Image Production #9
Which of the following is NOT related to the others? Rotor Target Filament Tungsten disk
Filament-the rotor, target, and tungsten disc will all be located at the anode end of the x-ray tube. The filament is at the cathode end.
How can voltage be induced into a conductor? 1. Move a wire through a magnetic field 2. Move a magnetic field across a wire 3. Place a wire in a varying magnetic field
1, 2, 3-An English physicist, Michael Faraday, discovered that electricity couldbe produced by any of these methods
A well-organized quality control program will assure which of the following? Minimal exposure to patients Consistent radiographic quality Minimum down-time of equipment
1, 2, and 3
Which of the following is/are found in the detector elements of a flat-panel detector? Charge collection area Capacitor Thin-film transistor
1, 2, and 3-these components capture and transmit the latent image
What is the unit of electrical current Watt Farad Volt Ampere
Ampere 1 ampere is 1 coulomb of charge passing a point in a conductor per second/ 1 coulomb = 6.3 x 10 to the 18th electrons
Tapping windings of the autotransformer to supply voltage to the step-up transformer is the purpose of which of these? kVp selector Voltmeter Voltage compensator Rheostat
kVp selector-if there is a potential difference of 220 volts between the 2 ends of the autotransformer, the kVp selector taps onto the autotransformer to provide a percentage of the 220 volts
Which of the following is the factor of choice to adjust/correct image receptor exposure? kVp mAs SID Filtration
mAs
Which of the following are advantages of using FPD's for digital fluoro compared to II fluoroscopy? Rectangular image Post-processing of images Better contrast resolution
All the above-collimation can be smaller when it is not necessary to compensate for the II's circular image. Post-processing and contrast resolution are the main advantages of digital fluoro
Thin Film Transistors TFT are found in which type of digital system? Indirect digital flat panels Direct digital flat panels Charge-coupled devices all the above
All the above-each of these has its own x-ray capture material, capacitor for storing electrons, and TFT to read the charge collected during the exposure
What is the device called that measures electrical current? Capacitor Ammeter Voltmeter Ground
Ammeter-the unit for current is amperage, it's measured with an ammeter
The photodetector generally used with a TFT array in direct capture digital imaging is Aluminum oxide Amorphous selenium Zinc cadmium sulfide Amorphous Silicon
Amorphous selenium
How fast do high speed anodes rotate? 1500 rpm 3400 rpm 5000 rpm 10000 rpm
10,000 to help dissipate heat, anodes that normally rotate at 3,400 RPM (revolutions per minute), will be increased to 10,000 RPM
In a 60 cycle alternating current, how many alternations are there every second? 30 60 90 120
120-in a 60 cycle generator, the current changes direction (alternates) every 180 degrees or twice per cycle (360 degrees in a cycle)
The incoming line voltage is 220 volts. 55% of the turns on the autotransformer are used. What is the voltage sent to the step-up transformer? 121 V 121 kV 220 V 220 kV
121 volts-if 100% were used then 220 v would be sent to step-up transformer. So since 55% used then it's 121 volts.
Important guidelines regarding monitor display and lighting display workstations include: 1. Maximal ambient lighting and reflection 2. Minimal veiling glare 3. Luminance of at least 171 candelas/m2
2 and 3
How can the production of scatter be reduced? 1. Increase kVp 2. Use close collimation 3. Increase beam filtration
2 only The less tissue that is exposed the less chance of scatter radiation being produced. Therefore, collimate as close to the area of interest as possible.
In indirect capture with FPD's what order are they top to bottom, in an indirect FPD? 1. Photodiode layer 2. Fluorescent layer 3. TFT Layer
2, 1, 3 X-rays strike the fluorescent layer and light is emitted. The light strikes the photodiode layer and electrons are released. Those electrons are captured in the TFT layer and stored in a capacitor.
When an image is extracted from a flat-panel detector the following occurs. Put the events in the proper order. 1. Data is digitized by an analog to digital converter (ADC) 2. Data is read from the columns and rows, line by line 3. A histogram is created and analyzed by software
2, 1, then 3 After the exposure, the charged capacitors are read line by line; the electrical impulse (analog) is converted to digital date; a histogram is a plot of those numbers.
According to Ohm's law, what would the resistance be if the voltage is 110 volt and the current is 5 ampere? 22 ohm 55 220 550
22 ohm Ohm's law states that V=IR os R= V/I R=110/5=22
When changing from non-grid to 8:1 grid, how much would the mAs have to be increased. 2x 3x 4x 5x
4x An 8:1 ratio grid will absorb 4x more scatter than no grid so the radiograph would be 4x underexposed. The mAs would have to be increased 4x to compensate for this.
When the distance between 2 charged bodies is cut in half, how much will the force between them increase? 2x 4x 6x 8x
4x, same as inverse square law, if distance is cut in half the intensity will be 4x
Requirements for tilting x-ray table to be used for fluoroscopy are
90 degrees to the feet and 30 degrees to the head
Which of the following will create the most electrical resistance? Long wire with small diameter? Short wire with small diameter Long wire with large diameter Short wire with large diameter
A long wire with a small diameter Resistance in a conductor is determined by the type of material the conductor is made from, the length of the conductor and the diameter of the conductor
Which of the following happens when a wire moves through a magnetic field? An electromotive force is induced in the wire The resistance in the wire increases The magnetic field disappears
An electromotive force is induced in the wire-when a wire moves through a magnetic field-an electromotive force (EMF) is produced, which in turn causes the electrons to move. This creates a current
Where in the x-ray circuit is the timer located? In the secondary circuit Between the autotransformer and the step-up transformer Before the step-down transformer Between the rectified and the x-ray tube
Between the autotransformer and the step-up transformer The timer is on the primary side of the x-ray circuit and opens the circuit to complete an exposure
Which of the following is placed in a circuit in case the current surges during the exposure? Transformer Breaker switch Choke coil Rectifier
Breaker switch-designed to open the circuit if an increase in current could damage the electrical devices
A wider (increased) window width (Select the 2 that apply) A Decrease the range of densities B Increase the image contrast C Increase the range of densities D Decreases the image contrast
C, D Increase the range of densities Decrease the image contrast
When changing from half-wave to full-wave rectification... A. X-ray quantity remains unchanged; quality doubles B. Both x-ray quantity and quality remain unchanged C. X-ray quantity doubles; quality remains unchanged. D. Both X-ray quantity and quality double.
C. X-ray quantity doubles; quality remains the same/
What is a device called that stores electrical charges? Capacitor Ammeter Voltmeter Ground
Capacitor-have the ability to store electrical charges even when a machine is turned off. That is why a radiographer should never remove the cover from electrical equipment in the x-ray room
The latent image in a FPD is formed by which of the following? Trapped electrons Charged capacitors Electrical resistance Detector elements
Charged capacitors-when a DR FPD is exposed to x-rays, electrons are released and stored in a capacitor. These charged capacitors form the latent image
What is the name of the closed path over which electric current flows? Circuit Differential Airway Ampere
Circuit-consists of wires and electrical devices that are connected for the purpose of allowing electrons to flow
Of the following, which will create the least electrical resistance? Copper Aluminum Tungsten Lead
Copper-b/c it's outer shell electrons are loosely bound. Silver has less resistance, but copper is cheaper and therefore, used for most wiring
What is the unit of electrical charge? Ampere Volt Coulomb Farad
Coulomb-the SI unit
The flow of electrons is known as what? Voltage Space Charge Current Capacitance
Current-this is determined by the voltage and the resistance in the conductor
According to the anode heel effect, when radiographing a throacic spine in AP projection, T-12 should be nearest to which letters of the diagram? A----Closest to anode B C D----closest to cathode
D. Cathode-since the heel of the anode absorbs x-raus going toward the A (anode) end of the beam, the highest intensity would be toward the D end of the beam. This is where you want your thickest anatomical part, in this case T-12
What is the purpose of the anode in an x-ray tube? Emits electrons decelerates electrons Focuses electrons Repels electrons
Decelerates electrons-to produce x-rays, high speed electrons haveto be decelerated or stopped. The high atomic # of tungsten (74) makes for a high density material to decelerate the electrons.
If the voltage is stepped-up, what happens to the current on the secondary side of the transformer? Increases Decreases Stays the same stepped-up
Decreases-since energy can neither be created nor destroyed, when the voltage is stepped-up, because of the transformer ratio, the current must decrease to maintain the same power on both sides.
Which of the following types of current supplies the x-ray tube? Alternating current Two way current Direct current Saturated current
Direct current-alternating current leaves the step-up transformer and enters the rectification circuit which changes it to pulsating direct current through the x-ray tube.
What are the swirling currents called that are induced in transformers and produce heat losses? Eddy currents Transformer currents Lamination currents Hysteresis currents
Eddy currents-iron not only a good core material, it is also a conductor. Therefore, as the magnetic field lines move across it, electrons are affected. This moving of electrons is called EDDY CURRENTS
What is it called when a solenoid has an iron core in its center? Electroflux " Electromagnet Diamagnet
Electromagnet-the iron core becomes magnetized when current is passed through the coil of wire (solenoid). This increases the strength of the magnetic field surrounding the solenoid
What causes the most x-ray tube failures Heating of the anode Multiple exposures Cracked glass Excessive heat
Excessive heat-when tube not warmed up properly, the rotor held down for too long or repeated exposures near the tube limit are made that excessive heat is generated that causes tubes to fail.
From the following list select the factors that are most likely to impact the SR (image sharpness) (3) FSS kVp OID mAs SID
FSS, OID, SID
Which of the following parts would make up the cathode end of the x-ray tube? Filaments and rotor Rotor and rotating disk Filaments and focusing cup Rotor, rotating disk, and target
Filaments and focusing cup--cathode end is only 2 filament wires and focusing cup *Don't want a C- minus in radiography, that's basically an FFF
The number of cycles per second that are associated with an alternating current are known as the current's what? Frequency Period Wavelength Amplitude
Frequency-how frequently the generator makes a complete revolution (cycle) is its frequency Amplitude-max height of the wave-intensity Period-time required to complete 1 cycle of the wave
Which type of rectification will supply the x-ray tube with the greatest power? Self Half-wave Full-wave Sine-wave
Full wave---means arranging the rectifiers so the alternating current will flow in the same direction through the x-ray tube
A coil of wire rotating through a magnetic field produces an electric current. What does this describe? Motor Rectifier Generator Transformer
Generator-a device that generates electric current (electricity) is called a generator
An electrical charge can be neutralized if it is conducted to what? Ground Metal pipe Magnet Battery
Ground-to ground an object means to connect the object to a path where the potential is zero. This would allow a negative object to lose electrons or a positive object to draw electrons
The formula mA x kVp x time, is used to determine which of the following?
Heat units-For three phase equipment this will be multiplied by 1.35 or 1.41 depending on whether it is 6-pulse or 12-pulse
What determines the quantity of electrons that will be accelerated across the tube? Focal spot size kilovoltage Anode speed Heating of the filament
Heating of the filament-heating the tungsten filament wire to temperatures between 2000-3000 degrees Celsius releases electrons for the production of x-rays.
Which of the following will produce the least load on an x-ray tube? High kVp, High mAs High kVp, Low mAs Low kVp, High mAs All will produce an equal load
High kVp, Low mAs The quantity of electrons (mAs) striking the anode determines the amount of heat produced. High kVp with low mAs will produce the same exposure with less heat
Select the factor(s) that have an effect on digital image resolution: I Pixel density II Window level III Pixel pitch IV Matrix Size V Window width
I, III, V Pixel Density Pixel Pitch Matrix Size
As the x-ray tube gets older, what happens to the temperature of the filament? Increases Decreases Varies Remains the same
Increases-since the filament wire gets thinner because of vaporization of the tungsten, the resistance gets greater. This causes the temperature to increase, emitting more electrons.
What type of motor drives the rotating anode? Synchronous Induction Direct Current Inductive Reactance
Induction--it's called an induction motor because the stator is on the outside of the glass and it INDUCES the rotor on the inside of the tube to spin.
why is an x-ray tube immersed in oil? Reduce noise Prevent sparking Insulation Filtration
Insulation-insulates high-voltage components of the tube from the tube housing. This protects the radiographer from potential electric shock. The oil also dissipates much of the heat from the tube
If line voltage changes because of demands by other users, automatic adjustments are made to which of the following? Step-up transformer Rheostat Line voltage compensator Prereading voltmeter
Line voltage compensator-is adjusted for changes i nthe incoming line voltage. This was done manually in older machines and automatically in newer equipment
What is the voltage supplied to the autotransformer called? Peak voltage Effective voltage Average voltage Line voltage
Line voltage-this incoming line voltage ranges from 200-240 volts and seems to fluctuate depending on various factors. This can be a problem in the generation of x-rays
Which of the following post-processing terms serve to suppress image noise? (2 of them) High-pass filtering Low-pass filtering Smoothing Sharpening
Low-pass filtering Smoothing
What is a material called that will attract small pieces of iron? Solenoid Helix Magnet Compound
Magnet-a magnet is defined as any material that has the ability to attract iron
Which of the following happens when the current in a conductor increases? Magnetic field increases M F decreases Resistance increases M F changes direction
Magnetic field strength increases-since there is a magnetic field associated with every moving charged object, the greater the # of charged objects the greater the magnetic field strength
What surrounds every electrical current? Insulation Sound waves Magnetic field E-M radiation
Magnetic field-any time there is a moving charged object, there will be a magnetic field associated with it. An electric current is a flow of negatively charged electrons.
Which of the following meters does NOT register until an x-ray exposure is made? Prereading kilovoltmeter Prereading ammeter Kilovoltmeter Milliammeter
Milliammeter-this measures the current that goes through the x-ray tube. Therefore, no measurement can be made until an exposure is made
Which of the following causes pitting of the x-ray tube target? Using both filaments at once Using the small focus all the time Moderate overloading of the tube Malfunction of high speed rotor
Moderate overloading of the tube-excessive temps during a single exposure causes surface melting and pitting. Thjs vaporization of the tungsten disk is a normal effect of high mA exposures
Which of the following works by sending an alternating current through a coil of wire that has been placed within a magnetic field? Motor Transformer Generator Solenoid
Motor-an alternating current is passed through the coil, a fluctuating magnetic field is produced. This magnetic field is repelled and attracted by the stationary magnetic field, causing the motor to spin.
If used properly, will an x-ray tube last forever? Yes No, the anode will disintegrate No, the filament wire will break No, the focus will melt away
No, the filament wire will break Even with normal use, the filament wire slowly vaporizes because of the high temps. Eventually it will burn out, much like a light bulb.
The unit for resistance? Volt Watt Ampere Ohm
Ohm-represents the characteristics of a material that inhibits the flow of electrons, it is determined, by length, diameter, and type of conductor
When an exposed flat panel is electronically read, which of the following is true? The entire flat panel contributes to the image Only the center of the flat panel contributes to the image Only the exposed detectors of the flat panel contributes to the image
Only the exposed detectors of the flat panel contributes to the image
What is the formula for electrical power? P=VR P=IR P= W/T P=IV
P=IV Power is determined by simply multiplying the voltage times the amperage. P=I(IR) is essentially the same formula but is referred to as the power loss formula
What are materials called that are weakly attracted to a magnet? Sumagnetic Diamagnetic Paramagnetic Ferromagnetic
Paramagnetic-these have an odd # of elecrons in their atoms, but most of the electron's spins cancel each others' magnetic effects. (ex. Aluminum) Ferromagnetic-attracted to magnet ex iron Non magnetic-rubber
What is the technical name for a CR imaging plate? PSL CR cassette Photostimulable phosphor plate Photosensitive photon absorber
Photostimulable phosphor plate-The imaging plate contains a phosphor which is barium fluorohalide compound that is doped with europium
What are the 2 kinds of electrical charges? Ground and ampere Volt and ampere Positive and Negative Coulomb and volt
Positive and negative-these charges come from the charges associated with an electron and a proton.
Automatic exposure control (AEC) was used for an erect abdomen but the SID was left at 72" SID instead of moving it to 40". The image will be: Underexposed Overexposed Properly exposed Fogged
Properly exposed-the AEC will remain on until the proper # of x-rays have struck the ionization chamber or until the backup time is reached. In most cases the result would be a properly exposed image.
Which of the following layers of the CR imaging plate protects the phosphor layer during handling? Backing layer Protective layer Support layer Conductive layer
Protective layer-this transparent layer made of polyester plastic
What effect does adjusting the filament control have on the production of x rays? Controls the quantity energy quality penetrating power
Quantity-adjusting the filament control increases or decreases the current through the filament wires. This affects the # (quantity) of electrons "boiled off" which in turn controls the # of x rays
The changing of alternating current to direct current is known as what? Transformation Rectification Conversion Electrification
Rectification-through the use of one-way electrical devices known as rectifiers, an alternating current (current that changes direction) can be changed so it only goes in one direction (direct current)
Which of the following layers of a CR imaging plate is sandwiched between the phosphor layer and the conductive layer? Support layer Protective layer Laminate layer Reflective layer
Reflective layer-this absorbs the laser light but reflects the photostimulable luminescence
What device would be used when the milliamperage is set on the control panel? Milliammeter Rheostat Autotransformer Step-up transformer
Rheostat-(variable resistor) controls the amount of current going to the step-down transformer. The step down transformer steps down the voltage and steps up the current to the cathodes filament wires. Milliammeter measures the tube current and is wired between the rectifier and the x-ray tube
Which of the following is NOT needed to produce x-rays? Availability of electrons Electrons set in high speed motion Electrons stopped suddenly Rotating anode
Rotating anode-x-rays are produced whenever high speed electrons are stopped. Dental x-rays are produced with a stationary anode.
The action of materials that absorb x-ray energy and emit visible light in response is termed Magnification Scintillation Emission Detection
Scintillation
What type of transformer core is most widely used in radiographic equipment? Open core Closed core Shell type Air type
Shell type-has its primary and secondary coils wrapped on top of each other, maximizing the effects of mutual induction
According to the line focus principle, how does the effective focal spot compare to the actual focal spot. Smaller Larger Brighter Sharper
Smaller-the size of the effective focal spot is determined by the length of the filament wire and the angle of the target. If the target angle is less than 45 degrees, then the effective focal spot is smaller than the actual focal spot.
Which of the following materials would make the best transformer core? Plastic Aluminum Wood Soft iron
Soft iron-iron is a material whose atoms are easily rearranged when the magnetic field surrounding it changes. This is necessary to efficiently transfer the energy from the primary to the secondary. (or single coil of wire with an iron core)
What is a current carrying coil of wire called? Solenoid Rectifier Spring Rheostat
Solenoid-a coil of wire is called a helix. When current is passed through the coil it is called a solenoid
Adjacent to the output phosphor of the digital fluoroscopy image intensifier tube is TV camera and CCD Fiber optic bundle and CCD Fiber optic bundle and TV camera TV camera only
TV Camera and CCD
Which of the following determines the strength of a magnetic field? The magnets diameter The # of magnetic field lines in an area The spin of the magnet How tightly the magnet is wrapped
The number of magnetic field lines in an area The more magnetic field lines (aka flux lines) there are in an area, the stronger the magnetic field will be.
What is the major reason for using alternating current? X-ray tubes require it Rectifiers cannot work without it Transformers cannot operate without it Current cannot flow without it
Transformers cannot operate without it Alternating current creates the fluctuating magnetic field a transformer needs to transfer energy from the primary side to the secondary side
Which of the following is the current indicated by the milliammeter? Saturation current Tube current Rectified current Maximum current
Tube current-measures current that has passed through the x-ray tube
In a modern, rotating anode x-ray tube, which of the following will coat the tungsten disk? Tungsten rhenium alloy T molybdenum alloy T copper alloy T lead alloy
Tungsten rhenium allow-alloying tungsten with rhenium allows the target to expand rapidly during the exposure, withstanding the stresses which can cause cracking
The target of an x-ray tube is made from what metal? Lead Copper Tungsten Molybdenum
Tungsten-it's high atomic #74 enhances the production of x-rays in the diagnostic range.
What determines the transformer ratio? Size of wire Turns of wire Type of wire Current in wire
Turns in wire-transformer ratio compares the # of turns in the primary coil to the # of turns of wire in the secondary coil. A step-up transformer may have a 20:20,000 ratio
Which of the following causes electrons to move in a conductor? Voltage Amperage Wattage Charge
Voltage-the force or push or pull on the electrons. It is a result of the attraction and repulsion forces associated with the electric fields at the ends of the conductor
When will a space charge be present in the x-ray tube? Never, it is outside the tube Whenever the rotor is engaged Whenever the machine is turned on There is always a space charge
Whenever the rotor is engaged-the electrons that surround the filament wires create the space charge. This is only present when the rotor is engaged, causing the filament wire to be heated.
