Radiotherapy in Dermatological Conditions

The term “radiotherapy” naturally includes all kinds of atomic energy, but our clinical experience with these fundamental forces is at present limited to the α particles, β particles, and that part of the electro-magnetic spectrum represented by X rays and the γ rays of radium. The α particles are nuclei of helium which have velocities of 9000 to 20,000 miles per second. They carry double positive charges which attract two electrons on collision with an atom, and then become indistinguishable from helium atoms. They are unable to penetrate a sheet of paper and, therefore, their energy is dissipated and their effect produced in the upper layers of the epidermis. Thorium X preparations, with a half-life period of 3·6 days, provide a convenient source of α particles, and they are at present much used for the treatment of capillary nævi and appear to be of value in some cases of psoriasis, lichen simplex, some types of sclerodermia, etc. Radon, which has been incorporated in wax or ointment, is also a good source of α rays. From both of these radioactive substances β and γ rays are produced by later disintegration products, but it is thought that with the usual techniques the effects of the β and γ rays are insignificant.