The Output of Various Types of X-ray Machines and the Influence of Wave Form on Quality of X Radiation

Abstract

An accurate knowledge of the amount and the distribution with wavelength of the energy emitted from an X-ray tube under any particular form of potential and current is of vital importance in X-ray therapy. If it were possible to predict the nature of the energy distribution from a knowledge of the applied potential and the tube current, it might be anticipated that a standardisation of treatment routine would be possible. The measurement of the tube current and the voltage is, however, not sufficient for this purpose, and it is well known that a third factor—the wave form of the applied potential—can greatly influence both the quantity and the quality of the radiation emitted. It has been found that for different plants, with the same maximum potential and the same current, the energy-wave-length curves can differ considerably and the total energy may vary by as much as a factor of two. It is therefore evident that the potential wave form plays a very profound part in the radiation output of various machines. The X-ray intensity varies directly as the current through the tube. The measurement of the tube current is comparatively simple, as no question of wave form enters, since the milliammeter integrates or averages the current passing through it, no matter in what way it pulsates. The measurement of the potential is both more important and more difficult, and the means of measurement are much less satisfactory.