Some New Methods of Radiotherapy

There have been many advances in treatment with X-Rays and radioactive su stances. This is an account of those recently adopted and those to be used in futu in the Radiotherapy Department at Bristol. t There are two great difficulties in using Deep X-Rays for the treatment of maligna disease. First, " Deep " X-Rays do not penetrate really deeply. Their effective rafl& is a few centimetres deeper than the skin, and it is still impossible with ordinary Pe \ X-Rays to give an adequate dose to the centre of the pelvis, to lung roots and o& phagus, or even to deeper lymph glands in the supraclavicular region. This is PoS , ' however, by using the X-Rays generated by voltages between two and ten million vol These rays and machines are called " supervoltage ". e The second difficulty under which the X-Ray therapist labours is that the o .j of rays needed to get rid of a growth is commonly rather close to the dose which excessively damage the normal tissue within the beam. In other words the " t^ peutic ratio " is poor. Here also supervoltage rays have a definite advantage beca ^ bone and cartilage, which are very easily damaged by ordinary X-Rays, are easily damaged by supervoltage X-Rays. In fact all the unwanted reactions 01 patient, both skin effects and radiation sickness, are definitely less with supervou t> Supervoltage machines are, however, very large and costly?for example, a * million-volt machine (a " linear accelerator ") costs about ?40,000. RADIOACTIVE COBALT 't Since the atomic energy piles at Harwell and elsewhere have been working, 1 ^ been possible to make radioactive cobalt. Radioactive cobalt has one useful prop^js it emits rays nearly the same as those from a three-million-volt X-Ray machine. Q[ means that if we can get enough radioactive cobalt and enclose it in the m-^ply a large mass of protecting material, we can get a beam of 2-3 million volt rays by leaving a hole in the side of the protecting mass. jjo-Up till now only Canada and the U.S.A. have been able to provide enough * active cobalt to give as much power as an actual supervoltage machine. Such a. beam unit from Canada has been presented to Mount Vernon Hospital, Mid and has een installed there. We _ Bristol are now installing a cobalt beam unit, big enough to comp1 …