Variations in dose distributions by the use of independent asymmetric jaws. A new technique for irradiation of localized carcinoma of the prostate

The use of independent jaws set asymmetrically in the moving field technique with bilateral arcs allows the entirely new dose distributions be obtained. The basic principle of this technique is that, with the use of moving field technique with bilateral arcs, the independent jaw more proximate to the central ray (axis) of beam must always be on the side of the critical organ. In this area the characteristic deformation of isodoses and the formation of very steep dose slope occur. We consider as optimum technique for the target irradiation of the prostatic carcinoma the moving field technique with bilateral 105 degrees arcs with 20 MeV X-ray beam of linear accelerator and with independent jaws set asymmetrically, when the independent jaw more proximate to the central ray is always + 1.5 cm from the central ray of the beam.