Chapter 5 Key Terms Flashcards
Actual focal spot
the physical area of the focal track that is impacted
Anode
the positive side of the x-ray tube; serves as a target surface for high-voltage electrons from the filament, conducts the high voltage from the cathode back into the x-ray generator circuity, and serves as the primary thermal conductor
Anode assembly
consists of anode, stator, and rotor
Anode cooling charts
permits the calculation of the time necessary for the anode to cool enough for additional exposures to be taken
Anode heel effect
due to the geometry of the angled anode target, the radiation intensity is greater on the cathode side
Cathode
the negative side of the x-ray tube; produces a thermionic cloud, conducts the high voltage to the gap between the cathode and the anode, and focuses the electron stream as it heads for the anode
Cathode assembly
consists of the filament, focusing cup, and associated wiring
Dual-focus
a two-filament arrangement within the x-ray tube
Effective focal spot
the area of the focal spot that is projected out of the tube toward the object being radiographed
Envelope
the entire cathode and anode assembly is housed within this glass or metal structure
Extrafocal radiation
photons that were not produced at the focal spot; also called off-focus radiation
Filament
a small coil of thin thoriated tungsten wire
Focal point
the portion of the anode where the high-voltage electron stream will impact
Focal spot
the portion of the anode where the high-voltage electron stream will impact
Focal track
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
Focus
the portion of the anode where the high-voltage electron stream will impact
Focusing cup
a shallow depression in the cathode assembly designed to house the filament
Fractional focal spot
a very small focal spot; usually a fraction of a millimeter in size
Grid-biased
a type of tube that quickly regulates the flow of electrons, producing x-ray photons
Grid-controlled
a type of tube that quickly regulates the flow of electrons, producing x-ray photons
Grid-pulsed
a type of tube that quickly regulates the flow of electrons producing x-ray photons
Housing cooling charts
permits the calculation of the time necessary for the housing to cool enough for additional exposures to be made
Leakage radiation
any photons that escape from the housing except at the port
Line-focus principle
used to reduce the effective area of the focal spot
Off-focus radiation (extrafocal radiation)
photons that were not produced at the focal spot
Protective housing
the entire cathode and anode assembly is housed within this metal structure
Radiographic tube rating charts
a guide regarding the most common technical factor combinations that can be used without overlooking the tube
Rotating anodes
an anode assembly that turns during exposure
Rotor
a hollow copper cylinder or cuff that is attached to the anode disk by a molybdenum shaft
Saturation current
as kVp increases, a greater percentage of the thermionically emitted electrons are driven toward the anode
Space charge effect
as more and more electrons build up in the area of the filament, their negative charges begin to oppose the emission of additional electrons
Stationary anodes
an anode assembly that is immobile
Stator
induction-motor electromagnets that turn the anode
Target
the portion of the anode where the high-voltage electron stream will impact
Tube rating charts
provides a guide regarding the most common technical factor combinations that can be used without overloading the tube
Window
a structure where the primary x-ray beams exit the envelope, which allows less absorption or scatter of photons
Wiring
the parts within the cathode assembly that connect the elements of the assembly together
