Test on Linear Quadratic Model in Radiotherapy

Question 1: The theoretical tumour control probability (TCP) curve is uniquely described by two parameters: its gradient at the 50% response level and the dose to achieve 50% response.

A. Yes

B. No

Explanation: The study materials state that the 'Theorectical response curve' (which represents TCP) is 'Uniquely described by two parameters: - gradient at 50% response level D50% - dose to achieve 50% response'.

Question 2: The LQ-model assumes that the inactivation of tumour cells is primarily caused by double strand breaks (DSB).

A. Yes

B. No

Explanation: The study materials state, under 'Assumptions: Basics of the LQ-model (1)', that 'Cells are inactivated by double strand breaks (DSB)'.

Question 3: Based on the provided study materials, what is a typical alpha/beta (α/β) value for tumour tissue?

A. 1-4 Gy

B. Approximately 10 Gy

C. Greater than 6 Gy when the shoulder is wide

D. Less than 0.5 Gy

Explanation: The study materials state that 'Typical α / β -values for tumour tissue are approximately 10 Gy'.

Question 4: According to the study materials, what does the Biologically Effective Dose (BED) represent?

A. The total dose (D) required to achieve 50% tumour control.

B. The theoretical total dose needed to produce a specific biological effect (E) with infinitely small dose per fraction.

C. The dose level at which alpha-damage and beta-damage are equivalent.

D. The average number of lethal hits per clonogenic cell in a tumour.

Explanation: The study materials state that BED 'can be understood as the theoretical total dose which would be required to produce the effect E with infinitely small dose per fraction (low dose rate).' Option 0 describes D50% or the concept of tumour control probability. Option 2 describes the alpha/beta ratio. Option 3 refers to 'm' in the Poisson statistics model for cell inactivation.

Question 5: If a total dose of 66 Gy is given in 1.5 Gy fractions, the equivalent total dose in 2 Gy fractions (EQD2) is higher for an alpha/beta ratio of 1 than for an alpha/beta ratio of 10.

A. Yes

B. No

Explanation: According to the study materials, for a total dose of 66 Gy given in 1.5 Gy fractions: for α/β = 10, EQD2 = 63 Gy; for α/β = 1, EQD2 = 55 Gy. Therefore, the EQD2 for α/β = 1 (55 Gy) is lower, not higher, than for α/β = 10 (63 Gy).