From Big Medical Encyclopedia

The FACTOR of CHANGE of the DOSE (FCD) — the criterion used at quantitative assessment of the radio modifying effect caused by use of protective agents (radioprotectors) or radio sensitizers.

FID is expressed by the relation of ravnoeffektivny doses:

FID =,


where Dop and Recreation center — the doses causing effects, identical in size, in experience (i.e. using the radio modifier) and in control (without use of the radio modifier).

At assessment of protective action of radioprotectors (see) size FID always more than 1, and during the use of radio sensitizers (see. The radio sensibilizing substances) less than 1. The most reliable quantitative assessment of FID is received by means of the curves of survival applied during the studying of radio-sensitivity biol. objects (see Radiochuvstvitelnost).

In scientific literature the term «factor of reduction of a dose» (FUD) entered at the beginning of the 50th 20 century after opening of radioprotectors meets. With the advent of radio sensitizers it became difficult to use this term since the words «increase» and «reduction» begin with one letter in this connection practice included the term «factor of change of a dose».

See also Beam damages, Radiation.

Bibliography: Yarmonenko of S. P. R

diobiologiya of the person and animals, M., 1984. S. P. Yarmonenko.