FRCR Radiobiology 3

Question 1

Relative biological effectiveness (RBE) is defined as:

Accepted Answer

The ratio of a reference radiation dose to the test radiation dose required to produce the same biological effect

Answer

RBE is the ratio of the reference radiation dose (typically 250 kV X-rays or Co-60) to the test radiation dose needed to produce the same biological effect.

Question 2

Which type of radiation has the highest linear energy transfer (LET)?

Accepted Answer

Alpha particles

Answer

Alpha particles have the highest LET (~80–100 keV/μm), depositing energy densely over a very short distance, resulting in high RBE and significant biological damage.

Question 3

Reoxygenation in tumors during fractionated radiotherapy refers to:

Accepted Answer

Movement of previously hypoxic tumor cells into better-oxygenated positions after irradiation kills oxic cells

Answer

Reoxygenation occurs when previously hypoxic tumor cells receive improved oxygen supply after radiation kills surrounding oxygenated cells, increasing the radiosensitivity of remaining tumor cells.

Question 4

Which of the following is NOT one of the classic '5 Rs' of radiobiology?

Accepted Answer

Regeneration

Answer

The 5 Rs of radiobiology are Repair, Redistribution, Repopulation, Reoxygenation, and Radiosensitivity; 'Regeneration' is not part of this framework.

Question 5

The abscopal effect in radiotherapy refers to:

Accepted Answer

Tumor regression at sites distant from the irradiated field

Answer

The abscopal effect describes regression of tumors at sites outside the irradiated field, thought to be mediated by systemic immune activation triggered by local radiation.

FRCR - Fellowship of the Royal College of Radiologists Practice Test

FRCR - Fellowship of the Royal College of Radiologists Practice Test

FRCR Radiobiology 3