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R a d i u m 229
or the gradation of reaction corresponding with increased dosage. We
were able to demonstrate to our own satisfaction that an erythema may
be produced by gamma ray applications, and that a considerable increase
in dosage does not materially increase the degree of primary reaction.
We were unable to determine what degree of reaction should be called
an erythema. Variations m skin texture and pigmentation added to our
difficulties. Maximum dosage was also difficult to determine because
one's idea of dosage limitations necessarily vary with the type and location
of the lesion. A second degree bum may be expected from an application
of 200 mg. hours at 2.5 mm. on the average skin of the covered
parts of the body. Where cosmetic results are of importance, the single
application had best be kept below 150 mg. hours at the same distance,
dosage at greater distances being governed by the law of inverse ratio
of proportion. Greater dosage may of course be indicated by the necessity
for complete destruction of malignant tissue. By increasing the focal
distance and changing the time according to the law of inverse ratio of
proportion, other factors being equal, we obtained practically the same
degree of reaction, but of greater area and more uniformity. We believe
that unless the pathologic condition is of limited extent, applications
had best he made with, for instance, a focal distance of 10 instead
of 5 mm. This advantage is enhanced by the fact that as the focal dis-
Flt. *.—Temporary epilation—four hours. 55 mg., fully screened, 5 mm. distance.
tance increases the disproportion between surface and depth dosage decreases.
GAMMA KAY APPLICATIONS TO THK SCALP
The Plaque.—The application of 10 mg. of radium element to the
scalp in the form of half strength fiat applicators filtering with 1.2 mm.
brass and approximately 1 mm. rubber for four hours did not produce
an erythema, but resulted in an epilation in twenty-one days. Regrowth
was complete two months later. This was the minimum filtered application
to produce epilation. Similar applications for six, seven, eight and
nine hours produced epilation without erythema, and as the length of
the application increased regrowth was more lardy, some occurring as
late as the fifth month after epilation. The eight and nine hour applications
resulted in a depilalion that did not entirely regrow. A ten hour
application resulted in a faint erythema and practically complete permanent
depilation.
Tubes: To obtain further information regarding the erythema dose
of the gamma ray on the scalp. 50 mg. of radium was incased in 0.5 mm.
of silver, 1 mm. of brass and 1 mm. of rubber, and this was applied