Caesium 137 Sources for Use in Intracavitary and Interstitial Radiotherapy

The construction and properties of ¹³⁷Cs sources suitable to replace radium tubes and needles in general use are described. It is found that the exposure distribution in water around these sources is very nearly the same as that produced by their radium equivalents. The results of a test for the presence of ¹³⁴Cs are given showing that the contribution of this isotope to the dose-rate is less than 6 per cent. The relative advantages possessed by ¹³⁷Cs for this application are discussed.