[Optimization of the isodosis in case of radiotherapy with asymmetric target volumes]

By superimposing only two moving fields, it is nearly always possible to adapt an 80% isodose to asymmetric target volumes. By means of wedge filters, it is possible to create asymmetric 80% isodoses with only one irradiation field. The authors compare four different moving field techniques for the irradiation of the left kidney region with regard to the radiation exposure of various transverse body regions. If wedge filters are used for moving field therapy, the average dose values of the different organs are generally significantly inferior to those measured in case of conventional moving field therapy. The reduction of the total volume exposure by 20% and of the liver exposure by nearly 50% is most favorable. Another great advantage is the complete sparing of the remaining kidney. These quantitative advantages are supplemented by the qualitative factor concerning the considerably simplified therapy planning and the easy focussing.