X-ray Production Part 1 Flashcards
What are the 2 important components of the tubehead?
X-ray tube
Power supply/generator
: Exposure time, kVp and mA selectors
Exposure button (dead-man type)
Indicator light and audible signal
I. Control panel
:Power supply + x-ray tube
◦Glass envelope◦Insulating oil
◦Metal housing◦Tube window
◦Aluminum filters◦Lead collimator
II. Tubehead
How many power supplies are in tubehead?
2
Is there insulating oil in x-ray tube?
No it is a vacuum
What are the 2 components of the cathode? +or _
Cathode (-)
Filament and Focusing cup
_____ (cathode)
Made of tungsten
SOurce of electrons
Heated with low voltage source and emits electrons at a rate proportional to its temp (thermionic emission)
Filament
_______ (cathode)
Made of molybdenum
Negatively charged
Focuses electrons into narrow beam directed to the focal spot
Focusing cup
Heated with low voltage source and emits electrons at a rate proportional to its temp is called ________
thermionic emission
What are the two components of the anode?
Anode (+)
Tungsten target
Copper stem
_______ (anode)
Transform the kinetic energy of the colliding electrons into x-ray photons
Highly inefficient: produces 99% heat and 1% x-rays
Tungsten target
_______ (anode)
Works as a thermal conductor to remove the heat from the tungsten avoiding target melting
Copper stem
Tungsten has a ______ atomic number: efficient production of x-rays
High
Tungsten has a _____ melting point
High
Tungsten has a ______ thermal conductivity
High
Tungsten has a ______ vapor pressure: helps maintain vacuum in tube at high temps
Low
Which transformer/power supply generates power for cathode/ generates electrons?
Low voltage power supply
What are the conditions necessary for x-ray production?
- Separation of electrons
- Production of high-speed electrons
- Concentration of electrons
- Sudden stoppage of electron steam
Low voltage supply from low voltage power supply heats filament and produces thermionic emission
Separation of electrons
High potential difference is produced between the cathode and anode by applying a high voltage between them using the high voltage transformer on the anode to create the potential difference between cathode and anode
Production of high-speed electrons
Electron beam is focused by the focusing cup and directed to the focal spot; focusing cup is neg charged
Concentration of electrons
Upon
Sudden stoppage of electron steam
Area on the target to which the focusing cup directs the electrons and from which the x-rays are produced
Size is important for image quality
Smaller= more heat
Focal spot
What are the 2 ways to overcome the heat issue of a small focal spot?
Rotating anodes Stationary anodes (line focus principle)
- Allows heat at the focal spot to spread out over a large surface (dark band)
- Medical devices
Rotating anode
Angling the target to achieve a smaller effective focal spot than the actual focal spot
Results in sharper radiographic image while maintaining the original surface area of the target for heat dissipation
Line-focus principle (stationary anode)
The projection of the focal spot perpendicular to the target
Actual focal spot
The projection of the focal spot perpendicular to the electron beam
Effective focal spot
Which focal spot in the stationary anode is always smaller?
Effective focal spot
____ provides a low-voltage current to heat the x-ray tube filament (cathode)
Step down transformer
_____ generates a high potential difference to accelerate electrons from the cathode to the focal spot on anode
Step up transformer
◦Electromagnetic device that either increases or decreases the voltage in a circuit.
Transformer
What are the 3 types of transformers in x-ray tube?
Step down
Step up
Autotransformer
What is the step down transformer regulated by?
mA switch
Increasing the mA will have what effect on number of electrons?
More electrons
_______
Used to convert 110 to 20 volts to 3-5 volts to heat the filament
Step-down transformer
______
Used to convert 110 to 20 volts to 60,000-100,000 volts to move the electrons across the tube
Step up transformer
What is the step up transformer regulated by?
kV setting
Increasing the kV will have what effect on energy of electrons traveling from cathode to anode?
Increase energy
Actual time of exposure
◦Timing circuit:
delay of ½ second to heat the filament
◦Time delay circuit:
◦Determines amount of time the high voltage circuit is applied across the x-ray tube (amount of time x-rays are produced)
Exposure timer:
controls the acceleration of electrons from cathode to anode
kV (kilovoltage):
controls heating of the filament
mA (milliamperage):
___ removes low energy x-rays not used in the radiographic image
Aluminum disc
_______: controls the time in which x-rays are produced
Exposure time
