RT Radiation Biology 2

Question 1

Compared to low-LET radiation, high-LET radiation has a relative biological effectiveness (RBE) that is:

Accepted Answer

Higher — more biologically effective per unit dose

Answer

Lower — less biologically effective per unit dose

Answer

Equal — the same effectiveness per unit dose

Answer

Variable — depends only on dose rate, not LET

Question 2

In the linear-quadratic model S = e^(–αD – βD²), the αD (linear) component represents:

Accepted Answer

Single-hit (single-track) lethal cell killing

Answer

Two-hit (double-strand break) cell killing

Answer

Sublethal damage repair

Answer

Repopulation between fractions

Question 3

What is 'reoxygenation' in the context of tumor radiobiology?

Accepted Answer

The re-establishment of oxygen supply to previously hypoxic tumor cells after irradiation

Answer

Adding oxygen gas to radiation beams to increase ionization

Answer

Breathing supplemental oxygen during radiation treatment sessions

Answer

The use of hyperbaric oxygen chambers post-treatment

Question 4

Which tissues have a LOW alpha/beta ratio of approximately 2–3 Gy?

Accepted Answer

Late-responding tissues such as spinal cord and lung

Answer

Rapidly proliferating tumors (e.g., head and neck cancers)

Answer

Acutely responding tissues like oral mucosa and skin

Answer

Hematopoietic (bone marrow) tissues

Question 5

The Bergonié-Tribondeau law states that cells are MORE radiosensitive when they:

Accepted Answer

Have high mitotic activity and are less differentiated

Answer

Are highly differentiated with low mitotic activity

Answer

Have a high intracellular oxygen concentration

Answer

Are in late S phase of the cell cycle

Question 6

What is 'sublethal damage repair' (SLDR) in radiobiology?

Accepted Answer

Repair of radiation-induced lesions that, if unrepaired, could accumulate into lethal damage

Answer

Permanent, irreversible damage that prevents cell division

Answer

Damage only to RNA, not to DNA

Answer

Repair processes that occur exclusively in tumor cells

Question 7

What is the Tumor Control Probability (TCP) in radiation oncology?

Accepted Answer

The statistical likelihood that a given radiation dose will eradicate all clonogenic tumor cells

Answer

The probability that all normal tissue complications are avoided

Answer

The ratio of irradiated tumor volume to total tumor volume

Answer

The percentage of patients who achieve partial response