Principles of a New Therapy with High Speed Electrons

Abstract

ONE of the most important problems of radiation therapy is the quest for a radiation, the main effects of which can be localized in a definite zone of depth. We know that this could not be attained in the past. All the kinds of radiations used at the present time are most active at the surface. Their effects decrease with the depth and cannot be limited to a definite zone. A solution of these problems would be of fundamental importance for radiation therapy. It is the object of the following article to point out why the radiations used formerly are not satisfactory in this respect. It is also pointed out that, in principle, this problem can be solved by the use of high speed electrons. In addition, the effects of high speed electrons upon the human organism are shown herein for the first time. An opportunity is given herewith to form an opinion on the entire problem of therapy with high speed electrons. It is the purpose of this article to stimulate further research. What Are High Speed Electrons?—We know that physically there are two types of radiations: the electromagnetic wave radiations and the corpuscular rays. The field of electromagnetic wave radiation, including long wave heat rays, visible light, ultra-violet light, Grenz rays, x-rays, and, finally, the gamma rays of radium, has been thoroughly investigated. All these radiations are being used therapeutically. The second type, the corpuscular rays, has so far not been applied in therapy. We may disregard occasional preliminary experiments, soon abandoned on account of insufficient range. For the very same reason it is unnecessary, for the time being, to consider the heavier positively charged particles. The neutrons, discovered by Chadwick in 1932, which have a sufficient range, will be discussed separately later on. Also the negatively charged particles, namely, rather soft cathode rays and beta rays, have so far not been suitable for practical use in radiation therapy because of their insufficient range. Therapy with negatively charged particles took a decisive turn in 1932, when Brasch and Lange were able to experiment with electrons of 1.7 and 2.4 million volts. There is no principal difference between electrons, cathode rays, or beta-rays; these are only different terms for the same kind of radiation. We shall use the differentiating term “high speed electrons” to indicate that the electrons have been accelerated artificially with voltages of several million volts. By the velocity the range in tissues is increased to an extent which could not be attained before. Herein lies the basically new feature. The Production of High Speed Electrons.—It would lead us too far from the matter under discussion to explain the technical construction of the apparatus which is described in detail in Strahlentherapie, 44, 505, 1933.