[Efficient parameters of grid diaphragms for the radiation therapy of malignant tumors]

In larger size malignant tumors it is necessary to raise a dose of irradiation and to increase field sizes whereas tolerant doses for normal tissues and stroma are reduced with an increase in the volume of irradiation. The adjustment of these two alternative requirements can be achieved with the help of grid diaphragms creating more sparing conditions of the irradiation of normal organs and tissues as a result of inhomogeneous dose distribution. The authors consider some mathematical models for assessment of the quality of an inhomogeneous dose field formed by using grid diaphragms. In this case the sparing of normal organs and tissues results only from a decrease in the volumes of irradiated normal tissues. The proposed mathematical models can be used for a choice of optimum parameters of grid diaphragms.