Supervoltage Therapy: A review of Present Day Facilities and Techniques

A critical review is given of the principal machines used for high energy therapy, namely the Resonant Transformer, the 2 MeV Van de Graaff, the Cobalt-60 apparatus, the Linear Accelerator and the main types of Betatron. The latter include the Siemens 15-17 MeV, the Allis Chalmers 24 MeV and the Brown Boveri 31-35 MeV machines. An attempt is made to compare the performance and therapeutic value of the various types of machine and, within approximate limits, arrive at some estimate of their relative cost in treating, for example, an average patient to a tumour dose of 5000 r. This relative cost depends not only on the initial cost of the machine and building but also on the dose rate and ease of setting up, both of which determine the number of patients that can be treated in a day. Broadly, the cost per patient is about the same for the Linear Accelerator and Cobalt Units while that for the Betatron (using x-rays) appears to be considerably higher: this is largely due to its relatively low output of x-rays. Electron therapy, for which the Betatron is admirably suited, has attractive features and the physical characteristics of this form of treatment are discussed. References are given to the principal works on the physical aspects of supervoltage therapy.