There is an optimal LET value for the production of a biologic effect because: 

A. lower LET values involve "wasting" of radiation energy. 

B. this LET value corresponds to an average separation between ionizing events which is approximately equal to the diameter of the DNA molecule. 

C. radiations with higher LET values have a low probability of producing a double-strand break by the passage of a single charged particle. 

▣ The oxygen enhancement ratio is: 

A. equal to the survival of cells irradiated under hypoxic conditions divided by the survival under aerobic conditions for a fixed radiation dose 

B. greater at low radiation doses than at high radiation doses 

C. the same regardless of radiation quality (LET) 

D. equal to the dose of radiation under hypoxic conditions divided by the dose of radiation under aerobic conditions that results in the same biological effect 

E. 2.5-3 for high LET radiation

▣ Which of the following statements about oxygen effect is true? 

A. Oxygen enhancement ratio is less after high doses than after low doses 

B. Oxygen effect is most pronounced with neutrons and alpha particles 

C. Oxygen effect is not as effective with low LET radiations 

D. Oxygen effect is most pronounced with high LET radiations 

E. None of the above 

▣ Concerning RBE, OER and LET, which of the following statements is true? 

A. Maximum cell killing per dose delivered occurs at an LET corresponding to approximately 1000 keV/μm 

B. RBE changes the most over the LET range of 0.1 to 10 keV/μm 

C. The relationship between OER and LET is bell-shaped 

D. RBE decreases with increasing LET above about 100 keV/μm 

E. OER increases with LET 

▣ The RBE of alpha particles for aerated cells compared with that for hypoxic cells is: 

A. Equal 

B. Lower 

C. Greater 

D. Dependent upon the endpoint being measured 

E. The same as the OER

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