BIOLOGICAL EFFECTS OF RADIATION 
FROM SIMULATED Pu POWER SOURCES IN DOGS 
F. A. Kallfelz, C. L. Comar, P. H. Craig and A. P. Casarett* 
I Biological effects of radiation from simulated ^Pu 
! power sources are being studied using the Labrador Re- 
triever as the experimental animal. The simulated 
sources consist of a combination of ^Cf (to provide 
the neutron component of a 30 watt ^Pu source) and 
Dogj^ooy Bremsstrahlung (to provide the additional 
photon flux needed). Sources are placed in the center 
of a spherical stainless steel capsule (333 ml volume) 
and the capsule is implanted in the left paralumbar 
fossa between the internal and external abdominal ob- 
lique muscles. Sources have been implanted which de- 
liver 1, 5, 15, or 70 times the radiation dose expected 
from a 30 watt ^Pu power source, and dose rates to 
various organs from these sources have been measured 
and calculated. A total of forty-eight dogs have been 
implanted to date. The maximum total accumulated 
dose in a single dog has been 37,000 Rad at 1 cm from 
the surface of the implantation capsule. 
Clinical evaluation of implanted dogs has revealed no 
alterations in any of the parameters measured except 
for a decreased total circulating lymphocyte count and 
a cessation of sperm production in the 70X animals. 
Six of the forty-eight animals have been killed (2- 
70X, 2-15X, and 2-blanks). Post-mortem examination 
has revealed a complete cessation of spermatogenesis 
and a striking reduction in lymphocyte population of 
the spleen and mesenteric lymph nodes in the 70X ani- 
mals. Similar, though less severe lesions have been seen 
in 15X dogs. In addition, one 70X dog developed a 
mast cell sarcoma at the implant site and the 15X and 
70X dogs killed after one year showed a reduction in 
numbers of megakaryocytes and erythropoietic ele- 
ments of the bone marrow in the vicinity of the im- 
plant. 
These preliminary results indicate that mammalian 
organisms may be able to tolerate the radiation dose in- 
cident with the use of °^Pu power sources for major 
cardiac assist devices. 
INTRODUCTION** 
Over the past few years, considerable atten- 
tion has been focused on the feasibility of using 
a radioisotope fueled power source for circula- 
tory support systems. A number of radionu- 
* Department of Physical Biology, New York State Veterinai'y 
College, Cornell University, Ithaca, New York 14850. 
*• Supported by AEC Contract AT (11-1 ) 3167. 
elides have been considered as possible fuels; 
however, it is now felt that ^^^Fu is probably 
the isotope of choice for such applications.^ 
Current concepts regarding the use of nuclear 
energy sources to power such systems include 
estimates that approximately a 30-50 watt plu- 
tonium-238 source might be necessary to pro- 
vide sufficient power over about a ten-year pe- 
riod of useful life. One of the major questions 
concerning the eventual use of such devices in 
the human population regards the possible ra- 
diation hazard from such sources. We are cur- 
rently investigating the biological effects of ra- 
diation from nuclear power sources which 
might be used to power an artificial heart. 
MATERIALS AND METHODS 
Animal Model 
Large dogs were selected as the animal to be 
used in this study. In an attempt to reduce vari- 
ability, purebred Labrador Retriever dogs are 
being used ; these animals weigh approximately 
30-40 kg when nlature and are hence roughly 
one-third to one-half the size of a standard man. 
Since mature human beings would be the most 
likely candidates for implantation of such de- 
vices all animals have been allowed to mature to 
at least one year of age before being introduced 
into the study. 
A spherical stainless steel capsule, 333 ml in 
volume, has been used as the basic implantation 
device. The sphere is hollow and contains a 
small central cavity, accessible by a screw plug, 
for the placement of radiation sources. A stain- 
less steel cap is cemented over the threaded plug 
after placement of sources in the central cavity. 
The unit is then covered with medical grade sil- 
icone rubber (Silastic Medical Adhesive Type 
A) and sterilized under ethylene oxide before 
implantation. 
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