RADIUMTHERAPY. Since 1913 the name Curietherapy has been applied, particularly in France, as a generic term to therapeutic methods in which radioactive bodies are employed. The term radiumtherapy is used primarily for curietherapy carried out by means of radium, and (by extension) by radioac tive bodies derived from radium.
Radiumtherapy dates from the times immediately following the discovery of radium by the Curies (1898) ; it succeeded observation of the effects produced on the skin by radium tubes kept in its vicinity (Becquerel, P. Curie). The first case-notes on radiumtherapy were published by Danlos (1904).
There are two methods of employing radioactive bodies thera peutically. One consists in introducing them into the blood, so that they may be diffused throughout the organism : this is called general curietherapy. The other consists in producing a local action in the form of limited fields of radiation, and this is called local or focal curietherapy.
Radium is no longer employed in general curietherapy, because, owing to its insolubility and slowness in disintegration, it remains for a long time, and not without danger, in the organism. It is, however, possible to inject radon (radium emanation), a solution or suspension of the active deposit of radon (radium A, B, C), or radium F or polonium (see RADIUM). In practice the gaseous radon is used.
Radon can be employed without danger because it does not accumulate (being eliminated by pulmonary ventilation) and lasts a very short time (period of semi-disintegration = 3.85 days). It is administered either by inhalation, or as a drink, or by subcutaneous or intravenous injection. By inhalation in closed
cabinets an equilibrium lasting several hours can be established between the radon content of the confined atmosphere and that of the interior of the organism. The inhalation of the gases given off by the waters of radioactive mineral springs is a variety of general curietherapy. It is believed that radioactivity is a highly important factor in the efficacy of certain mineral springs.
It is in the treatment of some general diseases, of which chronic rheumatism is the most favourable type, that general curiether apy has been employed with the highest degree of success. The injection of considerable quantities of radon has also been advo cated in the treatment of cancer, but the efficacy of this treat ment requires confirmation.
The physiological and therapeutic actions of radioactive bodies introduced into the interior of the organism are sure and power ful, but insufficiently known; their use is not devoid of risk (par ticularly on account of their destructive effect on the haema topoietic cells). For this purpose, substances of the radium family have alternatives in the homologous substances of the thorium family. Thorium X in particular has a period of semi-disinte gration of the same order as that of radon; it is not volatile, and is less rapidly eliminated than radon.
II. Focal Curietherapy.—This has gained a very important place in medical practice. In this method, radium and radon are superior to other radioactive bodies. The superiority of radium is due to the relatively large quantities available (now measur able in grammes) and to the constancy of its radiation, which is itself a result of the slowness with which spontaneous destruction proceeds. The chief advantage of radon is that the radium solu tions from which it is periodically extracted can be preserved from loss. Notwithstanding the somewhat rapid decrease of radia tion in the case of radon, the biological effects of a radium focus and a radon focus are approximately the same, if the rays are purified by filtration through similar screens.