Chapter 5 Exam Flashcards
Anode side is the _______ side of the tube
positive
Anode (positive side of the tube) made of _______ because it has a very high _____ _____ and a high ______ ______ (__)
tungsten, melting point, atomic number (74)
anode serves as:
A target for electron interaction to produce x rays.
As an electrical and thermal conductor
what does the x-ray tube guard against?
leakage radiation
photons inside the x-ray tube housing leave through the ______ and are the ______ _____
window, primary beam
the x-ray tube housing protects against:
electric shock
inside the housing, the x-ray tube is surrounded by ____ (______ ____) - possible cooling fan
oil (dissipate housing)
the main purpose of the x-ray tube is to maintain a ______ within the tube to prevent _______ ______
vacuum, electrical arcing
__% of the electrons that hit the anode target are turned into heat, and __% are converted to x-ray
99%, 1%
what is the advantage of a rotating anode?
spreads the heat produced during x-ray production over a larger surface area
anode is made of:
copper (shaft)
molybdenum (disc base and core)
tungsten (outside)
the anode is rotates using an:
induction motor
what are the two parts of the induction motor?
stator & rotor
what is the stator made up of?
electromagnets arranged in pairs around the rotor
what is the rotor made up of?
iron core (iron bars embedded in the copper shaft) surrounded by coils
what happens when you press the exposure button half way down?
Stator windings energized
sequentially & rotor accelerated to designated rpm
what happens when you press the exposure button all the way down?
Filament is Heated-Electrons cloud is forming
“BEEP” – kVp is applied, electrons strike the anode, photons are produced
When the angle of the target face is less than __ degrees, the effective focal spot will be smaller than the actual
45
The target angles are __ to __ degrees for a general-purpose tube (__ degrees is the most common)
7 to 18, 12
The smaller the anode angle, the ______ the effective focal spot will be while maintaining a large actual focal spot area
smaller
The _____ the effective focal spot, the sharper the image will be
smaller
Smaller anode angle = _____ heel effect
larger
Effective focal spot size is where:
the x-rays come out
Anode heel effect:
intensity is more toward the cathode
Cathode side is the ______ side of the tube
negative
Cathode provides:
and is made up of:
The source of electrons needed for x-ray production
The filaments and the focusing cup
Dual focus tubes have ___ filaments
2
Each filament is a coil of wire made of:
tungsten with 1-2% of thorium
Focusing cup is made of _____ and surrounds the ________ back and sides, leaving the front open and facing the anode target
nickel, filaments
The focusing cup receives a strong ______ charge from the secondary circuit that forces the _______ together into a cloud as they are boiled off the _______ through electrostatic repulsion
negative, electrons, filament
Inside the x-ray tube, the induction motor turns the anode at approximately ____ rpm
3400
Once the space charge reaches a size commensurate with the current used, it becomes difficult for additional electrons to be emitted
space-charge effect
3 things needed to produce x-rays
A large potential difference to give kinetic energy (provided by kVp)
A vehicle in which kinetic energy can ride (provided by mAs)
A place for interaction (the target of the anode)
The overall density of our image is the ____
black
thee difference between the whites and blacks is:
contrast
A measure of the amount of heat stored in a particular device
heat units
how to calculate heat units
kVp x mA x s x c
single phase formula:
mA x time x kVp
three phase formula:
mA x time x kVp x 1.35
high frequency formula:
mA x time x kVp x 1.40
Which if the following reduces leakage radiation to required standards?
Protective housing
Which component of the x-ray tube us responsible for concentrating the electron cloud?
Focusing cup
The x-ray tube is part of the:
X-ray circuit secondary
A technique of 80 kV, 400 mA, 0.8 seconds is to be used on a 3-phase, 12-pulse machine. How many heat units are produced with a single exposure?
36,096
The intensity of the x-ray beam is less:
which side?
On the anode side
Causes of tube failure are most often related to which of the following?
Thermal characteristics
What metal is added to the filament to increase thermionic emission and extend tube life?
Thorium
A small anode target angle:
results in?
Results in an increase in anode heel effect
A dual focus tube refers to a tube with:
Two filaments
The purpose of the line focus principle is to create which of the following?
Large actual and small effective focal spot size
A technique of 50 kV, 100 mA, 0.1 seconds is to be used on a 3-phase, 6-pulse machine. How many heat units are produced with a single exposure?
675
