RT Radiation Biology 3

Question 1

The therapeutic ratio (therapeutic index) in radiation oncology is BEST defined as:

Accepted Answer

The comparison of tumor control probability (TCP) to normal tissue complication probability (NTCP)

Answer

The therapeutic ratio compares TCP to NTCP; a favorable therapeutic ratio means meaningful tumor control can be achieved at doses that produce acceptable (low) rates of normal tissue complications.

Question 2

Hypofractionation in radiation therapy is BEST described as:

Accepted Answer

Using fewer fractions with a larger dose per fraction than conventional schedules

Answer

Hypofractionation uses larger doses per fraction (e.g., 2.5–20+ Gy per fraction) delivered in fewer sessions, exploiting the radiobiological properties of tumors with low α/β ratios such as prostate cancer.

Question 3

The 'bystander effect' in radiation biology refers to:

Accepted Answer

Radiation-induced damage occurring in cells that were NOT directly irradiated

Answer

The bystander effect describes biological damage (DNA strand breaks, mutation, apoptosis) in cells that received no direct radiation exposure, triggered by signals (e.g., cytokines, reactive oxygen species) from irradiated neighboring cells.

Question 4

For most solid tumors, the PRIMARY mechanism of radiation-induced cell death in rapidly proliferating cells is:

Accepted Answer

Mitotic catastrophe (reproductive cell death)

Answer

Mitotic catastrophe (reproductive death) is the dominant mechanism for most solid tumor cells; lethally damaged cells attempt mitosis but fail to divide successfully, dying at or after attempted division.

Question 5

Electron-affinic compounds such as misonidazole are used as radiosensitizers because they:

Accepted Answer

Mimic oxygen by accepting electrons in hypoxic cells, fixing radiation damage

Answer

Nitroimidazole compounds like misonidazole diffuse into hypoxic tumor regions and, like oxygen, accept electrons from radiation-induced free radicals, 'fixing' (making permanent) the DNA damage that would otherwise be repaired.

RT - Radiation Therapist Certification Practice Test

RT - Radiation Therapist Certification Practice Test

RT Radiation Biology 3