Principles of Radiology Flashcards
What are x-rays? Examples? (4)
- A form of electromagnetic radiation
- Examples:
- Gamma rays
- Radio waves
- Visible light
- TV waves
What is a radiograph?
An image produced on film due to x-rays
How do electromagnetic waves move?
In an X & Y axis
T/F: X-rays have a shorter wavelength than visible light, therefore they can penetrate object when visible light is reflected or absorbed
True
What is it in X-rays that allows certain materials to fluoresce?
Photons do this, they cause “excitement.”
Therefore, we can record images
T/F: Light and X-rays act like waves traveling thru space
True
T/F: Light and X-rays act like particles when interacting with matter
True
T/F: Light and X-rays don’t travel in straight lines
False. They don’t, therefore, they cannot go around corners
T/F: Light and X-rays diverge from a point source
True
T/F: X-rays are affected by magnetic fields
False! They are NOT affect by magnetic fields
T/F: X-rays travel at the speed of light
True
Where do X-rays come from? How does it work?
- An x-ray tube!
- How it works:
- Fast moving electrons hit a metal target
- 99% of energy is converted to heat
- 1% of energy is converted to x-rays
Basic parts of the x-ray tube (4)
- Air evacuated glass chamber
- Cathode
- Anode
- Cooling mechanism
Air evacuated glass chamber
Prevents electrons from colliding with air molecules
Cathode
Source
How it works
- Source of electrons
- Negative end - 1-2 wire filaments within wells of focusing cup
- Filaments are heated to critical temp and electrons are boiled off.
These electrons are then accelerated toward the anode
Anode
- Target for electrons from cathode
- Where x-rays are created
- Positive end
Focal spot
- A small focal spot produces a more detailed image
- Small filaments produce limited number of electrons
Effective focal spot
Angling the target a small degree will produce a small effective focal spot
Heel effect
- Angled anode leads to more energy on cathode side of beam due to partial absorption of beam into anode.
- Therefore, one should place thicker body parts toward the cathode side of the beam to produce more uniform image
T/F: One should place thicker body parts toward the cathode side of the beam to produce more uniform image due to the Heel Effect
True
T/F: Cooling mechanisms are required in x-ray machines because filament may get as hot as 3000 F
True
T/F: Stationary anode has a tungsten target embedded in block of copper. This design is used in dental & portable x-rays
True
T/F: Rotating anode won’t dissipate heat and makes a larger focal spot. This will increase image detail
False.
It WILL dissipate heat and makes a SMALLER focal spot that will INCREASE image detail
In regards to X-ray care, do not… (4)
- Drop or hit xray tube
- Leave machine on continuously
- Hold down the rotor “ride the rotor”
- Make too many high energy exposures in rapid succession
T/F: X-rays can only make shadow images.
Small beam = sharp shadow
Large beam = fuzzy shadow
True!
Rectifier definition
Changes AC to DC
Grid definition
Absorbs some scatter
Electron definition
Neg charged atomic particle
Photon definition
Packet of energy
Focal spot definition
Specific region on the target where the xray leaves to the world
