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120 terms

Equipment Operation and Quality Control

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All of the following are associated with the anode...
-the focal track
-the heel effect
-the line focus principle
The type of x-ray tube designed to turn on and off rapidly, providing multiple short, precise exposures, is
grid-controlled
typical examples of digital imaging include
-MRI
-CT
-CR
Component parts of a CT gantry include
-high voltage generator
-multidetector array
-x-ray tube
Which of the following circuit devices operate(s) on the principle of self-induction?
-autotransformer
-choke coil
If exposure factors of 85 kV, 400 mA, and 12 ms yield an output exposure of 150 mR, what is the milliroentgens per millampereseconds (mR/mAs)?
31
If a high-voltag transformer has primary turns and 50,000 secondary turns and i supplied by 220 V and 100 A, what are the secondary voltage current?
200 mA and 110 kV
What does a full wave rectification look like?
...
When using the smaller field in a dual-field image intensifier,
the image is magnified
The minimum response time of an automatic exposure control (AEC)
is the shortest possible exposure time
The electron cloud within the x-ray tube is the product of a process called
thermionic emission
Which of the following causes pitting, or many small surface melts, of the anode's focal track?
repeated, frequent overloading
Which of the following is (are) characteristics of the x-ray tube?
-the target material should have a high atomic number and a high melting point
-the useful beam emerges from the port window
-the cathode assembly recieves both low and high voltages
A parallel-plate ionization chamber recieves a particular charge as x-ray photons travel through it. This is the operating principle of which of the following devices?
AEC
Which of the following will serve to increase the effective energy of the x-ray beam?
-increase in added filtration
-increase in kilovoltage
Which of the following combinations would pose the least hazard to a particular anode?
1.2 mm focal spot, 92 kV, 1.5 mAs
The number 2 in the figure indicates the
...
Congruence of the x-ray beam with the light field is tested using
radiopaque objects
Delivery of a large exposures to a cold anode or the use of exposures exceeding tube limitation can result in
-cracking of the anode
-rotor-bearing damage
If the primary coil of a high-voltage transformer is supplied by 220 V and has 400 turns and the secondary coil has 100,000 turns, what is the voltage induced in the secondary coil
55kV
What is the relationship between kV and HVL (half value layer)?
As kV increases, the HVL increases
As window level increases
brightness increases
Which of the following is/are components of the secondary, or high voltage, side of the x-ray circuit?
rectification system
Patient dose during fluoroscopy is affected by
-distance between the patient and the input phosphor
-amount of magnification
-tissue density
A back-up timer for the AEC serves to
-protect the patient from overexposure
-protect the x-ray tube from excessive heat
Which of the following devices converts electrical energy to mechanical energy?
motor
the essential function of a phototimer is to
terminate the x-ray exposure once the IR is correctly exposed
A slit camera is used to measure
-focal spot size
-spatial resolution
In which of the following examinations would an IP front with very low absorption properties be especially important?
mammography
Which of the will improve the spatial resolution of image intensified images?
-a very thin coating of cesium iodide on the input phosphor
-a smaller diameter input screen
The advantages of collimators over aperature diaphragms and flare cones include
-the variety of field sizes avaliable
-mire efficient beam restriction
Which of the following occurs during Bremsstrahlung (brems) radiation production?
an electron makes a transition from an outer to an inner electron shell
Characteristics of the metallic element tungsten include
-ready dissipation of heat
-high melting point
-high atomic number
What image depicts the ion-chamber-type automatic exposure control (AEC)
...
The voltage ripple associated with a three-phase, six-pulse rectified generator is about
13%
the device that recieves the remnant beam, converts it into light, and then increases the brightness of that light is the
image intensifier
A high speed electron entering the tungsten target is attracted to the positive nucleus of a tungsten atom and, in the process, is decelerated. This results in
Bremsstrahlung radiation
All of the following are components of the image intensifier
-photocathode
-focusing lens
-accelerating anode
Components of digital imaging include
-computer manipulation of the image
-formation of an electronic image on the radiation detector
Which of the following is used in digital fluoroscopy, replacing the image intensifier's television camera tube?
charge-coupled device
A three-phase timer can be tested for accuracy using a synchronous spinning top. The resulting image looks like a
solid arc, with rhe angle (in degrees) representative of the exposure time
the regular measurement and evaluation of radiographic equipment components and their performance is most accurately termed as
qualty control
the procedure whose basic operation involves reciprocal motion of the x-ray tube and film is
tomography
In fluoroscopy, the automatic brightness control is used to adjust the
kilovoltage (kV) and milliamperage (mA)
When the radiographer selects kilovoltage on the control panel, which device is adjusted?
autotransformer
Star and wye configurations are related to
three phase transformer
What is the device that directs the light emitted from the image intensifier to various viewing and imaging apparatus?
beam splitter
As electrons impinge on the anode surface, less than 1% of their kinetic energy is changed to
x-rays
Which of the following contribute(s) to inherent filtration?
-x-ray tube glass envelope
-x-ray tube port window
A quality-control (QC) program includes checks on which of the following radiographic equipment conditions?
-reproducibility
-linearity
-positive beam limitation/autmatic collimation
What x-ray tube component does the number 6
...
Characteristics of x-ray photons include
-a penetrating effect on all matter
-an ionizing effect on air
All the following x-ray circuit devices are located between the incoming power supply and the primary coil of the high voltage transformer
-the timer
-the kilovoltage meter
-the autotransformer
Which of the following systems function(s) to compensate for changing patient/part thicknesses during fluoroscopic procedures?
automatic brightness control
Disadvantages of moving grids over stationary grids include which of the following?
-they can prohibit the use of very short exposure times
-they increase patient radiation dose
The functions of a picture archiving and communication system (PACS) include
-acquisition of digital images
-storage of digital images
How many half value layers will it take to reduce an x-ray beam whose intensity is 78 R/min to an intensity of less than 10 R/min?
3
The kV setting on radiographic equipment must be tested annually and must be accurate to within
+/- 2kV
An incorrect relationship between the primary beam and the center of a focused grid results in
-grid cut off
-insufficient radiographic density
the x-ray tube in a CT imaging system is most likely to be associated with
a pulsed x-ray beam
the radiograph shown was made using a
single phase, full wave rectified unit
Conditions that contribute to x-ray tube damage include
-lengthy anode rotation
-exposures to a cold anode
The total brightness gain of an image intensifier is the product of
-flux gain
-minification gain
Which of the following information is necessary to determine the maximum safe kilovoltage using the appropriate x-ray tube rating chart?
-milliamperage and exposure time
-focal spot size
A spinning-top device can be used to evaluate
-timer accuracy
-rectifier failure
A device used to ensure reproducibility radiographs, regardless of tissue-density variations, is the
automatic exposure control
the device used to change alternating current to unidirectional current is
a solid state diode
If the distance from the focal spot to the center of the collimators mirror is 6 in., what distance should the illuminator's light bulb be from the center of the mirror?
6 in
To maintain image clarity in an image intensifier system, the path of electron flow from the photocathode to the output phosphor is controlled by
electrostatic lenses
the image intensifier tube's input phosphor functions to convert
x-rays to light
Which of the following equipment is mandatory for performance of a myelogram?
tilting x-ray table
Deposition of vaporized tungsten on the inner surface of the x-ray tube glass window
acts as additional filtration
design characteristics of x-ray tube targets that determine heat capacity include the
-rotation of the anode
-diameter of the anode
-size of the focal spot
Which of the following terms describes the amount of electric charge flowing per second
current
the brightness level of the fluoroscopic image can vary with
-milliamperage
-kilovoltage
-patient thickness
Which of the following does this figure represent?
Bremsstrahlung radiation
Which of the following is the correct formula for determining heat units for a three phase 12 pulse x-ray machine?
mA X time X kV X 1.41
Component parts of a CT imaging system include a(n)
-high frequency generator
-x-ray tube
-operator console
With what frequency must radiographic equipment be checked for linearity and reproducibility?
annually
Which part of an induction motor is located within the x-ray tube glass envelope?
rotor
a technique chart should be prepared for each AEC x-ray unit and should contain which of the following information for each type of examination?
-photocell(s) used
-optimum kilovoltage
-backup time
Which part of an induction motor is located outside the x-ray tube glass envelope?
stator
Moving the image intensifier closer to the patient during fluoroscopy
-decreases the SID
-decreases patient dose
-improves image quality
This image illustrates the
line focus principle
If a radiogrph exposed using an AEC is over exposed becuase an exposure shorter than the minimum response time was required, the radiographer generally should
decrease the milliamperage
Exposures less than the minimum response time of an AEC may be required when
-using high milliamperage
-using fast film-screen combinations
Which of the following is/are associated with magnification fluroscopy?
-higher patient dose than nonmagnification fluoroscopy
-higher voltage to the focusing lens
-image intensifier focal point closer to the input phosphor
Advantages of battery-powered mobile x-ray units include their
-ability to store a large quantity of energy
-ability to store energy for extended periods of time
Which of the following modes of a trifield image intensifier will result in the highest patient dose?
its 12 in mode
Off focus or extrafocal, radiation is minimized by
restricting the x-ray beam as close to its source as possible
Circuit devices that permit electrons to flow in only one direction are
solid state diodes
An AEC device can operate on which of the following principles?
-a photomultiplier tube charged by a fluororecent screen
-a parallel plate ionization chamber charged by x-ray photons
Which of the following functions to increase the milliamperage?
increase in heat of the filament
If 92 kV and 15 mAs were used for a particular abdominal exposure with single phase equipment, what milliampere-seconds calue would be required to produce a similar radiograph with three phase 12 pulse equipment?
7.5
Fractional focus tubes with a 0.3 mm focal spot or smaller, have special application in
magnification radiography
In the radiographic rating chartsshown in
...
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...
fsdfkbn
...
referring to the anode cooling chart in the figure if the anode is saturated with 300,000 heat units (HU) how long will the anode to cool before another 160,000 HU can be safely applied?
4 minutes
Which of the following devices is used to control voltage by varing resistance?
rheostat
Anode angle will have an effect on the
-severity of the heel effect
-focal spot size
-heat load capacity
light sensitive AEC devices are known as
phototimers
Which of the following devices is (are) component(s) of a typical fluoroscopic video display system?
-tv camera
-tv monitor
which of the following is most closely related to this figure
high kV
Which of the following formulas would the radiographer use to determine the total number of heat units produced with a given exposure using three-phase, six pulse equipment?
mA X time X kV X 1.35
With three-phase equipment the voltage across the x-ray tube
-is 87% to 96% of the maximum value
-is at nearly constant potential
Radiographs from a particular single phase full wave rectified x-ray unit were overexposed using known correct exposures. A spinning top test was performed at 200 mA, 0.05 sec, and 70 kV, and 8 dots were visualizedon the finished film. which of the following is indicated?
the 0.05 sec time station is inaccurate
Which of the following combinations will offer the greatest heat loading capabilit?
10 degree target angle, 1.2 mm actual focal spot
Which of the following would be appropriate IP front materials?
-magnesium
-bakelite
how often are radiographic equipment kV settings required to be evaluated?
annually
what x-ray tube component does the number 8 in this figure indicate?
focal track
The filtering effect of the x-ray tubes glass envelope and its coolant are referred to collectively as
inherant filtration
accurate operation of the AEC device depends on
-positioning of the object with respect to the photocell
-beam restriction
the image intensifier's input phosphor generally is composed of
cesium iodide
the total number of x-ray photons produced at the target is contingent on the
-tube current
-target material
-square of the kilovoltage
a photostimuable phosphor plate is used with
CR
x-ray tubes used in CT imaging systems must be capable of
-high short exposure rating
-tolerating millions of heat units
-high speed anode rotation
the device used to test the accuracy of the x-ray timer is the
spinning top
QA was being performed on a three-phase full wave rectified x-ray unit. a synchronous spinning top test was performed using 300 mA, 60 ms, and 70 kV, and a 22 degree arc was observed on the test film. which of the following is most correct about the results?
the test results are satisfactory
Which of the following statements regarding dual absorptiometry is (are) true?
-it is low dose procedure
-two x-ray photon energies are used
-photon attenuation by bone is calculated