Photon Interactions PPT Flashcards
What is Coherent Scattering also known as?
Conerent Scattering is also known as elastic scattering, Thomson scattering, unmodified scattering, classical scattering, and Rayleigh scattering.
What is the result of the energy interaction in Conerent Scattering?
The energy is taken up from the beam and scattered in all directions, but none of the energy is absorbed. This is a form of attenuation without absorption.
Is Conerent Scattering important in practical radiotherapy?
This interaction is of little importance in practical radiotherapy.
What is the photoelectric effect?
The photoelectric effect is the phenomenon where photons interact with electrons, causing the photons to disappear altogether after interacting with the inner-shell electron.
How does the probability of absorption vary for photoelectric effect?
The probability of absorption varies inversely with the cube of energy and directly with the cube of atomic number (Z³/E³).
What is the primary mode of interaction in diagnostic radiology?
The primary mode of interaction in diagnostic radiology is the photoelectric effect.
What effect does the photoelectric effect have in radiology?
The photoelectric effect is responsible for the contrast effect in radiology.
What is the Compton effect?
The Compton effect refers to the scattering of a photon by an outer orbital electron.
What happens during Compton scattering?
During Compton scattering, a photon interacts with an outer orbital electron, imparting some of its energy to the electron, which ejects it from orbit.
What is a Compton electron?
The ejected electron from the atom during Compton scattering is called a Compton electron.
What happens to the photon after it interacts with an electron?
The photon continues on an altered path, scattered, with less energy (longer wavelength) than before the collision.
What is Compton Scattering also known as?
Compton Scattering is also known as modified, incoherent, and inelastic scattering.
What are the results of the Compton effect?
The Compton effect results in both attenuation and absorption.
How effective is concrete in shielding megavoltage equipment?
Concrete is as good as lead in shielding megavoltage equipment.
What does the direction of scatter depend on?
The direction of the scatter depends on the energy of the incident photon.
What is the relationship between photon energy and forward scatter?
As the photon energy increases, there is a corresponding increase in the forward scatter of the beam.
What is 90 degree scatter associated with?
What is 180 degree scatter associated with?
0.511 MeV
0.255 MeV.
What is Pair Production?
When a photon with energy in excess of 1.02 MeV passes close to the nucleus of an atom, the photon disappears, and a positron and an electron appear.
What is the result of Pair Production in terms of attenuation and absorption?
Pair production results in attenuation of the beam with absorption.
What happens to the positron created in Pair Production?
The positron loses its energy by interaction with an electron to give rise to two annihilation photons, each having 0.51 MeV energy.
How does atomic number affect pair production?
The probability of pair production increases with the atomic number (Z^2)
What is the energy of an incident x-ray photon in pair production?
The energy of an incident x-ray photon is 0.511 MeV.
What is photodisintegration?
Photodisintegration is a reaction that occurs when a photon has energy greater than the binding energy of the nucleus itself.
What is the main use of photodisintegration?
The main use of photodisintegration is for energy calibration of machines producing high energy photons.
