Anode and Energy/Heat Flashcards
What is needed to slow down/stop the electrons that are going at a high rate of speed?
target
Focal track
actual area on the target that the incoming electrons hit
AFS
actual focal spot
location of photon production
EFS
effective focal spot
area on patient the beam is projected onto
When the electrons undergo thermionic emission what do they possess and why?
potential energy, since they are at rest
When voltage is applied to the anode, what do the electrons possess and why?
kinetic energy, since they are moving
What is the term that describes the way the beam travels after being created at the anode?
isotropically
What percentage of kinetic energy of electrons is converted to heat?
99.8%
What percentage of kinetic energy of electrons is converted to useful x-rays?
less than 1%
Radiation
transfer of heat by emission of infrared radiation
When is the heat dissipated by the radiation?
during exposure
What does the anode emit when it glows red hot?
infrared radiation
What is off-focus radiation?
x-rays produced outside of the focal track (electrons bounce off of anode)
What does off-focus radiation increase?
patient dose
What does off-focus radiation decrease?
spatial resolution and contrast
What is leakage radiation?
compromises in the tube housing that allow x-ray photons to exit
Conduction
heat is transferred from one area of an object to another
What is the path of conduction?
goes from anode, to rotor, to the glass
Convection
transfer of heat by the movement of a heated substance from one place to another
What does the heated glass enclosure raise the temperature of?
the oil bath
What is the path of convection?
goes from glass to oil bath, oil bath to the tube housing, from tube housing to the room air
What does a damaged focal track (target) result in?
an image blur
How fast can anodes spin up to in most tubes during exposure?
3400 RPM
How fast can anodes spin up to in high capacity tubes?
10,000 RPM
What do fast spinning anodes allow for in a tube?
more heat tolerance
A pitted anode occurs when…
exposures are made on a non-spinning anode
