test 2 - quizlet Flashcards
what are the 5 different xray interactions with matter
classic compton photoelectric pair production photodisintegration
this x ray interaction causes atoms to release an equal energy photon with the wavelength equal to incident photon, what xray interaction is this
classic (coherent or thompson)
T/F: at 70kVp, a very few coherent scatter xray photons are produced
True
T/F: compton scattered xray energy is EQUAL to the difference between the energy of the incident xray photon and energy of the ejected election
True
This occurs when incident photon interacts with outer shell electron which results with ejection of “Compton” or secondary electron. The x-ray than continues with less energy and in different direction. The energy of the ejected electron equals to the binding energy of outer shell electron plus the kinetic energy with which it leaves the atom.
compton effect
T/F: compton scatter x ray retains almost all of its energy and causes more ionizing events before losing all of its energy
TRUE
compton scatter probability (increase or decrease) with an increase in x ray energy
decrease
T/F: Compton-effect probability does not depend on the atomic number (Z) of the involved atoms regardless whether its a soft tissue or bone. An increase of total mass density will, however increase Compton interaction.
TRUE
T/F: compton contributes to lowering radiographic contrast and causing radiation to the patient and staff
TRUE
The relative frequency of Compton compared to photoelectric (Increases or Decreases) with increasing energy of the x-photons
increases
a form of interaction of x rays when a relatively lower energy photon interacts with the electron in the atom and removes it from its shell
photoelectric effect
the photoelectric probability will be maximum when what 3 conditions are met
1) The energy of the incident photon is equal to or just greater than the binding energy of the electron in its shell and when the electron is tightly bound (as in inner or K shell)
2) The electron is removed and called a “photoelectron”
3) The incident x-ray photon is then completely absorbed in the process
The Photoelectric absorption is one of the reasons for ___________ of the X-ray beam as it passes through different matters
attenuation
if the atomic number (Z) of the medium increases, PE will (increase or decrease) accordingly
increase
if the x ray photon energy (E) increases or doubles, PE will be (increased or decreased)
decreased
True or False: Small changes in Atomic Number (Z) can be responsible for a significant changes in PEA
TRUE: high Z such as lead (Z=82) are useful shielding material
True or False: Photoelectric interaction will not occur unless the incident photon has the energy equal to or just greater than the electron binding energy of K-shell electron
TRUE
An increase in x-photon energy will result with a decrease (reduction) in Photoelectric effects in comparison to Compton effect.
TRUE
Increased atomic number (Z) of the absorber will have no direct effect on Compton scatter, However, an increase in total mass density of the matter will result in proportionate increase in Compton scatter
TRUE
True or False: Photoelectric Absorption is the most significant contribution to radiographic image formation and unfortunately a major contribution to radiation dose to the patient
TRUE
An increase of x-photon energy (kVp) will result with (Increased or Decreased) absolute Photoelectric interaction
decreased
What are the 5 Radiographic densities identified on the radiographic image?
air fat soft tissues bone metal
True or False: Photoelectric Absorption is the most significant contribution to radiographic image formation and unfortunately a major contribution to radiation dose to the patient
TRUE
An increase of x-photon energy (kVp) will result with (Increased or Decreased) absolute Photoelectric interaction
decreased
What are the 5 Radiographic densities identified on the radiographic image?
air fat soft tissues bone metal
When an incident x-photon has sufficient energy it may come too closely to interact with the nucleus of the atom. Such interaction will cause x-photon to disappear and in its place a pair of positron(+) and (-) charged electron are produced by the nucleus
pair production
Is it possible to get Pair Production in diagnostic x-ray imaging?
No, X-rays of 1,000,000 MeV are required and Since diagnostic x-rays are within 30-150 kVp Pair production does not occur
When x-photons possess energies above approx 10 MeV. They will escape any interaction with the electrons and be completely absorbed (disintegrated) by the nucleus.
photodisintegration
True or False: X-photons within an energy range that would produce Photodisintegration are not used during any diagnostic imaging procedures
TRUE
In diagnostic imaging and Radiography only 2 x-ray production mechanisms are important: what are these 2 x-ray production methods?
bremsstrahlung and characteristic
Radiographic _______ are used to remove “clean up” Compton scatter
grid
True/False: During image formation Compton scatter contributes no useful information to the image
TRUE
As tissue Atomic Number (Z) increases what happens to:
- Compton scatter
- Photoelectric absorption
- exposure of the film
- No change
- Many more Photoelectric effects
- Fewer X-ray transmission, leaving the film white
Differential absorption occurs principally due to some x-rays absorbed as PE, some deflected as scatter and others passing through the body tissues without interaction, thus exposing the film.
how does differential absorption occur
As x-ray energy increases what happens to:
- Compton scatter
- Photoelectric effects
- exposure of the film
- Fewer Compton scatter
- Many fewer Photoelectric effects
- More x-photons expose the film by transmitting through tissues turning the film black
As tissue Atomic Number (Z) increases what happens to:
- Compton scatter
- Photoelectric absorption
- exposure of the film
- No change
- Many more Photoelectric effects
- Fewer X-ray transmission, leaving the film white
As tissue mass density increases what happens to:
- Compton scatter
- Photoelectric effect
- exposure of the film
- Proportional increase in Compton
- Proportional increase in Photoelectric effects
- Proportional reduction in x-ray transmission.
