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RADT 334 X-ray tube

radiographic physics review covering x-ray tube

QuestionAnswer
What are the 5 main components of the X-ray tube? Support system, protective housing, enclosure, cathode, anode
What are the external parts of the X-ray tube? Support system, protective housing, enclosure
What are the internal parts of the X-ray tube? Cathode and Anode
What guards against excessive radiation exposure and electric shock and controls leakage and scatter radiation, isolates the high voltages and provides a means to cool the tube? protective housing
What is the x-ray tube components contained within? glass or metal enclosure
This maintains a constant electric potential between the electrons of the tube current and the enclosure metal enclosure tubes
What is a vacuum containing two electrodes? x-ray tube
What are the two electrodes of the x-ray tube? anode and cathode
What is the glass or metal enclosure usually made of? Pyrex
What is the negative side of the x-ray tube? cathode
What are the two primary parts of the cathode? filament and focusing cup
coil of wire that emits electrons when heated filament
where the filament is embedded negatively charged to keep electron beam to a small area of the anode focusing cup
when the cloud of electrons make it hard for subsequent electrons to be emitted because of electrostatic repulsion space charge effect
what is the phenomenon called when the current through the filament is sufficiently high, the outer-shell electrons of the filament atoms are "boiled-off" and ejected from the filament thermionic emission
what are filaments usually made of thoriated tungsten
what is the most common cause of tube failure tungsten vaporization with deposition in the inside of the glass enclosure
why are filaments usually made out of tungsten? because tungsten provides for higher thermionic emission than other metals; also does not vaporize easily
how is the x-ray tube current adjusted? by controlling the filament circuit
which focal spot is used when better spatial resolution is required (bone work) small focal spot
which focal spot is used when large body parts are imaged and when higher techniques are used to generate high heat large focal spot
what is the positive side of the x-ray tube that conducts electricity and radiates heat and contains the target anode
what are the two types of anodes? rotating and stationary
what are the three functions of the anode electrical conductor, mechanical support for the target, and thermal dissipater
what is the area of the anode struck by the electrons from the cathode target
why is tungsten the material of choice for the target high atomic number, thermal conductivity, and high melting point
why is molybdenum and graphite used for the anode? lower mass density (lighter) and high melting point
what is possible with the rotating anode? higher tube currents and shorter exposure times
what is the rotating anode powered by? an electromagnetic induction motor
what is the actual x-ray source (where x-rays are emitted) the focal spot
the area projected onto the patient and image receptor effective focal spot
where electron interacts with target actual focal spot
what does the the line-focus principle result in? an effective focal spot size much less than the actual focal spot size
the smaller the anode angle, the ____ the heel effect larger
what does the heel effect result in? smaller effective focal spot and less radiation intensity on the anode side of the x-ray beam
What are some examples where the anode heel effect would be used to an advantage? foot, chest, abdomen
what does excessive heat result in? reduced x-ray tube life
what is the most frequent cause of abrupt failure electron arcing
three important types of x-ray tube rating charts radiographic rating chart, anode cooling chart, and housing cooling chart
which is the most important x-ray tube rating chart because it conveys which radiographic techniques are safe and unsafe for tube operation radiographic rating chart
why would a rotating anode be used. to produce high-intensity x-ray beams in a short time
when would a stationary anode be ideal? when high tube current and power are not required; examples, dental imaging systems and portable imaging systems
the thermal capacity of an anode and its heat dissipation characteristics are contained in this rating chart anode cooling chart
most frequent cause of abrupt tube failure electron arcing from the filament to the enclosure because of vaporized tungsten
two ways tube failure can occur from maintaining the anode at elevated temperatures for prolonged periods and from increasing the temperature of the anode too rapidly causing the anode to crack
Created by: haleygesselman