QA
This QA parameter confirms agreement between the optical distance indicator and the actual treatment distance.
What is ODI accuracy?
This x-ray production process produces a continuous energy spectrum.
What is bremsstrahlung radiation?
This phase of the cell cycle is generally the most resistant to radiation damage.
What is the S phase?
This effect has no threshold and probability increases with dose.
What is a stochastic effect?
This QA concept ensures the measured dose matches the planned dose within ±5% for IMRT.
What is patient-specific QA?
The maximum energy of bremsstrahlung photons produced in an x-ray tube is determined by this parameter.
What is tube voltage (kVp)?
This type of DNA damage is more lethal to the cell and is commonly caused by the direct action of radiation.
What is a double-strand break?
According to NCRP guidelines, this is the annual whole-body dose limit for radiation workers.
What is 50 mSv (5 rem)?
This linac QA parameter evaluates dose output constancy and must remain within ±3% for daily checks.
What is output constancy?
This photon interaction probability is independent of atomic number and depends on electron density.
What is Compton scattering?
This parameter on the cell survival curve represents the dose required to reduce the surviving fraction of cells to 37%
What is D₀?
This type of radiation effect has a dose threshold, and severity increases as dose increases.
What is a deterministic effect?
For photon beam calibration, this condition requires that the number of electrons entering a volume equals the number exiting.
What is electronic equilibrium?
This interaction requires a photon energy of at least 1.022 MeV and produces two 0.511 MeV photons traveling in opposite directions.
What is pair production?
This radiobiological concept explains why hypoxic tumor cells become more radiosensitive between fractions.
What is reoxygenation?
This shielding material is preferred for megavoltage photon beams due to cost, strength, and neutron moderation.
What is concrete?
This TG-43 parameter represents the air-kerma strength of a brachytherapy source and is expressed in units of U.
What is source strength (Sₖ)?
In a polyenergetic x-ray beam, the second HVL is typically larger than the first because of this phenomenon.
What is beam hardening?
This hypothesis assumes there is no safe dose of radiation and that cancer risk increases linearly with dose.
What is the linear no-threshold (LNT) model?
This NCRP limit applies to occupational exposure to the lens of the eye.
What is 150 mSv (15 rem)?