Exposure to External and Internal Radiation —
in Vivo Measurement of Radionuclides in Man; Body Burden and
Project Title:
Kinetic Factors, Computer Applications
16, Technical Progress in FY 1973:
(Cont'd. )
i
RX-01-01-(b)
The Pu-238, Be neutron trradiation facility currently employed for totalbody neutron activation analysis has shown itself to be superior in many
respects to the previously employed 14 MeV neutron generator,
In the first
year of its operation, over 300 activation analyses have been performed on
patients. The precision of the technique for measurement of calcium, sodium,
and chlorine has been +1, 2, and 2% respectively. The precision for the
measurement of phosphorus however, has not been satisfactory (+ 4%).
Efforts
are being made to improve the precision of this latter measurement primarily
by means of an improved computer program for analysis of the gamma spectral
data,
Efforts are also in progress to improve the operation of the activation
technique and to apply it to the analysis of other elements in the human body.
(Cohn)
oN
In the efforts to define the radiation dose response curve between
zero and the natural dose rate, screening studies directed to the selection
of the most suibable organism and end point were continued. Most of the
organisms considered were found to have such small responses at low doses
as to not be useable for obtaining statistically significant results with
feasible population numbers. The best organism now appears to be a strain
of Eschericia coli identified as ATCC strain #10798 C,E, Clifton K-12 (A).
In "Etude Radiobiologigue Du Systems Lysogene D'E.Coli K12. II Induction
Par Les Rayons X.,
Etude Des Faibles Doses. "Annales de L'Institute Pasteur
90, 458-81 (1956), Marcovich reported on the effects of x rays on the
induction of K-12(A) to produce A phage, using radiation doses as low
as 0,3R. This is apparently the lowest dose for which an effect has been
recorded in bacteria,
In the current studies the K12 (A)
is grown under
various conditions, the free \} phage is harvested and the phage is plated
with the indicator strain, ATCC # 12435, J. Lederberg W 1485, The end
point measured is the number of plaques formed perplate, When grown under
:
-
normal background conditions in a medium with reduced potassium content
there is one plaque per 104 cells. The results under reduced background
conditions are not available yet. Another aspect of the study is underway
using 250 KVP x rays at various doses up to 1200 R to verify the dose-
effect curve reported by Marcovich.
Among the new computing programs developed is one that generates
theoretical x-ray spectra associated with a given KVP and with specified
filters. This is part of a combination of theoretical and experimental
mehes to the development of special filters that utilize the K-edge
fnuity in the mass absorption coefficients of various elements to
.Yadiographs and to reduce patient radiation doses by cutting out
x rays ‘of energies above and below those desired.
This method may also
become useful in enhancing the contrast associated with certain labeling
elements, particularly iodine,
in problems such as gall bladder visuali-
zation and in thyroid studies.
Combinations of silver, tin, rhodium,
gadolinium, and cadmium filters used with 30, 35, 40, 70, 80, and 90 KVP
(See Continuation Sheet)
1419174
.
RX- 19