- 30 -
t
The work of Laskin, et al, though not specifically
"involving deep respiratory tissue, does demonstrate a source
intensity-response curve for lung tissue’?,
A Ru-106
°
cylindrical source was implanted in the bronchi of rats, and
cancers were observed to arise from the bronchial epithelium.
_ The response curve
indicates a substantial response
(7 percent)
_ even at 0.008 uCi burden, and a slow, approximately logarithmic
_increase of tumor incidence over three orders of magnitude.
in the source intensity.
Corresponding first-year doses to
adjacent bronehial epithelium varied from 103 rad to 106 rad’,
_Animals were followed until death and it was observed that
the tumor incidence generally increased with the dose accumulated
at death.
The lowest accumulated dose associated with a
cancer was 1400
rad.
For an accumulated dose of the order of
106 rad the incidence was approximately two-thirds.
-_—
Cember
—~—
._ fortified glass beads (0.3 u diameter) with several microcuries
of Sr-90, and single beads were implanted in the lungs of
rats.
Tumors were observed in 7 of 23 animals.
In a second
_@xperiment Cember exposed rat lungs to Ce-144 particles.
For
49/ Laskin, S., M. Kuschner, N. Nelson, B. Altshuler, J.4.
Hariecy and M. Daniels, "Carcinoma of the lung in rats éxpcsed
to the beta-radiation of intra-bronchial rutheniuml96 pelicts
“it.
Dose response relationshivus,” J.
1963, pp. 219-231.
Natl.
Cancer Inst.
si,
“SO0/
Altshuler, B., "Dosimetry fror a rnut96-coateod mlatinum
pellet," Radiation Res. 9, 1958, pp. 626-632.
rN hw