-
conditions.
14 -
Water or soft tissues exposed to one roentgen
(r) receive an absorbed dose of very nearly one rad.
defined,
As
the roentgen cannot be applied to radiations other
than X rays or gamma rays.
To compare the effectiveness of absorbed doses of
radiation delivered in different ways,
the term relative
biological effectiveness (RBE) is used.
is the rem.
By definition,
The unit of RBE
one rad of X rays,
gamma rays
or beta rays is equivalent to one rem but one rad of alpha
rays is equivalent to about 10 rem.
Dose in rad x RBE =
dose in rem.
Blological Effects of Ionizing Radiations
_ The ionizations that occur when nuclear radiations
pass through a gas or a phosphor make it possible for radioactivity to be detected and measured,
tions,
and the same ioniza-
when they occur in tissusof living organisms,
are
primarily responsible for the biological effects that occur
as a result of irradiation.
The answer to the question,
"Why are radioisotopes harmful?", is that they emit ionizing
radiations which are capable of injuring or destroying cells.
However, precise information on the exact manner in which