radiobiological principles in radiation therapy

Bergonie and Tribondeau

In 1906, two French scientists,

theorized and observed that radiosensitivity was a function of

the metabolic state of tissue being irradiated.

Law of Bergonie and Tribondeau.

Their law maintains that actively mitotic and undifferentiated

cells are most susceptible to damage from ionizing

radiation.

Repair

-the process of rejoining DNA strands.

reoxygenation

occurs as the sensitive, well-oxygenated tumor cells are killed and the tumor

shrinks

repopulation

-the ability of the cell population to continue to divide and to replace dying and

dead cells

redistribution

-reflects the variability of a cell’s radiosensitivity over the cell cycle

-Cells in different parts of the reproductive cycle have different sensitivities

-M is the most sensitive, and late S is the least sensitive

- Radiation exposure kills more of the cells in the M phase, and more cells in the S phase survive

Radiosensitivity

-the relative susceptibility of cells, tissues, organs, organisms, or other substances to the injurious action of

radiation