The
two views were eventually resolved, but only after
meating of the ICRU in 1928 (1).
x-radiation was defined as
the
second
At this vathering the “quantity” of
the Roentgen, equal,
with additional detatled
est in the
specifications,
1 ubiquitous
seems evident that the word “quautity” was meane to be interpreted in the
to one electrostatic unit of charge in one ce of air.
ic agent a
physical sense, i.%., as a measure of the field or source strength.
in the rea
However, due
in part
tu ambiguity among the words “amount”,
Lt
“quantity”,
and
“dose", and in part to the fact that air and tissue lave close tw the sate
cine (Md) -
electron density,
sure (LLE) ‘0
equal-, or proportional to the physician's “amount”, i.e., dose.
he gpeget
de
8
? (Ph)5 tne
TRY
ber unit mass, as
time endursed
this preemptive move,
the "rep" and
then the
the unit of absorbed dose.
exposure, with the Roentgen as
3) theme was
the unit, was
rad,
as evidenced by
with dimensions of energy
However,
retained.
the quantity
With improved
{astrumentation and the use of phantoms for measurement in depth,
se
necessitating the use of
red bY thos¢
principal
this
system has continued to work well for HLE, even when high-LET radlations,
the
cation of
The ICRU in
the later aduption of
wa
opt,
SPs
ae
"dose",
and defined PY i
a tumor:
Thus
almost immediately the Roentgen was widely described as the unit of x-ray
agiSEBS
mary pjects
ing ©
». put me an
the physicist's “quantity” of radiation was approximately
the concept of relative biolo,leal effectiveness
(RBE), were introduced into the radiotherapy of tumors.
h
The basic principle involved in the above described controversy can be
the probability
ge, ot whic
stated as follows: For a physician (or anyoue) to estimate
ry (Lees an
of a serious of lethal consequence of stochastic agent traasfer, preferred
aggentially
is an evaluation of the severity of injury sustained by the casualty.
able
Backing this, aa estimate of the dose of the offending agent is the next
t consider
fall-back position.
is
5
WL Cy of
quantity wa ine &
That
that relates to what is happeniug in the individual of conceru, be that
1a per unit .
individual an organ or a cell.
fiow from " te
Low~Level Radiation Exposure
anetey flvenss’
It was observed quite early that cancer could result from HLE.
ician ve
dowever, only much later was it widely appreciated that the "single
ther ©
cell-origzinating” ertfects,
ythema B
n er
to say,
Exposure is of little-or no help in this regard.
needed for prognosis evaluation is an object-orlented quantity
3
rime spent in a
cancer and heritable effects, must also he
taken
seriously, even at very low doses, or laryer doses at very low dose tates,
1,e., following LLE.
It was also apparent that the basic phenomena
involved fell into the category of Ph,
particularly its subdisciplines of
epidemiolovy and accident statistics.
However, no effort was made to
4meter °
~205-
5012961
f