X-ray Tube Components Flashcards
what are the three main components of x-ray imaging systems that influences the flow of electrons?
- operating console
- generator
- x-ray tube
what does manipulating the intensity do?
amount of x-radiation used during imaging
what does manipulating the quality of x-radiation do?
affecting the penetrability/energy of the x-radiation
what does the generator provide?
provide a consistent power (voltage) needed to create x-ray photons
what does a near constant potential provide?
minimal energy fluctuation
high voltage generators = ____ image quality + _____ patient dose
increases image quality
decreases patient doses
what are components of an x-ray tube?
anode, cathode – encased in a protective housing
what 3 things does the protective housing provide?
- prevents electric shock
- reduction from leaking radiation
- protection of the internal components
what is the purpose of metal/glass envelopes?
- to maintain the vacuum inside the tube and
- structural support
why is the vacuum necessary?
- it allows for more efficient x-ray production by maintaining tube current
& to extend the tube’s life
what are the three pros of metal envelopes over a glass one?
- prevents arcing
- enables higher tube currents
- improves heat dissipation
what is arcing? what causes it?
arcing = tube failure
caused by deposits from tungsten vaporization
what is the purpose of a window in the metal envelope?
allows for maximum emission of useful x-ray photons with the least amount of absorption
which end is the window located on?
anode (near target)
what is the purpose of a cathode?
to produce electrons
what is the difference between the cathode and anode?
cathode = negative side
anode = positive side
what are the two primary parts of the cathode?
- filament
- focusing cup
what does the filament do?
it is a coil that has electrons accumulating at
once there is enough electrons, it is released and the electrons will then be accelerated towards the metal target
what does the coil size of the filament correlate to?
focal spot size (fss)
what does the different sizes of filaments affect?
spatial resolution + heat
what is the purpose of the focusing cup?
electrostatically confines the electrons so they can be directed towards the target
what does the anode do?
produces x-rays + provides mechanical support for the target
what are the three components of the anode?
- bearing assembly
- rotor
- target
what is the bearing assembly covered BY? covered IN?
covered by the rotor
covered in oil
what is the purpose of the bearing assembly?
allows for smooth rotation of the anode disk and to allow for heat to be conducted away from the X-ray tube
where do you find the stator?
tube-like structure surrounding the rotor outside of the envelope
what is the purpose of the stator?
makes the TARGET rotate by electromagnetic induction
what is the purpose of the rotor?
to prevent transmission of heat from the disk to the bearings
what is the purpose of the target?
to produce x-rays when the electrons from the cathode strikes it
where are the focal spot(s) located on the target?
on the angled portion of the target
why are there angles on the target?
reduces the damaging effects of heat on the focal spot while allowing for spatial resolution
steeper angles = _____ (smaller/larger) SA = ______ (increased/decreased) heat concentration = irradiation of ____ (narrower/wider) sections of anatomy = ______ (increased/decreased) spatial resolution
STEEPER angles = LARGER SA = DECREASED heat concentration = irradiation of WIDER sections of anatomy = DECREASED spatial resolution
4 key differences between CT xray tubes + general radiography.
- larger focal spot sizes
- not too big angle (~12 degrees)
- larger and thicker targets
- faster target rotation speeds
what are some cons of the all-metal target disks?
heavy, fixed, poor heat dissipation + short tube life
what is a common design for a ct target in helical/spiral ct scanner?
brazed graphite
what are some pros to the brazed graphite?
able to withstand more heat and longer tube life
full metal disc and brazed graphite discs are some basic ct target designs, what is the other that was listed?
chemical vapor deposition graphite
what are the pros to a chemical vapour deposition graphite disc?
able to be large but lightweight, high heat storage ability and cools fast
what are the key differences between GR and CT x-ray tubes?
ct targets rotate faster + use materials designed to manage heat
what are the key differences between GR and CT x-ray tubes?
ct targets rotate faster + use materials designed to manage heat
