[A computer-supported method for the direct production of shielding blocks and compensators for radiotherapy]. / Computergestützte Methode zur unmittelbaren Herstellung von Abschirmblöcken und Kompensatoren für die Strahlentherapie.

The homogeneous irradiation of irregularly shaped targets with high doses and the simultaneous protection of the equally irregular surrounding high risk regions can be carried out with the help of shielding blocks and compensation filters specially cut for individual use. The machines offered on the market that help in their production have serious drawbacks in spite of the advanced technology used. These machines with limited usage are not only expensive but also require personnel to control the several steps the production of the blocks and filters involves. Safer radiotherapy however demands a more intensive use of these protective measures. However, it is now possible to overcome the drawbacks we have mentioned. The projection of the contours of the block marked on the X-ray on the shielding blocks can be carried out directly with the help of the computer that directs the radiotherapy. This computer could be connected to a multipurpose CNC milling machine. Similarly, one could, in the near future, use the data from computed tomograms in the computer used to plan the radiotherapy to mould three dimensional compensation filters. The cutting out of the negative moulds from Styrodur, the casting with fluid metal alloys, the imprecision that follows, as well as the health hazards and environmental pollution attached to his process could then be avoided, not to speak of the possibility of total reutilization of the rests. The positioning of the block ensemble can follow effortlessly and with precision on the lucite plates which have been drilled to accommodate the blocks.

[Dose distribution of electrons obtained from linear accelerators equipped with a beam scanning system]. / Dosisverteilung von Elektronen aus Linearbeschleunigern mit Strahl-Scanning-System.

Homogeneous distribution of electrons used for therapeutic purposes and obtained from accelerators, is achieved by means of Potter-Bucky diaphragms or by repeated, staggered, sawtooth-shaped sweeping movements of the electron beam (scanning) over the radiation field. The repetition of the scanning process (number of scans) can result in long measurement times for achieving a sufficiently homogeneous, dosimetrically adequate distribution of the electrons. This "time problem" makes it imperative to achieve good homogeneity while keeping the number of scans as low as possible. To solve the problem, the scanning movement of the electron beam is simulated by a computer programme and the interdependence of the homogeneity of the irradiation field and number of scans is investigated. Since changing the ratio of the two deflection rates exercises a significant influence, it is mandatory in dosimetry to pay close attention to a strict observance of the deflection rates.