RADIATION INJURY ITS PATHOULNE SIS AND THERAPY
207
TABLE 3
Lhsoy
SPE: IES
Mouse
Rat.
Lo
Guinea pig ..
Rabbit ....
Monker. .
Dog
. .
TYPE Ob RAGEST ION
.
.
.
Swine ...
Sheep.
.
Goat...
Burro..
.
.
'
Absorhed
dose 1m Tracts
dose int
mudventer
1250 KVP x-ray
443
638
, 250 KVP x-ray
251
200
200
2950
250
KVP
KVP
KVP
KVP
x-ray
x-ray
x-ray
x-ray
| 1000 KVP x-ray
' Gamma appron. 0.7 mev.
.
Ar
expen tre
200 KVP a-ray
Gamma approx. 1.1 mev.
640
337
S05
760
796
400
731
546
244
510
247
350
651
237
256
524
205
Representative LDgo per 30 day values for a numberof species are given
in Table I (Bond and Robertson). The absorbed dose in rads is the siguifi-
cant parameter that determines the degree of biological response. All
mortality data in the table refer to conditions of exposure such that dose
distribution throughout the bodyis essentially uniform, The dose at mudcenter has no particular significance except that it is convenient and represents the approximate dose that all tissues received (no single parameteris
adequate to characterize an exposure under conditions of nonuniform dose
distribution through the tissues). It can be seen at once from the table
that the 1.D,,) values showno consistent pattern as air dose. Expressed as
absorbed dose, however, the LDgo values for large animals are considerably
smaller than for small species, and the degree of variation among species
is less with large animals. The LD5¢ of man is not known with anv degree
of accuracy; however, it is expected that for uniform whole body exposure
the value is approximately 300 to 400 r, expressed as muidcentertissue dose.
‘The distribution of deaths as a function of time after irradiation varies
with the dose of radiation and with species. For example, with the dog in
the lethal range, the mean survival time is approximately 12 days, with
deaths occurring 6 to 26 days after exposure. With doses of 1000 to 1500 r,
some deaths occur earlier (8rd and 4th days) and the toxic symptoms of
vomiting, anorexia, and diarrhea become more prominent. With doses of
1500 to 6000 r, all dogs die on the 3rd and 4th day. Severe diarrheais present.
With the mouse, the distribution of deaths after irradiation with doses less
than an LDso is essentially unimodal with peak of deaths occurring 11 days
after exposure (Cronkite, Bond, Chapmanand Lee). In the LDgo range the
deaths become bimodal with a peak at 4 to 6 days and another at 11 days
5012804
,