Define scattering power
The capacity of a material to deviate incoming radiation from its original path. Defined as increase in mean square angle of scattering per unit of mass thickness of the medium
Define linear stopping power
Average energy lost by a charged particle per unit distance of travel through a medium
Define air kerma
Kinetic energy transferred from indirectly ionizing radiation to charged particles per unit mass of air. Unit: Gy
Define reference air kerma rate
Air kerma rate measured in air at a distance of 1 meter from the source’s centre, corrected for air attenuation and scattering
Define air kerma rate
Air kerma per unit time
Unit: Gy/s or Gy/hr
Define air kerma rate constant
Air kerma rate in vacuo, at a specified distance from a point source of a given radionuclide, per unit activity
Unit: (Gym^2)/(Bqs)
Define air kerma strength
Product of air kerma rate in vacuo at a specified distance from the source’s centre and the square of that distance
Define linear energy transfer coefficient
The fraction of photon energy transferred to kinetic energy of charged particles per unit thickness of material
Define linear attenuation coefficient
Fraction of a photon beam’s intensity reduced per unit thickness of a material due to absorption and scattering
Define energy absorption coefficient
Fraction of photon energy absorbed by the material per unit thickness of the absorber. It excludes the fraction of energy lost to secondary processes such as bremsstrahlung.
state the Paddick formula for conformity index
PCI = (target volume receiving prescribed dose)^2 / (target volume x volume receiving prescribed dose)
state the formula for homogeneity index
HI = (D2% - D98%)/ D50%
state the formula for dose-gradient index
DGI = V50%/V100%
state the formula for conformity index for SABR treatments
CI = (reference isodose volume)/ PTV
define basal dose rate in Paris system for interstitial brachytherapy
The average of minimum dose rates between adjacent sources in the central plane
