Teletherapy design problems.

The use of radium and x-rays for therapeutic purposes has a long and distinguished history. Radium and x-ray machines, although of proved value, have some irritating limitations. The most important of these, concerning the biological response of tissue to radiation, are not considered in this discussion. Others are inherent in the design of physical machinery, which in turn depends upon the source of radiation. With radioactive sources, it is not only possible but also practical to design machines which will respond to every legitimate demand of the radiotherapist. It is very probable that teletherapy units can be made and maintained more economically than can x-ray machines. Especially for higher voltages, artificial radioactive sources are in competition with roentgen rays and radium, and the basic principle of teletherapy design should be to meet and to better the desirable features of the historical irradiation apparatus. Radioactive sources have released us from the 1 curie per gram specific activity...