RT Radiation Biology

Question 1

Which of the following correctly lists the 4 R's of radiobiology?

Accepted Answer

Repair, Reoxygenation, Redistribution, Repopulation

Answer

The 4 R's of radiobiology are Repair, Reoxygenation, Redistribution, and Repopulation, which describe how cells and tissues respond between fractions of radiation.

Question 2

Which phase of the cell cycle is considered MOST radiosensitive?

Accepted Answer

M phase (mitosis)

Answer

M phase (mitosis) and the G2/M boundary are the most radiosensitive parts of the cell cycle because DNA is condensed and cells are actively dividing.

Question 3

What is the oxygen enhancement ratio (OER) for high-LET radiation such as fast neutrons?

Accepted Answer

Approximately 1.0 (no oxygen enhancement)

Answer

High-LET radiation has an OER close to 1.0, meaning oxygen does not significantly enhance radiation damage because the dense ionization tracks cause direct DNA damage regardless of oxygen.

Question 4

What is the primary purpose of the linear-quadratic (LQ) model in radiation therapy?

Accepted Answer

Predicting cell survival and comparing fractionation schedules

Answer

The LQ model (S = e^(–αD – βD²)) is used to predict cell survival after irradiation and to compare the biological equivalence of different fractionation schedules using the BED formula.

Question 5

Which cell cycle phase is considered MOST radioresistant?

Accepted Answer

Late S phase

Answer

Late S phase is the most radioresistant phase of the cell cycle because cells are actively synthesizing DNA and have increased repair capacity through homologous recombination.

RT - Radiation Therapist Certification Practice Test

RT - Radiation Therapist Certification Practice Test

RT Radiation Biology