X-Ray Tube Construction/Components
The filament is located on which side of the x-ray tube?
Cathode/Negative side
What material is the anode usually coated with?
Tungsten
A dual-focus tube has two...
Filaments
What is the percentage of kinetic energy that becomes heat within the tube?
99%
A single-phase unit using 100 kVp, 200 mA, and 0.2 seconds produces this many heat units.
4,000 HU
What tube component acts as the source of x-rays?
The focal spot
What does the line focus principle describe?
Decreasing the anode target angle to reduce the effective focal spot size
Why is tungsten used to construct the filament?
Because it has a high melting point
Thermionic emission at the filament produces this...
Space charge effect
What is the formula for calculating heat units for a three-phase, 6-pulse unit?
kVp x mAs x 1.35
There are three external structures of the x-ray tube. They are the support structure, housing and...
The glass envelope
The thicker part of the patient should be positioned on which side of the tube?
Cathode side
What is the typical filament length?
1 to 2 cm
What is the speed that high-capacity tubes can reach?
10,000 rpm
An 80 kVp, 300 mA, 0.1 s exposure on a 3-phase 6-pulse generator produces this many HUs.
3,240 HU
Which x-ray tube support system is the most widely used?
The ceiling support system
What is the most common overcall cause of tube failure?
Tungsten vaporization within the tube
What is the phenomenon that occurs as electrons boil off the filament and repel each other?
Space charge effect
What can happen when using long exposure times?
Tube failure
A high-frequency generator using 120 kVp, 500 mA, 0.05 s produces this many heat units.
How does the anode rotate?
Through the use of the stators and rotor creating a magnetic field
What does the anode heel effect describe?
There is lower x-ray intensity on the anode side of the beam due to the electrons/photons having to move through the target and end up being absorbed by the target itself
What is a problem that develops inside aging tubes due to tungsten coating the glass?
Arcing
What does a tube rating chart demonstrate?
Maximum, safe, exposure times
A 3-phase, 12-pulse generator using 70 kVp and 50 mAs produces this many heat units.
4,935 HU