Dosage Control in Interstitial Radium Therapy

The use of the γ rays of radium, and of X rays, in the treatment of neoplasms is dependent upon the delivery of a lethal dose to the tumour cells without destruction of the surrounding normal tissues. Different tumours display different degrees of radio-sensitivity, thus requiring different minimal dose levels. Failure to deliver at least the minimal lethal dose to the whole tumour is followed by failure to destroy it, and often prejudices any further attempt at treatment. On the other hand, it is possible that unduly high doses may so damage the neighbouring normal tissues that there is interference with tumour response, although frank necrosis does not occur. As the biological effects of radiation vary with the overall time of delivery, the lethal dose must be delivered over the correct period of time.