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10 CASES
14 CASES
O= OVER 20 YEARS AT INITIAL EXPOSURE
™x=UNDER 20 YEARS AT INITIAL EXPOSURE
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I5 *YEARS OLD
x
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tb
2
4
tt
6 8
td
10 [2 4 16 18
dd
20 22 24 26 2B 30
dt
32 34 36
td
38 40 42 44 46 48
YEARS CARRIED
gle intra-
Fic. 44.—Difference in concentration of ?*Ra in persons exposed before and after age 20
Figure 45 shows the results obtained by Sears et
to
al.) in the vertebrae of high-level radium dogs which
E
were sacrificed serially at different times after injec-
tion. There would appearto be nosignificant difference
' in the rate of fall of the hotspots and the diffuse activity. Likewise, two other studies in dogs with *Ra™
aud Ca failed to show any significant difference
between the loss from the hotspots and from thediffuse
| lubel of the cortex of the tibia between one month and
ane year after injection. However, the loss in the
whole-body retention between these two times was less
>
x
=
|OE
-
5
=
Oo
a
values shown here suggest a lower rate of loss of ac| tivity from the hotspots compared with the diffuse.
Between 3 days and 100 days the loss in activity was
| ubouta faetor of 4 for the hotspots and a factor of 10
‘es 45- # for the diffuse. Figure 47 gives the best values we have
leon able to obtain for the human data. Here the loss
ut the
in
the hotspot activity over a period of 25 years is a
re two;
factor
of 3.6, while that for the diffuse is a factor of 10
ths as (
over
the
same period for the mid-cortex of the tibia.
comThe values plotted for the hotspots at short times after
‘owth,
beling ¥ mn] ection were calculated from the injected dose assume two
ing that the hotspots in the bone were formed at the
luate Z “ame concentration as the 228Ra/g Ca in the blood. This
ptake § Ws found to be true for dogs.'#) Recently, the diffuse
luhcl was shown to be 0.48 and 0.35 of the uniform label
Average Hotspot
¥=.74517-247
*%
5
ONE
E
Average Diffuse
xy Y=-0781~-159
0
pe
than 40%.
Figure 46 shows a similar plot for Ca as observed
| for hotspots and diffuse uptake for rabbits." The
x
Kx
F
<
<t
a
©
Maximum Hotspot
0.0!
Lj
10
Litiuul
TL
toil
100
1,000
jtft
10,000
DAYS
Fic, 45—Diminution of “Ra in canine vertebrae
in two radium cases studied at 140 days and 400 days
after injection of radium, compared to an average
value of 0.43 found for about 20 cases at 25 years after
injection.'®) This suggests that the diffuse level in the
tibial cortex divided by the uniform label for the whole
skeleton does not change appreciably with time.
There would appear to be some doubt as to whether
the diffuse label and the hotspot levels vary between
different bones. All the animal work: * ® would sug-
gest that the diffuse level found in the vertebrae is
about a faetor of two higher than that found in the
mid-shaft of the tibia at short times after injection.