FRCR Radiobiology

Question 1

According to the linear-quadratic model, what is the typical alpha/beta ratio for late-responding normal tissues?

Accepted Answer

1–3 Gy

Answer

8–10 Gy

Answer

15–20 Gy

Answer

5–7 Gy

Question 2

Which phase of the cell cycle is most sensitive to ionizing radiation?

Accepted Answer

G2/M phase

Answer

Early S phase

Answer

G1 phase

Answer

Late S phase

Question 3

What type of DNA damage is most responsible for radiation-induced cell death?

Accepted Answer

Double-strand breaks

Answer

Single-strand breaks

Answer

Base modifications

Answer

DNA-protein cross-links

Question 4

The oxygen enhancement ratio (OER) for low-LET radiation such as X-rays is approximately:

Accepted Answer

2.5–3.0

Answer

1.0

Answer

1.5

Answer

4.0–5.0

Question 5

Which of the following best defines the therapeutic ratio in radiotherapy?

Accepted Answer

The difference between tumor control probability and normal tissue complication probability

Answer

The ratio of alpha to beta values in the LQ model

Answer

The ratio of tumor control dose to normal tissue tolerance dose

Answer

The ratio of dose per fraction to total dose

Question 6

According to the Bergonié and Tribondeau law, which cells are most radiosensitive?

Accepted Answer

Rapidly dividing, undifferentiated cells

Answer

Highly differentiated, slowly dividing cells

Answer

Post-mitotic cells with high metabolic activity

Answer

Cells in G0 phase with low oxygen tension

Question 7

In the linear-quadratic (LQ) model, the linear (α) component of cell kill represents:

Accepted Answer

Cell kill proportional to dose, representing lethal double-strand breaks from a single event

Answer

Sublethal damage that can be repaired between fractions

Answer

Cell kill proportional to the square of the dose

Answer

Cell kill occurring only at high dose rates