Chapter 6 Study Questions
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| show | --1.source of electrons--2.appropriate target material--3.high voltage--4.a vacuum
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| What are the basic parts of a cathode assembly? | show 🗑
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| show | This narrows the stream as it goes to the anode.
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| show | During thermionic emission the electrons build in the area of the filament and their negative charges oppose the production of more electrons
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| show | --1.It has a high melting point--2.is difficult to vaporize--3.high atomic number enhances diagnostic x-ray photos--4.heat-conducting ability
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| show | When there is a decrease in the anode angle, there will be a decrease in the effective focal spot. When there is an increase in the anode angle, there will be an increase in the effective focal spot.
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| How does the anode heel affect radiation intensity? | show 🗑
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| What is the advantage of a high-speed rotor? | show 🗑
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| show | This permits electrons to flow without encountering the gas atoms of air.
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| show | Any photon that escapes from the housing except at the port.
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| How is off-focus radiation produced? | show 🗑
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| Actual Focal Spot | show 🗑
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| Anode | show 🗑
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| Anode Assembly | show 🗑
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| Anode Cooling Chart | show 🗑
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| Anode Heel Effect | show 🗑
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| show | The negative side of the x-ray tube; produces a thermionic cloud, conducts the high voltage to the gap between the cathode and anode, and focuses the electron stream as it heads for the anode.
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| Cathode Assembly | show 🗑
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| Dual Focus | show 🗑
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| show | The area of the focal spot that is projected out of the tube toward the object being radiographed.
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| Envelope | show 🗑
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| show | Photons that were not produced at the focal spot; also called off-focus radiation
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| show | A small coil of thin thoriated tungsten wire
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| Focal Point | show 🗑
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| show | The portion of the anode where the high-voltage electron stream will impact; also: target, focus, focal point, actual focal spot
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| show | The portion of the anode where the high-voltage electron stream will impact; when discussing a rotating anode this describes the circular path that will be impacted by the electron beam
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| Focus | show 🗑
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| Focusing Cup | show 🗑
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| Fractional Focal Spot | show 🗑
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| Grid-Biased Tube | show 🗑
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| Grid-Controlled Tube | show 🗑
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| show | A type of tube that quickly regulates the flow of electrons, producing x-ray photons; also: grid-controlled, grid-biased
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| show | Permits the calculation of the time necessary for the housing to cool enough for additional exposures to be made
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| show | Any photons that escape from the housing except at the port
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| Line-Focus Principle | show 🗑
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| show | Photons created somewhere in the tube other than the focal spot; can cause ghosting; not a result of scatter from patient; exit through tube window
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| show | The entire cathode and anode assembly is housed within this metal structure
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| show | A guide regarding the most common technical factor combinations that can be used without overloading the tube; also: tube rating chart
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| show | An anode assembly that turns during exposure
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| show | A hollow copper cylinder or cuff that is attached to the anode disk by a molybdenum shaft
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| show | Filament phenomenon; as kVp increases, a greater percentage of the thermionically emitted electrons are driven toward the anode and is reached when there are no further thermionic electrons to be driven toward the anode; effects efficiency
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| show | As more and more electrons build up in the area of the filament, their negative charges begin to oppose the emission of additional electrons
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| show | The ejection of electrons from the surface of the wire due to increased heat, causing an electron cloud; also: thermionic emission, electron cloud
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| show | An anode assembly that is immobile
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| Stator | show 🗑
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| Target | show 🗑
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| show | Provides a guide regarding the maximum technical factor combinations for each filament of each tube that can be used without overloading the tube plotted in mA, kV, and time
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| Window | show 🗑
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| show | The parts within the cathode assembly that connect the elements of the assembly together
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| show | to produce a thermionic cloud
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| What is the alloy called that is used in the filament? | show 🗑
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| show | Rhenium and molybdenum
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| show | As anode target material.
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| show | During thermionic emission, electrons build at the filament and oppose production of more electrons.
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| What is the purpose of the focal cup? | show 🗑
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| show | Once the current reaches a certain kVp, increasing kVp will not produce more electrons.
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| mA controls what? | show 🗑
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| kVp controls what? | show 🗑
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| Where are grid-biased tubes found? | show 🗑
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| Recorded detail are impacted by what? | show 🗑
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| What is filament length? | show 🗑
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| show | 1-2 mm
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| What is filament thickness? | show 🗑
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| show | To provide sufficient resistance to the flow of electrons so that the heat produced will cause thermionic emission to occur.
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| What is the purpose of the cathode? | show 🗑
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| The envelope of x-ray tubes can be made from what? | show 🗑
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| What are 2 causes of tube failure? | show 🗑
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| Vaporized tungston deposits on the inner surface of the glass envelope can cause what? | show 🗑
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| show | nickel
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| The focusing cup has what electrical charge? | show 🗑
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| What 3 functions does the anode have? | show 🗑
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| show | the anode
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| show | Gives precise control of the thermionic cloud. Changes charge of focusing cup from negative to positive to stop electrons from flowing.
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| show | --1.stationary--2.rotating
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| Stationary anodes are limited to what? | show 🗑
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| Why does diagnostic radiography utilize rotating anodes? | show 🗑
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| show | in all directions
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| show | causes exiting electron beam to be focused into a narrower stream
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| What are stationary anodes composed of? | show 🗑
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| show | Molybdenum with the target focal track material being rhenium-alloyed tungsten backed by a thicker layer of molybdenum or graphite.
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| show | 74
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| What benefit does rhenium provide? | show 🗑
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| show | 42
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| show | It's ability to emit a more uniform range of lower energy photons which permit better soft tissue imaging.
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| show | vaporization of focal track material; reduces efficiency
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| show | berylium
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| What is the advantage of a graphite backed anode? | show 🗑
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| What is the purpose of an anode warm-up procedure? | show 🗑
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| show | Does not require an elaborate tube warm-up procedure.
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| What is the point source of x-ray photons in addition to being the point that OID and SID are measured from? | show 🗑
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| Which anodes have a greater heat-loading capacity? | show 🗑
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| show | --1.actual focal spot--2.target angle
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| show | --1.filament size--2.angle of anode
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| show | --1.As the actual focal-spot size increases, the effective focal spot size increases--2.When the target angle is less than 45-degrees, the effective focal spot is smaller than the actual focal spot.
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| Most common diagnostic x-ray angle is what? | show 🗑
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| show | 7-17 degrees
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| show | Self-induction motor magnets that turn the anode.
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| Where are stators? | show 🗑
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| Of what is the rotor composed and how is it attached? | show 🗑
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| show | Liquids produce gas at high temperatures and reduce the vacuum in the tube.
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| show | Name of the tone a high-speed rotating cuff makes at 5000-7000 rpm capable of shattering the glass envelope.
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| What is a common cause of tube failure? | show 🗑
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| show | pyrex or metal
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| show | they eliminate the problem of tungston erosion
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| show | To maintain the vacuum.
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| Where is the window on the envelope? | show 🗑
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| What is purpose of the protective housing? | show 🗑
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| show | the primary beam
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| show | lead-lined cast steel
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| show | LEAKAGE RADIATION MUST BE LIMITED TO 100mR/hr @ 1 METER!!!
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| show | --1.Insulates--2.Promotes cooling
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| What additional devices might help cool the housing/oil? | show 🗑
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| show | kVp, mA, and time
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| show | --1.Radiation(99%)--2.Conduction--3.Convection
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| show | reduced x-ray tube life
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| What are the 7 recommendations for extending tube life? | show 🗑
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