What is an x-ray? Flashcards
What is an x-ray?
It’s a wave packet of energy called a photon.
It can penetrate human tissues and create an image
Who discovered x-rays?
Wilhelm Roentgen (1895)
Do all x-ray machines produce the same photons?
No
Why don’t all photons pass through the patient?
Because they have different energy levels: low energy stop inside a patient, high energy can pass right through
Is it just one photon required to take an x-ray?
No, it uses millions of photons to constitute an x-ray beam
Are wavelengths of x-rays considered long or short?
Short
Do x-rays have high photon energy or low?
High - it’s ionising radiation
What is the difference between x-rays and gamma rays?
Nothing, they are identical. They are both ionising.
BUT x-rays are man-made, but gamma rays are naturally occurring
What produces gamma radiation?
Radioisotopes.
Rocks and soil in earth’s crust, outer space, certain foods
Approx how much background gamma radiation does a person annually receive?
~ 2.6 mSv
What 4 things that can happen when an x-ray hits a pt?
Transmitted unchanged (high energy).
Absorbed (low energy and disappears)
Scatter + absorption (some loss of energy)
Pure scatter ( no loss of energy)
What is the trajectory of an x-ray?
They travel in straight lines
What medium is required for x-rays to work?
No medium is required
What level do they interact at in the patient?
They interact at an atomic level
How are the damaging effects of x-rays classified?
- Somatic deterministic effects (certainty effects) - can be acute or chronic
- Somatic stochastics effects
- Genetic stochastic effects
What are the acute (short-term) somatic deterministic effects of x-rays?
radiation sickness
coma
death
What are the chronic (long-term) somatic deterministic effects of x-rays?
hair loss
obliterative endarteritis (damage to blood vessels)
cataract formation
What does stochastic mean?
Chance - governed by laws of probability
What is the main, important difference between deterministic and stochastic effects?
Deterministic effects have a threshold dose, which stochastic effects does not
What is an example of a somatic stochastic effect?
Cancer induction
Why is dosage not important when considering damage severity in somatic stochastic effects?
Because the dosage does not affect the severity of the damage.
It only affects the PROBABILITY of that damage occurring
Who does the genetic stochastic effects affect?
The offspring of the irradiated person
Is there a safe dose of radiation in dentistry?
No. there is always a risk, so the use of them needs to be justified.
How are detrimental deterministic effects prevented when using radiation?
Having rules and guidelines based on scientific evidence.
Limit probability of stochastic effects to acceptable levels - reduce risk by reducing dose
Do deterministic effects have a high or low threshold dose?
High
