Photon interaction Flashcards
what does incident mean?
falling upon or striking
what does ionization mean?
removal of an electron from an atom
What is scatter?
change in direction
what causes scattering?
interaction between photon and an object that has enough atoms to change the direction of the photon
What does photon transmission mean?
means there was no physical contact between the photon and atom, straight through.
Dark area on the radiograph represents…
are where the x ray hit without encountering anything thing
What is another name for Coherent Scattering?
it is also known as classical scatter
Describe Coherent Scattering (classical)
It is when a low energy photon come into contact with valence shell electron, excites it, causing the electron to produce photon of equal energy. No useful information, but add to noise and degrade image.
In compton effect, describe the energy level of photon interacting with the atom, which shell of electron it is interacting with, and what the characteristic of the scattered photon, AND how the compton effect affect the radiograph?
photon energy level: moderate to high energy,
it interacts with the outershell electrons, ejecting it
the photon that is produced is a lower value than the incident photon
it causes image noise
in radiology, what is the most common scatter that is dealt with?
Compton Scatter
Describe Photoelectric effect: 1. what type of energy?, where does it interact. 2. is the photon absorbed? 3. what gets ejected? and what is it called after it has been ejected? 4. what is it dependent on? 5. if it has been ionized at certain shell, what is it called? 6. when is PE most probable? 7. what range of KVP is PE dominant? and why? 8. what does atomic number has to do with this?
moderate to high energy, with inner shell of the atom. the photon is completely absorbed, as inner shell electron gets ejected, it becomes photoelectron. PE depends entirely on the which shell it has been ionized from. if it has been ionized at k shell, it is call K-characteristic photon, it is most probable when electron binding energy is slightly less than energy of incident photon. the range of kVp is 25-150kVp, cause of photon absorption.
Pair Production: 1 level of energy of the photons and location of interaction. 2 what is the required photon energy? 3 what two electrons appear ? 4 what is stage two of pair production called?
higher energy photons, dealing with nuclear electrostatic field. 1.02 MeV. Positron and Negatron (becomes oribting e), stage 2 of pair production is called annihilation reaction.
describe annihilation reaction
it is the stage 2 of the pair production photon interaction. when the positron comes to a rest, combine with the free floating e and then disappear, then give rise to two photons going in different direction at value of .51MeV each.
Describe photodisintegration, what photon energy level are we dealing with? what does the nucleus emit?
10MeV, emits a nucleon or other nuclear fragment.
what is differential absorption?
results of x ray photon interaction within the body.
