DOSAGE ONE AND TWO CENTIMETERS UNDER
THE SKIN FROM UNFILTERED X-RAYS
WILHELM STENBTROM
State Institute for the Study of Maligwnt Diseaae, Bufldo, N. Y.
H. R. Gaylord, Director
Received for publication May 15, 1923
Cancer of the skin and a number of other skin diseases respond favorably to treatment with unfiltered X-rays if an adequate dose is given. It is often desirable to give two to three
times an erythema dose on the lesion, The question, therefore,
arises as to how deep the reaction will penetrate. Will the
normal tissue under the lesion be destroyed? We can measure
the dose at the depth of one or two centimeters in the ordinary
way with an ionization chamber or with photographic films,
using water or some organic substance for absorption material.
It is not probable, however, that such measurements of unfiltered rays are proportionaI to the effect in the tissue. We have,
therefore, decided to use the erythema produced on the skin as
a standard for such measurements.
Up to the present time we have carried out but two experiments with patients. Sheets of paraffin were used for absorption and scattering of the rays. Five circular fields 2 centimeters in diameter were given on the back of each patient. For
the first patient, the fields were distributed along the periphery
of a circle 12 centimeters in diameter, and for the second, they
were arranged in two rowH. The fields were made small because
we did not want to risk more than was necessary, and also because small fields are most common in this kind of treatment.
Fig. 1 shows the distribution of the areas and how they were
treated in the first case. Area No. 2 showed a little more reaction than No. 1, indicating that more than 50 per cent of the
surface dose is given under 1 centimeter of paraffin (estimated
18
19
DOSAGE FROM UNFILTERED X-RAYS
to 60 per cent). Area No. 3 showed still greater reaction while
No. 4 showed the same reaction as No. 2. No. 5 showed the
greatest reaction.
The details of the experiment are given in Table I. Column
2 gives the thickness of the paraffin layer through which the
TABLE
1.
Kelley-Koett machine. Coolidge tube.
90 kv. Effective = 127 kv. peak; 10 ma.; 23 cm. focus-skin dietance.
No filter; field circular, 2 cm. diameter.
Paraffin
1 cm.
2 cm.
2 cm.
-
Min.
Depth Dose for 100
Per Cent Erythema
Dose on Skin
(Estimated)
Depth
Dose
3
6
9
12
15
100
50
33
25
20
100
120
160
120
180
100
60
53
30
36
rays had to pass before reaching the skin. The time for each
field is given in column 3. If any other area on the skin had
shown an erythema exactly like No. 1, which was used as a
20
WILHELM STENSTROM
standard, then the depth dose would have been equal to the
corresponding figure in column 4. However, the reaction on
the different areas was heavier than on No. 1 and was eatimated as shown in column 5 with the reaction of No. 1 chosen
as 100. From these figures the depth-doses of column 6 were
calculated.
Area No. 1 showed a small blister and the other areas blistered
completely. However, the tissue under the skin was not affected. Area No. 6 blistered 14 days after radiation, and all
the areas were blistered within one month. One month later
they were all healed.
No
rqpw
1 Crithenr
FIQ.2.
This experiment showed that the depth-dose was heavier than
had been suspected (compare columns 4 and 6). Smaller doses,
therefore, were used for the second experiment as is shown in
Area
No.
Paraffin
1
2
3
4
5
0 om.
1 om.
1 om.
2 em.
2 om.
Min.
--
3.0
4.3
5.0
7.5
8.6
Depth Dole for 100
Per Cent Erythema
Doae on Skin
(EOtimated)
Depth
100
100
75
85
80
100
63
51
32
32
70
60
40
35
90
DM
DOSAGE FROM UNFILTERED X-RAYS
21
Fig. 2 which also gives the distribution of the fields. The
same voltage, niilliamperage, etc., were used as before. Other
details and the results are given in Table 2. All fields were
tanned but there was no blistering. A slight difference in color
made it possible to estimate the skin dose as shown in column 5.
An estimation of the degree of erythema from the color is,
of course, somewhat arbitrary. From the two experiments,
we can, however, conclude that the dose a t 1 centimeter depth
is more than 50 per cent and less than 60 per cent of the skin
dose and that it lies between 25 per cent and 35 per cent a t 2
centimeters. As probable values, we get 54 per cent and 32
per cent of the skin dose a t a depth of 1 and 2 centimeters.