936 
GENETIC AND BIOLOGICAL EFFECTS OF RADIATION 
Figure 4. — Frontal and lateral X-rays of primate showing RES-50 capsule in situ in the left iliac fossa. 
neutron and photon radiation of circulatory de- 
vice power source magnitude without gross ill 
effect. Such radiation does not preclude success- 
ful reproduction. 
(3) Histopathological expression of the re- 
sponse to the radiation appears to be limited 
to the tissue within 1 cm of the radiation cap- 
sule after up to 26 months of continuous expo- 
sure. Changes which are seen appear mild and 
do not interfere with any normal physiological 
function. No neoplastic changes have been ob- 
served. 
It should be emphasized that the radiation 
sources studied were fabricated and implanted 
without radiation shielding. The tissue dose 
rates produced by these sources are at least 
three times greater than what realistically can 
be expected from eventual power source cap- 
sules, in which greater ^^^Pu purity, improved 
geometry, and radiation shielding will atten- 
uate tissue dose rates. 
These preliminary animal model studies are 
by no means conclusive. Although there appear 
to be no reasons to suspect that the biologic 
response of canine tissue to thermal and nuclear 
radiation is fundamentally different than the 
human tissue response, the possibility does ex- 
ist. It. is also clear that in order to define the 
biologic sequellae of chronic simultaneous ex- 
posure to heat and radiation, many more ani- 
mals would have to be studied for longer periods 
of time than are included in our experience. 
These studies are encouraging, however, and 
the data lend support to the notion that eventual 
application of totally implanted nuclear power 
sources for artificial cardiac support systems 
is feasible. 
REFERENCES 
1. Section XII: Implantable energy systems, in Ar- 
tificial Heart Program Conference. Ed. R. J. Heg- 
yeli, U.S. Government Printing Office, Washington, 
pp. 913-1109, 1969. 
2. Harvey, R. J., Robinson, T. C, Bernhard, W. F., 
Norman, J. C, vanSomeren, L., LaFarge, C. G. 
