Definitions Flashcards
Percent depth dose
the ratio of dose at depth in tissue to the dose at electronic equilibrium on the beam axis. The ratio of dose at Dmax to dose at a certain depth in tissue.
Hypertension
a dizzy feeling associated with sitting or standing after a prolonged period of bed rest
Usage factor
the fraction of TIME in a treatment day in which a beam will be pointed at a particular barrier
Workload
the OUTPUT of the linac in a day
Occupancy factor
the fraction of time in a day a person will be OCCUPYING a space behind a particular barrier
Dose profile
a representation of the dose in an irradiated volume, as a function of spatial position along a single line
Linear attenuation coefficient (u)
fraction of photons attenuated per unit thickness
The shape of the isodose curves depends largely on two things:
field size and flattening filters
Irradiated volume
the volume larger than the treatment volume receiving some significant dose
Tumor volume
the actual physical dimensions of the tumor, including regions of presumed occult spread
As SSD increases, the depth dose….
increases
Exposure is measured in
C/ kg
Rad is measured in
J/ kg
Stopping power
the rate of kinetic energy lost per unit path length
Compton interaction is independent from…..
atomic number. Only photon and free electron
