▶ Potentially lethal cell damage is associated with which of the following factors? 

A. Radiation exposure is separated by time 

B. Post-irradiation conditions are modified 

C. Pre-irradiation conditions are modified 

D. Two of the above 

E. All of the above

▶ Exponentially growing cells were maintained at 37°C and irradiated with either a single dose of 6 Gy of X-rays or two 3 Gy fractions separated by either 2 hours or 8 hours. The surviving fractions for the three treatments were 0.03, 0.12 and 0.09, respectively. The two processes that best account for these differences in survival are: 

A. reassortment and repopulation 

B. reoxygenation and repair 

C. repopulation and reassortment 

D. repair and reassortment 

E. repair and reoxygenation 

▶ Cells are irradiated with graded doses of X-rays, and clonogenic cell survival is plotted against radiation dose, producing a survival curve. The width of the shoulder of the curve is reflective of: 

A. Delayed cell death after irradiation 

B. Repair of sub-lethal damage 

C. Repair of potential lethal damage 

D. Repopulation of tumors 

E. Response to hypoxia 

▶ Repair of sublethal damage applies only to: 

A. Gamma rays 

B. Neutrons

C. X-rays 

D. Two of the above 

E. None of the above 

▶ Which of the following statements about the dose rate effect on cellular damage is true? 

A. High dose rates are less efficient in producing damage 

B. Low dose rates are less efficient in producing damage 

C. The dose rate range over which SLDR most contributes to the dose rate effect for X-rays is 1-5 Gy/min 

D. Treatment of cells during irradiation with an agent that inhibits DNA repair would have a greater impact on the surviving fraction of cells irradiated at the high dose rate 

E. The total number of ionizations produced decreases at the high dose rate