hanes C1 sae tated da ae2 alle Bs edt talioe,
98
0 (parent)
|
1
|
2
227h
28Ra
228A¢
2287 h
Half-life
;
|
|
LAX 10M y
5.75 y
6.13 h
L.Oly
0.14 us
3.1m
an
22P 6
208T |]
0.34; 0.97; others up
33 (0.17)
67
77
36
6.05
2.20
8.78
1.77
wa
9
10
55
42 (0.83)
Oo
60.5 m
QC
21273)
10.6 h
WHA
8
212Ph
10
053
6.26
0.3387)
0.663)
=
3.62 d
54.58
0.165
WR
*4Ra
220Fim
216Po
7
;
R
4
5
6
Principal gamma-ra:
a
energies
Particle emitted
and energy, MeV
ca
3
Nuclide
Oe
|
tre
Serial number
of decay product
Decay PARAMETERS OF THE Th Decay SpERrES
Q
TABLE 34.
0.241 (weak)
—
—_
0.239
0.73 (weak)
—
0.58; 2.62; and othe
‘* Only gamma rays greater than 0.10 MeVin energy and more than 1% abundant arelisted.
determination of radiation dose. However, dosimetry
in these cases is a problem of great complexity since
energy is deposited within the tissues not only by the
parent nuclide, *8°Th, but also by a long series of radioactive descendants (Table 34), each of which is translocated according to its own peculiar metabolic characteristics. Other problems also serve to complicate the
dosimetry, such as the very nonuniform distribution
of the colloid in the bodyand in anyone organ, as well
as the self-absorption of the radiation within aggregates of Thorotrast particles.
The general metabolic patterns of behavior of the
longer lived nuclides *°Th, 2°8Ra, 2°8Th and 774Ra
can be described in broad outline from the work of
Rundo,‘**#) Rotblat,“?) Kaul-®) and their coworkers
in Europe, and of Hursh‘*-!) and Marinelli@? ) and
their collaborators in the United States. To a lesser
extent, data are also available on the metabolism of
the shorter-lived daughter products 72°Em,‘!%15, 14)
212Pb, and “!*Bi.: ©) However, much of this knowledge
is based on a very small numberof tissue measurements, which particularly for the shorter-lived daughter products, is very scantyindeed.
The present program of investigation was undertaken with the aims of (1) checking the validity of
some of the currently accepted data on Thorotrast
MATERIALS AND METHODS
Sources of Tissue Samples Analyzed
The attainment of the main objectives of th
vestigation required a study of tissue samples
typical Thorotrast patients, most of whom re:
injections of the material 20 to 30 years previ
To this end, various smal] autopsy samples we:
tained for analysis through the kind cooperat
several physicians who had an interest in the 1
trast problem, However, it proved extremely di
to gain access to more than a very small num!
such specimens at a sufficiently early time after
for the study of the shorter-lived daughter pro.
For this reason—but also to obtain data on the
metabolism of Thorotrast—the investigation of
term Thorotrast patients was supplemented ir
ways. Firstly, short-term studies were conduct:
terminal cancer patients injected intravenously th
a catheter with known amounts of Thorotras:
lected tissue samples were examined promptly
death. Secondly, a series of animal experiment:
performed using rats and dogs injected intraven
and then sacrificed after intervals up to about 2
from the time of injection for prompt examinati
the tissues. These animal experiments were i1mp<
metabolism and (2) studying particularly the metabolism of the shorter-lived thorium daughter products,
“28Ac, 74Ra, 772Pb, and *4*Bi. On the basis of this
for the understanding they afforded of the behav
the short-lived nuclides, ?88Ac, 777Pb, and 71°Bi.
ing of the factors on which the dosimetry of Thorotrast
determination of the 73*Bi activities.
knowledge it was hoped to obtain a better understand-
depends. This report also seeks to summarize the more
important measurements of other workers in this field,
and hence to derive the current “best estimates” of the
radiation dose delivered to the tissues of Thorotrast
patients.
in such cases could the measurements be comm
at sufficiently early times after death (<1 hr) to
Radwactivity Measurements
Small samples of tissue weighing up to abou
were used for the radioactivity determinations.
growth and decay of 7*8Ac, 7?°Pb, and 7°°T1 wer