The uses of a cobalt unit for radiotherapy.

X-rays generated at a kilovoltage of 250 have been used in the treatment of malignant disease for about 30 years. It was found that when high doses were given, damage to the skin and subcutaneous tissues was frequent. After desquamation of the skin had subsided, pigmentation followed and during the succeeding i8 months permanent and unsightly telangiectasis developed. This was often associated with a variable amount of fibrosis of the soft tissues. With conventional X-ray therapy the maximum dose fell on the skin, which therefore suffered most severely. The absorption of X-rays in tissue increases with increase in the atomic weights of the elements composing the tissues. Thus, absorption of X-rays in bone is two and a half times higher than in soft tissues, mainly due to the high calcium content of the skeleton.