[Calculation of the dose distribution with time in the planning of radiation treatment]

Until recently the effect of a dose fractionation regimen was disregarded in radiation therapy planning. A devised method of the calculation of iso-TDF-dose maps made it possible to obtain iso-effective distributions where radiation exposures in different dose fractionation regimens are presented in the form of isoline in TDF units. The method of the calculation of iso-effective maps allowed us to analyse the effect of the procedure of the implementation of a radiotherapeutic plan and the conditions of dose rate fixing. The author cites by way of an example the calculation of a 3-field static irradiation of esophageal cancer with 5 fractions a week. All possible variants of the implementation of this therapeutic plan were studied. Daily irradiation of all the planned fields has been shown optimum. This conclusion is corroborated by the literature data. The absolute value of the TDF factor in the adjacent healthy organs and tissues increases noticeably using in the calculations isodose curves fixed to the dose in the focus depth as compared to the dose fixing on the surface. Isoeffective maps can be successfully used for an analysis of clinical and therapeutic results.