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Derivation of the HSEF
‘Le
cueve
ts?
The derivation of the HSEF is described in detail elsewhere
(3,11-13).
The basic input information consists of quite accurately
determined organ absorbed dose-cell response data, for a series of
radiations covering a wide span of qualities.
In addition, it is necessary
in in the
to have quite accurately determined microdosimetric data, that will provide
ion
both the number of hits per cell and the hit-size distributions.
of
These.
The areas = “*
distributions overlap, as can be seen in Figure 4.
the upper
assume that hits of a given size in a small enough target will have the
It is reasonable to
same effectiveness, independent of the hit size distribution of origin.
The effectiveness of the different distributions can then be obtained, and
the regions of overlap provide independent information on the effectiveness
of the individual hit sizes.
deconvolution process,
It is then possible, by an iterative
to arrive ultimately at an HSEF that most accurately
fits the input data.
This derivation is purely empirical,
f.e.,
it is
independent of
assumptions or theories about molecular or other subcellular mechanisms of
sizes
fF
the
action of
the radiations,
In other words, most 1€ not all of available
wodels or theories of radfobiological action begin with assumptions about
LET or
raed by the -
mechanisms, e.g.,
i the required
all of the cell transformations observed.
pacn could
.
1), and it courts
“ in LET is 0%
that double strand breaks may be responsible for some or
In derfving the HSEF, on the
other hand, only observed quantal responses are used.
Anomalies in the Present System
Several anomalies in the set of typical cell “dose response” curves
it refers.
-hets
shown in Fig. 1 can be pointed out immediately.
1
response is of individual cells,
doses»
organ.
cancers are
It is
the “dose”
taken to be axiomatic
that
é
P
re lationship,
che total n
; in the
the stimulus
to an individual,
be
Although the ie agent is purported to be
energy, Fig. 1 shows a number of "dose
be a
For instance, although the
the average for the entire
it a cell or an organ, must be measured at the same level as the initial
biological response.
exposures
its
+
umber of.
2
id be determined
oa
agent.
Also, as seen with lithium ions,
response” curves for that same
the same particle but with
different energies results in markedly different curve slopes.
In fact, by
suitable choice of particle and energy, more and more curves can readily be
added to the set until the roughly triangular area represented by the
curves is filled in completely and constitutes an area (Fig. 7).
This
shows the fallacy and futility of the present dose-response curve-RBE
-
owet