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What causes x-ray beams to be polyenergetic (many energies) and heterogeneous (different kinds)? (Note: this is after electrons hit the anode))
Due to different interactions between high-speed electrons from the cathode and tungsten atoms of the anode.
If 90 kV is selected for x-ray production, what range of energies can be expected?
Approximately 30-90 kV, so the lowest can be about 1/3 of the energy level.
What property of tungsten makes it useful for medical imaging?
High atomic number
Why is tungsten useful in the medical field?
It has energy levels that are useful for medical applications.
Why did early pioneers who studied x-radiation suffer radiation-induced afflictions?
Because x-rays are invisible, and safety standards had not been set at the time.
What happens when certain chemicals are activated by x-rays?
They fluoresce or glow when activated by x-rays, such as barium platinocyanide, rare earths, and calcium tungstate phosphors.
What are some events where the effects of radiation became more apparent?
Atomic bomb, Three-Mile Island, Chernobyl, and Fukushima Daiichi.
What are a few long-term effects of radiation poisoning?
Erythema, alopecia, cataracts, and leukemia
How do Geiger counters and ionization chambers detect radiation?
They detect radiation by using x-rays' ability to ionize gas through interaction with outer shell electrons.
What is leakage radiation?
Radiation emitted from the x-ray tube housing in all directions except the useful beam.
What is scatter radiation?
Radiation that has interacted with an atom and been redirected from its original path.
How does scatter radiation differ from primary radiation?
Scatter radiation has less energy than primary radiation.
Can x-rays be focused by a lens like light?
No, x-rays cannot be focused by a lens unlike light.
What is the role of the focusing cup in the x-ray tube?
The focusing cup does not focus electrons but guides the electron stream into a narrower path.
How does the focusing cup affect x-ray photons? (Note: The narrow stream of electrons (cathode ray) is still applied to x-rays from conversion)
It produces x-ray photons that are closer together as a beam.
How do x-rays travel from the source?
X-rays travel in a straight line and diverge (spread out) from the source. (Note: Like light from a flashlight)
What happens when x-rays interact with an object?
They can scatter in a different direction.
At what speed do x-rays travel?
X-rays travel at the speed of light.
Are x-rays affected by electric or magnetic fields?
No, x-rays are electrically and magnetically neutral and not influenced by electric or magnetic fields.
How do x-rays affect photographic film?
X-rays ionize silver halide crystals in the film emulsion.
What happens after the silver halide crystals are ionized?
The film is processed, producing varying degrees of blackness.
What does the x-ray beam consist of?
The x-ray beam consists of many energies.
What does 70 kV determine in an x-ray beam?
70 kV determines the energy or penetrating ability of the x-ray beam.
What happens to the energy of some photons in the 70kv x-ray beam?
Some photons (or quanta) will have energies of 70 kV or less. (Note: Quanta, x-ray, photon are all synonymous)
What does 5 mAs determine in x-ray production?
The amount of electrons present to produce the x-rays and the length of time such electrons are allowed to flow.
What happens to weaker quanta in the body?
Weaker quanta will not have enough energy to pass through and will be absorbed or attenuated (absorbed) by tissue.
What happens to higher quanta in the body?
Higher quanta will penetrate the bones and muscles to form an image on the radiograph.
How does the thickness of the material influence x-ray attenuation (absorption)?
A thicker piece of material absorbs more x-rays than a thinner piece of the same material. (Note: it's saying that thicker materials take in more x rays so that's how x rays are weaker)
How does the density and atomic number of the material influence x-ray attenuation (absorption)?
The material with the higher density or atomic number will attenuate more x-rays than a material with a low density or atomic number.
What is an example of a material that attenuates (absorbs) more x-rays?
Bone will attenuate more x-rays than air/gas.
How does bone attenuate (absorb) x-rays?
Bone attenuates x-rays, reducing the number of x-rays that interact with the image receptor (IR) underneath the patient.
What does bone look like on the radiograph?
Bone appears as white on the radiograph.
How does strong and weak x-rays interact with air?
Air is thin and has a low atomic number, allowing strong and weak x-rays to pass through.
What does air look like on a radiograph? (Note: The reason why lungs appear dark is because they have air in them)
Air produces black shades on the radiograph as the x-rays pass through and interact with the IR.
Why do stronger x-rays pass through muscle and fat but not bone?
Since muscle and fat are less dense than bone, stronger x-rays pass through them and interact with the IR.
How does muscle and fat appear on a radiograph?
Creates gray shades on the radiograph.
