Chapter 3: Interaction Of Radiation With Matter Flashcards
Average number of primary and secondary ion pairs produced per unit lenth of the charged particle’s path
Specific ionization
Transfer of some of the incident particles energy to electrons in the absorbingmaterial promoting them to electron orbits father from the nucleus
Excitation
The electron will return to a lower energy level with the emission of the excitation energy in the form of electromagnetic radiation or Auger electrons
De excitation
Result of ionization, consisting of an ejected electron and positively charged atom
Ion pair
Ejected electrons possess sufficient energy to produce further ionizations (definition)
What do you call these electrons
Secondary ionization
Delta rays
Defined as the distance the particle travels
Path length
Defined as the depth of penetration of the particle in matter
Range
Measure of the average amount of energy deposited locally in the absorber per unit path length
Linear energy transfer
Refers to an interaction that deflects a particle or photon from its original trajectory
Scattering
A scattering event in which the total kinetic energy of the colliding particles is unchanged
Elastic
When scattering occurs with a loss of kinetic energy
Inelastic
Radiation emission accompanying electron deceleration
Bremsstrahlung
4 major types of xray and gamma ray photon interaction
Rayleigh scattering
Compton scattering
Photoelectric absorption
Pair production
Incident photon interacts with and excites the TOTAL ATOM as opposed to individual electrons
Rayleigh Scattering
Occurs mainly with very low energy xrays such as those use in mammography (15 to 30 keV)
Rayleigh Scattering
Does ionization occur in Rayleigh Scattering
No
Also referred to as coherent or classical scattering
Rayleigh scattering
Also called inelastic or non classical scattering
Compton scattering
Predominant interaction of xray and gamma ray photons in diagnostic energy range with soft tissue
Compton scattering
All of the incident photon energy is transferred to an electron, which is ejected from the atom.
Photoelectric absorption
This xray interaction improves attenuation between tissues with slightly different atomic numbers, thereby improving image contrast
Photoelectric effect
Xray or gammay ray interacts with the electric field of the nucleus of an atom
Pair production
is the removal of photons from a beam of xrays or gamma rays as it passes through matter
Attenuation
Fraction of photons removed from a monoenergetic beam of xrays or gamma rays per unit thickness of material
Linear attenuation coefficient
Defined as the thickness of material required to reduce the intensity of an xray or gamma ray beam to one half of its initial value.
Half value layer
Refers to an experimental configuration that is designed to exclude scattered photons from being measured by the detetctor
Narrow beam geometry
The beam is sufficiently WIDE that a substantial fraction of scattered photons remain in the beam
Broad beam geometry
This is an ESTIMATE of PENETRATION power of the xray beam
Effective energy
The sift of the xray spectrum to higher effective energies as the beam transverses matter
Beam hardening
Kinetic energy released in matter
Defined at th ekinetic energy transferred ri charged particlesby indirectly ionizing radiration per unit mass
Kerma
Number of photons or particles passing through a unit cross sectional area
Fluence
Fluence rate + unit area per unit time
Flux
Amount of energy passing through a unit cross sectional area
Energy fluence
Defined as the energy imparted by ionizing radiation per unit mass of irradated materal
Absorbed dose
*this is designed for all types of ionizing radiation
Amount of electrical charge produced by ionizing electromagnetic raidation per mass
Exposure
Total amount of energy deposited in matter
Product of the dose and the mass over which the energy is imparted
Imparted energy
To modify the dose to reflect the relative effective of the type of radiation in producing biologic damage
Radiation weighing factor
Product of the absorbed dose and the radiation weighing factor
Equivalent dose
The sum ofthe products of the equivalent dose to each organ or tissue irradiated and the corresponding weighting factor for that organ or tissue is called…
Effective dose
Particle interaction, where energy transferred to an e- < binding energy
Results in the release of EM radiation/Auger electrons
Excitation
Particle interaction where in the transferred energy > binding energy
Results in an ion pair (Ejected e- and atom+) -emission-> Delta rays
Ionization
Defined as the probability distribution of xray photons as function of photon energy (keV)
Bremsstrahlung Radiative Interaction
calculated through mass energy TRANSFER coefficient
KERMA (Kinetic Energy Releases in Matter)
calculated from mass energy ABSORPTION coefficient
Absorbed Dose
