FRCR Radiation Physics and Dosimetry Flashcards

Which unit is used to express absorbed radiation dose in the SI system?

Answer: Gray (Gy)

The Gray (Gy) is the SI unit of absorbed dose, defined as 1 joule of energy deposited per kilogram of tissue.

What does the radiation weighting factor (wR) account for when calculating equivalent dose?

Answer: Biological effectiveness of different radiation types

The radiation weighting factor adjusts for the relative biological effectiveness of different types of ionizing radiation when calculating equivalent dose in Sieverts.

Which of the following best describes the half-value layer (HVL) of an X-ray beam?

Answer: Thickness of material that reduces beam intensity by 50%

The HVL is the thickness of a specified material required to reduce the X-ray beam intensity (or air kerma rate) to exactly half its original value.

In X-ray production, which interaction is primarily responsible for the continuous bremsstrahlung spectrum?

Answer: Deceleration of electrons in the Coulomb field of nuclei

Bremsstrahlung ('braking radiation') is produced when high-speed electrons are decelerated by the strong electric field of target nuclei, emitting X-ray photons with a continuous energy spectrum.

What is the primary purpose of added filtration in a diagnostic X-ray tube?

Answer: Remove low-energy photons to reduce patient skin dose

Added filtration (typically aluminum) preferentially attenuates low-energy photons that would be absorbed by the patient's skin without contributing to image formation.

Which quantity is used to express the stochastic radiation risk to a whole organism accounting for tissue sensitivity?

Answer: Effective dose (Sieverts)

Effective dose uses tissue weighting factors (wT) to sum equivalent doses across all irradiated organs, giving a single value proportional to overall stochastic risk.