[Comparison of measured relative isodose distributions in tangential stationary fields of Co-60 radiation with calculated isodose plans (author's transl)].

The relative isodose distributions in tangential stationary fields are measured in rectangular phantoms by means of four different methods: film measurements, thermoluminescence probes, ionization chamber, and semiconductor probes. The different measuring methods are compared, and the influence exercised by the part of the field running in the air is examined. Within the scope of their applicability, all measuring methods produce the same values which differ only by +/- 1%. It is possible to reach a better estimation of the dose distribution in the depth of the "partial fields" (a part of which is running in the air) by reducing adequately a "complete field". Furthermore, isodose distributions of measured "partial fields" are compared with calculations from a programme for the irradiation planning (programme COMRAD), and they are discussed. It is shown that the losses due to scattered radiation are not rendered by the calculation.