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RA.PIUM 23
X-RAY AND RADIUM THERAPY IN UROLOGY.*
By George Gilbert Smith, M. I).. F. A. C. S.. Boston.
(From the Huntington Memorial Hospital)
Any discussion of the place of radiation in a specialty such as urology,
in which widely varying types of pathological lesions occur, necessitates
a recognition of the different forms in which radiation may be
employed. It may not be amiss, therefore, to review briefly the physics
of radium and the roentgen ray, and to establish first a clear conception
of the different ways in which these measures may be used.
At the Huntington Memorial Hospiial the total supply of radium
is kept in solution in a flask. From ihe solution of radium a gas is constantly
being given off; this gas is purified and led into a glass capillary
tube less than a millimeter in diameter. Different lengths of this tube.
with varying quantities of the gas imprisoned within each segment, are
sealed off by heat. The gas is radium emanation (radon) ; it contains solid
particles of Radium A, Radium B and Radium C. From these substances
are given off the different kinds of rays. The emanation therefore has
the radioactive property of radium, and supplies the same source of Beta
and Gamma rays as does the clement Radium; the difference lies in its
vastly greater rapidity of disintegration. Kmanation loses 50% of its
potency every 3.S5 days, whereas radium itself loses one-half its radioactivity
in something under 1700 years. For practical purposes, the
emanation is the better form in which to employ the radioactive principle,
because it is more capable of subdivision into very minute quantities.
It is, we may say. more flexible, and the danger of losing the source of
our radioactivity is done away with. The maximum amount of emanation
accumulated from 1 milligram of radium over a considerable period
of time is termed a millicurie.
From the radium emanation and its products are given off three kinds
of "rays." The Alpha rays arc positively charged material particles,
really helium atoms, liberated from the radioactive substances with an
initial velocity of 9000-12000 miles per second. These rays, since they
arc absorbed by the thinnest layer of metal or by a sheet of note pajier,
never got beyond the glass which contains the emanation. Consequently
they are of no practical interest when radium is used in any sort of
container.
Beta rays are negatively charged electrons of varying degrees of penetration.
The softest Beta rays approximate the Alpha rays; the hardest
or swiftest have one hunderd times the penetrating power of Alpha rays.
Yet even the hardest Beta rays are absorbed to a large extent by 1 centimeter
of epithelial tissue. To get any effect from these rays, therefore,
the source of radiation must be applied closely to the tissues upon which
an effect is desired.
Gamma rays are not particles or electrons, but are undulations of
the ether, or electro-magnetic waves, similar to X-Rays. but of shorter
wave length and consequently of greater penetration. An idea of their
penetrating power is given by the fact that the hardest Gamma rays will
penetrate even a foot of lead without being entirely absorbed.
•Rcprinled by permission from The Boston Medical and SurRical Journal. Vol. 192.
335-3*0, Feb. 19, 1925.