terms ot
i.e,
the size of
the fon cascade,
the “hit size" or cell dose.
distributiodn of
is
taken as
Thus,
the magnitude of
one obtains not only
the
the
the stochastically delivered hit sizes, but also the
number of discrete hits for the given amount of exposure.
instrument represents a single cell,
the
readout can be
hit,
Since
tyutal
the
in terms of
hits/exposed cell.
The microdosimeter registers essentially all impinging
charged particles.
However,
extremely small exposures,
cells,
t.e.,
the
with scaling factors as large as 103 | and with
it provides the ratio hic/(hit plus unhit)
fraction of exposed cells hit at least once.
It can
quantify "interspersed" partial body radiation, in which some contiguous
cells
are
hit and
otners
are
An additional
not,
important characteristic
of stochastic cell particle encounters is time rate.
dose deliveries
can be varted at will.
The mean time between
Thus a single cell TCV can be
subjected to from none up to a very large number of encounters, in an
arbitrarily short period of time.
Examples of microdosimetric distributions,
LET's are shown in Figure 4.
for radiations of three
The amount of eneryy deposited has been
designated the “specific energy” (4-6), with dimensions the same as those
of absorbed dose, namely,
energy/mass.
However, because of
the need
the noun additionally as both an adjective and verb, and for brevity,
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Fig. 4
Microdostmetric z distributions for three radiations
of different qualities.
Note that the varfance of the mean
value can be quite large, and that the distributions overlap.
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