week 3: xray production Flashcards
the stators of the anode induction motor are (inside/outside) the glass enveloped
outside
what are the three conditions necessary for xray production?
- source
- acceleration
- stoppage of e-
Explain the two most common ways an x-ray tube assembly is orientated
?
X-rays not in the controlled beam that escape through the protective housing surrounding the x-ray tube
leakage radiation
what is the purpose of the lead lining?
radiation protection
what is the window in the glass envelope?
a thinned/shaved area for xray photons to exit
what is the function of the glass envelope?
allows air to be completely evacuated from xray tube, insulation of electrical shock, dissipates heat
function of oil in the tube
dissipates heat, insulation from electrical shock
true/false: tungsten filament has a charge at normal state
false; it does not have a charge. Tungsten will release electrons when heated
what is the function of the focusing cup?
because the focusing cup is negative, it repels electrons and helps focus stream of electrons from filament toward anode target
what is the charge of the focusing cup? what is it made out of?
negative charge; nickel
the formed cloud around the filament during thermionic emission
space charge
refers to the tendency of the space charge to prevent more electrons to be boiled off
the space charge effect
the high temp where the filament is not “boiling off” electrons
saturation current
the flow of e- from cathode to anode
tube current
what is tube current measured in?
milliamperes
why is tungsten used as the metal of choice for cathode filament?
high heat capacity d/t high atomic number
what are the three basic functions of the anode?
- electrical conductor
- thermal dissipater
- mechanical support
what is the name of the motor in the anode?
induction motor
what are the consequences of the line focus principle?
heat capacity increased d/t increased surface area while creating a smaller beam so image quality is sharpened
what is the difference between the effective and the actual focal spot?
effective = xray photon (exiting)
actual = the literal/actual place the e- are hitting the anode and turning into xray photons
what’s another word for actual focal spot size?
real (Graham’s)
what’s another word for effective focal spot size?
apparent (Graham’s)
what is the most common angle degree? (from powerpoint?)
12 degrees
what is the range of the beveled angle?
5-20 degrees
intensity of beam is (more/less) on the anode side. what is this due to?
less; anode heel effect
anode heel effect would lead you to want the “head of the patient” on the (anode/cathode) side
anode
% range for anode - CR - cathode due to the anode heel effect
75–100–120
total filtration is the combination of what?
inherent filtration + added filtration
What is the leakage radiation maximum?
100 mR/h or 1mGy/h measured at 1 meter from the tube
