the radiographic mode using higher milliamperage settings (D). Tube current is measured in hundreds of milliamperes (mA) rather than less than 5 mA, as in image intensified fluoroscopy. This is not a problem, as the exposures are made in rapid succession and in a pulsed manner (also called pulsed progression fluoroscopy). (Bushong, 9 th ed., pp. 437-438).

Which of the following modes of a trifield image intensifier will result in the highest patient dose? A Its 25-cm. mode B Its 17-cm. mode C Its 12-cm. mode D Diameter does not affect patient dose

he Correct Answer is: C Most image-intensifier tubes are either dual-field or trifield, indicating the diameter of the input phosphor. When a change to a smaller-diameter mode is made, the voltage on the electrostatic focusing lenses is increased, and the result is a magnified but dimmer image. The milliamperage will be increased automatically to compensate for the loss in brightness with a magnified image, resulting in higher patient dose in the smaller-diameter modes. (Bushong, 10th ed., p. 407)

Which part of an induction motor is located outside the x-ray tube glass envelope? A Filament B Focusing cup C Stator D Rotor

he Correct Answer is: C 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 anode is a 2- to 5-in. diameter molybdenum or graphite disc with a beveled edge. The beveled surface has a focal track of tungsten and rhenium alloy. The anode rotates at about 3,600 rpm (high-speed anode rotation is about 10,000 rpm), so that heat generated during x-ray production is evenly distributed over the entire track. Rotating anodes can withstand delivery of a greater amount of heat for a longer period of time than stationary an

A QA program serves to keep patient dose to a minimum keep radiographic quality consistent ensure equipment efficiency A 1 only B 1 and 2 only C 1 and 3 only D 1, 2, and 3

he Correct Answer is: D A QA program includes regular overseeing of all components of the imaging system—equipment calibration, film and cassettes, processor, x-ray equipment, and so on. With regular maintenance, testing, and repairs, equipment should operate efficiently and consistently. In turn, radiographic quality will be consistent, and repeat exposures will be minimized, thereby reducing patient exposure. (Carlton and Adler, 4th ed., pp. 480-481)

In order to erase a CR PSP storage plate, it must be exposed to high-intensity: A Heat B X-radiation C Microwaves D Light

he Correct Answer is: D High intensity visible light (D) produces the wavelength energy necessary to release residual stored energy from these imaging plates. Some residual energy remains stored in the IP after it has been scanned in a CR reader. In order to prevent artifacts on successive radiographic images, it is important to rid the IP of all stored energy. To do this, a high intensity light that is brighter than the stimulating laser light is exposed to the release of any residual stored energy (signal) in the IP. Heat (A) is used in thermal printers used to print hard copy digital images. X-radiation (B) would deposit energy within the image plate, rendering it useless for subsequent diagnostic radiographic exposures. Microwaves (C) are not used as an energy source to erase CR image plates. (Seeram p. 56; Shephard p. 3

Which of the following is (are) characteristic(s) of a 16:1 grid? 1. It absorbs a high percentage of scattered radiation. 2. It has little positioning latitude. 3. It is used with high-kVp exposures. A 1 only B 1 and 3 only C 2 and 3 only D 1, 2, and 3

he Correct Answer is: D High-kilovoltage exposures produce large amounts of scattered radiation, and therefore high-ratio grids are used in an effort to trap more of this scattered radiation. However, accurate centering and positioning become more critical to avoid grid cutoff. (Selman, p 243)

In digital imaging, artifacts arise from a number of sources, including which of the following? A Imaging hardware B Image processing software C Operator error artifacts D All of these may be sources of image artifacts

he Correct Answer is: D In digital imaging, artifacts arise from a number of sources. Imaging hardware artifacts include aged, cracked phosphor storage plates and mishandled and poorly cared for IPs. Image processing software artifacts can arise from incorrectly selected processing algorithms or from exposure field recognition issues from improper collimation, positioning, or sizing. Operator error artifacts can arise from incorrectly stored IPs, incorrect use of equipment, inaccurate selection of factors, etc. (Seeram, p. 67, 68)

radiograph made with a parallel grid demonstrates decreased receptor exposure on its lateral edges. This is most likely due to A static electrical discharge B the grid being off-centered C improper tube angle D decreased SID

he Correct Answer is: D The lead strips in a parallel grid are parallel to one another and, therefore, are not parallel to the x-ray beam. The more divergent the x-ray beam, the more likely there is to be cutoff/decreased receptor exposure at the lateral edges of the image. This problem becomes more pronounced at short SIDs. If there were a centering or tube angle problem, there would be more likely to be a noticeable receptor exposure loss on one side or the other. (Carlton and Adler, 4th ed., p. 260)

ll the following are associated with the anode except A the line-focus principle B the heel effect C the focal track D thermionic emission

he Correct Answer is: D The rotating anode has a target (or focal spot) on its beveled edge that forms the target angle. As the anode rotates, it constantly turns a new face to the incoming electrons; this is the focal track. The portion of the focal track that is bombarded by electrons is the actual focal spot, and because of the target's angle, the effective or projected focal spot is always smaller (line-focus principle). The anode heel effect refers to decreased beam intensity at the anode end of the x-ray beam. The electrons impinging on the target have "boiled off" the cathode filament as a result of thermionic emission. (Selman, 9th ed., pp. 138-139)

The brightness level of the fluoroscopic image can vary with milliamperage kilovoltage patient thickness A 1 only B 1 and 2 only C 1 and 3 only D 1, 2, and 3

he Correct Answer is: D 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)

One advantage of digital imaging in fluoroscopy is the ability to perform "road-mapping." Road-mapping 1. keeps the most recent fluoroscopic image on the screen. 2. aids in the placement of guidewires and catheters. 3. reduces the need for continuous x-ray exposure to the patient. A 1 only B 1 and 2 only C 2 and 3 only D 1, 2, and 3

he Correct Answer is: D 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)

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

he Correct Answer is: D Off-focus and scatter radiation outside of the exposure field would be detected as additional information and, therefore, would widen the histogram (A), resulting in a processing error. Histogram analysis errors can result in rescaling errors and exposure indicator determination errors. Windowing (B) is a post-processing method of adjusting the brightness and contrast in the digital image. There are two types of windowing: level and width. Window level adjusts the overall image brightness. When the window level is increased, the image becomes less bright. When decreased, the image brightness increases. Window width adjusts the ratio of white to black, thereby changing image contrast. Narrow window width provides higher contrast (short-scale contrast), whereas wide window width will produce an image with less contrast (long-scale contrast). Improper pre-exposure anatomical selection (C) (e.g., selecting chest versus the intended foot selection) can interfere with proper histogram assignment (and display) for the anatomical part of interest. In digital image subtraction (D), the pixel values from post-contrast images are electronically subtracted from pixel values from the first pre-contrast (mask) image to show contrast-filled blood vessels with the other structures (e.g., bone) removed in order to enhance the diagnostic impressions of the radiologist, and is unrelated to histogram changes. (Seeram, 1 st ed., p. 37; Carroll, 3rd ed p 469; Carlton and Adler, 6th ed, p279).

Which of the following technical changes would best serve to remedy the effect of very dissimilar tissue densities? A Use of short exposure time B Use of a high-ratio grid C High-kilovoltage exposure factors D High milliampere-seconds exposure factors

he The Correct Answer is: C When tissue densities within a part are very dissimilar (e.g., the chest), the radiographic result (especially analog) can be unacceptably high contrast. To "even out" these exposure values and produce a more appropriate scale of grays, exposure factors using high kilovoltage should be employed. The higher the grid ratio, the higher is the resulting contrast. Use of short exposure time is always encouraged to reduce the possibility of motion unsharpness but has no impact on varying tissue densities. Exposure factors using high milliampere-seconds generally result in excessive receptor exposure, frequently obliterating much of the gray scale. (Bushong, 8th ed., p. 273; Shephard, p. 200)

Consider the diagram below of an ionization chamber with a cathode, an anode, and a neutral gas contained within a sealed radiolucent compartment. Bombarding the chamber with ionizing radiation will yield a source of electrons through which interaction? Coherent scattering B Photoelectric interaction C Bremsstrahlung D Pair production

he answer is B. The five interactions of x-ray photons are with matter, not just the atoms and molecules inside the patient. A novice student may not realize that those reactions apply to AEC ionization chambers and image receptors as well. The key to understanding is recognizing which of the four choices meets these criteria: -The phenomenon described is initiated by an x-ray photon. -A free electron is available after the phenomenon has occurred. Coherent scattering begins with an x-ray photon but does not produce a negative ion through ionization (A). Bremsstrahlung doesn't fit either criterion, as it is a means of x-ray production, not an interaction (C). Both photoelectric interaction and pair production fit the criteria (D). The photoelectric interaction is the correct choice because pair production occurs at higher energy levels than energies found within the diagnostic range (B). When a photon enters the cell, it ionizes an air molecule, perhaps nitrogen, and creates both a positive and a negative ion. The positive ions will feel a coulomb force attraction to the cathode, and the negative ions (photoelectrons) will be pulled toward the anode. Notice that ions don't begin forming in meaningful numbers until x-rays enter the chamber. (Johnston and Fauber, 2nd ed., pp. 76, 188)

A radiographic technique of 80 kilovoltage peak (kVp), 500 milliamperes (mA), and 0.25 seconds is selected for a radiographic exposure. How many heat units (HU) would be produced from this single exposure on a high frequency x-ray unit? A 10,000 B 13,500 C 14,100 D 14,500

he answer is D. Heat units (HU) for radiographic tubes are calculated by using the following formula: kVp × mA × time (in seconds) × a correction factor (c). The correction factors are as follows: 1.0 for single-phase x-ray units, 1.35 for three-phase, 6-pulse x-ray units, 1.41 for three-phase 12-pulse x-ray units, 1.45 for high-frequency x-ray units. The calculation for this exposure would be as follows: 80 kVp × 500 mA × 0.25 seconds × 1.45 = 14,500 (D). Choice (A) was found by using a correction factor of 1, choice (B) was found by using a correction factor of 1.35, and choice (C) was found by using a correction factor of 1.41. (Johnston and Fauber, 2nd ed., p. 58)

f a high-voltage transformer has 100 primary turns and 35,000 secondary turns, and is supplied by 220 V and 75 A, what are the secondary voltage and current? A 200 A and 77 V B 200 mA and 77 kVp C 20 A and 77 V D 20 mA and 77 kVp

he correct answer is (B). 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 is dependent on the transformer ratio-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: