This single curve is
exposure E (the open circle on the curve marked F).
for any LET radiation, or mixture, obtained with LLE only.
The hit size
distributions for the given radiation are provided in the upper right hand
corner.
This distribution, as opposed to those in Fig. 2, is normalized to
1.0. If this distribution is then multipled by the HSEF, shown in the
center right panel,
the product will represent the distribution of
quantally responding cells, shown in the right lower panel.
The areas
under this distribution represent the number of hit cells in the upper
normalized distribution that respond quantally.
Multiplying this value by
the number of hit cells given by the open circle in linear curve F in the
left panel yields the total incidence I, of quantally responding cells, for
exposure E, shown as
the solid circle on curve Tae
It {is emphasized that the “normalized distributions” approach depicted
in Fig. 6 is for illustrative purposes only.
Neither “linear, non-
threshold” relationship, nor distributions for different LET's need be
referred to or used in practice (it is superfluous to provide a curve for
the
risk of a hit versus exposure-~the distribution of hit sizes
suffices).
That is to say, for any given exposure, whatever the LET or
mixtures of LET's, only a single distribution would be recorded by the
microdosimeter.
Direct application of the HSEF would yield the required
“risk coefficient".
Thus, in practice, the cell dose approach could
obviate the need for multiple “dose response” curves (Fig. 1), and it could ‘
replace the concept of LET entirely.
the average mean of
Conceptually,
the "T" in LET is not
the energy depositions in tissue.
Rather,
it refers
to
the amounts of energy deposited in the cell TCVs--the cell doses.
The approach described above applies strictly only tq LLE and
“simple cell” systems.
to
Since at least the bulk of human cancers are
monoclonal, and thus presumably of single cell origin, an HSEF could also
be determined for carcinogenesis in mammals.
only
to those malignantly
transformed cells,
were expressed as a cancer.
=
However, the HSEF would apply Ce
a
ae
for a
given exposure,
that
OP]
en
Required additionally would be a relationship 2
ag
for the incidence of expressed cancers as a function of the total number of:
di
transformed cells.
Sut
It is possible, with present advances in the
identification of cell types, that this relationship could be determined
directly.
24
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