▼ Which of the following statements about cell-cycle dependent radiation sensitivity is correct? 

A. G1 phase cells have the highest DNA repair capability, thus are most resistant to radiation 

B. S-phase cells are more sensitive to radiation because the DNA replication can be blocked by DNA damages during S-phase 

C. Proliferative tissues are more sensitive than non-proliferative tissues. Therefore, S-phase cells are more sensitive than quiescent G1 or G0 cells 

D. G2 and M phase cells are most sensitive to radiation 

E. G0 phase are very sensitive, almost as sensitive as cells in M phase.

▼ The variation of cell radiosensitivity with cell cycle might be due to: 

A. changes in the amount or form of the DNA and/or changes in the level of naturally occuring sulfhydryl compounds in the cell. 

B. changes in the oxygen enhancement ratio. 

C. the activation of different members of the cyclin-dependent kinase family.

▼ The RBE of a given beam does not depend on: 

A. the total dose delivered to the tissue. 

B. the number of fractions in which the dose is delivered to the tissue (in the case of a fractionated regimen). 

C. the dose-rate (in the case of continuous irradiation). 

D. the type of irradiated tissue. 

E. the endpoint studied. 

F. the phase of the cell cycle in which the irradiated cells are at the moment the irradiation begins. 

G. the radiation quality (LET). 

▼ Which of the following statements is correct about Relative Biological Effect (RBE)? 

A. RBE is the ratio of doses of two different radiations that produce the same survival fractions 

B. RBE is the ratio of survival fractions produced by the same doses of two different radiations 

C. Beta-particles have higher RBE values than alpha-particles 

D. High LET radiation have lower RBE values than low LET radiation 

▼ What is the effect on both RBE and the α/β ratio as the LET for the type of radiation increases up to 100 keV/μm? 

A. Both remain the same 

B. Both increase 

C. Both decrease 

D. The RBE decreases while the α/β increases 

E. The RBE increases while the α/β decreases