[Standard grid diaphragms in the telegammatherapy of malignant tumors]

The paper is concerned with the problem of uneven irradiation of tumors using standard grid diaphragms on Soviet gamma-apparatuses. It has been shown that the utmost spatial heterogeneity is formed by using the C-4 grid with the source-surface distance (SSD) of 47 cm. The degree of spatial heterogeneity formed by the C-3, C-2, C-1 and C-5 grids is less pronounced. An increase in SSD results in the formation of more even irradiation. In uneven irradiation of tumors the nature of dose fractionation changes and it should be taken into account in the planning of radiotherapy.