Ideally we would like to have a law analogous to Newton's Laws of Motion or Ohm's Law which would predict exactly the kind and amount of injury produced in a given cell following an exposure to radiation. Unfortunately, such a law remains yet to be discovered. The oldest, and perhaps best, rule of thumb was developed by two French radiobiologists, Bergonie and Tribondeau, in 1906. It offers a prediction about the relative sensitivity of two different types of cells or tissues to radiation.
Cells have a long dividing future.
Cells are of an unspecialized type. The first condition can be determined by measuring the cell cycle time, i.e., the time between divisions. The second property refers to the fact that many cells go through phases in an overall life cycle. Cells with a long dividing future would be those in the early immature phases where they are still dividing. The last criterion, unspecialized, needs further comment.