What happens when x-ray hit you or your patients? Flashcards
What are two effects when x-ray interact at the atomic level?
- Photoelectric effect
- Compton scatter
what is the Photoelectric effect?
Photoelectric effect happens when the x-ray interacts with an inner shell electron.
Requires all the x-ray energy to eject that electron from the atom, the x ray becomes fully absorbed.
If more x-rays are absorbed less x-rays hit the detector and that part will look whiter.
why do denser objects look more radiopaque?
Denser objects have a higher atomic number so are going to absorb more x-rays, so the image will look more radiopaque.
why do these atoms become ionised?
The atom now has a positive charge as it has lost electrons, and the atom has become ionised.
what is Compton scatter?
Scatter occurs when the x-ray interacts with an outer shell electron. As the outer electron is further away from the nucleus less energy is required to remove the electron from the atom, so uses part of the x-rays energy. The atom still becomes ionised and contributes to dose.
why does compton scatter lead to a poor quality image?
As it only uses part of the x-rays energy to eject the electron from the atom, the x-ray gets redirected with less energy in a different direction. They reduce the image quality and contrast, because where the x-ray hits the detector does not correlate with the anatomy that the x-ray passes through.
how does x-rays interacts at a molecular level?
Damage can occur to the DNA molecules through direct ionizing radiation.
Vast majority of ionising radiation effects DNA indirectly through water molecules.
These water molecules becomes ionised and breakdown to produce free radicles that damage DNA.
how does x-rays interacts at a cellular level?
If the DNA becomes damaged there two potential outcomes:
* Cell death
* Cell mutation
What does cell death lead to
Cell death leads to deterministic effects – these affects will definitely occur once a threshold dose is passed (skin reddening, hair loss, cataracts).
what does cell mutation lead to?
Cell mutation leads to stochastic (chance) effects – May be induced from any dose of radiation, depends on laws of probability. There is no safe dose! If your body is not able to repair the DNA damage it can reproduce and develop into a malignancy. (Radiation induced cancers).
what is the correlation between dose and the risk of inducing cancer?
The probability of inducing cancer is low with low doses of radiation.
the severity of the effect is also increased with a high dose.
