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 ratio of high-LET to low-LET radiation delivered during treatment

Answer

The percentage of patients achieving a complete pathological response

Answer

The ratio of treatment dose to the equipment-calibrated reference dose

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

Delivering many small daily fractions over a prolonged treatment course

Answer

Treating patients with radiation less than once per week

Answer

Delivering radiation at a lower dose rate to reduce normal tissue injury

Question 3

The 'bystander effect' in radiation biology refers to:

Accepted Answer

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

Answer

Radiation effects occurring exclusively in directly irradiated cells

Answer

The shielding of adjacent normal cells from radiation by tumor cells

Answer

The protective effect of neighboring healthy cells on irradiated tumor 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

Necrosis from direct membrane disruption

Answer

Apoptosis triggered by p53-independent pathways

Answer

Autophagic cell death

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

Increase tumor blood flow, improving oxygenation

Answer

Inhibit DNA repair enzymes in all cells equally

Answer

Sensitize cells by blocking them in the radiosensitive S phase

Question 6

In radiation oncology, 'tolerance dose' for a normal tissue is BEST defined as:

Accepted Answer

The maximum dose that a normal tissue can receive without an unacceptable risk of serious complications

Answer

The minimum dose required to control 50% of tumors

Answer

The dose at which 100% of treated cells are killed

Answer

The lowest dose that causes any measurable biological response

Question 7

QUANTEC (Quantitative Analysis of Normal Tissue Effects in the Clinic) provides radiation oncologists with:

Accepted Answer

Evidence-based dose-volume constraints and complication models for normal tissues

Answer

A quantum computing algorithm for IMRT optimization

Answer

A standardized patient questionnaire for reporting acute toxicity

Answer

Quality assurance tolerances for linear accelerator output calibration