¥
adequate
the average probabllity of
to evaluate
the quantal response at any
With LLE, on the other hand, each point on the curve shown
given dose D.
represents an entire population of cells, and the interest focuses on how
many in
that population will be seciously injured or killed.
number of cells hit,
Here
the
the distribution of hit sizes, and an HSEF, are
FRACTION OF ORGANS
RESPONDING QUANTALLY
Q
ZONE }
Lue f
HLE
eee
F<<t0}
Frmio;, zap
Fig. 9
Schematic showing the transition, for cell lethality,
from LLE where absorbed dose is not appropriate, to HLE where
‘ey is curve A, which is hoth an exposure~quantal
it is.
(tethal) response function for cells, and a dose-effect curve
for the next highest level of biological organization, the
At low exposures the focus {s on evaluating the number
organ.
At laree exposures the
of cell elements responding quantally,.
focus is om the degree to which function of che cell systeu,
the organ, has been compromised by massive cell killing. This
determines the probability of the organ, and therefore the
ocgantsm responding quantally (lethally).
oe
we ae of
al Teas Uae ss
——+
-
Relationship between RBE and the HSEF
AS seen from Eq (1) above,
Tihs
the RBE, with LLE,
the organ ahsorbed dose D is equal to ZF.
is simply
the ratio of zF for
the standard
radiation, divided by zF for the test high-LET radiation,
varies with radiation quality,
is
to be a measure of
lUowever,
the values of F should be made equal
the influence of quality only, as indicated by
-223-
nme
ec Day
ee dhe sas wate wine Se ery ee
6
FRACTION OF CELLS
RESPONDING QUANTALLY
reguired for cisk evaluacion,
since
{if RBE
F