A beam director for small field x-ray therapy.

In order to achieve exact adjustment of the applicator during irradiation of the head using the technique of multiple very small circular fields we have used with success a beam directing apparatus composed of the following parts: a special cylindrical applicator and a reduced “shell” (made individually for each patient) with direction discs and centring rod. The special cylindrical applicator (Fig. 1) has an internal diameter of 40 mm and it is ended by a section of Plexiglass. The transparent wall of the end is marked with four coloured grooved lines parallel to the axis of the applicator and spaced at intervals of 90 deg. The reduced “shell” (Fig. 2). The foundation consists of two bands 20 mm wide and 4 mm thick. They are made of plastic such as is used for making surgical splints. The first band is passed round the greatest circumference of the head, over the forehead and temples to the occipital region. The second band goes from one temple over the chin to the other temple. These two foundation band...