APPROACHES TO THE QUANTITATIVE ESTIMATION
RADIATION INJURY AND LETHALITY“*
OF
By Gronran A. Sacuzr
Division of Biological and Medical Research, Argonne National Laboratory, Lemont, [Uinois
INTRODUCTION
of turning-over cell populations have begun
There are serious difficulties in the way of a
satisfactory quantitative theory of the lethal
action of ionizing radiations. Since only the
occurrence of an
all-or-none end-point is
observed, the yield of information from exper-
iments is small.
The nature of the end-point
is ill-defined, because several kinds of injury
contribute and the relationships among them
that determine the boundary between viable
and inviable states are not yet known.
More-
over, several kinds of physiologic injury that
have been studied are known to have non-linear
dependence on dose and on time, especially
when
the
injury approaches
lethal
levels.
[7,8].
The age-dependence of radiosensitivity
is under investigation [9-11]. Strain and species
differences in lethal responses are being explored
{12-14], but differences with respect to specific
physiologic responses are not yet under systematic study. The nature of the statistical
relation of mortality to injury is being examined
[15].
The above are a few examples of research
under way on sometopics that are of immediate
relevance to the overall problem of radiation
lethality. Many others have not been men-
tioned.
Some problems have not yet been put
under investigation.
Foremost among theso is
the question of the way in which injury in
Thereis also the limitation on the predictability
of response imposed by the differences between
several independent systems interacts to in-
performance from time to time.
ceived, but o realization in any meaningful and
individuals and by the fluctuation of individual
These questions must be answered in order
to provide the foundation on which to build
an adequate general theory in which lethality
becomes an understandable consequence of the
failure of adjustment of organisms to their
environment.
The most significant research
contributions in the present period are those
which throw light on one or another specific
aspect of the total problem.
The recovery
process is being intensively studied, especially
bythe paired-dose technique [1-4]. The sensitivity of specific organ-systems or body regions
is under active investigation[5,6]. Theoretical
and experimental approaches to the dynamics
fluence lethality.
The outline of an integrated
theory embracing all these aspects can be con-
useful sense is not yet within reach.
The mathematical treatment of radiation
lethality presented below is to be regarded as
an approach which is specifically devised to
establish some. properties of the lethal response
to radiations. The characteristics of radiation
lethality revealed by this type of analysis are,
like the other physiologic characteristics enumerated above, part of the total response to be
accounted for by an adequate theory. In
short, the application of a mode of mathematical
analysis to lethality does not constitute ipso
factv a theory of that subject.
“Work performed under the auspives of the U. 8. Atomle Energy Commission.
101