High Voltage X-ray Tubes in the U.S.A. Part I

Abstract

In recent years a number of X-ray tubes operated at voltages between 500 and 1,000 K.V. have been used in the U.S.A. for the treatment of deep tumours. These tubes must ultimately be judged by their performance in clinical practice, but their users are reluctant to make a report of this nature until greater experience has been gained. At present, therefore, their discussion must be restricted to technical and financial aspects, and to considerations of utility. Nevertheless it is desirable to bear in mind the reasons which have led to the development of these more complicated and costly installations. They may be summarised as follows:— 1. Theory suggests that the shorter the average wavelength of the radiation used, the greater will be the depth dose obtained, and this is supported by experience with the lower voltage type of X-ray tube. 2. It is possible that shorter wavelength radiation is preferable for biological reasons, so that such radiation should receive an adequate trial. 3. Radium is a source of short wavelength radiation which fulfils the requirements of (1) and (2) better than X rays from any high voltage X-ray tube which can be built at present. However there are considerable differences in the techniques of using gamma rays and X rays, so that it is desirable to test the combination of X-ray technique and short wavelength radiation. Moreover, there is not sufficient radium available to treat all deep tumour cases, so that an alternative source of short wavelength radiation is valuable.