Modification of Radiation Response

Question 1

Potentially Lethal Damage

Answer 1

can be modified after irradiation. if cells are prevented from dividing for 6 h or
more after irradiation.

Question 2

Sublethal damage

Answer 2

can be repaired in hours. describes the increase in survival if a dose of radiation is split into fractions separated in time.

Question 3

3 R of radbio

Answer 3

Repair of sublethal damage;
Reassortment by the progression of survivors through the cell cycle;
Repopulation if the interval between fractions > cell cycle time

also reoxigenation - process by which hypoxic cells at the time of irradiation become oxygenated afterwards

Question 4

Oxygen Enhancement Ratio

Answer 4

OER = D0(hypoxia)/D0(oxygenated)

= dose(hypoxia)/dose(oxygenated) for the same biological effect. Hypoxic needs higher dose to kill the cell

Question 5

High LET OER

Answer 5

Does not make big difference

Question 6

Radiosensitizers

Answer 6

Agents that enhance the response of cells to radiation.
Ideally, radiosensitizers would selectively sensitize tumor cells while
having no effect on normal tissues.

Question 7

Sensitization enhancement ratio SER

Answer 7

D0(without sensitizer)/D0(with sensitizer)

Question 8

Hypoxic cell cytotoxins - Bioreductive agents

Answer 8

Drugs that are preferentially toxic to hypoxic cells.Metronidazole Misonidazole

Question 9

Dose Reduction Factor (DRF)

Answer 9

Protection Factor (PF) = dose of radiation in the presence of the drug / dose of radiation in the absence of the drug to produce a given level of effect

Question 10

WR2721

Answer 10

Radioprotectors. Mechanism of action is the scavenging of free radicals

Question 11

Amifostine

Answer 11

only radioprotective drug approved by the FDA.