X-Ray Machine Flashcards
Where x-rays are produced
X-ray tube
Evacuated glass bulbs with positive and negative electrodes
X-ray tubes
X-ray tubes are special types of — which are electronic tube with 2 electrodes (+,-)
diode
The x-ray tube consists of a (1) and (2) embossed wtithin an envelope and then enclosed in a (3)
- cathode
- anode
- protective housing
X-rays emitted through the window of the tube
Useful beam
X-rays that escape from the protective housing (extra radiation)
Leakage radiation
2 Funtions of the diala oil
- Insulator against electric shock
- Thermal cushion to dissipate heat
External components of the x-ray machine
- Protective housing
- Glass/metal enclosure /envelope
Guards tagainst excessive radiation exposure
Protective housing
Incorporates specially designed high-voltge receptacle to protect against electric shock (to prevent electrocution
Protective housing
Provides mechanical support and protects the tube from damage caused by rough handling
Protective housing
Mainstains vacuum inside the tube
Glass/ metal enclosure/envelope
Early x-ray tube
Crookes tube
Modern x-ray tube
Coolidge tube
Differentiate crookes tube and coolidge tube
The crookes tube is an early x-ray tube, but is not a vaccum tube. Rather, it contained controlle quantites of gas.
The coolidge tube on the other hand, is a modern x-ray tube which is a vaccum tube.
What is the glass ecnlosure made up of?
Pyrex glass
As it ages, it causes arcing and tube failure
Glass enclosure
As the glass enclosure ages, what does it cause?
arcing and tube failure
It maintains constant electric potential between the electrons of the tube current and enclosure
Metal enclosure
An x-ray enclosure that has a longer life and is less likely to fail
Metal enclosure
The metal enclosur emaintains constant (1) between the electrons of the (2) and (3)
- electric potential
- tube current
- enclosure
Are of glass or metal enclosure
Window
Why is the x-ray tube’s window thin?
To allow maximum emission of x-rays
Internal components of the x-ray tube
- Cathode
- Anode
Negative side of the tube
Cathode
2 primary parts of the cathode
- Filament
- Focusing cup
3 Functions of the Cathode
- Produce thermionic cloud
- Conduct high voltage to the gap between cathode and anode
- Focus the electron stram as it heads for the anode
Small coil of thin thoriated tungsten wire
Filament
Thickness and length of the filament
0.1-0.2 mm thick;
1-2 cm long, 2mm diameter
When heated, this emits electrons
Filament
When the current through the filament is sufficiently high, the outer shell electron of the filament atom are (1) and (2) from the filament — (3)
- “boiled off”
- ejected
- thermionic emission
Required temperature for thermionic emission to take place
2, 200° C
The filament is a small coil of thin — wire
thoriated tungsten
Shallow depression in the cathode assemblyl assigned to house the filment
Focusing cup
It’s purpose is to narrow the thermionic cloud as it is driven toward the anode
Focusing cup
What is the focusing cup made out of
Nickel
Negatively charged to electrostatically confine the electron beam to a small area of the anode
Focusing cup
Positive side of the tube
Anode
3 Fuctions of the anode
- Serves as a target surface for the hig-voltage electron from the filament (source of x-rays)
- Conducts high voltage from the cathode back into the x-ray generator circuitry
- Serves as primary thermal conductor
2 Types of Anode
- Stationary Anode X-ray Tube
- Rotating Anode X-ray TUbe
Where are stationary and rotating x-ray tube usually used?
Stationary: dental and portable x-ray
Rotating: general x-ray
Area of anode struck by the electrons from the cathode
Target
3 other terms for the target
- Focal spot
- Focal point
- Focal track
The stationary target consists of (1) embedded in a (2) angled end of (3)
- rhenium-alloyed tungsten
- 45°
- copper rod
Rotating target: Entire rotating disk which has a dimension of (1) is the target (made up of [2])
- 5-13cm
- tunsten alloy
High capacity x-ray tubes have (1) or (2) layered under the
- molybdenum
- graphite
What is the material of choice for the target for general rafiography, and give 3 reasons why
TUNGSTEN
1. Atomic number
2. Thermal conductivity
3. High meting point
Tungsten meting point
3,410°C
Differentiate the copper block from the anode stem
Copper block is stationary and is made up of copper. Anode is rotating and is made up of molybdenum.
Mechanically supports the tungsten target and removes heat efficiently from the tungsten target due to its high heat conductivity
Copper block
The shaft between the anode and rotor
Anode stem
Why is the anode stem so narrow?
So as to reduce thermal conductivity
Normal x-ray tubes rotate (1) rpm (revolutions per minute)
While high capacity machines can reach up to (2) rpm
- 3,400
- 10,000
Used to turn the anode
Induction motor (rotating)
2 components of the induction motor
- Stator
- Rotor
A series of electromagnets equally spaces around the neck of the tube
Stator
Differentiate the stator and rotor on the induction motor in terms of where they can be seen
The stator is a part outside of the glass/ metal enclosure while the rotor is a part inside of the galss/ metal enclosure
Shaft made up of bars of copper and soft iron fabricated in one mass
Rotor
What is the rotor made up of?
bars of copper and soft iron
Copper and soft iron are — whic hmeans they are attracted to magnet
Ferromagnetic
HEAT DISSIPATION
The purpose of the stem is to (1) the heat out of the x-ray tube. This is different compared to the roating anode which (2) radiates away the heat through the (3). The stationary anode will conduct the heat out of the tube to the (3).
- conduct
- radiates away
- surroundign oil
