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Which of the following milliampere-seconds value should be used with three-phase, 12-pulse equipment to produce a similar radiographic density to a chest x-ray that was performed with single phase equipment using exposure factors of 84 kVp and 8 mAs? A. 4 mAs B. 8 mAs C. 16 mAs D. 24 mAS

Correct answer: (A) 4 mAs. Explanation: Three-phase equipment has less voltage ripple and the voltage never drops to zero. It is more efficient that single-phase equipment, only 2/3 of the original milliampere-seconds is required. Using three-phase, 12-pulse equipment, only half of the original milliampere-seconds value is necessary to produce a radiograph of similar density to one produced using single-phase equipment.

Which of the following will adjust the radiographic contrast in computed radiography? A. Adjustment of window width B. Change in the imaging plate C. Decrease of the area of irradiation D. Adjustment of window level

Correct answer: (A) Adjustment of window width. Explanation: In digital radiography and computed radiography, as the window width is adjusted, the radiographic contrast is changed in inverse proportion. As the window width is increased, the radiographic contrast decreases, which reflects the increased number of gray tones seen. Adjustment of the window level is directly proportional to changes in the brightness of the image. Radiographic contrast in digital radiography is primarily determined by the processing algorithms used.

What is the smallest particle of an element that retains the characteristic of the element? A. Atom B. Electron C. Molecule D. Mole

Correct answer: (A) Atom. Explanation: An atom is the smallest component of an element that has the chemical properties of the element. Atoms consist of a nucleus with combinations of neutrons and protons and one or more electrons bound to the nucleus by electrical attraction. An electron is an elementary particle with a negative charge that can exist independently or as a component of an atom. A molecule is the smallest physical unit of an element or a compound. It consists of one or more like atoms in an element and two or more different atoms in a compound. A mole is the amount of a substance that is expressed in grams and contains 6.022 x 1023 molecules, ions, or atoms of the substance.

What lies immediately below the reflective layer of a PSP storage plate? A. Base B. Phosphor layer C. Lead foil D. Antistatic layer

Correct answer: (A) Base. Explanation: The layers of the PSP storage plate are: 1. Barium fluorohalide is usually granular or turbid phosphors 2. Reflective layer 3. Base 4. Antistatic layer 5. Lead foil 6. Over the top of the barium fluorohalide is a protective layer A PSP storage plate that is within the IP has a layer of europium-activated barium fluorohalide that is mixed with a binder and serves as the image receptor when it is exposed traditionally. The layer looks like an intensifying screen in an x-ray cassette. The barium fluorohalide is turbid phosphors or granular, which provides less x-ray absorption and more light diffusion compared to needle shaped or columnar phosphors like cesium iodide. A reflective layer beneath the barium fluorohalide layer directs emitted light toward the CR reader. The base lies below the reflective layer and behind the base there is the antistatic layer and lead foil, used to absorb backscatter. The top of the barium fluorohalide layer is covered by a protective layer.

How is the image brightness adjusted in computed radiography? A. Change the window level B. Increase the exposure C. Use of fluoroscopy D. Doubling the kilovoltage

Correct answer: (A) Change the window level. Explanation: There is a direct relationship between the window level and image brightness. Window level, the midpoint of densities, adjusts the image brightness throughout the range of densities in CR. Changes in the window width adjust the radiographic contrast in post-processing mode in an inverse proportion, so that as the window width decreases, the contrast increases and fewer gray tones are shown.

Which of the following instruments is commonly used in QA programs to measure varying degrees of x-ray exposure? A. Densitometer B. Sensitometer C. Penetrometer D. Spinning top

Correct answer: (A) Densitometer. Explanation: A densitometer measures the different densities on a radiographic image and gives them a numeric value. A sensitometer is used to give a precise exposure to a film emulsion. A penetrometer, also known as an aluminum step wedge, can be used to show variations in contrast resulting from kilovoltage. A spinning top tests the accuracy of the x-ray machine or rectifers.

When using 30 inch SID and a 14 x 17 inch IR to radiograph a structure with homogenous density, which of the following is most likely to occur? A. Density variation at opposite ends of the IR B. Short scale contrast C. Production of quantum mottle D. Production of fog from scatter

Correct answer: (A) Density variation at opposite ends of the IR. Explanation: Divergence of the x-ray photons from the tungsten target occurs more readily toward the cathode end of the tube, but as x-rays diverge toward the anode, they are absorbed by the anode "heel," which results in a greater intensity of x-ray photons at the cathode end of the beam and the corresponding portion of the radiograph. This is the anode heel effect and it is more pronounced with shorter SID and larger IR sizes that result in greater divergence of the x-ray beam.

Which of the following is produced as a result of thermionic emission? A. Electron cloud B. Recoil electron C. Characteristic photon D. Photon scatter

Correct answer: (A) Electron cloud. Explanation: In preparation for x-ray production, the filament in the cathode is heated and electrons are "boiled off" to create an electron cloud around the filament. This is also known as a space charge. The focusing cup that surrounds the filaments on three sides has a negative charge applied. This concentrates the electrons that are boiling off the filaments, repelling them in a narrower stream towards the anode.

Which of the following is used to maximize heat loading potential of an x-ray machine? A. Falling load generator B. AEC C. TLD D. Phototimer

Correct answer: (A) Falling load generator. Explanation: The falling load generator is a modern generator that is used to take advantage of the short time capability and heat loading potential of an x-ray tube to calculate the most efficient method to obtain the mAs set by the radiographer. The first portion of the exposure begins at the highest mAs possible, decreasing to the next safe but lower level for the tube when the maximum heat load is reached at the initial setting. The exposure continues at lower mA at the shortest possible time until desired mAs is reached.

Which of the following does not affect the exposure rate of the primary beam? A. Field size B. Milliamperage C. Kilovoltage D. Distance

Correct answer: (A) Field size. Explanation: The size of the field is not related to the exposure rate, although it does influence the amount of scattered radiation. Milliamperage has an important influence on the exposure rate. Kilovoltage has an effect on the exposure rate because it regulates the quality of the beam and the number of high energy photons at the target. Distance is related to the exposure rate through the inverse square law.

Which of the following refers to a grid with strips that are angled to coincide with the divergence of the beam? A. Focused B. Rhombic C. Parallel D. Crosshatch

Correct answer: (A) Focused. Explanation: Focused grids are grids with lead strips angled to coincide with divergence of the x-ray beam. They are used within specific ranges of SID, determined by a grid radius. The grid radius, also called the focal distance or focal range, should be wide for low-ratio grids and narrow for high-ratio grids. The focal range or grid radius is stated on the front of the grid. A linear grid has lead strips parallel to one another. A crosshatch grid consists of two linear grids perpendicular to each other. It has superior scatter absorption, but require perfect positioning and centering. No angulation of the x-ray beam is acceptable.

All of the following are used to control production of scattered radiation when the beam reaches the patient except: A. Grid use B. Collimation C. Optimization of the kVp D. All of the above are used to control production of scattered radiation

Correct answer: (A) Grid use. Explanation: Grids do not affect the production of scattered radiation, but they remove scattered radiation from the beam before it strikes the image receptor. Collimation restricts the x-ray beam. This results in alignment of the x-rays and reduces production of scatter. When the kilovoltage is increased in an x-ray machine, the photons interact with the atoms through the Compton reaction, resulting in scattering of photons. This adds to production of fog on the radiation image and presents a hazard to personnel in fluoroscopic procedures. Optimization of kVp can reduce or control scatter.

Which of the following does not operate on the principles of an automatic exposure control (AEC) device? A. Induction of current in a conductor through motion of magnetic fields. B. Photomultiplier tube charged by a fluorescent screen. C. Parallel plate ionization chamber charged by x-ray photons. D. All of the above are associated with use of an AEC device.

Correct answer: (A) Induction of current in a conductor through motion of magnetic fields. Explanation: Motion of magnetic fields inducing a current in a conductor refers to the principle of mutual induction. One type of AEC is a phototimer, which measures light. A fluorescent screen beneath the cassette glows in response to emergence of photons from a part. At a predetermined charge, the exposure is automatically terminated. Another type of AEC is a parallel plate ionization chamber, which is a radiolucent chamber between the patient and the IR. Photons emerging from the patient enter the chamber and ionize the air within it until a predetermined charge is reached and the exposure is automatically terminated.

What is the cause of the artifact displayed in the image below? A. Insufficient sampling of high frequency digital signals B. Static electricity C. Cracked intensifying screen D. Motion artifact

Correct answer: (A) Insufficient sampling of high frequency digital signals. Explanation: The artifact seen in the image above represents "aliasing," which occurs as a result of insufficient sampling of high frequency digital signals. It is sometimes caused by using a grid cassette in the Bucky tray and can be corrected by use of a moving grid or by selection of a high grid frequency. Static electricity produces a "lightening" pattern. Cracked intensifying screen can result in crescent shaped white lines. Motion artifact usually produces blurring.

Which of the following studies requires a focal-spot size that is 0.33 mm or less? A. Magnification radiography B. Tomography C. Bone radiography D. Fluoroscopy

Correct answer: (A) Magnification radiography. Explanation: To reproduce fine detail without focal-spot blurring in magnification radiography, the fractional focal spot must be 0.3 mm or smaller. Unless a small focal spot is used, the focal spot blur will be magnified with the object under study. A small fractional focal spot can be used in bone radiography to help magnify bony structures like hairline fractures, but it is not essential.

The purpose of a short exposure time when performing a chest radiography is required for which of the following reasons? A. Minimization of involuntary movement B. Production of short scale contrast C. Reduction of patient inconvenience D. Avoidance of focal-spot blur

Correct answer: (A) Minimization of involuntary movement. Explanation: Although the patient can suspend respiration during a chest x-ray, involuntary motion, particularly the action of the heart, should be minimized by using a short exposure time when imaging the chest.

The resolution or recorded detail of an image is expressed as: A. Modulation transfer function B. Latitude C. Kilovolts D. Relative speed

Correct answer: (A) Modulation transfer function. Explanation: The modulation transfer function (MTF) is also known as the line spread function or line pairs per millimeter. The measurement of line pairs per mm can be performed using one of several available resolution test patterns. Resolution refers to the closeness with which fine details can be associated while being recognized as separate. LSP is measured using a 10 um x-ray beam. The MTF measures the amount of lost information between the object and the image receptor.

Which of the following is associated with barium fluorohalide? A. PSP storage plates B. Rare earth intensifying screens C. Filament D. Image intensifiers

Correct answer: (A) PSP storage plates. Explanation: The PSP storage plate uses a europium-activated barium fluorohalide layer that acts as the image receptor and is exposed in a traditional manner to receive the latent image. This latent image can be stored for about 8 hours before noticeable fading occurs. CR cassettes do not have film or intensifying screens. The IP serves as a protective cover for the PSP/storage plate within and can be used in the Bucky tray or immediately underneath the part being examined.

Which of the following findings is seen in the radiograph below? A. Poor inspiration B. Congestive heart failure C. Over-penetration D. Pleural effusion

Correct answer: (A) Poor inspiration. Explanation: The radiograph shows the patient has poor inspiration. This will crowd the lung markings and may appear as though the patient has interstitial disease. Ten posterior ribs visualized on a radiograph indicate excellent inspiration, although visualization of nine posterior ribs is acceptable in patients who are hospitalized. Only 8 posterior ribs are seen. The patient is also slightly rotated towards the right and the film is somewhat underpenetrated.

Which of the following is a component of the design of contemporary rectifiers? A. Silicon-based semiconductors B. Silicone-based conductors C. Transistors D. Cathode ray tubes

Correct answer: (A) Silicon-based semiconductors. Explanation: An x-ray tube needs direct current to function and a rectifier is used to change alternating current from the step-up transformer to direct current. Rectifiers are solid state diodes made of silicon-based n-type and p-type semiconductors. They are placed between the step-up transformer and the x-ray tube. A rectifier unit with four diodes will provide full-wave rectification for a single-phase generator. A rectifying unit with 6 or 12 diodes can provide full-wave rectification for three-phase equipment.

Which of the following is true when comparing the input phosphor of the image intensifier to the output phosphor? A. The input phosphor is larger. B. The input phosphor is fixed in size but the size of the output phosphor can vary. C. The input phosphor absorbs electrons, output phosphor absorbs light photons. D. The input phosphor emits electrons and the output phosphor emits light photons.

Correct answer: (A) The input phosphor is larger. Explanation: The input phosphor on the image intensifier receives remnant radiation that emerges from the patient and converts it into fluorescent light. It is 6 to 9 times larger than the output phosphor.

Which of the following is true when comparing a stationary grid to a moving grid? A. The patient dose is increased with a moving grid. B. Short exposure times are required for a moving grid. C. Moving grids result in phantom images when the anatomic part moves in parallel with the grid motion. D. A and B E. All of the above are true

Correct answer: (A) The patient dose is increased with a moving grid. Explanation: Patient exposure to radiation is increased when using a moving grid compared to use of a stationary grid. Moving grids require longer exposure times to allow for removal of grid lines..

Which of the following will increase when the kVp is decreased from 100 to 85? A. Wavelength B. Optical density C. Gray scale D. A and B E. B and C F. All of the above

Correct answer: (A) Wavelength. Explanation: Kilovoltage changes affect both the quantity and quality of the x-ray beam. When the kilovoltage is decreased by 15%, the radiographic density will be cut in half. A small kVp produces an image of high contrast with very few grays visible. This is referred to as a short gray scale. A high kVp will produce an image with low contrast and the gray scale will lengthen. The x-rays produced by decreased kilovoltage will have lower energy, with a longer wavelength.

What is the acceptable range for the target angle? A. 0 to 10 degrees B. 7 to 20 degrees C. 0 to 90 degrees D. 10 to 45 degrees

Correct answer: (B) 7 to 20 degrees. Explanation: Electrons produced at the cathode strike the target on the focal spot, also called the focal track. This focal track is beveled to produce the target angle, which allows for a larger actual focal spot while producing a smaller effective focal spot. The effective focal spot is the area that is seen by the image receptor. The larger the focal spot, the greater the heat capacity and the smaller the effective focal spot, the greater sharpness of the radiographic image, in accordance with the line-focus principle. The target angle may be between 7 and 20 degrees, depending upon the design of the x-ray tube.

How long will an exposed image plate retain its image? A. 2 hours B. 8 hours C. 12 hours D. 24 hours

Correct answer: (B) 8 hours. Explanation: No film or intensifying screens are used in computed radiography, so the cassettes are designed to protect the image plate within. CR cassettes can be used directly under a part of interest or in the Bucky tray, since the image is not light sensitive. The cassette has a backing of lead foil that serves to absorb backscatter. Within the cassette, a photostimulable phosphor image plate (IP or PSP) with a layer of europium-activated barium fluorohalide serves as the IR. It receives a latent image after exposure in the traditional manner and can store the image for several hours before noticeable fading occurs.

If the distance from the focal spot to the center of the mirror of the collimator is 8 inches, how far should the distance be from the illuminator's light bulb to the center of the mirror? A. 4 inches B. 8 inches C. 12 inches D. 16 inches

Correct answer: (B) 8 inches. Explanation: A collimator assembly is comprised of a series of lead shutters, a light bulb, and a mirror. The mirror and light bulb project the size, location, and center of the irradiated field. The beam of light emitted from the bulb is deflected by the mirror, which is placed at an angle of 45degrees in the path of the light. The focal spot and light bulb must be exactly the same distance from the center of the mirror in order for the projected beam to be the same size as the x-ray beam.

Which of the following is used to convert energy to digital form in fluoroscopy? A. Flux capacitor B. Analog to digital converter C. Collimator D. AEC

Correct answer: (B) Analog to digital converter. Explanation: Video signals from the television camera used in fluoroscopy are analog. The analog signal is sampled, producing a stepped representation of the analog video signal in an analog to digital converter. The numerical values of each step are stored to produce a matrix of digital image data.

Which of the following terms refers to the positive electrode of the x-ray tube? A. Cathode B. Anode C. Capacitor D. Filament

Correct answer: (B) Anode. Explanation: There are two electrodes in an x-ray tube. The positive electrode is the anode and the negative electrode is the cathode. The cathode filament is heated to incandescence and releases electrons through thermionic emission. The electrons travel to the anode, where they decelerate, resulting in production of x-rays. Capacitor-discharge mobile units can make short, precise exposures using a grid-controlled tube that uses a molybdenum-focusing cup as the switch, allowing strict control of the flow between anode and cathode.

Which of the following devices is used to ensure consistency of radiographic quality in different exposures? A. Collimator B. Automatic exposure control C. Falling load generator D. Electronic timer

Correct answer: (B) Automatic exposure control. Explanation: Timers are used to regulate the duration of x-ray exposure. They are wired in the circuit between the autotransformer and high-voltage transformer. An automatic exposure control (AEC) is used to provide consistency of radiographic quality, but relies upon the skill of the radiographer, who must have accurately position the part over ionization sensors. This requires both positioning skill and knowledge of the surface and internal anatomy.

Which of the following operates using self-induction? A. Induction transformer B. Autotransformer C. Step-down transformer D. Step-up transformer

Correct answer: (B) Autotransformer. Explanation: An autotransformer is also known as a variable transformer. It provides for the variation of voltage flowing in the x-ray circuit that is applied to the x-ray tube. The autotransformer is used to provide a small increase in voltage before the step-up transformer. It is the site where kVp settings are made. An autotransformer is composed of a single coil of wire with an iron core that operates on the principle of self-induction. The single coil of wire incorporates both primary and secondary coils of the transformer. The primary turns are fed 220 V from the supply into the radiology department. The secondary turns are selected using the kVp select control.

At which of the following locations is focal spot blur greatest? A. Anode end x-ray beam B. Cathode end x-ray beam C. It increases with the SID D. Along the course of the central ray

Correct answer: (B) Cathode end x-ray beam. Explanation: Focal spot blur occurs when photons emerge from a large focal spot. The projected focal spot is greatest at the cathode end of an x-ray tube, which results in the greatest amount of blur at the cathode end of the radiograph. Blur becomes progressively smaller toward the anode end of the x-ray tube and corresponding part of the radiograph.

What is the location of the focusing cup? A. Anode B. Cathode C. Control panel D. X-ray tube window

Correct answer: (B) Cathode. Explanation: The cathode, or negative electrode in the x-ray tube, contains a large and small filament made of tungsten. The filaments are heated during x-ray exposure to a level that results in thermionic emission, characterized by "boiling off" electrons that are needed in preparation for production of x-rays. The cathode assembly includes the focusing cup, which surrounds the filaments on three sides. A negative charge is applied to the focusing cup, which concentrates electrons that boil off the filaments into a narrower stream, repelling them in the direction of the anode. The focusing cup is sometimes used as an electronic grid to turn tube current on and off rapidly, which permits precise and very short exposure times needed for rapid serial exposures.

Which of the following is depicted in the figure below? A. Nine-penny test B. Collimator accuracy calibration C. Focal spot size test D. Screen resolution test

Correct answer: (B) Collimator accuracy calibration. Explanation: A collimator is one device used to restrict the primary beam. It is attached to the head of the x-ray tube and has two sets of shutters, one near the tube port window to control the amount of off-focus radiation leaving the tube, and a second set of two adjustable shutters for field length and width. The radiographer adjusts the second set of shutters to change with field size and shape. A collimator also has a light-localization apparatus consisting of a small bulb to illuminate the field and a mirror. The focal spot of the tube and the light bulb must be equidistant from the center of the mirror in order to correspond accurately. If this does not occur, the IR alignment may be off and sometimes requires a repeat examination. A collimator accuracy test should be performed regularly as part of any QA program. The collimator should be accurate to within 2% of the SID. The nine-penny test is also used to evaluate collimator accuracy.

Which of the following is not part of the high-voltage generator? A. Rectifier B. Collimator C. Filament transformer D. High voltage transformer

Correct answer: (B) Collimator. Explanation: The high voltage generator of a diagnostic x-ray system is often located in the radiographic room. It converts low energy to high energy that is necessary for x-ray production. It consists of the filament transformer, high voltage transformer, and the rectifier. A high voltage transformer is only one component of a high-voltage generator. The purpose of the rectifier is to convert alternating current to direct current that is needed for operation of the x-ray tube.

Which of the following is the purpose of an electric generator? A. Thermionic emission of electrons B. Converts mechanical energy into electricity C. Turns electricity into mechanical energy D. Converts electrons into x-ray photons

Correct answer: (B) Converts mechanical energy into electricity. Explanation: An electric generator is a device that converts mechanical energy to electrical energy, usually producing alternating current. Electricity is converted into mechanical energy by a electric motor. Thermionic emission refers to the process by which electrons boil off the filament in the cathode as it is heated. Electrons are converted to photons at the anode.

Which of the following results from an increase in the digital image matrix size in electronic imaging? A. Decrease in pixel depth B. Decrease in pixel size C. Decrease in resolution D. Decrease in field of view

Correct answer: (B) Decrease in pixel size. Explanation: Digital images are composed of a matrix of pixels (picture elements) in columns and rows. As the digital image matrix increases in size, more and smaller pixels are represented in the matrix, which leads to better resolution. Fewer pixels or larger pixels result in poor resolution. The depth of a pixel is related to the dynamic rage of gray shades and it is measured in bits. There are a greater number of bits in a pixel that has more shades of gray. A1-bit pixel (21), but a 4-bit pixel can display 16 shades of gray. Pixel depth is not related to resolution. The field of view refers to the area of the patient that is include in the matrix, but the matrix and field of view can be changed independently of each other.

Which of the following decreases contrast? A. Increase in grid ratio B. Decreased grid ratio C. Destructive pathological condition D. Decreased amount of irradiated tissue

Correct answer: (B) Decreased grid ratio. Explanation: A decrease in the grid ratio decreases contrast and increasing the grid ratio increases contrast, due to the ability of the grid to absorb scatter before it reaches the film. Film speed has no effect on contrast. Destructive pathological conditions and decreased amounts of irradiated tissue both increase contrast. Additive pathology decreases contrast - destructive pathology increases contrast. As the thickness of the body part increases, scatter is increased and this decreases contrast. An example of destructive pathology is osteoporosis. It decreases the thickness of the body part, increases scatter, and decreases contrast.

Which of the following is demonstrated in the radiograph seen below? A. Inadequate screen-film contact B. Double exposure C. Motion artifact D. Focal spot blur

Correct answer: (B) Double exposure. Explanation: Notice the superimposed structures on this image. If the distortion was the result of inadequate film screen contact, there would probably be localized blurriness, but normally the entire film is not affected. The bones of the hand are well-defined, which would not occur with motion. Focal spot blur also results in blurring of the anatomic structures in the image.

How is a rotating anode powered? A. Self induction B. Electromagnetic induction motor C. Alternating Current D. Thermogenic

Correct answer: (B) Electromagnetic induction motor. Explanation: A rotating anode is powered by an induction motor located outside of the x-ray tube. This motor turns a rotor inside the x-ray tube. The target is attached to the end of the rotor. A rotating anode provides greater heat dissipation compared to a stationary anode.

Which of the following is used on x-ray equipment to achieve a continually decreasing mA for the shortest exposure time? A. Phototimer B. Falling load generator C. Ionization chamber D. AEC

Correct answer: (B) Falling load generator. Explanation: A falling load generator uses the tube heat-loading potential and takes advantage of extremely short time capabilities to calculate the most efficient method of obtaining the required mAs, which is set by the radiographer. The x-ray tube begins at the highest level possible for the first portion of the exposure, decreasing the mA to the next lowest level that can be handled by the tube when the maximum heat load of the tube is reached for the initial mA. The exposure continues, using progressively lower levels of mA for the shortest possible times until the desired mAs is reached.

Scattered radiation on an image results in which of the following? A. Increased grid cutoff B. Fog C. Increased contrast D. Increased density

Correct answer: (B) Fog. Explanation: Scattered radiation is produced in the Compton interaction of an incident x-ray photon and tissue. Scattered rays that exit the body will hit the image receptor from a variety of angles as a result of their change in direction after contact with the tissue. They do not contribute useful information to the image, but they produce a low-contrast fog over the image. Grid cutoff results from misaligned x-ray tube and it results in increased contrast from absorption of some x-rays from the primary beam.

Which of the following increases contrast? A. Decrease in the OID B. Increased collimation C. Increase focal spot size D. Decreased grid ratio

Correct answer: (B) Increased collimation. Explanation: Collimation has a direct effect on contrast. When the beam size is reduced, the amount of irradiated tissue decreases, decreasing the number of scatter events. The OID has a direct relationship with contrast, which increases with the air gap technique. Focal spot size does not affect contrast. A decreased grid ration will result in less contrast. Higher grid ratios absorb a greater amount of scattered radiation, resulting in increased contrast.

Which of the following is not normally included in performance of high-quality mammographic examinations? A. Use of a compression device B. Low contrast C. X-ray tube with a small focal spot D. All of the above are normally used when performing a high-quality mammographic examination.

Correct answer: (B) Low contrast. Explanation: In order to be able to visualize microcalcifications and subtle density differences in breast tissue, which has low subject contrast, small focal-spot is required. High contrast is also necessary for accentuation of any differences in tissue density. Since breast material is thicker at the chest wall and thinner at the nipple, a compression device is necessary to even out differences in tissue thickness, decrease OID, and decrease the production of scattered radiation.

Electrical energy is converted to mechanical energy by which of the following? A. Generator B. Motor C. Rotor D. Transformer

Correct answer: (B) Motor. Explanation: A motor is a device that converts electrical energy to mechanical energy. A generator is used to convert mechanical energy to electrical energy. A rotor is one of the principle parts of an induction motor and is used to rotate the anode. A transformer is used to change the voltage.

Which of the following characterize high-frequency generators? A. Increased patient dose B. Nearly constant potential C. Large size D. High voltage percent ripple

Correct answer: (B) Nearly constant potential. Explanation: High frequency generators convert conventional 60-Hz full wave rectified power to a frequency between 500 and 25,000 Hz. A high frequency generator is compact in size and provides a waveform with almost constant potential and low voltage ripple, resulting in decreased patient dose as the result of reduction of the number of low-energy photons. Originally used in mobile x-ray, they have been used extensively in mammography and CT equipment.

Which of the following refers to grid frequency? A. Distance between lead strips divided by the height of the strips B. Number of lead strips per inch or per centimeter C. Height of the lead strips multiplied by distance between each strip D. Height of lead strips divided by distance between the strips

Correct answer: (B) Number of lead strips per inch or per centimeter. Explanation: Grids are constructed of lead strips separated by aluminum interspacers. The grid ratio is the height of the lead strips divided by the distance between the lead strips, ranging from 4:1 to 16:1. The grid frequency is the number of lead strips per centimeter or per inch. As the grid frequency increases, the thickness of the lead strips decreases and they become less visible. Grid frequencies range from 60 to 150 lines per inch. As the grid frequency and ratio increase, the grid becomes more selective, indicating a high efficiency of scatter cleanup.

What type of fluoroscopic artifact is represented by the schematic below? A. S effect B. Pincushion effect C. Vignetting D. Lag

Correct answer: (B) Pincushion effect. Explanation: Image intensifiers can produce specific artifacts, some of which may be the result of improper calibration. The schematic represents a pincushion distortion, which is a geometric, nonlinear magnification across the image. The difference in magnification at the image periphery is the result of the projection of the x-ray beam onto a curved input surface. It can be visualized by imaging a rectangular grid with the fluoroscope. An S distortion is caused by the differential effect of external electromagnetic fields, which is greater at the perimeter of the image intensifier compared to the center. Vignetting refers to a fall-off in brightness at the image periphery that results from unequal collection of light across the image intensifier. Lag is persistent luminescence after the x-ray stimulation is terminated. It results in poor temporal resolution of the dynamic image. In current fluoroscopic systems, lag is usually caused by the closed-circuit TV system.

What law governs the adjustment of milliamperage and exposure time to produce the correct mAs value to reproduce radiographic exposure when using different milliamperage or exposure times? A. Line-focus principle B. Reciprocity law C. Inverse square law D. Ohm's law

Correct answer: (B) Reciprocity law. Explanation: Various combinations of milliamperage and exposure time settings can produce the same milliampere-seconds value, resulting in identical radiographic density. This is known as the reciprocity law and allows the radiographer to manipulate exposure factors to decrease exposure time and motion unsharpness. The law can be stated: C1/C2 = T2/T1 Where C1 = Current 1, C2 = Current 2, T1 = time at C1 and T2 = time at C2.

Which of the following devices converts alternating current to direct current in an x-ray circuit? A. Step-up transformer B. Rectifier C. Falling load generator D. Autotransformer

Correct answer: (B) Rectifier. Explanation: An x-ray tube requires direct current to operate. Rectifiers are solid-state diodes that are placed between the step-up transformer and the x-ray tube to produce direct current from the alternating current from the step-up transformer.

Which of the following devices are operated on the principle of mutual induction? A. Generators B. Step-upTransformers C. Rectifiers D. Timers

Correct answer: (B) Step up transformers. Explanation: The principle of mutual induction refers to induction of electricity in a wire within a magnetic field surrounding another with current running through it. Step up and step down transformers operate on this principle.

Which of the following terms refers to a material that exhibits no resistance to electrical current below a critical temperature? A. Conductor B. Superconductor C. Semiconductor D. Insulator

Correct answer: (B) Superconductor. Explanation: A superconductor is a material that exhibits no resistance below a critical temperature. A semiconductor is a material that behaves as an insulator in some conditions but behaves as a conductor in other conditions. A conductor is any material that allows easy flow of electrons. An insulator is a material that does not allow electron flow.

Which of the following is powered by the capacitor in a capacitor-discharge mobile x-ray unit? A. Braking mechanism B. X-ray tube C. Machine locomotion D. All of the above

Correct answer: (B) X-ray tube. Explanation: Capacitor-discharge mobile x-ay units do not use batteries and must be charged before each exposure. A capacitor, sometimes called a condenser, is a device that stores electrical energy that is used in a mobile unit only to operate the x-ray tube. Capacitor-discharge mobile x-ray units are lighter than machines that require batteries and do not needs motors to drive or brake the machine, but the kilovoltage gradually decreases through the length of the exposure, as the capacitor discharges its electrical charge.

Which of the following uses direct current to operate? A. Closed-core transformer B. X-ray tube C. Autotransformer D. All of the above

Correct answer: (B) X-ray tube. Explanation: Transformers operate on alternating current, but x-ray tubes must be supplied with direct current. Alternating current consists of electrons streams that oscillate between two directions. Direct current refers to movement of electrons in one direction.

Which of the following formulas is used to determine the total number of heat units produced by three-phase six-pulse equipment? A. mA x s x kVp B. mAs x kVp x 1.35 C. mAs x kVp x 1.41 D. mAs x kVp x 3

Correct answer: (B) mAs x kVp x 1.35. Explanation: Heat units produced by single-phase equipment are calculated by multiplication of mA x time x kVp. When using three-phase six-pulse equipment, a correction factor is used. For three-phase, six-pulse unit, the correction factor is 1.35. For a three-phase, twelve-pulse unit, the correction factor is 1.41.

Which of the following directly affects the amount of exposure reaching the image receptor? A. OID B. mAs C. Focal spot size D. All of the above

Correct answer: (B) mAs. Explanation: The amount of exposure reaching the image receptor is directly controlled by mAs. kVp has a direct effect on exposure that is not proportional. It is governed by the 15% rule. The OID and focal spot affect the sharpness of the recorded detail. The OID has an inverse relationship with the exposure reaching the image receptor and the focal spot has no relationship to the exposure reaching the image receptor.

Which of the following exposure times is most appropriate using 400 mA with a 12:1 grid and 90 kVp to maintain the same radiographic density of an exposure made using 5 mAs and 105 kVp with a 5:1 grid at an SID of 60 inches? A. 0.6 s B. 0.03 s C. 0.06 s D. 0.1 s

Correct answer: (C) 0.06 s. Explanation: To improve the contrast in the image, the kilovoltage has been decreased by 15%, so the mAs should double from 5 mAs to 10 mAs. To account for the change in the grid ratio, which is increased from 5:1 to 12:1, the mAs should be adjusted based upon 10 mAs: mAs1/mAs2 = grid factor 1/grid factor 2 10/x = 2 (5:1 grid ratio factor)/5 (12:1 grid factor) 50 = 2x x = 25 mAs The exposure time required to produce 25 mAs with 400 mA is determined: (mA) (s) = 25 mAs 400 (s) = 25 mAs s = 0.0625 s

When using three-phase power, what is the approximate equivalent increase in kVp compared to single-phase equipment? A. 300% B. 15% C. 12% D. 6%

Correct answer: (C) 12%. Explanation: Use of three-phase power is equivalent to an approximate 12% increase in kVp compared to single-phase equipment. In other words, when performing an examination on three-phase or high-frequency equipment, the kVp values used may be decreased 12 to 16%. Three-phase units produce 12% more x-rays than single-phase units. High frequency units produce approximately 16% more x-rays than a single-phase unit.

What is the approximate voltage ripple associated with a three-phase, twelve-pulse rectified generator? A. 100% B. 41% C. 3.5% D. 13%

Correct answer: (C) 3.5%. Explanation: Voltage ripple is the percentage drop from the maximum voltage during each pulse of current. In single-phase rectified equipment, there is an increase to the maximum voltage value and a decrease to zero potential in one half-cycle, using the entire waveform. Three-phase rectification produces nearly constant potential, with only small drops in maximum potential between pulses. A three-phase 12-pulse generator has an approximate 3.5% voltage ripple and a three-phase-six pulse generator has a voltage ripple of 13%.

How many half-value layers are required to reduce an x-ray beam with an intensity of 80 R/min to an intensity of 5 R/min? A. 2 B. 3 C. 4 D. 5

Correct answer: (C) 4. Explanation: The half value layer can be used to express the quality of the x-ray beam. It refers to the thickness of an absorber that will decrease the intensity of the beam to one-half of its original level. In this case, the first HVL will reduce the intensity of the beam to 40 R/min. The second HVL will reduce the intensity of the beam to 20 R/min. The third HVL will reduce the beam intensity to 10 R/min and the fourth will reduce the beam intensity to 5 R/min.

What is the minimum energy required for an incident electron to eject a K-shell electron from a tungsten atom? A. 90 keV B. 80 keV C. 70 keV D. 60 keV

Correct answer: (C) 70 keV. Explanation: X-rays are produced in two primary reactions as high-speed incident electrons interact with the tungsten target. Characteristic radiation is produced when a high-energy electron with an electric charge of at least 70 keV may eject an electron from the K-shell of the tungsten atom, leaving a vacancy. An electron with higher energy drops down to fill the vacancy, emitting the difference in energy as a K-characteristic ray. Characteristic radiation comprises about 15% of the primary beam. Bremsstrahlung radiation comprises the majority of x-ray photons produced at the tungsten target.

Which of the following settings will double the density of a radiograph that is originally produced at 90 kVp and 10 mAs? A. 108 kVp, 10 mAs B. 100 kVp, 15 mAs C. 90 kVp, 20 mAs D. 85 kVp, 20 mAs

Correct answer: (C) 90 kVp, 20 mAs. Explanation: Density is directly controlled by mAs, which controls the current through the x-ray tube and the number of x-rays produced at the anode. Although kVp has an effect on density, it is governed by the 15% rule.

Which of the following exposure timers uses an ionization chamber to terminate exposure? A. Synchronous B. Mechanical C. AEC D. Manual

Correct answer: (C) AEC. Explanation: An automatic exposure control timer uses an ionization chamber with radiolucent material located in front of the film. As x-rays pass through the cell, they ionize the cell and at a pre-set level of ionization, the exposure is terminated. Cells must be calibrated to a unique film/screen combination when installed. The body part that is in front of the cell determines the length of time for the preset ionization level to be reached.

Which of the following is not a function of the x-ray tube protective housing? A. Protection from electric shock B. Minimize radiation leakage C. Absorb heat inside the tube's glass envelope D. All of the above are functions of an x-ray tube housing.

Correct answer: (C) Absorb heat inside the tube's glass envelope. Explanation: X-rays are produced within the x-ray tube when high-speed electrons interact with a tungsten target, but if the electrons strike other surfaces, x-rays can be produced and emitted in other directions. X-ray tubes have a lead-lined protective housing that can absorb this leakage. Leakage radiation may not exceed 100 mR/h at a distance of 1 meter from the tube. The tube housing also protects users from electric shock, since high voltage electricity is required for production of x-rays. X-ray production also results in production of heat, which can damage the tube. To protect the tube from this heat, an oil coolant is placed around the tube to absorb heat produced within the tube.

Which of the following is not a source of electromagnetic radiation? A. X-ray B. Gamma-ray C. Alpha particle D. All of the above are sources of electromagnetic radiation

Correct answer: (C) Alpha particle. Explanation: There are two categories of ionizing radiation, electromagnetic and particulate. X-rays and gamma-rays are electromagnetic forms of radiation energy. Alpha and beta particles are particulate forms of ionizing radiation.

Which of the following is the primary advantage of a rotating anode over a stationary anode? A. Increased exposure B. Decreased patient dose C. Better heat dissipation D. Less scatter

Correct answer: (C) Better heat dissipation. Explanation: The anode consists of a positive electrode within the x-ray tube. It is made of a metal target, usually a tungsten-rhenium alloy, embedded in a disk or base of molybdenum. The anode must be able to tolerate extremely high levels of heat that result from x-ray production. They rotate from 3300 to 10,000 rpm, depending on the design of the tube. An induction motor located outside the x-ray tube turns a rotor with the target attached on the inside of the tube. The primary advantage of a rotating anode is greater heat dissipation. The x-ray machine should not be turned off until the target has stopped rotating.

What type of radiation is produced at the anode when outer electron shells drop to fill a vacancy in the K-shell, releasing the difference in binding energy? A. Bremsstrahlung B. Compton C. Characteristic D. Photoelectric

Correct answer: (C) Characteristic. Explanation: Characteristic radiation accounts for approximately 15% of the x-ray beam. It is produced through the photoelectric effect when an incident electron collides with the K shell electron of a target atom, removing the K shell electron from orbit and ionizing the atom. An electron from an outer shell drops down to fill the vacancy in the inner shell, giving off energy in form of an x-ray photon.

Which of the following can result from the delivery of large exposures to a cold anode? A. Rotor-bearing damage B. Increased tube output C. Cracked anode D. All of the above

Correct answer: (C) Cracked anode. Explanation: Excessive heat to a target can result in pitting or localized melting of the focal track, which can result in buildup of vaporized tungsten deposits on the glass envelope, resulting in a filtering effect and decreasing the tube output. If a large quantity of heat is applied to a cold anode, it can result in enough surface heat to crack the anode. Bearing damage results from elevated anode temperatures for prolonged periods, including during fluorscopy, and can also be caused by repeated overhead exposures without sufficient cooling time between exposures. Excess heat conducted to the rotor bearings can cause increased friction and tube failure.

An x-ray tube is which of the following? A. Cathode B. Anode C. Diode D. Generator

Correct answer: (C) Diode. Explanation: An x-ray tube is a vacuum tube that is a diode, with a cathode and anode. It controls electric current through a vacuum from a cathode filament that emits electrons and an anode that has a positive charge and collects electrons.

Which of the following is not a function of the anode in an x-ray tube? A. Energy conversion B. Thermal dissipation C. Electron production D. Electron target

Correct answer: (C) Electron production. Explanation: Electrons are produced at the cathode filament and travel through the tube to the anode, where they interact with a target to produce x-rays. The anode consists of a stator and rotor, focal track and focal spot, and a target of tungsten embedded in a molybdenum disk. The anode functions as a specific energy converter, producing radiation and heat from electrical energy. Since heat is an undesirable by product of conversion, the anode is constructed to dissipate heat.

Which of the following will not increase when mA is increased? A. Heat of the filament B. Number of electrons that strike the anode C. Focal spot size D. Number of electrons released from the filament

Correct answer: (C) Focal spot size. Explanation: mA (milliamperage) is a measure of the quantity of electrical current that flows through the circuit. It represents the number of electrons that pass through a wire in the circuit each second. The control for mA on the console is the rheostat in the filament circuit, which controls the intensity of the electron flow rate. A higher mA will heat the x-ray tube filament to greater temperatures, causing more electrons to boil off by thermionic emission. As the mA is increased, more electrons are released and a greater number of electrons are available to strike the anode. The size of a focal spot is a function of the size of the cathode and angulation of the anode surface.

What is the structure labeled #2 in the diagram below? A. Anode B. Filament C. Focusing cup D. Tungsten target

Correct answer: (C) Focusing cup. Explanation: The cathode is the negative end of the x-ray tube made up of the filament(s) and a focusing cup. The structure labeled #2 is the focusing cup, which is usually made of molybdenum. It provides heat to the cathode filament for production of electrons.

What is represented by the number 5 on the diagram of a simplified x-ray circuit pictured below? A. Rectifier B. Step down transformer C. High voltage step-up transformer D. Autotransformer

Correct answer: (C) High voltage transformer. Explanation: In the diagram above, the figure numbered 5 represents the high voltage step-up transformer, which is the transformer that increases the voltage to allow production of high-energy electrons. The autotransformer is labeled #3; the step-down transformer, located at #8, reduces the voltage to the filament and thereby increases the current. The rectifier is labeled #6. The rectifier directs the current in one direction only through the tube.

Which of the following refers to emission of a nuclear fragment after energy is absorbed by the nucleus? A. Photoelectric effect B. Classic scatter C. Photodisintegration D. Compton scatter

Correct answer: (C) Photodisintegration. Explanation: Photodisintegration refers to the collision of a high-energy photon with an atomic nucleus. In the process, the photon is completely absorbed, and a neutron, proton, or alpha particle is ejected from the excited nucleus. At least 10 MeV is required for photodisintegration, which is more energy than found in diagnostic radiology. The photoelectric effect refers to an interaction between an x-ray and an electron during which the x-ray transfers all of its energy to the electron, ejecting the electron from the atom. The Compton effect refers to the interaction of a photon with an electron during which part of the energy of the photon is transferred. The photon energy is reduced and it moves in a new direction after the interaction, creating scatter. Classic scatter refers to an interaction of a low-energy x-ray photon with an atom, resulting in transfer of energy from the photon to the electron. The electron is not ejected, but it vibrates, emitting energy equal to the energy of the original photon, traveling in a new path.

What type of exposure timer is used to accurately duplicate radiographic densities? A. Impulse B. Synchronous C. Phototimer D. Electronic

Correct answer: (C) Phototimer. Explanation: A phototimer terminates the exposure automatically when the correct densities have been recorded on the IR. It is used to accurately duplicate radiographic densities, which allow accurate comparison in follow-up studies and can help decrease patient dose by limiting the number of retakes due to improper exposure. The phototimer must be accurately positioned and centered by the radiographer in order to work correctly. Impulse timers allow shorter exposures with greater precision than the synchronous timer, an older type of timer. Electronic timers can be used for exposures as short as 0.001s.

Which of the following refers to x-rays that are emitted through the window? A. Scatter radiation B. Remnant radiation C. Primary beam D. Low energy

Correct answer: (C) Primary beam. Explanation: The x-rays that are emitted through the window of the x-ray tube make up the primary beam. Scatter radiation occurs when the x-ray interacts with the irradiated tissue. Remnant radiation is the radiation that strikes the image receptor after the primary beam has passed through the tissue. Remnant radiation produces the photographic image on radiographic film.

Three-phase equipment: A. Produces x-rays with greater ripple than single-phase waveform B. Produces lower average energy x-rays compared to single-phase equipment C. Produces a greater number of x-rays per mAs than single-phase equipment D. Produces a constant potential current

Correct answer: (C) Produces a greater number of x-rays per mAs than single-phase equipment. Explanation: Current from three-phase equipment is produced by superimposition of three individual alternating currents that are out of step with one another by 120 degrees. This produces NEARLY constant potential current. The voltage ripple of a waveform from three-phase equipment ranges between 4% and 13%. A greater number of x-rays per mAs are produced, resulting in higher average energy x-rays than single-phase equipment.

Which of the following refers to a substance through which electromagnetic waves can travel? A. Resistance B. Radiopaque C. Radiolucent D. Insulator

Correct answer: (C) Radiolucent. Explanation: A radiolucent material is one through which electromagnetic waves can travel. Resistance refers to anything that hinders or opposes the electric current flow of charge particles. Radiopaque materials are materials through which electromagnetic waves cannot travel. Insulators are materials that do not allow electron flow.

In the simplified diagram of an x-ray circuit, what is represented by the number 6? A. Autotransformer B. Timer circuit C. Rectification D. Filament step-down transformer

Correct answer: (C) Rectification. Explanation: The blue portion of this diagram represents the main x-ray circuit. The tan portion is the filament circuit. The figure labeled 1 is the main breaker, which provides alternating current to power the circuit. 2 represents the exposure switch. 3 represents the autotransformer. 4 is the timer circuit, which stops the exposure. 5 is the high-voltage step-up transformer, which bumps up the voltage to provide adequate energy within the tube for production of high-energy electrons. 6 represents the four-diode rectification circuit, which directs the current in one direction. The filament circuit variable resistor, 7, adjusts the current going to the filament. At 8, the filament step-down transformer, the voltage is stepped down and the current increases. At 9, x-rays are created. The rotor stator is labeled 10. It operates on the principle of electromagnetic induction and is connected to the rotor, which is inside the tube.

What device is used to test the accuracy of a timer on an x-ray circuit? A. Sensitometer B. Dosimeter C. Spinning top D. Penetrometer

Correct answer: (C) Spinning top. Explanation: The spinning top is used to test accuracy of the timer in single-phase equipment. It is a metal disk with a hole in the outer edge. It is placed on a pedestal approximately 6 inches high and an exposure is made while the top spins. A full-wave rectified unit produces 120 x-ray photon impulses per second, so the film should record 12 dots in 0.1 s if the timer is accurate. A synchronous spinning top or oscilloscope is used to test timers in three-phase equipment, since they produce near constant potential instead of pulsed radiation.

Which of the following terms describes a transformer that moves from 1500 windings to 500 windings? A. Step up transformer B. High voltage transformer C. Step down transformer D. Filament transformer

Correct answer: (C) Step down transformer. Explanation: A transformer is used to change voltage from one level to another. A step down transformer decreases voltage from the primary coil to the secondary coil and increases current in the same proportion. It has more turns in the primary coil than in the secondary coil. It is used in the filament portion of the x-ray circuit to increase the flow of current to the cathode. An autotransformer allows fluctuations in the mains input voltage to be corrected before the current is fed to the high tension transformer.

What type of transformer is used in the high-voltage section of an x-ray circuit A. Failing load B. Step-down C. Step-up D. Autotransformer

Correct answer: (C) Step-up. Explanation: A step-up transformer is a high-voltage transformer that consists of primary and secondary coils. It requires alternating current to operate. The primary coil of the step-up transformer receives voltage from the autotransformer. Operating on the principle of mutual induction, a magnetic field surrounds the primary coil and induces an electrical current in the secondary coil within the force field. The voltage in the primary coil is boosted to thousands of volts in the secondary coil. The step-up in voltage is determined by the ratio of turns of the wires in the primary and secondary coils. This is the turn ratio, and as it increases, the resulting kilovoltage increases. The turns ratio can range between 500 and 1000, depending upon the machine.

Which of the following exposure timers operates based on the frequency of the alternating current supplied to the imaging system? A. Manual B. AEC C. Synchronous D. Phototimer

Correct answer: (C) Synchronous. Explanation: The synchronous timer consists of an electric motor that rotates at a constant speed determined by the frequency of the electrical current delivered to the timer. There are several types of manual timers, including electronic timers and mAs timers. A phototimer operates by measurement of the actual radiation exposure to the patient, which is transmitted to a film and measured, then used to terminate the exposure. Automatic exposure control timers typically use an ionization chamber to measure ionization as radiation passes through. At a predetermined level of ionization, the exposure is terminated.

When evaluating the adequacy of a chest radiograph, which of the following is true? A. There should be 8 posterior ribs visible. B. There should be ten anterior ribs visible. C. The distance between the vertebral processes and clavicle should be equidistant on both sides. D. You should be able to see the thoracic spine and its processes clearly through the heart.

Correct answer: (C) The distance between the vertebral processes and clavicle should be equidistant on both sides. Explanation: When evaluating the adequacy of a chest x-ray, penetration, inspiration, rotation, and angulation should be evaluated. Rotation is evaluated by comparing the distance between the vertebral processes and the ends of the clavicles, which should be equidistant on both sides. Inspiration is excellent if 10 posterior ribs are visible. Posterior ribs are the more visible ribs on a chest x-ray, and they appear almost horizontal, in contrast to the 45 degree angle of the anterior ribs. When determining if the radiograph has adequate penetration, the thoracic spine should just be seen through the heart.

What is the process of heating the cathode filament to boil off electrons? A. Bremsstrahlung interaction B. Characteristic interaction C. Thermionic emission D. Photoelectric effect

Correct answer: (C) Thermionic emission. Explanation: In preparation for production of x-rays, electrons are boiled off the cathode filaments of the x-ray tube as it is heated, known as thermionic emission. Two primary types of interaction produce x-rays as the incident electrons interact with tungsten atoms at the target (anode.) Bremsstrahlung radiation refers to the process by which energy is released when a projectile electron moves close to the nucleus and slows down, reducing the kinetic energy of the electron. The difference in energy is released as an x-ray photon. Characteristic radiation is produced when an incident electron collides with an inner shell electron of a target atom, removing the inner shell electron from the orbit. An outer shell electron falls in to the vacant spot, releasing the difference in binding energy in the form of an x-ray photon. The photoelectric effect refers to the interaction of an x-ray with tissue.

Which of the following is added to tungsten to increase the efficiency of the filament? A. Copper B. Cesium C. Thorium D. Lead

Correct answer: (C) Thorium. Explanation: Thorium is added to the cathode tungsten filament to increase efficiency and reduce vaporization, which can result in tube failure. Electrical resistance to the flow of electrons heats the filament to very high temperatures, resulting in thermionic emission.

After replacement of a grid, which of the following grid errors will result in normal exposure in the center with decreased exposure on the sides of the image receptor? A. Off-level B. Grid-focus decentering C. Upside down D. Lateral decentering

Correct answer: (C) Upside down. Explanation: Grids are used to reduce the amount of scatter radiation that reaches the image receptor. Scatter radiation is more likely to be absorbed in a grid as it travels in divergent paths compared to the image producing x-rays. Grids are usually used when the part thickness is 10 cm or greater or when the radiographer is using greater than 60 kVp. Grid errors can result when a grid is removed and replaced incorrectly. A focused grid should be placed with the labeled tube side facing the x-ray tube or an upside down grid error can result, characterized by normal exposure to the middle of the image receptor with decreased exposure on the sides. If the grid is not perpendicular to the central ray, an off-level error may be see. This is caused by the absorption of image-forming x-rays across the radiographic field with cutoff, or decreased exposure over the entire image receptor. Lateral decentering results in decreased exposure that is more noticeable on one side of the image receptor. Grid focus decentering refers to an error that results from a violation of the grid radius (grid focus) when using a focused grid, resulting in normal exposure in the middle of the image receptor and cutoff on all sides. The grid radius error is much less pronounced.

Which of the following directly affects the quality of x-rays produced? A. OID B. mAs C. kVp D. SID

Correct answer: (C) kVp. Explanation: The kVp directly controls the energy or quality of x-rays that are produces, as a greater potential difference exists between the cathode and anode with an increase in kVp. The increase in potential difference will cause electrons from the cathode to strike the anode with greater energy and in greater quantities, resulting in increased short-wavelength radiation that is high energy. kVp also has a direct effect on density that is governed by the 15% rule and is not directly proportional. The mAs controls the amount of radiation that exits the x-ray tube. There is a directly proportional relationship, so that an increase in mAs is reflected by the same amount of increase in number of x-rays exiting the x-ray tube. The OID and SID are not related to production of x-rays. The SID has an effect on density through the inverse square law.

A good quality x-ray is made without a grid using a 60-inch SID and 8 mAs. If the distance is changed to 40 inches and a 12:1 grid is used, what should the new milliamperage-seconds value be to achieve the same exposure? A. 7.0 mAs B. 10.5 mAs C. 14 mAs D. 18 mAs

Correct answer: (D) 18 mAs. Explanation: Using the inverse square law of radiation, the exposure rate increases as the distance between the radiation source and the IR decreases. The initial step is determination of the decrease in technical factors to compensate for the change in distance, so the density-maintenance formula is used to determine the new mAs value when changing the SID: mAs1/mAs2 = (D1)2/(D2)2 Using the given values: 8/x = 3600/1600 x = 3.6 (mAs) at 40 inch SID. To compensate for the addition of the 12:1 grid, this must be multiplied by the grid ratio factor of 5. The mAs required to produce an image of similar density to the original radiograph is 18 mAs.

Exposure factors of 70 kVp and 8 mAs are used with a 5:1 grid ratio. What should be the new milliamperage-seconds value if the grid ratio is changed to a 12:1 grid? A. 10 mAs B. 12 mAs C. 16 mAs D. 20 mAs E. 24 mAs

Correct answer: (D) 20 mAs. Explanation: To adjust exposure when changing from one grid ratio to another, the grid ratio conversion factors are: No grid = 1 x original mAs 5:1 grid = 2 x original mAs 6:1 grid = 3 x original mAs 8:1 grid = 4 x original mAs 12:1 grid = 5 x original mAs 16:1 grid = 6 x original mAs The formula for grid conversion is: mAs1/mAs2 = grid factor1/grid factor2 When substituting the quantities above: 8/x= 2/5 x = 20

What is the melting point of tungsten? A. 2540 degrees C B. 5000 degrees C C. 1720 degrees C D. 3370 degrees C

Correct answer: (D) 3370 degrees C. Explanation: Tungsten has a high atomic number and high melting point of 3370 degrees C with a low rate of evaporation. Tungsten is used as the anode target in x-ray production because it has a high melting point that allows it to tolerate the extremely high levels of heat that occur. The target of the anode is usually made of a tungsten-rhenium alloy embedded in a disk or base of molybdenum. Tungsten filaments are used in the cathode because of their high melting point, often with a small amount of thorium added to reduce vaporization.

If an exposure is made using 70 kVp and 8 mAs without a grid, what should the milliampere-seconds value be to reproduce the image using a 12:1 grid? A. 16 mAs B. 18 mAs C. 20 mAs D. 40 mAs

Correct answer: (D) 40 mAs. Explanation: To adjust exposure when changing from one grid ratio to anther, the grid ratio conversion factors are: No grid = 1 x original mAs 5:1 grid = 2 x original mAs 6:1 grid = 3 x original mAs 8:1 grid = 4 x original mAs 12:1 grid = 5 x original mAs 16:1 grid = 6 x original mAs The formula for grid conversion is: mAs1/mAs2 = grid factor1/grid factor2 When substituting the quantities above: 8/x= 1/5 x = 40

Which of the following is a disadvantage of a moving grid compared to a stationary grid? A. Increased patient dose B. Unable to use short exposure times C. Phantom images result when the part has parallel motion to the grid. D. A and B E. B and C F. All of the above are disadvantages of the moving grid.

Correct answer: (D) A and B. Explanation: Moving grids have several disadvantages. Lateral decentering occurs when the CR is not centered to the moving grid, resulting in diminished density. An increase in exposure is required to compensate. Moving grid mechanisms do not allow rapid oscillation required for short exposures, which are useful to reduce motion artifact. This contributes to increased patient dose. Moving grids are also also costly.

The autotransformer supplies power to which of the following? A. High voltage circuit B. Filament circuit C. Operating console D. A and B E. All of the above

Correct answer: (D) A and B. Explanation: The autotransformer operates on the principle of self-induction. It is used in a diagnostic x-ray unit to supply the two basic circuits: the step up transformer supplies high voltage to the x-ray tube and the other circuit contains a step-down transformer to heat the filament of the x-ray tube.

Which of the following is true when addressing exposure reproducibility in a quality assurance program? A. The kVp, mA, and time are tested in successive exposures. B. Variation in measured radiation intensity should not be more than 5%. C. Adjacent mA stations should be within 10% of one another. D. A and B E. B and C F. All of the above

Correct answer: (D) A and B. Explanation: When measuring exposure reproducibility as part of quality control of x-ray producing equipment, the kVp, mA, and time are tested in successive exposures, and variation in measured radiation intensity should not be greater than 5%. Option C relates to linearity, not reproducibility. Exposure linearity tests various mA-time combinations for a given mAs and adjacent mA stations should be within 10% of one another.

Which of the following factors affect the quality of an x-ray beam? A. kVp B. Filtration C. mAs D. A and B E. All of the above

Correct answer: (D) A and B. Explanation: mAs affects quantity of x-ray photons but does not affect quality of an x-ray beam. kVp has a greater effect on quality of the beam but also affects quantity. Filtration affects both quantity and quality of the beam.

Which of the following can be used to reduce the quantity of scattered radiation that reaches the IR? A. Air gap B. Stationary grid C. Use of a fast imaging system D. A and B E. B and C F. All of the above

Correct answer: (D) A and B. Air gap and stationary grid. Explanation: Collimation is the most important method for reduction of scattered radiation, which results in unwanted densities on the x-ray image. Optimal kilovoltage and compression are also useful, but scattered radiation continues to be generated within the imaged part. Air gaps introduced between the object and the IR may allow the scattered x-ray photons to avoid the IR. When using an air gap, the magnification will be increased, so the SID should often be increased to compensate. A grid can absorb a large percentage of that radiation before it reaches the IR. Grids are composed of alternating strips of lead and radiolucent spacers. The x-rays that are traveling in the same direction as the primary beam pass between the lead strips, but the scattered radiation travels in a variety of directions and is absorbed by the lead strips.

Which of the following does not contribute to radiographic contrast in an x-ray image? A. Pathology B. Muscle development C. Ascites D. All of the above contribute to radiographic contrast

Correct answer: (D) All of the above contribute to radiographic contrast. Explanation: Different types of tissue possess different densities, which results in variations in the absorption and attenuation of photons, known as differential absorption. This contributes to the scale of radiographic contrast on the finished image. Pathologic conditions can change the density of a tissue by destruction or addition. Muscle variations, including atrophy or hypertrophy, will decrease or increase tissue density. Abnormal fluid accumulations such as ascites increase the tissue density.

Which of the following describes the result of edge enhancement? A. Reversal of gray scale at the edge of an image B. Artificial increase in recorded detail at an edge of an image C. Artificial increase in spatial resolution at an image edge D. Artificial increase in the visibility at an image edge

Correct answer: (D) Artificial increase in the visibility at an image edge. Explanation: There are various post-processing steps to improve a radiographic image. Edge enhancement refers to improving the visibility of small high-contrast areas. Black/white reversal is reversal of the gray scale in the image. Changes in recorded detail in a radiographic image are dependent on OID, film screen speed, angle of the central ray, and focal spot size.

Which of the following devices used in an x-ray circuit operates on the principle of mutual induction? A. Autotransformer B. High-voltage transformer C. Filament transformer D. B and C E. A and C F. All of the above

Correct answer: (D) B and C. Explanation: The autotransformer operates on the principle of self -induction, but the filament and high-voltage transformers operate on mutual induction. Mutual induction refers to the production of current in a neighboring circuit as a result of current in the initial circuit. Mutual induction occurs when current is supplied to one of two coils located in close proximity. The magnetic field that is associated with the first coil interacts with the turns of the second coil and induces electromotive force in the second coil.

In which of the following devices is a photostimulable phosphor plate used? A. Radiographic intensifying screen B. Fluoroscopic intensifying screen C. Image intensified fluoroscopy D. Computed radiography

Correct answer: (D) Computed radiography. Explanation: In computed radiography, the image receptor is an imaging plate (IP) that is made of a photostimulable phosphor (PSP) applied to a semi-rigid support layer. The PSP is struck by the remnant rays exiting the patient, which transfer their energy to electrons in the phosphors. This places the electrons in a higher-level conductive layer, where they remain trapped until they are placed in the reader. The reader unit removes the IP from the cassette and a laser beam scans the PSPs, allowing electrons to relax into lower energy levels within the PSPs. Blue light is emitted as the electrons relax into lower energy levels. This blue light energy is then amplified by a photomultiplier and converted from analog to digital form. It is then sent to the computer for processing and can be viewed on a computer monitor.

What is the function of the input phosphor of the image intensifier tube? A. Conversion of electrons to light energy B. Conversion of kinetic energy to light C. Conversion of fluorescent light to electrons D. Conversion of x-rays to light

Correct answer: (D) Conversion of x-rays to light. Explanation: Remnant radiation that emerges from the patient is converted into a fluorescent light image by the input phosphor of the image intensifier. The photocathode is separated by a thin transparent layer from the input phosphor and it converts the fluorescent light image into an electron image that is focused by electrostatic lenses to the output phosphor.

Which of the following conditions will necessitate increased penetration or x-ray photon energy? A. Pneumothorax B. Emphysema C. Osteolytic metastases D. Edema

Correct answer: (D) Edema. Explanation: Penetration of a body part depends upon the density of the tissue. Certain pathologic conditions, known as additive conditions, increase tissue density and decrease the penetrability of x-rays. Edema is characterized by abnormal amounts of fluid collection in tissue and it decreases the penetrability, requiring increased x-ray photon energy for penetration. Pneumothorax, emphysema, and osteolytic metastases all decrease tissue density.

What is the purpose of a compensating filter? A. Elimination of scattered radiation B. Improving fluoroscopic imaging C. Absorption of low energy radiation that contributes to the patient dose without improving the image D. Even out the varying tissue densities

Correct answer: (D) Even out the varying tissue densities. Explanation: When there are a variety of tissue densities present in the part being radiographed, the lower density parts may become overexposed compared to the parts with greater density. As a result, a compensating filter is used to shield the areas of low density and the radiograph is performed using exposure factors set for the higher density structures. A compensating filter in chest radiography is thicker over the lung portion but the photons are allowed to pass easily to the mediastinum, which has a much greater density. Inherent and added filters absorb the low energy radiation that is not useful for the image production but that adds to the patient dose.

Which of the following receives remnant beam, converting it into light, then increasing the brightness of the light? A. Spot-film camera B. Output phosphor C. Monitor D. Image intensifier

Correct answer: (D) Image intensifier. Explanation: Remnant radiation that emerges from the patient is converted into a fluorescent light image by the input phosphor of the image intensifier. The photocathode is separated by a thin transparent layer from the input phosphor and it converts the fluorescent light image into an electron image that is focused by electrostatic lenses through the accelerating anode to the output phosphor, where it is converted back to light. The image from the output phosphor is displayed by a TV monitor.

Which of the following terms refers to the filtering effect that is due to the glass envelope of the x-ray tube and its oil coolant? A. Added filtration B. Compensating filtration C. Port filtration D. Inherent filtration

Correct answer: (D) Inherent filtration. Explanation: Filtration removes low-energy photons from the x-ray beam, since they do not contribute to the image but contribute to the skin dose. The glass envelope of the x-ray tube and the surrounding oil coolant comprise the inherent filtration of the x-ray tube, since these elements are a permanent part of the tube. They provide 0.5 to 1.0 AI equivalent filtration. Total filtration is the sum of inherent and added filtration.

Which of the following is not a type of exposure timer? A. Synchronous B. Electronic C. AEC D. Intermittent

Correct answer: (D) Intermittent. Explanation: The five types of exposure timers are manual, mechanical, synchronous, AEC, and electronic. Timers are wired in the circuit between the autotransformer and the high-voltage transformer. There are three types of manual timers: synchronous, electronic, and mAs timers. Synchronous timers are manual timers that use a synchronous motor that turns a shaft at 60 rps. The mAs timer measures the total tube current and is used with falling load generators. Electronic timers are controlled by microprocessors and are contained in most radiographic equipment. They allow exposure times of 0.001 second. An automatic exposure control, a timer used to provide consistency of radiographic quality, consists of a flat ionization chamber located between the patient and the IR.

What is the structure that is labeled X in the diagram below? A. Anode B. Cathode filament C. Focusing cup D. Rotor

Correct answer: (D) Rotor. Explanation: A rotating anode provides greater surface area for efficient heat dissipation. It operates on the principle of mutual induction. The rotating anode assembly includes a stator, which is a series of electromagnets that are spaced equally around the neck of the tube, outside the tube. The rotor is within the glass tube and turns the anode.

Which of the following changes in contrast occurs with use of beam restriction? A. Longer scale of contrast B. Decreased contrast C. No effect on contrast D. Shorter scale of contrast

Correct answer: (D) Shorter scale of contrast. Explanation: The use of beam restriction increases contrast, producing a shorter scale of greys. This effect occurs as the amount of irradiated tissue decreases, decreasing the number of scatter events.

The waveform associated with the highest percentage voltage ripple is: A. High frequency B. Three-phase 12-pulse C. Three-phase 6-pulse D. Single phase

Correct answer: (D) Single phase. Explanation: A single-phase current has a 100% drop in voltage between peak voltages. The lowest percentage voltage ripple occurs with high-frequency waveforms consisting of almost constant potential, which have less than 1% voltage ripple. The voltage drop between peak voltages is about 4% with a three-phase 12-peak waveform. A three-phase six-pulse waveform has an approximate drop of about 13% of voltage between peak voltages.

Which of the following describes the line-focus principle? A. X-rays travel to a distant focal point. B. X-rays travel in straight lines. C. The projected focal spot is larger than the actual focal spot. D. The projected focal spot is smaller than the actual focal spot.

Correct answer: (D) The projected focal spot is smaller than the actual focal spot. Explanation: The actual focal spot is the area on the tungsten target that is bombarded with electrons from the cathode filament. The effective focal spot refers to the foreshortening of the focus as it is projected down towards the IR. This is also known as line focusing. When a focal spot size is quoted, it refers to the projected (or effective) focal spot.

What is the artifact shown on the radiograph below? A. Grid cutoff B. Quantum mottle C. Double exposure D. Upside down cassette

Correct answer: (D) Upside down cassette. Explanation: An upside down cassette or panel causes the artifact seen in the figure above. Upside down cassette artifacts are white and focal. Springs or latches on the back of the cassette block the x-ray beam to cause the artifact. The lead backing absorbs some x-ray photons, resulting in an underexposed appearance. Grid cutoff results in artifacts that occur when x-ray photons are absorbed in the lead strips of an improperly aligned grid. Double exposure artifacts can usually be recognized by close observation of two sets of the same body part forming an appearance of 2 summated images. Quantum mottle is a noisy artifact that affects the entire image, resulting in a grainy appearance, poor contrast, and decreased sharpness.

Which of the following characterizes tomography? A. Visualization of structures is enhanced in the area of interest by blurring adjacent structures. B. A plane is visualized at the pivot point of the x-ray tube and film. C. The x-ray tube and film move in the same direction. D. Lower patient doses are possible. E. A and B are characteristic of tomography. F. A, B and C are characteristic of tomography. G. All of the above are characteristic of tomography.

Correct answer: (E) A and B are characteristic of tomography. Explanation: Tomography allows enhanced visualization of structures in the area of interest by blurring the adjacent structures. The x-ray tube and film move in opposite directions and a plane of interest is visualized at the pivot point of the x-ray tube and the film. The exposure time must be long enough to allow exposure throughout the tube and tomography has a high patient dose as a consequence.

Which of the following will increase the effective energy of an x-ray beam hitting an IR? A. Kilovoltage B. Milliamperage C. Filtration D. A and B E. A and C F. All of the above

Correct answer: (E) A and C. Explanation: Kilovoltage increases have a direct effect on the quality of x-rays in a beam. As the kilovoltage increases, there are more high-energy photons produced, increasing the average energy of the beam. Filtration removes low-energy photons, increasing the overall energy of the beam. Milliamperage changes the quantity of photons produced at the target but it is unrelated to the quality of x-ray photons produced.

Which of the following is most likely to be associated with the x-ray tube in a computed tomographic imaging system? A. Pulsed x-ray beam B. Low-speed anode rotation C. High production of heat units D. A and B E. A and C F. All of the above

Correct answer: (E) A and C. Explanation: The x-ray tube in a CT (computed tomographic) imaging system is most likely to be associated with high-speed anode rotation, high production of heat units, and a pulsed x-ray beam.

Which of the following is a part of the standard x-ray imaging system? A. Operating console B. X-ray tube C. High voltage generator D. A and B E. All of the above

Correct answer: (E) All of the above. Explanation: The components of an x-ray imaging system include a control console, located behind a lead barrier and operated by a technologist; an x-ray tube; and a high voltage generator, which converts low energy to high energy that is necessary for x-ray production. The x-ray control console has settings to adjust the kVp, mAs, an AEC, a rotor switch, and an exposure switch. The exposure switch may be single or dual. The x-ray tube is covered in lead lined protective housing. It contains a Pyrex glass or metal envelope that maintains a vacuum to increase the efficiency of x-ray production. The x-ray tube is a diode. Primary components of the cathode are the focusing cup and filament. Electrons generated by the cathode interact with the tungsten target of the anode to produce x-radiation. The x-ray beam exits the window.

Which of the following is associated with changes in the brightness of a fluoroscopic image? A. Changes in milliamperage B. Patient thickness C. Changes in kilovoltage D. A and C E. All of the above

Correct answer: (E) All of the above. Explanation: Changes in milliamperage and kilovoltage have a similar effect on fluoroscopic images as they do on traditional x-ray images. Increases in patient thickness or the density of the anatomic part that is being studied will diminish the brightness of the image.

Which of the following terms refers to the intensity of radiation that reaches the IR in electronic imaging? A. Field of view B. Exposure index C. Sensitivity number D. A and B E. B and C

Correct answer: (E) B and C. Explanation: Computed radiography (CR) systems provide an exposure indicator, known as a sensitivity number (S), exposure index (SI), or relative exposure index. Most manufacturers provide a chart that identifies the acceptable range of exposure indicator numbers for various types of examinations. A high S number is frequently associated with underexposure and a high EI number is often related to overexposure. Although CR offers wide latitude and automatic optimization of radiologic images, particularly useful in trauma and mobile radiography, patient dose is an important consideration. When automatic exposure control (AEC) is not used, CR provides compensation for 80% underexposure and 500% overexposure. Overexposure can increase the patient dose, while underexposure results in a poorer image quality. Field of view refers to the anatomic region that is being imaged.

Total brightness gain of the image intensifier results from which of the following? A. Focusing gain B. Flux gain C. Minification gain D. A and B E. B and C F. All of the above

Correct answer: (E) B and C. Explanation: Image intensifiers produce a brightness gain of 5,000 to 20,000 as a result of the minification gain and flux gain. The electron image is accelerated at high voltage (approximately 25 kV) to the output phosphor. Minification gain occurs as a result of the small size of the output phosphor relative to the input phosphor. The flux gain is the ratio of the number of x-ray photons at the input phosphor compared to the number of light photons at the output phosphor. The total brightness gain is the product of these two.

Which of the following is true of quality assurance requirements for filtration-beam quality? A. It is tested using a slit camera. B. Checked with a digital dosimeter. C. Adjacent mA stations should be within 10% of each other. D. A and C are true. E. B and C are true.

Correct answer: (E) Both B and C are true. Explanation: Filtration-beam quality is tested using a digital dosimeter. Half-value layer measurement is required. The effective focal-spot size is measured using a slit camera, pinhole camera, or star test pattern and should be within 50% of the size stated in equipment specifications. The exposure linearity is tested with a digital dosimeter using various mA-time combinations for a given mAs. Adjacent mA stations should be within 10% of one another.

Which of the following is not a property of a photon? A. Frequency B. Velocity C. Wavelength D. Amplitude E. Voltage

Correct answer: (E) Voltage. Explanation: The photon is the smallest amount of any type of electromagnetic radiation and has properties of both a wave and a particle. The properties of a photon include frequency, velocity, wavelength, and amplitude. Photons travel at the speed of light. They are electrically neutral and have no mass, but they have energy.

Which of the following factors do not affect the quantity of x-rays that reach the patient? A. kVp B. mAs C. Distance D. Filtration E. A, B and C F. None of the above choices are correct, since all of the above affect the quantity of x-rays that reach the patient.

Correct answer: (F) All of the above affect the quantity of x-rays that reach the patient. Explanation: All of the factors listed affect the quantity of radiation. (A) kVp affects both the quantity and quality of x-rays in the primary beam. (B) A change in mA or mAs means a change in the amplitude or quantity (exposure rate) of the X-ray emission spectrum at all energies. It does not affect quality of the beam. (C) Filtration consists of both inherent filtration and added filtration. Filtration reduces the intensity of the x-ray beam (quantity) and improves the quality of the x-ray beam. (D) Distance affects the exposure of the image receptor according to the inverse square law. Although it affects intensity of the beam, it has no effect on the quality of the radiation.

When using an x-ray tube rating chart, which of the following is needed to determine the maximum safe kilovoltage? A. Focal spot size B. Exposure time C. Milliamperage D. A and B E. B and C F. All of the above are needed

Correct answer: (F) All of the above are needed. Explanation: A radiographic rating chart allows the radiographer to determine the maximum safe kilovoltage for a particular exposure, based on the milliamperage and exposure time. The heat load that an anode can accept safely varies with the type of rectification and the size of the focal spot, so these variables must also be considered to determine the maximum safe kilovoltage for a particular exposure

The brightness of a fluoroscopic image varies with all of the following except: A. mA B. kVp C. Patient thickness D. A and B E. B and C F. All of the above can cause variations in brightness of a fluoroscopic image.

Correct answer: (F) All of the above can cause variations in brightness of a fluoroscopic image. Explanation: Early fluoroscopic procedures resulted in low intensity visual images. The image intensifier has been used since the 1950's to intercept x-ray photons and convert them to visible light photons and to amplify this light signal. The image intensifier in a modern fluoroscopy system is opposite the x-ray tube and consists of a cylindrical protective case with an input window to the vacuum, which allows x-ray photons to penetrate the case where they are absorbed by the input phosphor and converted to optical photons, a process known as luminescence. The optical photons are converted at the photocathode into photoelectrons, which are then accelerated by the electric field that is produced by strong electric potential difference in the image intensifier. These photoelectrons are collected at the output phosphor, where optical photons are produced from accelerated electrons. The brightness of the fluoroscopic image varies with the mA, kVp, and thickness of the patient.

Which of the following affects the patient dose during fluoroscopy? A. Tissue density B. Magnification C. Distance between the patient and the input phosphor D. A and B E. B and C F. All of the above

Correct answer: (F) All of the above. Explanation: As tissue density increases, a greater exposure dose is required to produce a quality image. As the image intensifier is moved closer to the patient during fluoroscopy, the SID and patient dose are both decreased. The intensity of the x-ray photons at the input phosphor of the image intensifier increases, which results in automatic decreases in milliamperage by the automatic brightness control, reducing the patient dose. The magnification decreases as the OID decreases when image intensifier is moved closer to the patient during fluoroscopy.

Off-focus radiation results in which of the following? A. Increased patient dose B. Expanded focal spot size C. Reduced image contrast D. A and B E. B and C F. All of the above

Correct answer: (F) All of the above. Explanation: Off-focus radiation extends the focal spot size, reduces image contrast, and results in a modest increase in the skin dose. Off focus radiation refers to electrons that bounce off of the focal spot. They strike other areas of the target, causing x-rays to be produced outside of the focal spot.

Which of the following has an effect on the blur or geometric unsharpness? A. Distance between the source and object B. Distance between the source and the image C. Distance between the object and the image D. A and B E. B and C F. All of the above

Correct answer: (F) All of the above. Explanation: The distance between the source and the object and the SID are both inversely proportional to magnification. The OID is directly proportional to magnification, which increases with an increase in the OID. Geometric unsharpness is affected by changes in any of these factors.

Which of the following contributes to radiographic contrast? A. Milliamperage-seconds values B. Differing tissue densities C. Secondary scatter D. A and B E. B and C F. All of the above

Correct answer: E. Differing tissue densities and secondary scatter Explanation: The degree of difference between adjacent densities is the radiographic contrast and represents difference sin the properties of absorption between adjacent tissues. Milliamperage-seconds does not regulate contrast. It is regulated by the kilovoltage. Wavelength of the primary radiation and secondary scatter are characteristics of x-rays that contribute to contrast.

Which of the following is increased with a step-down transformer? A. Current B. Voltage C. Resistance D. Teslas

Correct answer: (A) Current. Explanation: A step-down transformer produces a decrease in voltage and increase in current. It is used to reduce the voltage at the filament. A step-up transformer produces an increase in voltage and decrease in current. It supplies high voltage to the x-ray tube. Resistance refers to impedance to the flow of electricity in a circuit. Teslas are a unit of magnetic flux density.

Which of the following will result from an increase in tube current? A. Increased x-ray photon quantity B. Increased x-ray photon quality C. Decreased x-ray photon quantity D. Decreased x-ray photon quality

Correct answer: (A) Increased x-ray photon quantity. Explanation: The current in the x-ray tube is represented in mAs. mAs affects only quantity, not quality of x-rays produced.

Which of the following cannot be used to couple the output phosphor with the Vidicon TV camera or charge-coupled device? A. Image distributor B. Closed circuit TV C. Fiber optics D. All of the above can be used to couple the output phosphor and Vidicon TV.

Correct answer: (B) Closed circuit TV. Explanation: The image intensifier's output phosphor displays a bright, small, inverted image. This image is transmitted to its destination by an image distributor, which can be a series of lenses and mirrors, or by fiber optics. The image distributor sends the majority of light to the TV for direct viewing and approximately 10% is sent to the IR.

If you use a center photocell instead of the lateral photocells when making a PA chest projection, what will result? A. Underexposure B. Overexposure C. Motion artifact D. Fog

Correct answer: (B) Overexposure. Explanation: The radiograph would be overexposed. When using automatic exposure devices, accurate selection and positioning of the photocell is essential. In this case, the AEC will stay on too long and the lungs will be overexposed.

Which of the following parts is labeled b on the x-ray image intensifier diagram pictured below? A. Scintillator crystal B. Fluorescent screen C. Photocathode D. Anode

Correct answer: (C) Photocathode. Explanation: B represents the photocathode. Incident light energy on the photocathode releases electrons in proportion to the x-ray intensity. A represents the scintillator crystal(s)/fluorescent screen that converts x-ray photons into light photons. D represents a fluorescent screen that converts the kinetic energy of the incident electrons into light photons. C represents electrostatic focusing lenses with a negative charge that accelerate the electrons toward their positive charge. They are positioned to focus the electrons to form an image.

Which of the following is used to allow the continuous rotation of the x-ray tube and simultaneous movement of the patient couch? A. Multiple detector arrays B. Electron beam CT C. Slip ring technology D. Cable array

Correct answer: (C) Slip ring technology. Explanation: Helical CT or spiral CT scanning refers to sixth generation CT scanning that allows the acquisition of volume multislice scanning using slip ring technology that allows continuous rotation of the x-ray tube using cables with simultaneous couch movement. Helical multislice scanners have up to 60 rows of detectors and can obtain uninterrupted data of 128 slices per rotation of the tube, providing 3D multiplanar reformation (MPR). Electron beam technology refers to fifth generation CT scanning.

Which of the following is not a function of a picture archiving and communication system (PACS)? A. Acquisition of digital images B. Storage of digital images C. Storage of analog images D. All of the above are functions of a PACS

Correct answer: (C) Storage of analog images. Explanation: A PACS is a picture archiving and communication system that receives digital images and displays them on monitors for interpretation. These systems allow storage and later retrieval of images, but analog images must be digitized to be received to a PACS system.

Which of the following materials is used to make the component labeled B in the diagram below (x-ray tube)? A. Cesium B. Molybdenum C. Tungsten D. Lead

Correct answer: (C) Tungsten. Explanation: The structure labeled B is the tungsten target for the electrons generated at the cathode end of the x-ray tube. It is usually made of a tungsten-rhenium alloy, which has a high melting point and atomic number. The target is embedded in a disk or base of molybdenum with a motor that rotates the target.

Compared to a rotating anode, how much area does a stationary anode provide for interaction with an electron beam? A. 10 x as much B. 1/10 C. 1/100 D. 1/1000

Correct answer: (D) 1/1000. Explanation: A rotating anode provides 1000 x the area for interaction with an electron beam compared to a stationary anode. As a result, dissipation of heat, the unwanted byproduct of x-ray production, is more efficient with a rotating anode.

Which of the following controls the path of electron flow from the photocathode to the output phosphor to maintain image clarity? A. The input phosphor B. The vacuum glass envelope C. The accelerating anode D. Electrostatic lenses

Correct answer: (D) Electrostatic lenses. Explanation: An image intensifier receives remnant radiation from the patient at the input phosphor and converts it to a fluorescent light image. The photocathode, made of a photoemissive alloy, is located adjacent to the input phosphor. The photocathode is usually made of cesium and antimony. The fluorescent light image is converted into an electron image when it strikes the photocathode. The electrons are focused by electrostatic focusing lenses through the accelerating anode to the output phosphor, where they are converted back to light.

Which of the following is the number of x-rays that pass a given point per a unit of time? A. Amplitude B. Wavelength C. Strength D. Frequency

Correct answer: (D) Frequency. Explanation: X-rays are part of the electromagnetic radiation spectrum and have characteristics of both waves and particles. They travel in straight lines as waves. A wavelength is the distance covered by one complete sine wave. Frequency, also called wave frequency, is a measurement of the total number of vibrations or oscillations made within a certain amount of time. This is equivalent to the number of waves that pass a given point per unit time. Electromagnetic radiation is transmitted in waves or particles at different wavelengths and frequencies. Wavelength and frequency are inversely proportional to one another. Short-wavelength rays are more penetrating and long-wavelength rays are less penetrating.

Which of the following convert AC power into DC power? A. Autotransformer B. Step-up transformer C. Step-down transformer D. Rectifier

Correct answer: (D) Rectifier. Explanation: Rectification is the process by which AC power (alternating current) is converted to DC power (direct current.) Although transformers require alternating current, the x-ray tube can only operate on direct current. Direct current refers to the flow of electrons in one direction only, but they oscillate in direction in alternating current.

Which of the following factors does not influence the resistance of a conductor? A. Cross sectional area B. Length C. Temperature D. Voltage

Correct answer: (D) Voltage. Explanation: Voltage is not a property of the conductor and does not influence the resistance of the conductor. The four factors that influence the resistance of a conductor are cross-sectional area, material type, length, and temperature.