2. Introduction
 In 1906 one of radiology's most important
discoveries was made-the law of Bergonie and
Tribondeau.
 By exposing rabbit testicles to ionizing radiation
and observing its effects, the relationship
between metabolic state and radiosensitivity
was established.

3. Statement
• Stem cells are radiosensitive.
• Immature or young cells and
tissues are more radiosensitive;
resistance to radiation increases
with increased cell maturity.

4.  Low metabolic rate decreases radiosensitivity
and high metabolic rate increases
radiosensitivity.
 High proliferation (reproductive) rate for cells
and fast growth rate increases the
radiosensitivity of those cells.