CMD CMD Radiation Physics & Radiobiology

Question 1

What is the unit of absorbed dose in the SI system used in radiation therapy dosimetry?

Accepted Answer

Gray (Gy)

Answer

Rad

Answer

Roentgen (R)

Answer

Sievert (Sv)

Question 2

Which interaction of radiation with matter is most responsible for the biological damage caused by therapeutic X-rays?

Accepted Answer

Compton scattering

Answer

Photoelectric effect

Answer

Pair production

Answer

Rayleigh scattering

Question 3

In radiobiology, what does the 'α/β ratio' characterize?

Accepted Answer

Tissue sensitivity to fractionation

Answer

Linear energy transfer of the beam

Answer

Ratio of scattered to primary photons

Answer

Oxygen enhancement ratio

Question 4

What is the approximate half-value layer (HVL) concept used to characterize in radiation therapy physics?

Accepted Answer

Beam quality and penetrating power

Answer

Dose rate at isocenter

Answer

Percentage depth dose at dmax

Answer

Output factor of a field size

Question 5

Which factor does the Tissue-Phantom Ratio (TPR) eliminate compared to Percent Depth Dose (PDD)?

Accepted Answer

Source-to-surface distance (SSD) dependence

Answer

Field size dependence

Answer

Energy dependence

Answer

Scatter dependence

Question 6

What radiobiological principle describes the repair of sublethal radiation damage between dose fractions?

Accepted Answer

The '4 Rs' of radiobiology — Repair

Answer

Reoxygenation

Answer

Redistribution

Answer

Repopulation