Technical MetJwds in Radium Therapy 237 



sites where such methods are still the best ; for instance, lesions 

 of the tongue where, owing to involuntary movement, it is 

 almost impossible to use any other method properly. 



No account of interstitial methods in treatment would be 

 complete without mention of radon technique. The gas from 

 radium can be purified so completely that one can handle quan- 

 tities that represent extreme purity ; the volume of 1 curie is just 

 less than 0.6 cubic millimeter, and one gram of radium in solu- 

 tion can yield 25 curies during the course of a year, so that 

 the total volume of pure gas is only 15 cubic millimeters; the 

 refinements of technique allow this to be shared among no less 

 than 10,000 capillary tubes which, when mounted in platinum, 

 serve as gamma-ray sources, their lengths ranging from 5 milli- 

 meters to 3 or 4 centimeters. 



In any technical discussion upon the use of radon, it soon be- 

 comes apparent that, in spite of contraindications, it continues 

 to be used because objections are outweighed by advantages. 

 It can be said that the outstanding advantage is the adaptability 

 that attends its use ; in other words, the size, shape, content, 

 and filtration can be altered to suit the clinical need of the 

 moment ; moreover, radon "seeds" can be inserted into the 

 tissues and left there without danger to the patient. Against 

 this, we have the decline of its activity, which renders it unsuit- 

 able for treatment which lasts more than a few days, the high 

 cost of running a radon center, and the danger to technicians 

 engaged in the work of purification and concentration of the 

 radon. 



Therapeutic Aims and Methods 



The three outstanding technical methods of using radium 

 (and radon) in treatment have been discussed. It remains to 

 say something of what is the aim behind these methods. What- 

 ever the radiotherapeutic method in treating malignant disease, 

 the aim is certainly to destroy all malignant cells, but it is 

 equally certain that in many cases this is quite imposible if any 

 regard is paid to the normal tissues of the body of the patient. 



