Xray Tube Flashcards
What is part of the cathode ?
Filament and focusing cup
What charge is the cathode
Negative
What charge is the anode
Positive
What kind of material is the filament made of ?
Thoriated Tungsten
What material is the focusing cup made of
Nickel
Target
May also be called the focal point, focal spot, or the focal track
Tube housing
Protects against leakage radiation and electric shock
Thermionic Emission
The process of boiling off electrons and produces a cloud of electrons by heating the filament
Space charge effect
Occurs when no more electrons can be boiled off the filament
Three components of anode.
Anode, stator and rotor
Is the primary thermal conductor of the tube
Anode
Two types of anodes
Rotating and stationary
Portion of the anode struck by electrons
Target
What is the anode made up of
Tungsten rhenium alloys
What does it mean to have two filaments
Dual focus tube
Why does the X-ray tube need to be warmed up
Prevent cracking and maintain vacuum
Purpose of rotating anode
Promote greater heat dissipation
What determines the number of electrons boiled off
mA
Anode heel effect
Absorption of X-rays produces in the tube by the anode, causes uneven distribution of X-ray intensity between the cathode and anode, more intensity on cathode side (fat cat)
Project area of X-ray beam
Effective focal spot
Cardinal rules of Radiationg Protection developed to prevent radiation injury
Time, distance, shielding
Why is tungsten used
High melting point and Difficult to vaporize
Atomic number of tungsten rhenium alloy
74
Who was the first fatality from X-rays in 1904
Clarence Dally
Area where electrons strike the anode
Focal spot
Who devised a fluoroscope
Thomas Edison
Who improved the crooked tube
William Coolidge
What was the first ever xray
Roentgens wife’s hand
Leakage radiation limit
100 milliroentgens per hour at 1 meter
When was X-rays discovered
Nov 8, 1895
Physical area of the focal track being hit by the electrons.
Actual focal spot
What is the environment inside the X-ray tube once all air has been removed
Vacuum
Who discovered X-rays
Wilhelm Conrad roentgen
Necessary qualities of the anode
High atomic number, high melting point, and high heat conduction ability
Heat tolerant Pyrex glass or metal
Envelope
What do electrons become when they hit the anode
Photons
What two things control the size of the effective focal spot
Size of the actual focal spot and anode target angle
What is the line focus principle
Spreads heat over a greater area of the anode and allows the effective focal spot to be smaller than the actual focal spot
What is the purpose of the glass envelope
Absorbs X-rays and ensure a vacuum
Purpose of the focusing cup
To group the electrons for their passage to the anode
A molybdenum shaft is used to connect the anode to the rotor because
It is a less dense metal with a high melting point that helps anode to spin faster
Purpose of the fan in the tube housing is to
Promote heat dissipation
Average anode rotation speeds in diagnostic ray tubes are in the ranges of :
3,000-10,000
These are all apart of production of X-rays
Electrons, target, high voltage , and vacuum
Is made of molybdenum and connects the anode to the rotor
Stem
What is the X-ray efficiency
1% X-ray , 99% heat
The only thing located outside of the envelope that consists of copper windings
Stator
Made of a copper cylinder in the step of the X-ray tube and is support by the high strength ball bearings
Rotor
What are two types of cathode failures
Tube arcing and filament breakage
What is it called when they are holes on the focal track
“Pitting”
What is anode layering
Assists with heat loading and increases X-ray tube thermal capacity. It is backed with molybdenum or graphite
What does the protective housing consist of
Metallic , supports X-ray tube, controls leakage and scatter radiation, provide mechanisms to cool tube
How can we extend the tube life
- tube warm up
- avoid frequent “boosting”
-use low mA when possible - use low speed rotation when possible
- follow rotating charts
- avoid rough handling
- listen to unusual sounds
What is off focus radiation
Undesirable part of the beam , not hitting anode, low energy and no diagnostic value, produces “ghosting”
What does X-ray stand for
The x in X-ray means unknown
What is the divergence of the beam
Energy that is coming out and what’s interacting with the patient
True or false
X-rays are invisible
True
True or false
X-rays can travel around corners
False
True or false
Taking X-rays is a safe profession
True
True or false
Radiation can cause harm to your body
True
Sequence of taking X-rays
- Current runs through the filament circuit
- Filament gets hot
- Filament glows
- Filament boils of electrons
- Electrons form a space cloud
- Electrons are repelled from the focusing cup
- Electrons are attracted by the anode
- Electrons move over to the anode
- Electrons slam into the anode at the target
- Electrons lose energy
- Light, heat and X-rays are produced
- Focal spot if formed
- X-rays are emitted isotropically
- X-rays are absorbed by the glass and metal housing
True or false
X-rays are electrically neutral
True
True or false
X-rays have mass
False (X-rays have no mass)
True or false
X-rays can be focused
False - can’t be focused or refracted
True or false X-rays travel in straight lines
True
ways to avoid dangers of radiation
- never stand in primary beam
-collomating as small as you can - never hold patient
-lead protection - radiation dose monitored through use of dosimeter
what type of body parts would the small filament focus on
small focusing body part (less heat)
what type of body parts would the large filament focus on
large focusing body parts (more heat)
what does the filament produce
filament produces electrons to produce image
what does the filament length and width impact
recorded detail or special resolution
Typically controlled by the xray circuitry and wont go hight that what is already set
Saturation Current
